make teal-macro look better.

author: Li Jin <dragon-fly@qq.com> 2020-10-23 17:32:48 +0800
committer: Li Jin <dragon-fly@qq.com> 2020-10-23 17:32:48 +0800
commit: 1c6a9651beffd9cbbb3641179f3a738d5555d3c9 (patch)
tree: 31f442c3685bf19e851f62c4b2957d445e313eac /spec
parent: a51a728d847e790329e41c75928a81630200b63f (diff)
download: yuescript-1c6a9651beffd9cbbb3641179f3a738d5555d3c9.tar.gz
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3 files changed, 6844 insertions, 13 deletions
diff --git a/spec/inputs/macro-teal.mp b/spec/inputs/macro-teal.mp
index 20444e1..9ce1bcd 100644
--- a/spec/inputs/macro-teal.mp
+++ b/spec/inputs/macro-teal.mp
@@ -2,6 +2,7 @@ $ ->
        import "moonp" as {:options}
        if options.tl_enabled
                options.target_extension = "tl"
+        package.path ..= "?.lua;./spec/lib/?.lua"
 macro expr to_lua = (codes)->
        "require('moonp').to_lua(#{codes}, reserve_line_number:false, same_module:true)"
@@ -9,19 +10,31 @@ macro expr to_lua = (codes)->
 macro expr trim = (name)->
        "if result = #{name}\\match '[\\'\"](.*)[\\'\"]' then result else #{name}"
-export macro text var = (name, type, value = nil)->
+export macro text local = (decl, value = nil)->
        import "moonp" as {options:{:tl_enabled}}
+        name, type = ($trim decl)\match "(.-):(.*)"
+        if not (name and type)
+                error "invalid local varaible declaration for \"#{decl}\""
        value = $to_lua(value)\gsub "^return ", ""
        if tl_enabled
                "local #{name}:#{$trim type} = #{value}", {name}
        else
                "local #{name} = #{value}", {name}
-export macro text def = (name, type, value)->
+export macro text function = (decl, value)->
        import "moonp" as {options:{:tl_enabled}}
+        import "tl"
+        decl = $trim decl
+        name, type = decl\match "(.-)(%(.*)"
+        if not (name and type)
+                error "invalid function declaration for \"#{decl}\""
+        tokens = tl.lex "function #{decl}"
+        _, node = tl.parse_program tokens,{},"macro-function"
+        args = table.concat [arg.tk for arg in *node[1].args],", "
+        value = "(#{args})#{value}"
        if tl_enabled
-                value = $to_lua(value)\match "function%(.*%)(.*)end"
+                value = $to_lua(value)\match "function%([^\n]*%)(.*)end"
-                "local function #{name}#{$trim type}\n#{value}\nend", {name}
+                "local function #{name}#{type}\n#{value}\nend", {name}
        else
                value = $to_lua(value)\gsub "^return ", ""
                "local #{name} = #{value}", {name}
@@ -35,11 +48,20 @@ end", {name}
        else
                "local #{name} = {}", {name}
-export macro text field = (tab, sym, func, type, value)->
+export macro text method = (decl, value)->
        import "moonp" as {options:{:tl_enabled}}
+        import "tl"
+        decl = $trim decl
+        tab, sym, func, type = decl\match "(.-)([%.:])(.-)(%(.*)"
+        if not (tab and sym and func and type)
+                error "invalid method declaration for \"#{decl}\""
+        tokens = tl.lex "function #{decl}"
+        _, node = tl.parse_program tokens,{},"macro-function"
+        args = table.concat [arg.tk for arg in *node[1].args],", "
+        value = "(#{args})->#{value\match "[%-=]>(.*)"}"
        if tl_enabled
                value = $to_lua(value)\match "^return function%(.-%)\n(.*)end"
-                "function #{tab}#{$trim sym}#{func}#{$trim type}\n#{value}\nend"
+                "function #{tab}#{sym}#{func}#{type}\n#{value}\nend"
        else
                value = $to_lua(value)\gsub "^return ", ""
                "#{tab}.#{func} = #{value}"
diff --git a/spec/inputs/teal-lang.mp b/spec/inputs/teal-lang.mp
index 3c9c79b..29769d5 100644
--- a/spec/inputs/teal-lang.mp
+++ b/spec/inputs/teal-lang.mp
@@ -3,10 +3,10 @@ $ ->
 import "macro-teal" as {$}
-$var a, "{string:number}", {value:123}
+$local "a:{string:number}", {value:123}
-$var b, "number", a.value
+$local "b:number", a.value
-$def add, "(a:number,b:number):number", (a, b)-> a + b
+$function "add(a:number, b:number):number", -> a + b
 s = add(a.value, b)
 print(s)
@@ -16,17 +16,25 @@ $record Point, [[
        y: number
 ]]
-$field Point, '.', new, "(x: number, y: number):Point", (x, y)->
+$method "Point.new(x:number, y:number):Point", ->
-        $var point, "Point", setmetatable {}, __index: Point
+        $local "point:Point", setmetatable {}, __index: Point
        point.x = x or 0
        point.y = y or 0
        point
-$field Point, ":", move, "(dx: number, dy: number)", (dx, dy)=>
+$method "Point:move(dx:number, dy:number)", ->
        @x += dx
        @y += dy
-$var p, "Point", Point.new 100, 100
+$local "p:Point", Point.new 100, 100
 p\move 50, 50
+$function "filter(tab:{string}, handler:function(item:string):boolean):{string}", ->
+        [item for item in *tab when handler item]
+$function "cond(item:string):boolean", -> item ~= "a"
+res = filter {"a", "b", "c", "a"}, cond
+for s in *res
+        print s
diff --git a/spec/lib/tl.lua b/spec/lib/tl.lua
new file mode 100644
index 0000000..aca748c
--- /dev/null
+++ b/spec/lib/tl.lua
@@ -0,0 +1,6801 @@
+local _tl_compat53 = ((tonumber((_VERSION or ''):match('[%d.]*$')) or 0) < 5.3) and require('compat53.module'); local assert = _tl_compat53 and _tl_compat53.assert or assert; local io = _tl_compat53 and _tl_compat53.io or io; local ipairs = _tl_compat53 and _tl_compat53.ipairs or ipairs; local load = _tl_compat53 and _tl_compat53.load or load; local math = _tl_compat53 and _tl_compat53.math or math; local os = _tl_compat53 and _tl_compat53.os or os; local package = _tl_compat53 and _tl_compat53.package or package; local pairs = _tl_compat53 and _tl_compat53.pairs or pairs; local string = _tl_compat53 and _tl_compat53.string or string; local table = _tl_compat53 and _tl_compat53.table or table; local _tl_table_unpack = unpack or table.unpack; local Env = {}
+local TypeCheckOptions = {}
+local LoadMode = {}
+local LoadFunction = {}
+local tl = {
+   load = nil,
+   process = nil,
+   process_string = nil,
+   gen = nil,
+   type_check = nil,
+   init_env = nil,
+}
+local inspect = function(x)
+   return tostring(x)
+end
+local keywords = {
+   ["and"] = true,
+   ["break"] = true,
+   ["do"] = true,
+   ["else"] = true,
+   ["elseif"] = true,
+   ["end"] = true,
+   ["false"] = true,
+   ["for"] = true,
+   ["function"] = true,
+   ["goto"] = true,
+   ["if"] = true,
+   ["in"] = true,
+   ["local"] = true,
+   ["nil"] = true,
+   ["not"] = true,
+   ["or"] = true,
+   ["repeat"] = true,
+   ["return"] = true,
+   ["then"] = true,
+   ["true"] = true,
+   ["until"] = true,
+   ["while"] = true,
+}
+local TokenKind = {}
+local Token = {}
+local lex_word_start = {}
+for c = string.byte("a"), string.byte("z") do
+   lex_word_start[string.char(c)] = true
+end
+for c = string.byte("A"), string.byte("Z") do
+   lex_word_start[string.char(c)] = true
+end
+lex_word_start["_"] = true
+local lex_word = {}
+for c = string.byte("a"), string.byte("z") do
+   lex_word[string.char(c)] = true
+end
+for c = string.byte("A"), string.byte("Z") do
+   lex_word[string.char(c)] = true
+end
+for c = string.byte("0"), string.byte("9") do
+   lex_word[string.char(c)] = true
+end
+lex_word["_"] = true
+local lex_decimal_start = {}
+for c = string.byte("1"), string.byte("9") do
+   lex_decimal_start[string.char(c)] = true
+end
+local lex_decimals = {}
+for c = string.byte("0"), string.byte("9") do
+   lex_decimals[string.char(c)] = true
+end
+local lex_hexadecimals = {}
+for c = string.byte("0"), string.byte("9") do
+   lex_hexadecimals[string.char(c)] = true
+end
+for c = string.byte("a"), string.byte("f") do
+   lex_hexadecimals[string.char(c)] = true
+end
+for c = string.byte("A"), string.byte("F") do
+   lex_hexadecimals[string.char(c)] = true
+end
+local lex_char_symbols = {}
+for _, c in ipairs({ "[", "]", "(", ")", "{", "}", ",", "#", "`", ";" }) do
+   lex_char_symbols[c] = true
+end
+local lex_op_start = {}
+for _, c in ipairs({ "+", "*", "/", "|", "&", "%", "^" }) do
+   lex_op_start[c] = true
+end
+local lex_space = {}
+for _, c in ipairs({ " ", "\t", "\v", "\n", "\r" }) do
+   lex_space[c] = true
+end
+local LexState = {}
+function tl.lex(input)
+   local tokens = {}
+   local state = "start"
+   local fwd = true
+   local y = 1
+   local x = 0
+   local i = 0
+   local lc_open_lvl = 0
+   local lc_close_lvl = 0
+   local ls_open_lvl = 0
+   local ls_close_lvl = 0
+   local errs = {}
+   local tx
+   local ty
+   local ti
+   local in_token = false
+   local function begin_token()
+      tx = x
+      ty = y
+      ti = i
+      in_token = true
+   end
+   local function end_token(kind, last, t)
+      local tk = t or input:sub(ti, last or i) or ""
+      if keywords[tk] then
+         kind = "keyword"
+      end
+      table.insert(tokens, {
+         x = tx,
+         y = ty,
+         i = ti,
+         tk = tk,
+         kind = kind,
+      })
+      in_token = false
+   end
+   local function drop_token()
+      in_token = false
+   end
+   while i <= #input do
+      if fwd then
+         i = i + 1
+         if i > #input then
+            break
+         end
+      end
+      local c = input:sub(i, i)
+      if fwd then
+         if c == "\n" then
+            y = y + 1
+            x = 0
+         else
+            x = x + 1
+         end
+      else
+         fwd = true
+      end
+      if state == "start" then
+         if input:sub(1, 2) == "#!" then
+            i = input:find("\n")
+            if not i then
+               break
+            end
+            c = "\n"
+            y = 2
+            x = 0
+         end
+         state = "any"
+      end
+      if state == "any" then
+         if c == "-" then
+            state = "maybecomment"
+            begin_token()
+         elseif c == "." then
+            state = "maybedotdot"
+            begin_token()
+         elseif c == "\"" then
+            state = "dblquote_string"
+            begin_token()
+         elseif c == "'" then
+            state = "singlequote_string"
+            begin_token()
+         elseif lex_word_start[c] then
+            state = "identifier"
+            begin_token()
+         elseif c == "0" then
+            state = "decimal_or_hex"
+            begin_token()
+         elseif lex_decimal_start[c] then
+            state = "decimal_number"
+            begin_token()
+         elseif c == "<" then
+            state = "lt"
+            begin_token()
+         elseif c == ":" then
+            state = "colon"
+            begin_token()
+         elseif c == ">" then
+            state = "gt"
+            begin_token()
+         elseif c == "=" or c == "~" then
+            state = "maybeequals"
+            begin_token()
+         elseif c == "[" then
+            state = "maybelongstring"
+            begin_token()
+         elseif lex_char_symbols[c] then
+            begin_token()
+            end_token(c)
+         elseif lex_op_start[c] then
+            begin_token()
+            end_token("op")
+         elseif lex_space[c] then
+         else
+            begin_token()
+            end_token("$invalid$")
+            table.insert(errs, tokens[#tokens])
+         end
+      elseif state == "maybecomment" then
+         if c == "-" then
+            state = "maybecomment2"
+         else
+            end_token("op", nil, "-")
+            fwd = false
+            state = "any"
+         end
+      elseif state == "maybecomment2" then
+         if c == "[" then
+            state = "maybelongcomment"
+         else
+            fwd = false
+            state = "comment"
+            drop_token()
+         end
+      elseif state == "maybelongcomment" then
+         if c == "[" then
+            state = "longcomment"
+         elseif c == "=" then
+            lc_open_lvl = lc_open_lvl + 1
+         else
+            fwd = false
+            state = "comment"
+            drop_token()
+            lc_open_lvl = 0
+         end
+      elseif state == "longcomment" then
+         if c == "]" then
+            state = "maybelongcommentend"
+         end
+      elseif state == "maybelongcommentend" then
+         if c == "]" and lc_close_lvl == lc_open_lvl then
+            drop_token()
+            state = "any"
+            lc_open_lvl = 0
+            lc_close_lvl = 0
+         elseif c == "=" then
+            lc_close_lvl = lc_close_lvl + 1
+         else
+            state = "longcomment"
+            lc_close_lvl = 0
+         end
+      elseif state == "dblquote_string" then
+         if c == "\\" then
+            state = "escape_dblquote_string"
+         elseif c == "\"" then
+            end_token("string")
+            state = "any"
+         end
+      elseif state == "escape_dblquote_string" then
+         state = "dblquote_string"
+      elseif state == "singlequote_string" then
+         if c == "\\" then
+            state = "escape_singlequote_string"
+         elseif c == "'" then
+            end_token("string")
+            state = "any"
+         end
+      elseif state == "escape_singlequote_string" then
+         state = "singlequote_string"
+      elseif state == "maybeequals" then
+         if c == "=" then
+            end_token("op")
+            state = "any"
+         else
+            end_token("op", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "lt" then
+         if c == "=" or c == "<" then
+            end_token("op")
+            state = "any"
+         else
+            end_token("op", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "colon" then
+         if c == ":" then
+            end_token("::")
+            state = "any"
+         else
+            end_token(":", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "gt" then
+         if c == "=" or c == ">" then
+            end_token("op")
+            state = "any"
+         else
+            end_token("op", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "maybelongstring" then
+         if c == "[" then
+            state = "longstring"
+         elseif c == "=" then
+            ls_open_lvl = ls_open_lvl + 1
+         else
+            end_token("[", i - 1)
+            fwd = false
+            state = "any"
+            ls_open_lvl = 0
+         end
+      elseif state == "longstring" then
+         if c == "]" then
+            state = "maybelongstringend"
+         end
+      elseif state == "maybelongstringend" then
+         if c == "]" then
+            if ls_close_lvl == ls_open_lvl then
+               end_token("string")
+               state = "any"
+               ls_open_lvl = 0
+               ls_close_lvl = 0
+            end
+         elseif c == "=" then
+            ls_close_lvl = ls_close_lvl + 1
+         else
+            state = "longstring"
+            ls_close_lvl = 0
+         end
+      elseif state == "maybedotdot" then
+         if c == "." then
+            state = "maybedotdotdot"
+         elseif lex_decimals[c] then
+            state = "decimal_float"
+         else
+            end_token(".", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "maybedotdotdot" then
+         if c == "." then
+            end_token("...")
+            state = "any"
+         else
+            end_token("op", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "comment" then
+         if c == "\n" then
+            state = "any"
+         end
+      elseif state == "identifier" then
+         if not lex_word[c] then
+            end_token("identifier", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "decimal_or_hex" then
+         if c == "x" or c == "X" then
+            state = "hex_number"
+         elseif c == "e" or c == "E" then
+            state = "power_sign"
+         elseif lex_decimals[c] then
+            state = "decimal_number"
+         elseif c == "." then
+            state = "decimal_float"
+         else
+            end_token("number", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "hex_number" then
+         if c == "." then
+            state = "hex_float"
+         elseif c == "p" or c == "P" then
+            state = "power_sign"
+         elseif not lex_hexadecimals[c] then
+            end_token("number", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "hex_float" then
+         if c == "p" or c == "P" then
+            state = "power_sign"
+         elseif not lex_hexadecimals[c] then
+            end_token("number", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "decimal_number" then
+         if c == "." then
+            state = "decimal_float"
+         elseif c == "e" or c == "E" then
+            state = "power_sign"
+         elseif not lex_decimals[c] then
+            end_token("number", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "decimal_float" then
+         if c == "e" or c == "E" then
+            state = "power_sign"
+         elseif not lex_decimals[c] then
+            end_token("number", i - 1)
+            fwd = false
+            state = "any"
+         end
+      elseif state == "power_sign" then
+         if c == "-" or c == "+" then
+            state = "power"
+         elseif lex_decimals[c] then
+            state = "power"
+         else
+            end_token("$invalid$")
+            table.insert(errs, tokens[#tokens])
+            state = "any"
+         end
+      elseif state == "power" then
+         if not lex_decimals[c] then
+            end_token("number", i - 1)
+            fwd = false
+            state = "any"
+         end
+      end
+   end
+   local terminals = {
+      ["identifier"] = "identifier",
+      ["decimal_or_hex"] = "number",
+      ["decimal_number"] = "number",
+      ["decimal_float"] = "number",
+      ["hex_number"] = "number",
+      ["hex_float"] = "number",
+      ["power"] = "number",
+   }
+   if in_token then
+      if terminals[state] then
+         end_token(terminals[state], i - 1)
+      else
+         drop_token()
+      end
+   end
+   return tokens, (#errs > 0) and errs
+end
+local add_space = {
+   ["word:keyword"] = true,
+   ["word:word"] = true,
+   ["word:string"] = true,
+   ["word:="] = true,
+   ["word:op"] = true,
+   ["keyword:word"] = true,
+   ["keyword:keyword"] = true,
+   ["keyword:string"] = true,
+   ["keyword:number"] = true,
+   ["keyword:="] = true,
+   ["keyword:op"] = true,
+   ["keyword:{"] = true,
+   ["keyword:("] = true,
+   ["keyword:#"] = true,
+   ["=:word"] = true,
+   ["=:keyword"] = true,
+   ["=:string"] = true,
+   ["=:number"] = true,
+   ["=:{"] = true,
+   ["=:("] = true,
+   ["op:("] = true,
+   ["op:{"] = true,
+   ["op:#"] = true,
+   [",:word"] = true,
+   [",:keyword"] = true,
+   [",:string"] = true,
+   [",:{"] = true,
+   ["):op"] = true,
+   ["):word"] = true,
+   ["):keyword"] = true,
+   ["op:string"] = true,
+   ["op:number"] = true,
+   ["op:word"] = true,
+   ["op:keyword"] = true,
+   ["]:word"] = true,
+   ["]:keyword"] = true,
+   ["]:="] = true,
+   ["]:op"] = true,
+   ["string:op"] = true,
+   ["string:word"] = true,
+   ["string:keyword"] = true,
+   ["number:word"] = true,
+   ["number:keyword"] = true,
+}
+local should_unindent = {
+   ["end"] = true,
+   ["elseif"] = true,
+   ["else"] = true,
+   ["}"] = true,
+}
+local should_indent = {
+   ["{"] = true,
+   ["for"] = true,
+   ["if"] = true,
+   ["while"] = true,
+   ["elseif"] = true,
+   ["else"] = true,
+   ["function"] = true,
+}
+function tl.pretty_print_tokens(tokens)
+   local y = 1
+   local out = {}
+   local indent = 0
+   local newline = false
+   local kind = ""
+   for _, t in ipairs(tokens) do
+      while t.y > y do
+         table.insert(out, "\n")
+         y = y + 1
+         newline = true
+         kind = ""
+      end
+      if should_unindent[t.tk] then
+         indent = indent - 1
+         if indent < 0 then
+            indent = 0
+         end
+      end
+      if newline then
+         for _ = 1, indent do
+            table.insert(out, "   ")
+         end
+         newline = false
+      end
+      if should_indent[t.tk] then
+         indent = indent + 1
+      end
+      if add_space[(kind or "") .. ":" .. t.kind] then
+         table.insert(out, " ")
+      end
+      table.insert(out, t.tk)
+      kind = t.kind or ""
+   end
+   return table.concat(out)
+end
+local last_typeid = 0
+local function new_typeid()
+   last_typeid = last_typeid + 1
+   return last_typeid
+end
+local ParseError = {}
+local TypeName = {}
+local table_types = {
+   ["array"] = true,
+   ["map"] = true,
+   ["arrayrecord"] = true,
+   ["record"] = true,
+   ["emptytable"] = true,
+}
+local Type = {}
+local Operator = {}
+local NodeKind = {}
+local FactType = {}
+local Fact = {}
+local KeyParsed = {}
+local Node = {}
+local function is_array_type(t)
+   return t.typename == "array" or t.typename == "arrayrecord"
+end
+local function is_record_type(t)
+   return t.typename == "record" or t.typename == "arrayrecord"
+end
+local function is_type(t)
+   return t.typename == "typetype" or t.typename == "nestedtype"
+end
+local ParseState = {}
+local ParseTypeListMode = {}
+local parse_type_list
+local parse_expression
+local parse_statements
+local parse_argument_list
+local parse_argument_type_list
+local parse_type
+local parse_newtype
+local function fail(ps, i, msg)
+   if not ps.tokens[i] then
+      local eof = ps.tokens[#ps.tokens]
+      table.insert(ps.errs, { y = eof.y, x = eof.x, msg = msg or "unexpected end of file" })
+      return #ps.tokens
+   end
+   table.insert(ps.errs, { y = ps.tokens[i].y, x = ps.tokens[i].x, msg = msg or "syntax error" })
+   return math.min(#ps.tokens, i + 1)
+end
+local function verify_tk(ps, i, tk)
+   if ps.tokens[i].tk == tk then
+      return i + 1
+   end
+   return fail(ps, i, "syntax error, expected '" .. tk .. "'")
+end
+local function new_node(tokens, i, kind)
+   local t = tokens[i]
+   return { y = t.y, x = t.x, tk = t.tk, kind = kind or t.kind }
+end
+local function a_type(t)
+   t.typeid = new_typeid()
+   return t
+end
+local function new_type(ps, i, typename)
+   local token = ps.tokens[i]
+   return a_type({
+      typename = assert(typename),
+      filename = ps.filename,
+      y = token.y,
+      x = token.x,
+      tk = token.tk,
+   })
+end
+local function verify_kind(ps, i, kind, node_kind)
+   if ps.tokens[i].kind == kind then
+      return i + 1, new_node(ps.tokens, i, node_kind)
+   end
+   return fail(ps, i, "syntax error, expected " .. kind)
+end
+local is_newtype = {
+   ["enum"] = true,
+   ["record"] = true,
+}
+local function parse_table_value(ps, i)
+   if is_newtype[ps.tokens[i].tk] then
+      return parse_newtype(ps, i)
+   else
+      local i, node, _ = parse_expression(ps, i)
+      return i, node
+   end
+end
+local function parse_table_item(ps, i, n)
+   local node = new_node(ps.tokens, i, "table_item")
+   if ps.tokens[i].kind == "$EOF$" then
+      return fail(ps, i)
+   end
+   if ps.tokens[i].tk == "[" then
+      node.key_parsed = "long"
+      i = i + 1
+      i, node.key = parse_expression(ps, i)
+      i = verify_tk(ps, i, "]")
+      i = verify_tk(ps, i, "=")
+      i, node.value = parse_table_value(ps, i)
+      return i, node, n
+   elseif ps.tokens[i].kind == "identifier" and ps.tokens[i + 1].tk == "=" then
+      node.key_parsed = "short"
+      i, node.key = verify_kind(ps, i, "identifier", "string")
+      node.key.conststr = node.key.tk
+      node.key.tk = '"' .. node.key.tk .. '"'
+      i = verify_tk(ps, i, "=")
+      i, node.value = parse_table_value(ps, i)
+      return i, node, n
+   elseif ps.tokens[i].kind == "identifier" and ps.tokens[i + 1].tk == ":" then
+      node.key_parsed = "short"
+      local orig_i = i
+      local try_ps = {
+         filename = ps.filename,
+         tokens = ps.tokens,
+         errs = {},
+      }
+      i, node.key = verify_kind(try_ps, i, "identifier", "string")
+      node.key.conststr = node.key.tk
+      node.key.tk = '"' .. node.key.tk .. '"'
+      i = verify_tk(try_ps, i, ":")
+      i, node.decltype = parse_type(try_ps, i)
+      if node.decltype and ps.tokens[i].tk == "=" then
+         i = verify_tk(try_ps, i, "=")
+         i, node.value = parse_table_value(try_ps, i)
+         if node.value then
+            for _, e in ipairs(try_ps.errs) do
+               table.insert(ps.errs, e)
+            end
+            return i, node, n
+         end
+      end
+      node.decltype = nil
+      i = orig_i
+   end
+   node.key = new_node(ps.tokens, i, "number")
+   node.key_parsed = "implicit"
+   node.key.constnum = n
+   node.key.tk = tostring(n)
+   i, node.value = parse_expression(ps, i)
+   return i, node, n + 1
+end
+local ParseItem = {}
+local SeparatorMode = {}
+local function parse_list(ps, i, list, close, sep, parse_item)
+   local n = 1
+   while ps.tokens[i].kind ~= "$EOF$" do
+      if close[ps.tokens[i].tk] then
+         (list).yend = ps.tokens[i].y
+         break
+      end
+      local item
+      i, item, n = parse_item(ps, i, n)
+      table.insert(list, item)
+      if ps.tokens[i].tk == "," then
+         i = i + 1
+         if sep == "sep" and close[ps.tokens[i].tk] then
+            return fail(ps, i)
+         end
+      elseif sep == "term" and ps.tokens[i].tk == ";" then
+         i = i + 1
+      elseif not close[ps.tokens[i].tk] then
+         return fail(ps, i)
+      end
+   end
+   return i, list
+end
+local function parse_bracket_list(ps, i, list, open, close, sep, parse_item)
+   i = verify_tk(ps, i, open)
+   i = parse_list(ps, i, list, { [close] = true }, sep, parse_item)
+   i = verify_tk(ps, i, close)
+   return i, list
+end
+local function parse_table_literal(ps, i)
+   local node = new_node(ps.tokens, i, "table_literal")
+   return parse_bracket_list(ps, i, node, "{", "}", "term", parse_table_item)
+end
+local function parse_trying_list(ps, i, list, parse_item)
+   local try_ps = {
+      filename = ps.filename,
+      tokens = ps.tokens,
+      errs = {},
+   }
+   local tryi, item = parse_item(try_ps, i)
+   if not item then
+      return i, list
+   end
+   for _, e in ipairs(try_ps.errs) do
+      table.insert(ps.errs, e)
+   end
+   i = tryi
+   table.insert(list, item)
+   if ps.tokens[i].tk == "," then
+      while ps.tokens[i].tk == "," do
+         i = i + 1
+         i, item = parse_item(ps, i)
+         table.insert(list, item)
+      end
+   end
+   return i, list
+end
+local function parse_typearg_type(ps, i)
+   local backtick = false
+   if ps.tokens[i].tk == "`" then
+      i = verify_tk(ps, i, "`")
+      backtick = true
+   end
+   i = verify_kind(ps, i, "identifier")
+   return i, a_type({
+      y = ps.tokens[i - 2].y,
+      x = ps.tokens[i - 2].x,
+      typename = "typearg",
+      typearg = (backtick and "`" or "") .. ps.tokens[i - 1].tk,
+   })
+end
+local function parse_typevar_type(ps, i)
+   i = verify_tk(ps, i, "`")
+   i = verify_kind(ps, i, "identifier")
+   return i, a_type({
+      y = ps.tokens[i - 2].y,
+      x = ps.tokens[i - 2].x,
+      typename = "typevar",
+      typevar = "`" .. ps.tokens[i - 1].tk,
+   })
+end
+local function parse_typearg_list(ps, i)
+   local typ = new_type(ps, i, "tuple")
+   return parse_bracket_list(ps, i, typ, "<", ">", "sep", parse_typearg_type)
+end
+local function parse_typeval_list(ps, i)
+   local typ = new_type(ps, i, "tuple")
+   return parse_bracket_list(ps, i, typ, "<", ">", "sep", parse_type)
+end
+local function parse_return_types(ps, i)
+   return parse_type_list(ps, i, "rets")
+end
+local function parse_function_type(ps, i)
+   local node = new_type(ps, i, "function")
+   node.args = {}
+   node.rets = {}
+   i = i + 1
+   if ps.tokens[i].tk == "<" then
+      i, node.typeargs = parse_typearg_list(ps, i)
+   end
+   if ps.tokens[i].tk == "(" then
+      i, node.args = parse_argument_type_list(ps, i)
+      i, node.rets = parse_return_types(ps, i)
+   else
+      node.args = { a_type({ typename = "any", is_va = true }) }
+      node.rets = { a_type({ typename = "any", is_va = true }) }
+   end
+   return i, node
+end
+local function parse_base_type(ps, i)
+   if ps.tokens[i].tk == "string" or
+      ps.tokens[i].tk == "boolean" or
+      ps.tokens[i].tk == "nil" or
+      ps.tokens[i].tk == "number" or
+      ps.tokens[i].tk == "thread" then
+      local typ = new_type(ps, i, ps.tokens[i].tk)
+      typ.tk = nil
+      return i + 1, typ
+   elseif ps.tokens[i].tk == "table" then
+      local typ = new_type(ps, i, "map")
+      typ.keys = a_type({ typename = "any" })
+      typ.values = a_type({ typename = "any" })
+      return i + 1, typ
+   elseif ps.tokens[i].tk == "function" then
+      return parse_function_type(ps, i)
+   elseif ps.tokens[i].tk == "{" then
+      i = i + 1
+      local decl = new_type(ps, i, "array")
+      local t
+      i, t = parse_type(ps, i)
+      if ps.tokens[i].tk == "}" then
+         decl.elements = t
+         decl.yend = ps.tokens[i].y
+         i = verify_tk(ps, i, "}")
+      elseif ps.tokens[i].tk == ":" then
+         decl.typename = "map"
+         i = i + 1
+         decl.keys = t
+         i, decl.values = parse_type(ps, i)
+         decl.yend = ps.tokens[i].y
+         i = verify_tk(ps, i, "}")
+      end
+      return i, decl
+   elseif ps.tokens[i].tk == "`" then
+      return parse_typevar_type(ps, i)
+   elseif ps.tokens[i].kind == "identifier" then
+      local typ = new_type(ps, i, "nominal")
+      typ.names = { ps.tokens[i].tk }
+      i = i + 1
+      while ps.tokens[i].tk == "." do
+         i = i + 1
+         if ps.tokens[i].kind == "identifier" then
+            table.insert(typ.names, ps.tokens[i].tk)
+            i = i + 1
+         else
+            return fail(ps, i, "syntax error, expected identifier")
+         end
+      end
+      if ps.tokens[i].tk == "<" then
+         i, typ.typevals = parse_typeval_list(ps, i)
+      end
+      return i, typ
+   end
+   return fail(ps, i)
+end
+parse_type = function(ps, i)
+   if ps.tokens[i].tk == "(" then
+      i = i + 1
+      local t
+      i, t = parse_type(ps, i)
+      i = verify_tk(ps, i, ")")
+      return i, t
+   end
+   local bt
+   local istart = i
+   i, bt = parse_base_type(ps, i)
+   if not bt then
+      return i
+   end
+   if ps.tokens[i].tk == "|" then
+      local u = new_type(ps, istart, "union")
+      u.types = { bt }
+      while ps.tokens[i].tk == "|" do
+         i = i + 1
+         i, bt = parse_base_type(ps, i)
+         if not bt then
+            return i
+         end
+         table.insert(u.types, bt)
+      end
+      bt = u
+   end
+   return i, bt
+end
+parse_type_list = function(ps, i, mode)
+   local list = new_type(ps, i, "tuple")
+   local first_token = ps.tokens[i].tk
+   if mode == "rets" or mode == "decltype" then
+      if first_token == ":" then
+         i = i + 1
+      else
+         return i, list
+      end
+   end
+   local optional_paren = false
+   if ps.tokens[i].tk == "(" then
+      optional_paren = true
+      i = i + 1
+   end
+   local prev_i = i
+   i = parse_trying_list(ps, i, list, parse_type)
+   if i == prev_i and ps.tokens[i].tk ~= ")" then
+      fail(ps, i - 1, "expected a type list")
+   end
+   if mode == "rets" and ps.tokens[i].tk == "..." then
+      i = i + 1
+      local nrets = #list
+      if nrets > 0 then
+         list[nrets].is_va = true
+      else
+         return fail(ps, i, "unexpected '...'")
+      end
+   end
+   if optional_paren then
+      i = verify_tk(ps, i, ")")
+   end
+   return i, list
+end
+local function parse_function_args_rets_body(ps, i, node)
+   if ps.tokens[i].tk == "<" then
+      i, node.typeargs = parse_typearg_list(ps, i)
+   end
+   i, node.args = parse_argument_list(ps, i)
+   i, node.rets = parse_return_types(ps, i)
+   i, node.body = parse_statements(ps, i)
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "end")
+   return i, node
+end
+local function parse_function_value(ps, i)
+   local node = new_node(ps.tokens, i, "function")
+   i = verify_tk(ps, i, "function")
+   return parse_function_args_rets_body(ps, i, node)
+end
+local function unquote(str)
+   local f = str:sub(1, 1)
+   if f == '"' or f == "'" then
+      return str:sub(2, -2)
+   end
+   f = str:match("^%[=*%[")
+   local l = #f + 1
+   return str:sub(l, -l)
+end
+local function parse_literal(ps, i)
+   if ps.tokens[i].tk == "{" then
+      return parse_table_literal(ps, i)
+   elseif ps.tokens[i].kind == "..." then
+      return verify_kind(ps, i, "...")
+   elseif ps.tokens[i].kind == "string" then
+      local tk = unquote(ps.tokens[i].tk)
+      local node
+      i, node = verify_kind(ps, i, "string")
+      node.conststr = tk
+      return i, node
+   elseif ps.tokens[i].kind == "identifier" then
+      return verify_kind(ps, i, "identifier", "variable")
+   elseif ps.tokens[i].kind == "number" then
+      local n = tonumber(ps.tokens[i].tk)
+      local node
+      i, node = verify_kind(ps, i, "number")
+      node.constnum = n
+      return i, node
+   elseif ps.tokens[i].tk == "true" then
+      return verify_kind(ps, i, "keyword", "boolean")
+   elseif ps.tokens[i].tk == "false" then
+      return verify_kind(ps, i, "keyword", "boolean")
+   elseif ps.tokens[i].tk == "nil" then
+      return verify_kind(ps, i, "keyword", "nil")
+   elseif ps.tokens[i].tk == "function" then
+      return parse_function_value(ps, i)
+   end
+   return fail(ps, i)
+end
+do
+   local precedences = {
+      [1] = {
+         ["not"] = 11,
+         ["#"] = 11,
+         ["-"] = 11,
+         ["~"] = 11,
+      },
+      [2] = {
+         ["or"] = 1,
+         ["and"] = 2,
+         ["is"] = 3,
+         ["<"] = 3,
+         [">"] = 3,
+         ["<="] = 3,
+         [">="] = 3,
+         ["~="] = 3,
+         ["=="] = 3,
+         ["|"] = 4,
+         ["~"] = 5,
+         ["&"] = 6,
+         ["<<"] = 7,
+         [">>"] = 7,
+         [".."] = 8,
+         ["+"] = 8,
+         ["-"] = 9,
+         ["*"] = 10,
+         ["/"] = 10,
+         ["//"] = 10,
+         ["%"] = 10,
+         ["^"] = 12,
+         ["as"] = 50,
+         ["@funcall"] = 100,
+         ["@index"] = 100,
+         ["."] = 100,
+         [":"] = 100,
+      },
+   }
+   local is_right_assoc = {
+      ["^"] = true,
+      [".."] = true,
+   }
+   local function new_operator(tk, arity, op)
+      op = op or tk.tk
+      return { y = tk.y, x = tk.x, arity = arity, op = op, prec = precedences[arity][op] }
+   end
+   local E
+   local function P(ps, i)
+      if ps.tokens[i].kind == "$EOF$" then
+         return i
+      end
+      local e1
+      local t1 = ps.tokens[i]
+      if precedences[1][ps.tokens[i].tk] ~= nil then
+         local op = new_operator(ps.tokens[i], 1)
+         i = i + 1
+         i, e1 = P(ps, i)
+         e1 = { y = t1.y, x = t1.x, kind = "op", op = op, e1 = e1 }
+      elseif ps.tokens[i].tk == "(" then
+         i = i + 1
+         i, e1 = parse_expression(ps, i)
+         e1 = { y = t1.y, x = t1.x, kind = "paren", e1 = e1 }
+         i = verify_tk(ps, i, ")")
+      else
+         i, e1 = parse_literal(ps, i)
+      end
+      while true do
+         if ps.tokens[i].kind == "string" or ps.tokens[i].kind == "{" then
+            local op = new_operator(ps.tokens[i], 2, "@funcall")
+            local args = new_node(ps.tokens, i, "expression_list")
+            local arg
+            if ps.tokens[i].kind == "string" then
+               arg = new_node(ps.tokens, i)
+               arg.conststr = unquote(ps.tokens[i].tk)
+               i = i + 1
+            else
+               i, arg = parse_table_literal(ps, i)
+            end
+            table.insert(args, arg)
+            e1 = { y = t1.y, x = t1.x, kind = "op", op = op, e1 = e1, e2 = args }
+         elseif ps.tokens[i].tk == "(" then
+            local op = new_operator(ps.tokens[i], 2, "@funcall")
+            local args = new_node(ps.tokens, i, "expression_list")
+            i, args = parse_bracket_list(ps, i, args, "(", ")", "sep", parse_expression)
+            e1 = { y = t1.y, x = t1.x, kind = "op", op = op, e1 = e1, e2 = args }
+         elseif ps.tokens[i].tk == "[" then
+            local op = new_operator(ps.tokens[i], 2, "@index")
+            local idx
+            i = i + 1
+            i, idx = parse_expression(ps, i)
+            i = verify_tk(ps, i, "]")
+            e1 = { y = t1.y, x = t1.x, kind = "op", op = op, e1 = e1, e2 = idx }
+         elseif ps.tokens[i].tk == "." or ps.tokens[i].tk == ":" then
+            local op = new_operator(ps.tokens[i], 2)
+            local key
+            i = i + 1
+            i, key = verify_kind(ps, i, "identifier")
+            e1 = { y = t1.y, x = t1.x, kind = "op", op = op, e1 = e1, e2 = key }
+         elseif ps.tokens[i].tk == "as" or ps.tokens[i].tk == "is" then
+            local op = new_operator(ps.tokens[i], 2, ps.tokens[i].tk)
+            i = i + 1
+            local cast = new_node(ps.tokens, i, "cast")
+            if ps.tokens[i].tk == "(" then
+               i, cast.casttype = parse_type_list(ps, i, "casttype")
+            else
+               i, cast.casttype = parse_type(ps, i)
+            end
+            e1 = { y = t1.y, x = t1.x, kind = "op", op = op, e1 = e1, e2 = cast, conststr = e1.conststr }
+         else
+            break
+         end
+      end
+      return i, e1
+   end
+   local function E(ps, i, lhs, min_precedence)
+      local lookahead = ps.tokens[i].tk
+      while precedences[2][lookahead] and precedences[2][lookahead] >= min_precedence do
+         local t1 = ps.tokens[i]
+         local op = new_operator(t1, 2)
+         i = i + 1
+         local rhs
+         i, rhs = P(ps, i)
+         lookahead = ps.tokens[i].tk
+         while precedences[2][lookahead] and ((precedences[2][lookahead] > (precedences[2][op.op])) or
+            (is_right_assoc[lookahead] and (precedences[2][lookahead] == precedences[2][op.op]))) do
+            i, rhs = E(ps, i, rhs, precedences[2][lookahead])
+            lookahead = ps.tokens[i].tk
+         end
+         lhs = { y = t1.y, x = t1.x, kind = "op", op = op, e1 = lhs, e2 = rhs }
+      end
+      return i, lhs
+   end
+   parse_expression = function(ps, i)
+      local lhs
+      i, lhs = P(ps, i)
+      i, lhs = E(ps, i, lhs, 0)
+      if lhs then
+         return i, lhs, 0
+      else
+         return fail(ps, i, "expected an expression")
+      end
+   end
+end
+local function parse_variable_name(ps, i)
+   local is_const = false
+   local node
+   i, node = verify_kind(ps, i, "identifier")
+   if not node then
+      return i
+   end
+   if ps.tokens[i].tk == "<" then
+      i = i + 1
+      local annotation
+      i, annotation = verify_kind(ps, i, "identifier")
+      if annotation and annotation.tk == "const" then
+         is_const = true
+      end
+      i = verify_tk(ps, i, ">")
+   end
+   node.is_const = is_const
+   return i, node
+end
+local function parse_argument(ps, i)
+   local node
+   if ps.tokens[i].tk == "..." then
+      i, node = verify_kind(ps, i, "...")
+   else
+      i, node = verify_kind(ps, i, "identifier", "argument")
+   end
+   if ps.tokens[i].tk == ":" then
+      i = i + 1
+      local decltype
+      i, decltype = parse_type(ps, i)
+      if node then
+         i, node.decltype = i, decltype
+      end
+   end
+   return i, node, 0
+end
+parse_argument_list = function(ps, i)
+   local node = new_node(ps.tokens, i, "argument_list")
+   return parse_bracket_list(ps, i, node, "(", ")", "sep", parse_argument)
+end
+local function parse_argument_type(ps, i)
+   local is_va = false
+   if ps.tokens[i].kind == "identifier" and ps.tokens[i + 1].tk == ":" then
+      i = i + 2
+   elseif ps.tokens[i].tk == "..." then
+      if ps.tokens[i + 1].tk == ":" then
+         i = i + 2
+         is_va = true
+      else
+         return fail(ps, i, "cannot have untyped '...' when declaring the type of an argument")
+      end
+   end
+   local i, typ = parse_type(ps, i)
+   if typ then
+      typ.is_va = is_va
+   end
+   return i, typ, 0
+end
+parse_argument_type_list = function(ps, i)
+   local list = new_type(ps, i, "tuple")
+   return parse_bracket_list(ps, i, list, "(", ")", "sep", parse_argument_type)
+end
+local function parse_local_function(ps, i)
+   local node = new_node(ps.tokens, i, "local_function")
+   i = verify_tk(ps, i, "local")
+   i = verify_tk(ps, i, "function")
+   i, node.name = verify_kind(ps, i, "identifier")
+   return parse_function_args_rets_body(ps, i, node)
+end
+local function parse_function(ps, i)
+   local orig_i = i
+   local fn = new_node(ps.tokens, i, "global_function")
+   local node = fn
+   i = verify_tk(ps, i, "function")
+   local names = {}
+   i, names[1] = verify_kind(ps, i, "identifier", "variable")
+   while ps.tokens[i].tk == "." do
+      i = i + 1
+      i, names[#names + 1] = verify_kind(ps, i, "identifier")
+   end
+   if ps.tokens[i].tk == ":" then
+      i = i + 1
+      i, names[#names + 1] = verify_kind(ps, i, "identifier")
+      fn.is_method = true
+   end
+   if #names > 1 then
+      fn.kind = "record_function"
+      local owner = names[1]
+      for i = 2, #names - 1 do
+         local dot = { y = names[i].y, x = names[i].x - 1, arity = 2, op = "." }
+         names[i].kind = "identifier"
+         local op = { y = names[i].y, x = names[i].x, kind = "op", op = dot, e1 = owner, e2 = names[i] }
+         owner = op
+      end
+      fn.fn_owner = owner
+   end
+   fn.name = names[#names]
+   local selfx, selfy = ps.tokens[i].x, ps.tokens[i].y
+   i = parse_function_args_rets_body(ps, i, fn)
+   if fn.is_method then
+      table.insert(fn.args, 1, { x = selfx, y = selfy, tk = "self", kind = "variable" })
+   end
+   if not fn.name then
+      return orig_i
+   end
+   return i, node
+end
+local function parse_if(ps, i)
+   local node = new_node(ps.tokens, i, "if")
+   i = verify_tk(ps, i, "if")
+   i, node.exp = parse_expression(ps, i)
+   i = verify_tk(ps, i, "then")
+   i, node.thenpart = parse_statements(ps, i)
+   node.elseifs = {}
+   local n = 0
+   while ps.tokens[i].tk == "elseif" do
+      n = n + 1
+      local subnode = new_node(ps.tokens, i, "elseif")
+      subnode.parent_if = node
+      subnode.elseif_n = n
+      i = i + 1
+      i, subnode.exp = parse_expression(ps, i)
+      i = verify_tk(ps, i, "then")
+      i, subnode.thenpart = parse_statements(ps, i)
+      table.insert(node.elseifs, subnode)
+   end
+   if ps.tokens[i].tk == "else" then
+      local subnode = new_node(ps.tokens, i, "else")
+      subnode.parent_if = node
+      i = i + 1
+      i, subnode.elsepart = parse_statements(ps, i)
+      node.elsepart = subnode
+   end
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "end")
+   return i, node
+end
+local function parse_while(ps, i)
+   local node = new_node(ps.tokens, i, "while")
+   i = verify_tk(ps, i, "while")
+   i, node.exp = parse_expression(ps, i)
+   i = verify_tk(ps, i, "do")
+   i, node.body = parse_statements(ps, i)
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "end")
+   return i, node
+end
+local function parse_fornum(ps, i)
+   local node = new_node(ps.tokens, i, "fornum")
+   i = i + 1
+   i, node.var = verify_kind(ps, i, "identifier")
+   i = verify_tk(ps, i, "=")
+   i, node.from = parse_expression(ps, i)
+   i = verify_tk(ps, i, ",")
+   i, node.to = parse_expression(ps, i)
+   if ps.tokens[i].tk == "," then
+      i = i + 1
+      i, node.step = parse_expression(ps, i)
+   end
+   i = verify_tk(ps, i, "do")
+   i, node.body = parse_statements(ps, i)
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "end")
+   return i, node
+end
+local function parse_forin(ps, i)
+   local node = new_node(ps.tokens, i, "forin")
+   i = i + 1
+   node.vars = new_node(ps.tokens, i, "variables")
+   i, node.vars = parse_list(ps, i, node.vars, { ["in"] = true }, "sep", parse_variable_name)
+   i = verify_tk(ps, i, "in")
+   node.exps = new_node(ps.tokens, i, "expression_list")
+   i = parse_list(ps, i, node.exps, { ["do"] = true }, "sep", parse_expression)
+   if #node.exps < 1 then
+      return fail(ps, i, "missing iterator expression in generic for")
+   elseif #node.exps > 3 then
+      return fail(ps, i, "too many expressions in generic for")
+   end
+   i = verify_tk(ps, i, "do")
+   i, node.body = parse_statements(ps, i)
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "end")
+   return i, node
+end
+local function parse_for(ps, i)
+   if ps.tokens[i + 1].kind == "identifier" and ps.tokens[i + 2].tk == "=" then
+      return parse_fornum(ps, i)
+   else
+      return parse_forin(ps, i)
+   end
+end
+local function parse_repeat(ps, i)
+   local node = new_node(ps.tokens, i, "repeat")
+   i = verify_tk(ps, i, "repeat")
+   i, node.body = parse_statements(ps, i)
+   node.body.is_repeat = true
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "until")
+   i, node.exp = parse_expression(ps, i)
+   return i, node
+end
+local function parse_do(ps, i)
+   local node = new_node(ps.tokens, i, "do")
+   i = verify_tk(ps, i, "do")
+   i, node.body = parse_statements(ps, i)
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "end")
+   return i, node
+end
+local function parse_break(ps, i)
+   local node = new_node(ps.tokens, i, "break")
+   i = verify_tk(ps, i, "break")
+   return i, node
+end
+local function parse_goto(ps, i)
+   local node = new_node(ps.tokens, i, "goto")
+   i = verify_tk(ps, i, "goto")
+   node.label = ps.tokens[i].tk
+   i = verify_kind(ps, i, "identifier")
+   return i, node
+end
+local function parse_label(ps, i)
+   local node = new_node(ps.tokens, i, "label")
+   i = verify_tk(ps, i, "::")
+   node.label = ps.tokens[i].tk
+   i = verify_kind(ps, i, "identifier")
+   i = verify_tk(ps, i, "::")
+   return i, node
+end
+local stop_statement_list = {
+   ["end"] = true,
+   ["else"] = true,
+   ["elseif"] = true,
+   ["until"] = true,
+}
+local stop_return_list = {
+   [";"] = true,
+   ["$EOF$"] = true,
+}
+for k, v in pairs(stop_statement_list) do
+   stop_return_list[k] = v
+end
+local function parse_return(ps, i)
+   local node = new_node(ps.tokens, i, "return")
+   i = verify_tk(ps, i, "return")
+   node.exps = new_node(ps.tokens, i, "expression_list")
+   i = parse_list(ps, i, node.exps, stop_return_list, "sep", parse_expression)
+   if ps.tokens[i].kind == ";" then
+      i = i + 1
+   end
+   return i, node
+end
+local function store_field_in_record(name, def, nt)
+   if def.fields[name] then
+      return false
+   end
+   def.fields[name] = nt.newtype
+   table.insert(def.field_order, name)
+   return true
+end
+local ParseBody = {}
+local function parse_nested_type(ps, i, def, typename, parse_body)
+   i = i + 1
+   local v
+   i, v = verify_kind(ps, i, "identifier", "variable")
+   if not v then
+      return fail(ps, i, "expected a variable name")
+   end
+   local nt = new_node(ps.tokens, i, "newtype")
+   nt.newtype = new_type(ps, i, "typetype")
+   local rdef = new_type(ps, i, typename)
+   local iok = parse_body(ps, i, rdef, nt)
+   if iok then
+      i = iok
+      nt.newtype.def = rdef
+   end
+   local ok = store_field_in_record(v.tk, def, nt)
+   if not ok then
+      fail(ps, i, "attempt to redeclare field '" .. v.tk .. "' (only functions can be overloaded)")
+   end
+   return i
+end
+local function parse_enum_body(ps, i, def, node)
+   def.enumset = {}
+   while not ((not ps.tokens[i]) or ps.tokens[i].tk == "end") do
+      local item
+      i, item = verify_kind(ps, i, "string", "enum_item")
+      if item then
+         table.insert(node, item)
+         def.enumset[unquote(item.tk)] = true
+      end
+   end
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "end")
+   return i, node
+end
+local function parse_record_body(ps, i, def, node)
+   def.fields = {}
+   def.field_order = {}
+   if ps.tokens[i].tk == "<" then
+      i, def.typeargs = parse_typearg_list(ps, i)
+   end
+   while not ((not ps.tokens[i]) or ps.tokens[i].tk == "end") do
+      if ps.tokens[i].tk == "{" then
+         if def.typename == "arrayrecord" then
+            return fail(ps, i, "duplicated declaration of array element type in record")
+         end
+         i = i + 1
+         local t
+         i, t = parse_type(ps, i)
+         if ps.tokens[i].tk == "}" then
+            node.yend = ps.tokens[i].y
+            i = verify_tk(ps, i, "}")
+         else
+            return fail(ps, i, "expected an array declaration")
+         end
+         def.typename = "arrayrecord"
+         def.elements = t
+      elseif ps.tokens[i].tk == "type" and ps.tokens[i + 1].tk ~= ":" then
+         i = i + 1
+         local v
+         i, v = verify_kind(ps, i, "identifier", "variable")
+         if not v then
+            return fail(ps, i, "expected a variable name")
+         end
+         i = verify_tk(ps, i, "=")
+         local nt
+         i, nt = parse_newtype(ps, i)
+         if not nt or not nt.newtype then
+            return fail(ps, i, "expected a type definition")
+         end
+         local ok = store_field_in_record(v.tk, def, nt)
+         if not ok then
+            return fail(ps, i, "attempt to redeclare field '" .. v.tk .. "' (only functions can be overloaded)")
+         end
+      elseif ps.tokens[i].tk == "record" and ps.tokens[i + 1].tk ~= ":" then
+         i = parse_nested_type(ps, i, def, "record", parse_record_body)
+      elseif ps.tokens[i].tk == "enum" and ps.tokens[i + 1].tk ~= ":" then
+         i = parse_nested_type(ps, i, def, "enum", parse_enum_body)
+      else
+         local v
+         i, v = verify_kind(ps, i, "identifier", "variable")
+         local iv = i
+         if not v then
+            return fail(ps, i, "expected a variable name")
+         end
+         if ps.tokens[i].tk == ":" then
+            i = verify_tk(ps, i, ":")
+            local t
+            i, t = parse_type(ps, i)
+            if not t then
+               return fail(ps, i, "expected a type")
+            end
+            if not def.fields[v.tk] then
+               def.fields[v.tk] = t
+               table.insert(def.field_order, v.tk)
+            else
+               local prev_t = def.fields[v.tk]
+               if t.typename == "function" and prev_t.typename == "function" then
+                  def.fields[v.tk] = new_type(ps, iv, "poly")
+                  def.fields[v.tk].types = { prev_t, t }
+               elseif t.typename == "function" and prev_t.typename == "poly" then
+                  table.insert(prev_t.types, t)
+               else
+                  return fail(ps, i, "attempt to redeclare field '" .. v.tk .. "' (only functions can be overloaded)")
+               end
+            end
+         elseif ps.tokens[i].tk == "=" then
+            local next_word = ps.tokens[i + 1].tk
+            if next_word == "record" or next_word == "enum" then
+               return fail(ps, i, "syntax error: this syntax is no longer valid; use '" .. next_word .. " " .. v.tk .. "'")
+            elseif next_word == "functiontype" then
+               return fail(ps, i, "syntax error: this syntax is no longer valid; use 'type " .. v.tk .. " = function('...")
+            else
+               return fail(ps, i, "syntax error: this syntax is no longer valid; use 'type " .. v.tk .. " = '...")
+            end
+         end
+      end
+   end
+   node.yend = ps.tokens[i].y
+   i = verify_tk(ps, i, "end")
+   return i, node
+end
+parse_newtype = function(ps, i)
+   local node = new_node(ps.tokens, i, "newtype")
+   node.newtype = new_type(ps, i, "typetype")
+   if ps.tokens[i].tk == "record" then
+      local def = new_type(ps, i, "record")
+      i = i + 1
+      i = parse_record_body(ps, i, def, node)
+      node.newtype.def = def
+      return i, node
+   elseif ps.tokens[i].tk == "enum" then
+      local def = new_type(ps, i, "enum")
+      i = i + 1
+      i = parse_enum_body(ps, i, def, node)
+      node.newtype.def = def
+      return i, node
+   else
+      i, node.newtype.def = parse_type(ps, i)
+      return i, node
+   end
+   return fail(ps, i)
+end
+local function parse_call_or_assignment(ps, i)
+   local asgn = new_node(ps.tokens, i, "assignment")
+   local tryi = i
+   asgn.vars = new_node(ps.tokens, i, "variables")
+   i = parse_trying_list(ps, i, asgn.vars, parse_expression)
+   if #asgn.vars < 1 then
+      return fail(ps, i)
+   end
+   local lhs = asgn.vars[1]
+   if ps.tokens[i].tk == "=" then
+      asgn.exps = new_node(ps.tokens, i, "values")
+      repeat
+         i = i + 1
+         local val
+         i, val = parse_expression(ps, i)
+         table.insert(asgn.exps, val)
+      until ps.tokens[i].tk ~= ","
+      return i, asgn
+   end
+   if #asgn.vars > 1 then
+      local err_ps = {
+         tokens = ps.tokens,
+         errs = {},
+      }
+      local expi = parse_expression(err_ps, tryi)
+      return fail(ps, expi or i)
+   end
+   if lhs.op and lhs.op.op == "@funcall" and #asgn.vars == 1 then
+      return i, lhs
+   end
+   return fail(ps, i)
+end
+local function parse_variable_declarations(ps, i, node_name)
+   local asgn = new_node(ps.tokens, i, node_name)
+   asgn.vars = new_node(ps.tokens, i, "variables")
+   i = parse_trying_list(ps, i, asgn.vars, parse_variable_name)
+   if #asgn.vars == 0 then
+      return fail(ps, i, "expected a local variable definition")
+   end
+   local lhs = asgn.vars[1]
+   i, asgn.decltype = parse_type_list(ps, i, "decltype")
+   if ps.tokens[i].tk == "=" then
+      if ps.tokens[i + 1].tk == "record" or
+         ps.tokens[i + 1].tk == "enum" then
+         local scope = node_name == "local_declaration" and "local" or "global"
+         fail(ps, i, "syntax error: this syntax is no longer valid; use '" .. scope .. " " .. ps.tokens[i + 1].tk .. " " .. asgn.vars[1].tk .. "'")
+      elseif ps.tokens[i + 1].tk == "functiontype" then
+         local scope = node_name == "local_declaration" and "local" or "global"
+         fail(ps, i, "syntax error: this syntax is no longer valid; use '" .. scope .. " type " .. asgn.vars[1].tk .. " = function('...")
+      end
+      asgn.exps = new_node(ps.tokens, i, "values")
+      local v = 1
+      repeat
+         i = i + 1
+         local val
+         i, val = parse_expression(ps, i)
+         table.insert(asgn.exps, val)
+         v = v + 1
+      until ps.tokens[i].tk ~= ","
+   end
+   return i, asgn
+end
+local function parse_type_declaration(ps, i, node_name)
+   i = i + 2
+   local asgn = new_node(ps.tokens, i, node_name)
+   i, asgn.var = parse_variable_name(ps, i)
+   if not asgn.var then
+      return fail(ps, i, "expected a type name")
+   end
+   i = verify_tk(ps, i, "=")
+   i, asgn.value = parse_newtype(ps, i)
+   if asgn.value then
+      asgn.value.newtype.def.names = { asgn.var.tk }
+   else
+      return i
+   end
+   return i, asgn
+end
+local ParseBody = {}
+local function parse_type_constructor(ps, i, node_name, type_name, parse_body)
+   local asgn = new_node(ps.tokens, i, node_name)
+   local nt = new_node(ps.tokens, i, "newtype")
+   asgn.value = nt
+   nt.newtype = new_type(ps, i, "typetype")
+   local def = new_type(ps, i, type_name)
+   nt.newtype.def = def
+   i = i + 2
+   i, asgn.var = verify_kind(ps, i, "identifier")
+   if not asgn.var then
+      return fail(ps, i, "expected a type name")
+   end
+   nt.newtype.def.names = { asgn.var.tk }
+   i = parse_body(ps, i, def, nt)
+   return i, asgn
+end
+local function parse_statement(ps, i)
+   if ps.tokens[i].tk == "local" then
+      if ps.tokens[i + 1].tk == "type" and ps.tokens[i + 2].kind == "identifier" then
+         return parse_type_declaration(ps, i, "local_type")
+      elseif ps.tokens[i + 1].tk == "function" then
+         return parse_local_function(ps, i)
+      elseif ps.tokens[i + 1].tk == "record" and ps.tokens[i + 2].kind == "identifier" then
+         return parse_type_constructor(ps, i, "local_type", "record", parse_record_body)
+      elseif ps.tokens[i + 1].tk == "enum" and ps.tokens[i + 2].kind == "identifier" then
+         return parse_type_constructor(ps, i, "local_type", "enum", parse_enum_body)
+      else
+         i = i + 1
+         return parse_variable_declarations(ps, i, "local_declaration")
+      end
+   elseif ps.tokens[i].tk == "global" then
+      if ps.tokens[i + 1].tk == "type" and ps.tokens[i + 2].kind == "identifier" then
+         return parse_type_declaration(ps, i, "global_type")
+      elseif ps.tokens[i + 1].tk == "record" and ps.tokens[i + 2].kind == "identifier" then
+         return parse_type_constructor(ps, i, "global_type", "record", parse_record_body)
+      elseif ps.tokens[i + 1].tk == "enum" and ps.tokens[i + 2].kind == "identifier" then
+         return parse_type_constructor(ps, i, "global_type", "enum", parse_enum_body)
+      elseif ps.tokens[i + 1].tk == "function" then
+         i = i + 1
+         return parse_function(ps, i)
+      else
+         i = i + 1
+         return parse_variable_declarations(ps, i, "global_declaration")
+      end
+   elseif ps.tokens[i].tk == "function" then
+      return parse_function(ps, i)
+   elseif ps.tokens[i].tk == "if" then
+      return parse_if(ps, i)
+   elseif ps.tokens[i].tk == "while" then
+      return parse_while(ps, i)
+   elseif ps.tokens[i].tk == "repeat" then
+      return parse_repeat(ps, i)
+   elseif ps.tokens[i].tk == "for" then
+      return parse_for(ps, i)
+   elseif ps.tokens[i].tk == "do" then
+      return parse_do(ps, i)
+   elseif ps.tokens[i].tk == "break" then
+      return parse_break(ps, i)
+   elseif ps.tokens[i].tk == "return" then
+      return parse_return(ps, i)
+   elseif ps.tokens[i].tk == "goto" then
+      return parse_goto(ps, i)
+   elseif ps.tokens[i].tk == "::" then
+      return parse_label(ps, i)
+   else
+      return parse_call_or_assignment(ps, i)
+   end
+end
+parse_statements = function(ps, i, filename, toplevel)
+   local node = new_node(ps.tokens, i, "statements")
+   while true do
+      while ps.tokens[i].kind == ";" do
+         i = i + 1
+      end
+      if ps.tokens[i].kind == "$EOF$" then
+         break
+      end
+      if (not toplevel) and stop_statement_list[ps.tokens[i].tk] then
+         break
+      end
+      local item
+      i, item = parse_statement(ps, i)
+      if filename then
+         for j = 1, #ps.errs do
+            if not ps.errs[j].filename then
+               ps.errs[j].filename = filename
+            end
+         end
+      end
+      if not item then
+         break
+      end
+      table.insert(node, item)
+   end
+   return i, node
+end
+function tl.parse_program(tokens, errs, filename)
+   errs = errs or {}
+   local ps = {
+      tokens = tokens,
+      errs = errs,
+      filename = filename,
+   }
+   local last = ps.tokens[#ps.tokens] or { y = 1, x = 1, tk = "" }
+   table.insert(ps.tokens, { y = last.y, x = last.x + #last.tk, tk = "$EOF$", kind = "$EOF$" })
+   return parse_statements(ps, 1, filename, true)
+end
+local VisitorCallbacks = {}
+local Visitor = {}
+local function visit_before(ast, kind, visit)
+   assert(visit.cbs[kind], "no visitor for " .. (kind))
+   if visit.cbs[kind].before then
+      visit.cbs[kind].before(ast)
+   end
+end
+local function visit_after(ast, kind, visit, xs)
+   if visit.after and visit.after.before then
+      visit.after.before(ast, xs)
+   end
+   local ret
+   if visit.cbs[kind].after then
+      ret = visit.cbs[kind].after(ast, xs)
+   end
+   if visit.after and visit.after.after then
+      ret = visit.after.after(ast, xs, ret)
+   end
+   return ret
+end
+local function recurse_type(ast, visit)
+   visit_before(ast, ast.typename, visit)
+   local xs = {}
+   if ast.typeargs then
+      for _, child in ipairs(ast.typeargs) do
+         table.insert(xs, recurse_type(child, visit))
+      end
+   end
+   for i, child in ipairs(ast) do
+      xs[i] = recurse_type(child, visit)
+   end
+   if ast.types then
+      for i, child in ipairs(ast.types) do
+         table.insert(xs, recurse_type(child, visit))
+      end
+   end
+   if ast.def then
+      table.insert(xs, recurse_type(ast.def, visit))
+   end
+   if ast.keys then
+      table.insert(xs, recurse_type(ast.keys, visit))
+   end
+   if ast.values then
+      table.insert(xs, recurse_type(ast.values, visit))
+   end
+   if ast.elements then
+      table.insert(xs, recurse_type(ast.elements, visit))
+   end
+   if ast.fields then
+      for _, child in pairs(ast.fields) do
+         table.insert(xs, recurse_type(child, visit))
+      end
+   end
+   if ast.args then
+      for i, child in ipairs(ast.args) do
+         if i > 1 or not ast.is_method then
+            table.insert(xs, recurse_type(child, visit))
+         end
+      end
+   end
+   if ast.rets then
+      for _, child in ipairs(ast.rets) do
+         table.insert(xs, recurse_type(child, visit))
+      end
+   end
+   if ast.typevals then
+      for _, child in ipairs(ast.typevals) do
+         table.insert(xs, recurse_type(child, visit))
+      end
+   end
+   if ast.ktype then
+      table.insert(xs, recurse_type(ast.ktype, visit))
+   end
+   if ast.vtype then
+      table.insert(xs, recurse_type(ast.vtype, visit))
+   end
+   return visit_after(ast, ast.typename, visit, xs)
+end
+local function recurse_node(ast,
+visit_node,
+visit_type)
+   if not ast then
+      return
+   end
+   visit_before(ast, ast.kind, visit_node)
+   local xs = {}
+   local cbs = visit_node.cbs[ast.kind]
+   if ast.kind == "statements" or
+      ast.kind == "variables" or
+      ast.kind == "values" or
+      ast.kind == "argument_list" or
+      ast.kind == "expression_list" or
+      ast.kind == "table_literal" then
+      for i, child in ipairs(ast) do
+         xs[i] = recurse_node(child, visit_node, visit_type)
+      end
+   elseif ast.kind == "local_declaration" or
+      ast.kind == "global_declaration" or
+      ast.kind == "assignment" then
+      xs[1] = recurse_node(ast.vars, visit_node, visit_type)
+      if ast.exps then
+         xs[2] = recurse_node(ast.exps, visit_node, visit_type)
+      end
+      if ast.decltype then
+         xs[3] = recurse_type(ast.decltype, visit_type)
+      end
+   elseif ast.kind == "local_type" or
+      ast.kind == "global_type" then
+      xs[1] = recurse_node(ast.var, visit_node, visit_type)
+      xs[2] = recurse_node(ast.value, visit_node, visit_type)
+   elseif ast.kind == "table_item" then
+      xs[1] = recurse_node(ast.key, visit_node, visit_type)
+      xs[2] = recurse_node(ast.value, visit_node, visit_type)
+   elseif ast.kind == "if" then
+      xs[1] = recurse_node(ast.exp, visit_node, visit_type)
+      if cbs.before_statements then
+         cbs.before_statements(ast, xs)
+      end
+      xs[2] = recurse_node(ast.thenpart, visit_node, visit_type)
+      for i, e in ipairs(ast.elseifs) do
+         table.insert(xs, recurse_node(e, visit_node, visit_type))
+      end
+      if ast.elsepart then
+         table.insert(xs, recurse_node(ast.elsepart, visit_node, visit_type))
+      end
+   elseif ast.kind == "while" then
+      xs[1] = recurse_node(ast.exp, visit_node, visit_type)
+      if cbs.before_statements then
+         cbs.before_statements(ast, xs)
+      end
+      xs[2] = recurse_node(ast.body, visit_node, visit_type)
+   elseif ast.kind == "repeat" then
+      xs[1] = recurse_node(ast.body, visit_node, visit_type)
+      xs[2] = recurse_node(ast.exp, visit_node, visit_type)
+   elseif ast.kind == "function" then
+      xs[1] = recurse_node(ast.args, visit_node, visit_type)
+      xs[2] = recurse_type(ast.rets, visit_type)
+      xs[3] = recurse_node(ast.body, visit_node, visit_type)
+   elseif ast.kind == "forin" then
+      xs[1] = recurse_node(ast.vars, visit_node, visit_type)
+      xs[2] = recurse_node(ast.exps, visit_node, visit_type)
+      if cbs.before_statements then
+         cbs.before_statements(ast)
+      end
+      xs[3] = recurse_node(ast.body, visit_node, visit_type)
+   elseif ast.kind == "fornum" then
+      xs[1] = recurse_node(ast.var, visit_node, visit_type)
+      xs[2] = recurse_node(ast.from, visit_node, visit_type)
+      xs[3] = recurse_node(ast.to, visit_node, visit_type)
+      xs[4] = ast.step and recurse_node(ast.step, visit_node, visit_type)
+      xs[5] = recurse_node(ast.body, visit_node, visit_type)
+   elseif ast.kind == "elseif" then
+      xs[1] = recurse_node(ast.exp, visit_node, visit_type)
+      if cbs.before_statements then
+         cbs.before_statements(ast, xs)
+      end
+      xs[2] = recurse_node(ast.thenpart, visit_node, visit_type)
+   elseif ast.kind == "else" then
+      xs[1] = recurse_node(ast.elsepart, visit_node, visit_type)
+   elseif ast.kind == "return" then
+      xs[1] = recurse_node(ast.exps, visit_node, visit_type)
+   elseif ast.kind == "do" then
+      xs[1] = recurse_node(ast.body, visit_node, visit_type)
+   elseif ast.kind == "cast" then
+   elseif ast.kind == "local_function" or
+      ast.kind == "global_function" then
+      xs[1] = recurse_node(ast.name, visit_node, visit_type)
+      xs[2] = recurse_node(ast.args, visit_node, visit_type)
+      xs[3] = recurse_type(ast.rets, visit_type)
+      xs[4] = recurse_node(ast.body, visit_node, visit_type)
+   elseif ast.kind == "record_function" then
+      xs[1] = recurse_node(ast.fn_owner, visit_node, visit_type)
+      xs[2] = recurse_node(ast.name, visit_node, visit_type)
+      xs[3] = recurse_node(ast.args, visit_node, visit_type)
+      xs[4] = recurse_type(ast.rets, visit_type)
+      if cbs.before_statements then
+         cbs.before_statements(ast, xs)
+      end
+      xs[5] = recurse_node(ast.body, visit_node, visit_type)
+   elseif ast.kind == "paren" then
+      xs[1] = recurse_node(ast.e1, visit_node, visit_type)
+   elseif ast.kind == "op" then
+      xs[1] = recurse_node(ast.e1, visit_node, visit_type)
+      local p1 = ast.e1.op and ast.e1.op.prec or nil
+      if ast.op.op == ":" and ast.e1.kind == "string" then
+         p1 = -999
+      end
+      xs[2] = p1
+      if ast.op.arity == 2 then
+         if cbs.before_e2 then
+            cbs.before_e2(ast, xs)
+         end
+         if ast.op.op == "is" or ast.op.op == "as" then
+            xs[3] = recurse_type(ast.e2.casttype, visit_type)
+         else
+            xs[3] = recurse_node(ast.e2, visit_node, visit_type)
+         end
+         xs[4] = (ast.e2.op and ast.e2.op.prec)
+      end
+   elseif ast.kind == "newtype" then
+      xs[1] = recurse_type(ast.newtype, visit_type)
+   elseif ast.kind == "variable" or
+      ast.kind == "argument" or
+      ast.kind == "identifier" or
+      ast.kind == "string" or
+      ast.kind == "number" or
+      ast.kind == "break" or
+      ast.kind == "goto" or
+      ast.kind == "label" or
+      ast.kind == "nil" or
+      ast.kind == "..." or
+      ast.kind == "boolean" then
+      if ast.decltype then
+         xs[1] = recurse_type(ast.decltype, visit_type)
+      end
+   else
+      if not ast.kind then
+         error("wat: " .. inspect(ast))
+      end
+      error("unknown node kind " .. ast.kind)
+   end
+   return visit_after(ast, ast.kind, visit_node, xs)
+end
+local tight_op = {
+   [1] = {
+      ["-"] = true,
+      ["~"] = true,
+      ["#"] = true,
+   },
+   [2] = {
+      ["."] = true,
+      [":"] = true,
+   },
+}
+local spaced_op = {
+   [1] = {
+      ["not"] = true,
+   },
+   [2] = {
+      ["or"] = true,
+      ["and"] = true,
+      ["<"] = true,
+      [">"] = true,
+      ["<="] = true,
+      [">="] = true,
+      ["~="] = true,
+      ["=="] = true,
+      ["|"] = true,
+      ["~"] = true,
+      ["&"] = true,
+      ["<<"] = true,
+      [">>"] = true,
+      [".."] = true,
+      ["+"] = true,
+      ["-"] = true,
+      ["*"] = true,
+      ["/"] = true,
+      ["//"] = true,
+      ["%"] = true,
+      ["^"] = true,
+   },
+}
+local PrettyPrintOpts = {}
+local default_pretty_print_ast_opts = {
+   preserve_indent = true,
+   preserve_newlines = true,
+}
+local fast_pretty_print_ast_opts = {
+   preserve_indent = false,
+   preserve_newlines = true,
+}
+function tl.pretty_print_ast(ast, mode)
+   local indent = 0
+   local opts
+   if type(mode) == "table" then
+      opts = mode
+   elseif mode == true then
+      opts = fast_pretty_print_ast_opts
+   else
+      opts = default_pretty_print_ast_opts
+   end
+   local Output = {}
+   local function increment_indent()
+      indent = indent + 1
+   end
+   if not opts.preserve_indent then
+      increment_indent = nil
+   end
+   local function add(out, s)
+      table.insert(out, s)
+   end
+   local function add_string(out, s)
+      table.insert(out, s)
+      if string.find(s, "\n", 1, true) then
+         for nl in s:gmatch("\n") do
+            out.h = out.h + 1
+         end
+      end
+   end
+   local function add_child(out, child, space, indent)
+      if #child == 0 then
+         return
+      end
+      if child.y < out.y then
+         out.y = child.y
+      end
+      if child.y > out.y + out.h and opts.preserve_newlines then
+         local delta = child.y - (out.y + out.h)
+         out.h = out.h + delta
+         table.insert(out, ("\n"):rep(delta))
+      else
+         if space then
+            table.insert(out, space)
+            indent = nil
+         end
+      end
+      if indent and opts.preserve_indent then
+         table.insert(out, ("   "):rep(indent))
+      end
+      table.insert(out, child)
+      out.h = out.h + child.h
+   end
+   local function concat_output(out)
+      for i, s in ipairs(out) do
+         if type(s) == "table" then
+            out[i] = concat_output(s)
+         end
+      end
+      return table.concat(out)
+   end
+   local function print_record_def(typ)
+      local out = { "{" }
+      for name, field in pairs(typ.fields) do
+         if field.typename == "typetype" and is_record_type(field.def) then
+            table.insert(out, name)
+            table.insert(out, " = ")
+            table.insert(out, print_record_def(field.def))
+            table.insert(out, ", ")
+         end
+      end
+      table.insert(out, "}")
+      return table.concat(out)
+   end
+   local visit_node = {}
+   visit_node.cbs = {
+      ["statements"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            local space
+            for i, child in ipairs(children) do
+               add_child(out, children[i], space, indent)
+               space = "; "
+            end
+            return out
+         end,
+      },
+      ["local_declaration"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "local")
+            add_child(out, children[1], " ")
+            if children[2] then
+               table.insert(out, " =")
+               add_child(out, children[2], " ")
+            end
+            return out
+         end,
+      },
+      ["local_type"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "local")
+            add_child(out, children[1], " ")
+            table.insert(out, " =")
+            add_child(out, children[2], " ")
+            return out
+         end,
+      },
+      ["global_type"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            add_child(out, children[1], " ")
+            table.insert(out, " =")
+            add_child(out, children[2], " ")
+            return out
+         end,
+      },
+      ["global_declaration"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            if children[2] then
+               add_child(out, children[1])
+               table.insert(out, " =")
+               add_child(out, children[2], " ")
+            end
+            return out
+         end,
+      },
+      ["assignment"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            add_child(out, children[1])
+            table.insert(out, " =")
+            add_child(out, children[2], " ")
+            return out
+         end,
+      },
+      ["if"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "if")
+            add_child(out, children[1], " ")
+            table.insert(out, " then")
+            add_child(out, children[2], " ")
+            indent = indent - 1
+            for i = 3, #children do
+               add_child(out, children[i], " ", indent)
+            end
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["while"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "while")
+            add_child(out, children[1], " ")
+            table.insert(out, " do")
+            add_child(out, children[2], " ")
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["repeat"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "repeat")
+            add_child(out, children[1], " ")
+            if opts.preserve_indent then
+               indent = indent - 1
+            end
+            add_child(out, { y = node.yend, h = 0, [1] = "until " }, " ", indent)
+            add_child(out, children[2])
+            return out
+         end,
+      },
+      ["do"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "do")
+            add_child(out, children[1], " ")
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["forin"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "for")
+            add_child(out, children[1], " ")
+            table.insert(out, " in")
+            add_child(out, children[2], " ")
+            table.insert(out, " do")
+            add_child(out, children[3], " ")
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["fornum"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "for")
+            add_child(out, children[1], " ")
+            table.insert(out, " =")
+            add_child(out, children[2], " ")
+            table.insert(out, ",")
+            add_child(out, children[3], " ")
+            if children[4] then
+               table.insert(out, ",")
+               add_child(out, children[4], " ")
+            end
+            table.insert(out, " do")
+            add_child(out, children[5], " ")
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["return"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "return")
+            if #children[1] > 0 then
+               add_child(out, children[1], " ")
+            end
+            return out
+         end,
+      },
+      ["break"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "break")
+            return out
+         end,
+      },
+      ["elseif"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "elseif")
+            add_child(out, children[1], " ")
+            table.insert(out, " then")
+            add_child(out, children[2], " ")
+            return out
+         end,
+      },
+      ["else"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "else")
+            add_child(out, children[1], " ")
+            return out
+         end,
+      },
+      ["variables"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            local space
+            for i, child in ipairs(children) do
+               if i > 1 then
+                  table.insert(out, ",")
+                  space = " "
+               end
+               add_child(out, child, space)
+            end
+            return out
+         end,
+      },
+      ["table_literal"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            if #children == 0 then
+               indent = indent - 1
+               table.insert(out, "{}")
+               return out
+            end
+            table.insert(out, "{")
+            local n = #children
+            for i, child in ipairs(children) do
+               add_child(out, child, " ", child.y ~= node.y and indent)
+               if i < n or node.yend ~= node.y then
+                  table.insert(out, ",")
+               end
+            end
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "}" }, " ", indent)
+            return out
+         end,
+      },
+      ["table_item"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            if node.key_parsed ~= "implicit" then
+               if node.key_parsed == "short" then
+                  children[1][1] = children[1][1]:sub(2, -2)
+                  add_child(out, children[1])
+                  table.insert(out, " = ")
+               else
+                  table.insert(out, "[")
+                  add_child(out, children[1])
+                  table.insert(out, "] = ")
+               end
+            end
+            add_child(out, children[2])
+            return out
+         end,
+      },
+      ["local_function"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "local function")
+            add_child(out, children[1], " ")
+            table.insert(out, "(")
+            add_child(out, children[2])
+            table.insert(out, ")")
+            add_child(out, children[4], " ")
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["global_function"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "function")
+            add_child(out, children[1], " ")
+            table.insert(out, "(")
+            add_child(out, children[2])
+            table.insert(out, ")")
+            add_child(out, children[4], " ")
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["record_function"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "function")
+            add_child(out, children[1], " ")
+            table.insert(out, node.is_method and ":" or ".")
+            add_child(out, children[2])
+            table.insert(out, "(")
+            if node.is_method then
+               table.remove(children[3], 1)
+               if children[3][1] == "," then
+                  table.remove(children[3], 1)
+                  table.remove(children[3], 1)
+               end
+            end
+            add_child(out, children[3])
+            table.insert(out, ")")
+            add_child(out, children[5], " ")
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["function"] = {
+         before = increment_indent,
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "function(")
+            add_child(out, children[1])
+            table.insert(out, ")")
+            add_child(out, children[3], " ")
+            indent = indent - 1
+            add_child(out, { y = node.yend, h = 0, [1] = "end" }, " ", indent)
+            return out
+         end,
+      },
+      ["cast"] = {},
+      ["paren"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "(")
+            add_child(out, children[1], "", indent)
+            table.insert(out, ")")
+            return out
+         end,
+      },
+      ["op"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            if node.op.op == "@funcall" then
+               add_child(out, children[1], "", indent)
+               table.insert(out, "(")
+               add_child(out, children[3], "", indent)
+               table.insert(out, ")")
+            elseif node.op.op == "@index" then
+               add_child(out, children[1], "", indent)
+               table.insert(out, "[")
+               add_child(out, children[3], "", indent)
+               table.insert(out, "]")
+            elseif node.op.op == "as" then
+               add_child(out, children[1], "", indent)
+            elseif node.op.op == "is" then
+               table.insert(out, "type(")
+               add_child(out, children[1], "", indent)
+               table.insert(out, ") == \"")
+               add_child(out, children[3], "", indent)
+               table.insert(out, "\"")
+            elseif spaced_op[node.op.arity][node.op.op] or tight_op[node.op.arity][node.op.op] then
+               local space = spaced_op[node.op.arity][node.op.op] and " " or ""
+               if children[2] and node.op.prec > tonumber(children[2]) then
+                  table.insert(children[1], 1, "(")
+                  table.insert(children[1], ")")
+               end
+               if node.op.arity == 1 then
+                  table.insert(out, node.op.op)
+                  add_child(out, children[1], space, indent)
+               elseif node.op.arity == 2 then
+                  add_child(out, children[1], "", indent)
+                  if space == " " then
+                     table.insert(out, " ")
+                  end
+                  table.insert(out, node.op.op)
+                  if children[4] and node.op.prec > tonumber(children[4]) then
+                     table.insert(children[3], 1, "(")
+                     table.insert(children[3], ")")
+                  end
+                  add_child(out, children[3], space, indent)
+               end
+            else
+               error("unknown node op " .. node.op.op)
+            end
+            return out
+         end,
+      },
+      ["variable"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            add_string(out, node.tk)
+            return out
+         end,
+      },
+      ["newtype"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            if is_record_type(node.newtype.def) then
+               table.insert(out, print_record_def(node.newtype.def))
+            else
+               table.insert(out, "{}")
+            end
+            return out
+         end,
+      },
+      ["goto"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "goto ")
+            table.insert(out, node.label)
+            return out
+         end,
+      },
+      ["label"] = {
+         after = function(node, children)
+            local out = { y = node.y, h = 0 }
+            table.insert(out, "::")
+            table.insert(out, node.label)
+            table.insert(out, "::")
+            return out
+         end,
+      },
+   }
+   local primitive = {
+      ["function"] = "function",
+      ["enum"] = "string",
+      ["boolean"] = "boolean",
+      ["string"] = "string",
+      ["nil"] = "nil",
+      ["number"] = "number",
+      ["thread"] = "thread",
+   }
+   local visit_type = {}
+   visit_type.cbs = {
+      ["string"] = {
+         after = function(typ, children)
+            local out = { y = typ.y, h = 0 }
+            table.insert(out, primitive[typ.typename] or "table")
+            return out
+         end,
+      },
+   }
+   visit_type.cbs["typetype"] = visit_type.cbs["string"]
+   visit_type.cbs["typevar"] = visit_type.cbs["string"]
+   visit_type.cbs["typearg"] = visit_type.cbs["string"]
+   visit_type.cbs["function"] = visit_type.cbs["string"]
+   visit_type.cbs["thread"] = visit_type.cbs["string"]
+   visit_type.cbs["array"] = visit_type.cbs["string"]
+   visit_type.cbs["map"] = visit_type.cbs["string"]
+   visit_type.cbs["arrayrecord"] = visit_type.cbs["string"]
+   visit_type.cbs["record"] = visit_type.cbs["string"]
+   visit_type.cbs["enum"] = visit_type.cbs["string"]
+   visit_type.cbs["boolean"] = visit_type.cbs["string"]
+   visit_type.cbs["nil"] = visit_type.cbs["string"]
+   visit_type.cbs["number"] = visit_type.cbs["string"]
+   visit_type.cbs["union"] = visit_type.cbs["string"]
+   visit_type.cbs["nominal"] = visit_type.cbs["string"]
+   visit_type.cbs["bad_nominal"] = visit_type.cbs["string"]
+   visit_type.cbs["emptytable"] = visit_type.cbs["string"]
+   visit_type.cbs["table_item"] = visit_type.cbs["string"]
+   visit_type.cbs["unknown_emptytable_value"] = visit_type.cbs["string"]
+   visit_type.cbs["tuple"] = visit_type.cbs["string"]
+   visit_type.cbs["poly"] = visit_type.cbs["string"]
+   visit_type.cbs["any"] = visit_type.cbs["string"]
+   visit_type.cbs["unknown"] = visit_type.cbs["string"]
+   visit_type.cbs["invalid"] = visit_type.cbs["string"]
+   visit_type.cbs["unresolved"] = visit_type.cbs["string"]
+   visit_type.cbs["none"] = visit_type.cbs["string"]
+   visit_node.cbs["values"] = visit_node.cbs["variables"]
+   visit_node.cbs["expression_list"] = visit_node.cbs["variables"]
+   visit_node.cbs["argument_list"] = visit_node.cbs["variables"]
+   visit_node.cbs["identifier"] = visit_node.cbs["variable"]
+   visit_node.cbs["string"] = visit_node.cbs["variable"]
+   visit_node.cbs["number"] = visit_node.cbs["variable"]
+   visit_node.cbs["nil"] = visit_node.cbs["variable"]
+   visit_node.cbs["boolean"] = visit_node.cbs["variable"]
+   visit_node.cbs["..."] = visit_node.cbs["variable"]
+   visit_node.cbs["argument"] = visit_node.cbs["variable"]
+   local out = recurse_node(ast, visit_node, visit_type)
+   local code
+   if opts.preserve_newlines then
+      code = { y = 1, h = 0 }
+      add_child(code, out)
+   else
+      code = out
+   end
+   return concat_output(code)
+end
+local ANY = a_type({ typename = "any" })
+local NONE = a_type({ typename = "none" })
+local NIL = a_type({ typename = "nil" })
+local NUMBER = a_type({ typename = "number" })
+local STRING = a_type({ typename = "string" })
+local OPT_NUMBER = a_type({ typename = "number" })
+local OPT_STRING = a_type({ typename = "string" })
+local VARARG_ANY = a_type({ typename = "any", is_va = true })
+local VARARG_STRING = a_type({ typename = "string", is_va = true })
+local VARARG_NUMBER = a_type({ typename = "number", is_va = true })
+local VARARG_UNKNOWN = a_type({ typename = "unknown", is_va = true })
+local VARARG_ALPHA = a_type({ typename = "typevar", typevar = "@a", is_va = true })
+local BOOLEAN = a_type({ typename = "boolean" })
+local ARG_ALPHA = a_type({ typename = "typearg", typearg = "@a" })
+local ARG_BETA = a_type({ typename = "typearg", typearg = "@b" })
+local ALPHA = a_type({ typename = "typevar", typevar = "@a" })
+local BETA = a_type({ typename = "typevar", typevar = "@b" })
+local ARRAY_OF_STRING = a_type({ typename = "array", elements = STRING })
+local ARRAY_OF_ALPHA = a_type({ typename = "array", elements = ALPHA })
+local MAP_OF_ALPHA_TO_BETA = a_type({ typename = "map", keys = ALPHA, values = BETA })
+local TABLE = a_type({ typename = "map", keys = ANY, values = ANY })
+local FUNCTION = a_type({ typename = "function", args = { a_type({ typename = "any", is_va = true }) }, rets = { a_type({ typename = "any", is_va = true }) } })
+local THREAD = a_type({ typename = "thread" })
+local INVALID = a_type({ typename = "invalid" })
+local UNKNOWN = a_type({ typename = "unknown" })
+local NOMINAL_FILE = a_type({ typename = "nominal", names = { "FILE" } })
+local NOMINAL_METATABLE = a_type({ typename = "nominal", names = { "METATABLE" } })
+local OS_DATE_TABLE = a_type({
+   typename = "record",
+   fields = {
+      ["year"] = NUMBER,
+      ["month"] = NUMBER,
+      ["day"] = NUMBER,
+      ["hour"] = NUMBER,
+      ["min"] = NUMBER,
+      ["sec"] = NUMBER,
+      ["wday"] = NUMBER,
+      ["yday"] = NUMBER,
+      ["isdst"] = BOOLEAN,
+   },
+})
+local DEBUG_GETINFO_TABLE = a_type({
+   typename = "record",
+   fields = {
+      ["name"] = STRING,
+      ["namewhat"] = STRING,
+      ["source"] = STRING,
+      ["short_src"] = STRING,
+      ["linedefined"] = NUMBER,
+      ["lastlinedefined"] = NUMBER,
+      ["what"] = STRING,
+      ["currentline"] = NUMBER,
+      ["istailcall"] = BOOLEAN,
+      ["nups"] = NUMBER,
+      ["nparams"] = NUMBER,
+      ["isvararg"] = BOOLEAN,
+      ["func"] = ANY,
+      ["activelines"] = a_type({ typename = "map", keys = NUMBER, values = BOOLEAN }),
+   },
+})
+local numeric_binop = {
+   ["number"] = {
+      ["number"] = NUMBER,
+   },
+}
+local relational_binop = {
+   ["number"] = {
+      ["number"] = BOOLEAN,
+   },
+   ["string"] = {
+      ["string"] = BOOLEAN,
+   },
+   ["boolean"] = {
+      ["boolean"] = BOOLEAN,
+   },
+}
+local equality_binop = {
+   ["number"] = {
+      ["number"] = BOOLEAN,
+      ["nil"] = BOOLEAN,
+   },
+   ["string"] = {
+      ["string"] = BOOLEAN,
+      ["nil"] = BOOLEAN,
+   },
+   ["boolean"] = {
+      ["boolean"] = BOOLEAN,
+      ["nil"] = BOOLEAN,
+   },
+   ["record"] = {
+      ["emptytable"] = BOOLEAN,
+      ["arrayrecord"] = BOOLEAN,
+      ["record"] = BOOLEAN,
+      ["nil"] = BOOLEAN,
+   },
+   ["array"] = {
+      ["emptytable"] = BOOLEAN,
+      ["arrayrecord"] = BOOLEAN,
+      ["array"] = BOOLEAN,
+      ["nil"] = BOOLEAN,
+   },
+   ["arrayrecord"] = {
+      ["emptytable"] = BOOLEAN,
+      ["arrayrecord"] = BOOLEAN,
+      ["record"] = BOOLEAN,
+      ["array"] = BOOLEAN,
+      ["nil"] = BOOLEAN,
+   },
+   ["map"] = {
+      ["emptytable"] = BOOLEAN,
+      ["map"] = BOOLEAN,
+      ["nil"] = BOOLEAN,
+   },
+   ["thread"] = {
+      ["thread"] = BOOLEAN,
+      ["nil"] = BOOLEAN,
+   },
+}
+local unop_types = {
+   ["#"] = {
+      ["arrayrecord"] = NUMBER,
+      ["string"] = NUMBER,
+      ["array"] = NUMBER,
+      ["map"] = NUMBER,
+      ["emptytable"] = NUMBER,
+   },
+   ["-"] = {
+      ["number"] = NUMBER,
+   },
+   ["not"] = {
+      ["string"] = BOOLEAN,
+      ["number"] = BOOLEAN,
+      ["boolean"] = BOOLEAN,
+      ["record"] = BOOLEAN,
+      ["arrayrecord"] = BOOLEAN,
+      ["array"] = BOOLEAN,
+      ["map"] = BOOLEAN,
+      ["emptytable"] = BOOLEAN,
+      ["thread"] = BOOLEAN,
+   },
+}
+local binop_types = {
+   ["+"] = numeric_binop,
+   ["-"] = {
+      ["number"] = {
+         ["number"] = NUMBER,
+      },
+   },
+   ["*"] = numeric_binop,
+   ["%"] = numeric_binop,
+   ["/"] = numeric_binop,
+   ["^"] = numeric_binop,
+   ["&"] = numeric_binop,
+   ["|"] = numeric_binop,
+   ["<<"] = numeric_binop,
+   [">>"] = numeric_binop,
+   ["=="] = equality_binop,
+   ["~="] = equality_binop,
+   ["<="] = relational_binop,
+   [">="] = relational_binop,
+   ["<"] = relational_binop,
+   [">"] = relational_binop,
+   ["or"] = {
+      ["boolean"] = {
+         ["boolean"] = BOOLEAN,
+         ["function"] = FUNCTION,
+      },
+      ["number"] = {
+         ["number"] = NUMBER,
+         ["boolean"] = BOOLEAN,
+      },
+      ["string"] = {
+         ["string"] = STRING,
+         ["boolean"] = BOOLEAN,
+         ["enum"] = STRING,
+      },
+      ["function"] = {
+         ["function"] = FUNCTION,
+         ["boolean"] = BOOLEAN,
+      },
+      ["array"] = {
+         ["boolean"] = BOOLEAN,
+      },
+      ["record"] = {
+         ["boolean"] = BOOLEAN,
+      },
+      ["arrayrecord"] = {
+         ["boolean"] = BOOLEAN,
+      },
+      ["map"] = {
+         ["boolean"] = BOOLEAN,
+      },
+      ["enum"] = {
+         ["string"] = STRING,
+      },
+      ["thread"] = {
+         ["boolean"] = BOOLEAN,
+      },
+   },
+   [".."] = {
+      ["string"] = {
+         ["string"] = STRING,
+         ["enum"] = STRING,
+         ["number"] = STRING,
+      },
+      ["number"] = {
+         ["number"] = STRING,
+         ["string"] = STRING,
+         ["enum"] = STRING,
+      },
+      ["enum"] = {
+         ["number"] = STRING,
+         ["string"] = STRING,
+         ["enum"] = STRING,
+      },
+   },
+}
+local show_type
+local function is_unknown(t)
+   return t.typename == "unknown" or
+   t.typename == "unknown_emptytable_value"
+end
+local show_type
+local function show_type_base(t, seen)
+   if seen[t] then
+      return "..."
+   end
+   seen[t] = true
+   local function show(t)
+      return show_type(t, seen)
+   end
+   if t.typename == "nominal" then
+      if t.typevals then
+         local out = { table.concat(t.names, "."), "<" }
+         local vals = {}
+         for _, v in ipairs(t.typevals) do
+            table.insert(vals, show(v))
+         end
+         table.insert(out, table.concat(vals, ", "))
+         table.insert(out, ">")
+         return table.concat(out)
+      else
+         return table.concat(t.names, ".")
+      end
+   elseif t.typename == "tuple" then
+      local out = {}
+      for _, v in ipairs(t) do
+         table.insert(out, show(v))
+      end
+      return "(" .. table.concat(out, ", ") .. ")"
+   elseif t.typename == "poly" then
+      local out = {}
+      for _, v in ipairs(t.types) do
+         table.insert(out, show(v))
+      end
+      return table.concat(out, " or ")
+   elseif t.typename == "union" then
+      local out = {}
+      for _, v in ipairs(t.types) do
+         table.insert(out, show(v))
+      end
+      return table.concat(out, " | ")
+   elseif t.typename == "emptytable" then
+      return "{}"
+   elseif t.typename == "map" then
+      return "{" .. show(t.keys) .. " : " .. show(t.values) .. "}"
+   elseif t.typename == "array" then
+      return "{" .. show(t.elements) .. "}"
+   elseif t.typename == "enum" then
+      return t.names and table.concat(t.names, ".") or "enum"
+   elseif is_record_type(t) then
+      local out = {}
+      for _, k in ipairs(t.field_order) do
+         local v = t.fields[k]
+         table.insert(out, k .. ": " .. show(v))
+      end
+      return "{" .. table.concat(out, ", ") .. "}"
+   elseif t.typename == "function" then
+      local out = {}
+      table.insert(out, "function(")
+      local args = {}
+      if t.is_method then
+         table.insert(args, "self")
+      end
+      for i, v in ipairs(t.args) do
+         if not t.is_method or i > 1 then
+            table.insert(args, show(v))
+         end
+      end
+      table.insert(out, table.concat(args, ","))
+      table.insert(out, ")")
+      if #t.rets > 0 then
+         table.insert(out, ":")
+         local rets = {}
+         for _, v in ipairs(t.rets) do
+            table.insert(rets, show(v))
+         end
+         table.insert(out, table.concat(rets, ","))
+      end
+      return table.concat(out)
+   elseif t.typename == "number" or
+      t.typename == "boolean" or
+      t.typename == "thread" then
+      return t.typename
+   elseif t.typename == "string" then
+      return t.typename ..
+      (t.tk and " " .. t.tk or "")
+   elseif t.typename == "typevar" then
+      return t.typevar
+   elseif t.typename == "typearg" then
+      return t.typearg
+   elseif is_unknown(t) then
+      return "<unknown type>"
+   elseif t.typename == "invalid" then
+      return "<invalid type>"
+   elseif t.typename == "any" then
+      return "<any type>"
+   elseif t.typename == "nil" then
+      return "nil"
+   elseif t.typename == "typetype" then
+      return "type " .. show(t.def)
+   elseif t.typename == "bad_nominal" then
+      return table.concat(t.names, ".") .. " (an unknown type)"
+   else
+      return inspect(t)
+   end
+end
+show_type = function(t, seen)
+   local ret = show_type_base(t, seen or {})
+   if t.inferred_at then
+      ret = ret .. " (inferred at " .. t.inferred_at_file .. ":" .. t.inferred_at.y .. ":" .. t.inferred_at.x .. ": )"
+   end
+   return ret
+end
+local Error = {}
+local Result = {}
+local function search_for(module_name, suffix, path, tried)
+   for entry in path:gmatch("[^;]+") do
+      local slash_name = module_name:gsub("%.", "/")
+      local filename = entry:gsub("?", slash_name)
+      local tl_filename = filename:gsub("%.lua$", suffix)
+      local fd = io.open(tl_filename, "r")
+      if fd then
+         return tl_filename, fd, tried
+      end
+      table.insert(tried, "no file '" .. tl_filename .. "'")
+   end
+   return nil, nil, tried
+end
+function tl.search_module(module_name, search_dtl)
+   local found
+   local tried = {}
+   local path = os.getenv("TL_PATH") or package.path
+   if search_dtl then
+      local found, fd, tried = search_for(module_name, ".d.tl", path, tried)
+      if found then
+         return found, fd
+      end
+   end
+   local found, fd, tried = search_for(module_name, ".tl", path, tried)
+   if found then
+      return found, fd
+   end
+   local found, fd, tried = search_for(module_name, ".lua", path, tried)
+   if found then
+      return found, fd
+   end
+   return nil, nil, tried
+end
+local Variable = {}
+local function fill_field_order(t)
+   if t.typename == "record" then
+      t.field_order = {}
+      for k, v in pairs(t.fields) do
+         table.insert(t.field_order, k)
+      end
+      table.sort(t.field_order)
+   end
+end
+local function require_module(module_name, lax, env, result)
+   local modules = env.modules
+   if modules[module_name] then
+      return modules[module_name], true
+   end
+   modules[module_name] = UNKNOWN
+   local found, fd, tried = tl.search_module(module_name, true)
+   if found and (lax or found:match("tl$")) then
+      fd:close()
+      local _result, err = tl.process(found, env, result)
+      assert(_result, err)
+      if not _result.type then
+         _result.type = BOOLEAN
+      end
+      modules[module_name] = _result.type
+      return _result.type, true
+   end
+   return UNKNOWN, found ~= nil
+end
+local standard_library = {
+   ["..."] = a_type({ typename = "tuple", STRING, STRING, STRING, STRING, STRING }),
+   ["@return"] = a_type({ typename = "tuple", ANY }),
+   ["any"] = a_type({ typename = "typetype", def = ANY }),
+   ["arg"] = ARRAY_OF_STRING,
+   ["assert"] = a_type({
+      typename = "poly",
+      types = {
+         a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ALPHA }, rets = { ALPHA } }),
+         a_type({ typename = "function", typeargs = { ARG_ALPHA, ARG_BETA }, args = { ALPHA, BETA }, rets = { ALPHA } }),
+      },
+   }),
+   ["collectgarbage"] = a_type({ typename = "function", args = { STRING }, rets = { a_type({ typename = "union", types = { BOOLEAN, NUMBER } }), NUMBER, NUMBER } }),
+   ["dofile"] = a_type({ typename = "function", args = { OPT_STRING }, rets = { VARARG_ANY } }),
+   ["error"] = a_type({ typename = "function", args = { STRING, NUMBER }, rets = {} }),
+   ["getmetatable"] = a_type({ typename = "function", args = { ANY }, rets = { NOMINAL_METATABLE } }),
+   ["ipairs"] = a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ARRAY_OF_ALPHA }, rets = {
+         a_type({ typename = "function", args = {}, rets = { NUMBER, ALPHA } }),
+      }, }),
+   ["load"] = a_type({
+      typename = "poly",
+      types = {
+         a_type({ typename = "function", args = { STRING }, rets = { FUNCTION, STRING } }),
+         a_type({ typename = "function", args = { STRING, STRING }, rets = { FUNCTION, STRING } }),
+         a_type({ typename = "function", args = { STRING, STRING, STRING }, rets = { FUNCTION, STRING } }),
+         a_type({ typename = "function", args = { STRING, STRING, STRING, TABLE }, rets = { FUNCTION, STRING } }),
+      },
+   }),
+   ["loadfile"] = a_type({
+      typename = "poly",
+      types = {
+         a_type({ typename = "function", args = {}, rets = { FUNCTION, ANY } }),
+         a_type({ typename = "function", args = { STRING }, rets = { FUNCTION, ANY } }),
+         a_type({ typename = "function", args = { STRING, STRING }, rets = { FUNCTION, ANY } }),
+         a_type({ typename = "function", args = { STRING, STRING, TABLE }, rets = { FUNCTION, ANY } }),
+      },
+   }),
+   ["next"] = a_type({
+      typename = "poly",
+      types = {
+         a_type({ typeargs = { ARG_ALPHA, ARG_BETA }, typename = "function", args = { MAP_OF_ALPHA_TO_BETA }, rets = { ALPHA, BETA } }),
+         a_type({ typeargs = { ARG_ALPHA, ARG_BETA }, typename = "function", args = { MAP_OF_ALPHA_TO_BETA, ALPHA }, rets = { ALPHA, BETA } }),
+         a_type({ typeargs = { ARG_ALPHA }, typename = "function", args = { ARRAY_OF_ALPHA }, rets = { NUMBER, ALPHA } }),
+         a_type({ typeargs = { ARG_ALPHA }, typename = "function", args = { ARRAY_OF_ALPHA, ALPHA }, rets = { NUMBER, ALPHA } }),
+      },
+   }),
+   ["pairs"] = a_type({ typename = "function", typeargs = { ARG_ALPHA, ARG_BETA }, args = { a_type({ typename = "map", keys = ALPHA, values = BETA }) }, rets = {
+         a_type({ typename = "function", args = {}, rets = { ALPHA, BETA } }),
+      }, }),
+   ["pcall"] = a_type({ typename = "function", args = { FUNCTION, VARARG_ANY }, rets = { BOOLEAN, ANY } }),
+   ["xpcall"] = a_type({ typename = "function", args = { FUNCTION, FUNCTION, VARARG_ANY }, rets = { BOOLEAN, ANY } }),
+   ["print"] = a_type({ typename = "function", args = { VARARG_ANY }, rets = {} }),
+   ["rawequal"] = a_type({ typename = "function", args = { ANY, ANY }, rets = { BOOLEAN } }),
+   ["rawget"] = a_type({ typename = "function", args = { TABLE, ANY }, rets = { ANY } }),
+   ["rawlen"] = a_type({
+      typename = "poly",
+      types = {
+         a_type({ typename = "function", args = { TABLE }, rets = { NUMBER } }),
+         a_type({ typename = "function", args = { STRING }, rets = { NUMBER } }),
+      },
+   }),
+   ["rawset"] = a_type({
+      typename = "poly",
+      types = {
+         a_type({ typeargs = { ARG_ALPHA, ARG_BETA }, typename = "function", args = { MAP_OF_ALPHA_TO_BETA, ALPHA, BETA }, rets = {} }),
+         a_type({ typeargs = { ARG_ALPHA }, typename = "function", args = { ARRAY_OF_ALPHA, NUMBER, ALPHA }, rets = {} }),
+         a_type({ typename = "function", args = { TABLE, ANY, ANY }, rets = {} }),
+      },
+   }),
+   ["require"] = a_type({ typename = "function", args = { STRING }, rets = {} }),
+   ["select"] = a_type({
+      typename = "poly",
+      types = {
+         a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { NUMBER, VARARG_ALPHA }, rets = { ALPHA } }),
+         a_type({ typename = "function", args = { NUMBER, VARARG_ANY }, rets = { ANY } }),
+         a_type({ typename = "function", args = { STRING, VARARG_ANY }, rets = { NUMBER } }),
+      },
+   }),
+   ["setmetatable"] = a_type({ typeargs = { ARG_ALPHA }, typename = "function", args = { ALPHA, NOMINAL_METATABLE }, rets = { ALPHA } }),
+   ["tonumber"] = a_type({ typename = "function", args = { ANY, NUMBER }, rets = { NUMBER } }),
+   ["tostring"] = a_type({ typename = "function", args = { ANY }, rets = { STRING } }),
+   ["type"] = a_type({ typename = "function", args = { ANY }, rets = { STRING } }),
+   ["FILE"] = a_type({
+      typename = "typetype",
+      def = a_type({
+         typename = "record",
+         fields = {
+            ["close"] = a_type({ typename = "function", args = { NOMINAL_FILE }, rets = { BOOLEAN, STRING } }),
+            ["flush"] = a_type({ typename = "function", args = { NOMINAL_FILE }, rets = {} }),
+            ["lines"] = a_type({ typename = "function", args = { NOMINAL_FILE, a_type({ typename = "union", types = { STRING, NUMBER }, is_va = true }) }, rets = {
+                  a_type({ typename = "function", args = {}, rets = { VARARG_STRING } }),
+               }, }),
+            ["read"] = a_type({
+               typename = "poly",
+               types = {
+                  a_type({ typename = "function", args = { NOMINAL_FILE, STRING }, rets = { STRING, STRING } }),
+                  a_type({ typename = "function", args = { NOMINAL_FILE, NUMBER }, rets = { STRING, STRING } }),
+               },
+            }),
+            ["seek"] = a_type({
+               typename = "poly",
+               types = {
+                  a_type({ typename = "function", args = { NOMINAL_FILE }, rets = { NUMBER, STRING } }),
+                  a_type({ typename = "function", args = { NOMINAL_FILE, STRING }, rets = { NUMBER, STRING } }),
+                  a_type({ typename = "function", args = { NOMINAL_FILE, STRING, NUMBER }, rets = { NUMBER, STRING } }),
+               },
+            }),
+            ["setvbuf"] = a_type({ typename = "function", args = { NOMINAL_FILE, STRING, OPT_NUMBER }, rets = {} }),
+            ["write"] = a_type({ typename = "function", args = { NOMINAL_FILE, VARARG_STRING }, rets = { NOMINAL_FILE, STRING } }),
+         },
+      }),
+   }),
+   ["METATABLE"] = a_type({
+      typename = "typetype",
+      def = a_type({
+         typename = "record",
+         fields = {
+            ["__call"] = FUNCTION,
+            ["__gc"] = a_type({ typename = "function", args = { ANY }, rets = {} }),
+            ["__index"] = ANY,
+            ["__len"] = a_type({ typename = "function", args = { ANY }, rets = { NUMBER } }),
+            ["__mode"] = a_type({ typename = "enum", enumset = { ["k"] = true, ["v"] = true, ["kv"] = true } }),
+            ["__newindex"] = ANY,
+            ["__pairs"] = a_type({ typeargs = { ARG_ALPHA, ARG_BETA }, typename = "function", args = { a_type({ typename = "map", keys = ALPHA, values = BETA }) }, rets = {
+                  a_type({ typename = "function", args = {}, rets = { ALPHA, BETA } }),
+               }, }),
+            ["__tostring"] = a_type({ typename = "function", args = { ANY }, rets = { STRING } }),
+            ["__name"] = STRING,
+            ["__add"] = FUNCTION,
+            ["__sub"] = FUNCTION,
+            ["__mul"] = FUNCTION,
+            ["__div"] = FUNCTION,
+            ["__idiv"] = FUNCTION,
+            ["__mod"] = FUNCTION,
+            ["__pow"] = FUNCTION,
+            ["__unm"] = FUNCTION,
+            ["__band"] = FUNCTION,
+            ["__bor"] = FUNCTION,
+            ["__bxor"] = FUNCTION,
+            ["__bnot"] = FUNCTION,
+            ["__shl"] = FUNCTION,
+            ["__shr"] = FUNCTION,
+            ["__concat"] = FUNCTION,
+            ["__eq"] = FUNCTION,
+            ["__lt"] = FUNCTION,
+            ["__le"] = FUNCTION,
+         },
+      }),
+   }),
+   ["coroutine"] = a_type({
+      typename = "record",
+      fields = {
+         ["create"] = a_type({ typename = "function", args = { FUNCTION }, rets = { THREAD } }),
+         ["close"] = a_type({ typename = "function", args = { THREAD }, rets = { BOOLEAN, STRING } }),
+         ["isyieldable"] = a_type({ typename = "function", args = {}, rets = { BOOLEAN } }),
+         ["resume"] = a_type({ typename = "function", args = { THREAD, VARARG_ANY }, rets = { BOOLEAN, VARARG_ANY } }),
+         ["running"] = a_type({ typename = "function", args = {}, rets = { THREAD, BOOLEAN } }),
+         ["status"] = a_type({ typename = "function", args = { THREAD }, rets = { STRING } }),
+         ["wrap"] = a_type({ typename = "function", args = { FUNCTION }, rets = { FUNCTION } }),
+         ["yield"] = a_type({ typename = "function", args = { VARARG_ANY }, rets = { VARARG_ANY } }),
+      },
+   }),
+   ["debug"] = a_type({
+      typename = "record",
+      fields = {
+         ["traceback"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = { THREAD, STRING, NUMBER }, rets = { STRING } }),
+               a_type({ typename = "function", args = { STRING, NUMBER }, rets = { STRING } }),
+            },
+         }),
+         ["getinfo"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = { ANY }, rets = { DEBUG_GETINFO_TABLE } }),
+               a_type({ typename = "function", args = { ANY, STRING }, rets = { DEBUG_GETINFO_TABLE } }),
+               a_type({ typename = "function", args = { ANY, ANY, STRING }, rets = { DEBUG_GETINFO_TABLE } }),
+            },
+         }),
+      },
+   }),
+   ["io"] = a_type({
+      typename = "record",
+      fields = {
+         ["close"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = {}, rets = { BOOLEAN, STRING } }),
+               a_type({ typename = "function", args = { NOMINAL_FILE }, rets = { BOOLEAN, STRING } }),
+            },
+         }),
+         ["flush"] = a_type({ typename = "function", args = {}, rets = {} }),
+         ["input"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = {}, rets = { NOMINAL_FILE } }),
+               a_type({ typename = "function", args = { STRING }, rets = { NOMINAL_FILE } }),
+               a_type({ typename = "function", args = { NOMINAL_FILE }, rets = { NOMINAL_FILE } }),
+            },
+         }),
+         ["lines"] = a_type({ typename = "function", args = { OPT_STRING, a_type({ typename = "union", types = { STRING, NUMBER }, is_va = true }) }, rets = {
+               a_type({ typename = "function", args = {}, rets = { VARARG_STRING } }),
+            }, }),
+         ["open"] = a_type({ typename = "function", args = { STRING, STRING }, rets = { NOMINAL_FILE, STRING } }),
+         ["output"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = {}, rets = { NOMINAL_FILE } }),
+               a_type({ typename = "function", args = { STRING }, rets = { NOMINAL_FILE } }),
+               a_type({ typename = "function", args = { NOMINAL_FILE }, rets = { NOMINAL_FILE } }),
+            },
+         }),
+         ["popen"] = a_type({ typename = "function", args = { STRING, STRING }, rets = { NOMINAL_FILE, STRING } }),
+         ["read"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = { NOMINAL_FILE, STRING }, rets = { STRING, STRING } }),
+               a_type({ typename = "function", args = { NOMINAL_FILE, NUMBER }, rets = { STRING, STRING } }),
+            },
+         }),
+         ["stderr"] = NOMINAL_FILE,
+         ["stdin"] = NOMINAL_FILE,
+         ["stdout"] = NOMINAL_FILE,
+         ["tmpfile"] = a_type({ typename = "function", args = {}, rets = { NOMINAL_FILE } }),
+         ["type"] = a_type({ typename = "function", args = { ANY }, rets = { STRING } }),
+         ["write"] = a_type({ typename = "function", args = { VARARG_STRING }, rets = { NOMINAL_FILE, STRING } }),
+      },
+   }),
+   ["math"] = a_type({
+      typename = "record",
+      fields = {
+         ["abs"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["acos"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["asin"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["atan"] = a_type({
+            typename = "poly",
+            a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+            a_type({ typename = "function", args = { NUMBER, NUMBER }, rets = { NUMBER } }),
+         }),
+         ["atan2"] = a_type({ typename = "function", args = { NUMBER, NUMBER }, rets = { NUMBER } }),
+         ["ceil"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["cos"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["cosh"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["deg"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["exp"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["floor"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["fmod"] = a_type({ typename = "function", args = { NUMBER, NUMBER }, rets = { NUMBER } }),
+         ["frexp"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER, NUMBER } }),
+         ["huge"] = NUMBER,
+         ["ldexp"] = a_type({ typename = "function", args = { NUMBER, NUMBER }, rets = { NUMBER } }),
+         ["log"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["log10"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["max"] = a_type({ typename = "function", args = { VARARG_NUMBER }, rets = { NUMBER } }),
+         ["maxinteger"] = NUMBER,
+         ["min"] = a_type({ typename = "function", args = { VARARG_NUMBER }, rets = { NUMBER } }),
+         ["mininteger"] = NUMBER,
+         ["modf"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER, NUMBER } }),
+         ["pi"] = NUMBER,
+         ["pow"] = a_type({ typename = "function", args = { NUMBER, NUMBER }, rets = { NUMBER } }),
+         ["rad"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["random"] = a_type({ typename = "function", args = { NUMBER, NUMBER }, rets = { NUMBER } }),
+         ["randomseed"] = a_type({ typename = "function", args = { NUMBER }, rets = {} }),
+         ["sin"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["sinh"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["sqrt"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["tan"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["tanh"] = a_type({ typename = "function", args = { NUMBER }, rets = { NUMBER } }),
+         ["tointeger"] = a_type({ typename = "function", args = { ANY }, rets = { NUMBER } }),
+         ["type"] = a_type({ typename = "function", args = { ANY }, rets = { STRING } }),
+         ["ult"] = a_type({ typename = "function", args = { NUMBER, NUMBER }, rets = { BOOLEAN } }),
+      },
+   }),
+   ["os"] = a_type({
+      typename = "record",
+      fields = {
+         ["clock"] = a_type({ typename = "function", args = {}, rets = { NUMBER } }),
+         ["date"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = {}, rets = { STRING } }),
+               a_type({ typename = "function", args = { STRING, OPT_STRING }, rets = { a_type({ typename = "union", types = { STRING, OS_DATE_TABLE } }) } }),
+            },
+         }),
+         ["difftime"] = a_type({ typename = "function", args = { NUMBER, NUMBER }, rets = { NUMBER } }),
+         ["execute"] = a_type({ typename = "function", args = { STRING }, rets = { BOOLEAN, STRING, NUMBER } }),
+         ["exit"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = { NUMBER, BOOLEAN }, rets = {} }),
+               a_type({ typename = "function", args = { BOOLEAN, BOOLEAN }, rets = {} }),
+            },
+         }),
+         ["getenv"] = a_type({ typename = "function", args = { STRING }, rets = { STRING } }),
+         ["remove"] = a_type({ typename = "function", args = { STRING }, rets = { BOOLEAN, STRING } }),
+         ["rename"] = a_type({ typename = "function", args = { STRING, STRING }, rets = { BOOLEAN, STRING } }),
+         ["setlocale"] = a_type({ typename = "function", args = { STRING, OPT_STRING }, rets = { STRING } }),
+         ["time"] = a_type({ typename = "function", args = {}, rets = { NUMBER } }),
+         ["tmpname"] = a_type({ typename = "function", args = {}, rets = { STRING } }),
+      },
+   }),
+   ["package"] = a_type({
+      typename = "record",
+      fields = {
+         ["config"] = STRING,
+         ["cpath"] = STRING,
+         ["loaded"] = a_type({
+            typename = "map",
+            keys = STRING,
+            values = ANY,
+         }),
+         ["loaders"] = a_type({
+            typename = "array",
+            elements = a_type({ typename = "function", args = { STRING }, rets = { ANY } }),
+         }),
+         ["loadlib"] = a_type({ typename = "function", args = { STRING, STRING }, rets = { FUNCTION } }),
+         ["path"] = STRING,
+         ["preload"] = TABLE,
+         ["searchers"] = a_type({
+            typename = "array",
+            elements = a_type({ typename = "function", args = { STRING }, rets = { ANY } }),
+         }),
+         ["searchpath"] = a_type({ typename = "function", args = { STRING, STRING, OPT_STRING, OPT_STRING }, rets = { STRING, STRING } }),
+      },
+   }),
+   ["string"] = a_type({
+      typename = "record",
+      fields = {
+         ["byte"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = { STRING }, rets = { NUMBER } }),
+               a_type({ typename = "function", args = { STRING, NUMBER }, rets = { NUMBER } }),
+               a_type({ typename = "function", args = { STRING, NUMBER, NUMBER }, rets = { VARARG_NUMBER } }),
+            },
+         }),
+         ["char"] = a_type({ typename = "function", args = { VARARG_NUMBER }, rets = { STRING } }),
+         ["dump"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = { FUNCTION }, rets = { STRING } }),
+               a_type({ typename = "function", args = { FUNCTION, BOOLEAN }, rets = { STRING } }),
+            },
+         }),
+         ["find"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = { STRING, STRING }, rets = { NUMBER, NUMBER, VARARG_STRING } }),
+               a_type({ typename = "function", args = { STRING, STRING, NUMBER }, rets = { NUMBER, NUMBER, VARARG_STRING } }),
+               a_type({ typename = "function", args = { STRING, STRING, NUMBER, BOOLEAN }, rets = { NUMBER, NUMBER, VARARG_STRING } }),
+            },
+         }),
+         ["format"] = a_type({ typename = "function", args = { STRING, VARARG_ANY }, rets = { STRING } }),
+         ["gmatch"] = a_type({ typename = "function", args = { STRING, STRING }, rets = {
+               a_type({ typename = "function", args = {}, rets = { STRING } }),
+            }, }),
+         ["gsub"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", args = { STRING, STRING, STRING, NUMBER }, rets = { STRING, NUMBER } }),
+               a_type({ typename = "function", args = { STRING, STRING, a_type({ typename = "map", keys = STRING, values = STRING }), NUMBER }, rets = { STRING, NUMBER } }),
+               a_type({ typename = "function", args = { STRING, STRING, a_type({ typename = "function", args = { VARARG_STRING }, rets = { STRING } }) }, rets = { STRING, NUMBER } }),
+            },
+         }),
+         ["len"] = a_type({ typename = "function", args = { STRING }, rets = { NUMBER } }),
+         ["lower"] = a_type({ typename = "function", args = { STRING }, rets = { STRING } }),
+         ["match"] = a_type({ typename = "function", args = { STRING, STRING, NUMBER }, rets = { VARARG_STRING } }),
+         ["pack"] = a_type({ typename = "function", args = { STRING, VARARG_ANY }, rets = { STRING } }),
+         ["packsize"] = a_type({ typename = "function", args = { STRING }, rets = { NUMBER } }),
+         ["rep"] = a_type({ typename = "function", args = { STRING, NUMBER }, rets = { STRING } }),
+         ["reverse"] = a_type({ typename = "function", args = { STRING }, rets = { STRING } }),
+         ["sub"] = a_type({ typename = "function", args = { STRING, NUMBER, NUMBER }, rets = { STRING } }),
+         ["unpack"] = a_type({ typename = "function", args = { STRING, STRING, OPT_NUMBER }, rets = { VARARG_ANY } }),
+         ["upper"] = a_type({ typename = "function", args = { STRING }, rets = { STRING } }),
+      },
+   }),
+   ["table"] = a_type({
+      typename = "record",
+      fields = {
+         ["concat"] = a_type({ typename = "function", args = { ARRAY_OF_STRING, OPT_STRING, OPT_NUMBER, OPT_NUMBER }, rets = { STRING } }),
+         ["insert"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ARRAY_OF_ALPHA, NUMBER, ALPHA }, rets = {} }),
+               a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ARRAY_OF_ALPHA, ALPHA }, rets = {} }),
+            },
+         }),
+         ["move"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ARRAY_OF_ALPHA, NUMBER, NUMBER, NUMBER }, rets = { ARRAY_OF_ALPHA } }),
+               a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ARRAY_OF_ALPHA, NUMBER, NUMBER, NUMBER, ARRAY_OF_ALPHA }, rets = { ARRAY_OF_ALPHA } }),
+            },
+         }),
+         ["pack"] = a_type({ typename = "function", args = { VARARG_ANY }, rets = { TABLE } }),
+         ["remove"] = a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ARRAY_OF_ALPHA, OPT_NUMBER }, rets = { ALPHA } }),
+         ["sort"] = a_type({
+            typename = "poly",
+            types = {
+               a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ARRAY_OF_ALPHA }, rets = {} }),
+               a_type({ typename = "function", typeargs = { ARG_ALPHA }, args = { ARRAY_OF_ALPHA, a_type({ typename = "function", args = { ALPHA, ALPHA }, rets = { BOOLEAN } }) }, rets = {} }),
+            },
+         }),
+         ["unpack"] = a_type({
+            typename = "function",
+            needs_compat53 = true,
+            typeargs = { ARG_ALPHA },
+            args = { ARRAY_OF_ALPHA, NUMBER, NUMBER },
+            rets = { VARARG_ALPHA },
+         }),
+      },
+   }),
+   ["utf8"] = a_type({
+      typename = "record",
+      fields = {
+         ["char"] = a_type({ typename = "function", args = { VARARG_NUMBER }, rets = { STRING } }),
+         ["charpattern"] = STRING,
+         ["codepoint"] = a_type({ typename = "function", args = { STRING, OPT_NUMBER, OPT_NUMBER }, rets = { VARARG_NUMBER } }),
+         ["codes"] = a_type({ typename = "function", args = { STRING }, rets = {
+               a_type({ typename = "function", args = {}, rets = { NUMBER, STRING } }),
+            }, }),
+         ["len"] = a_type({ typename = "function", args = { STRING, NUMBER, NUMBER }, rets = { NUMBER } }),
+         ["offset"] = a_type({ typename = "function", args = { STRING, NUMBER, NUMBER }, rets = { NUMBER } }),
+      },
+   }),
+}
+for _, t in pairs(standard_library) do
+   fill_field_order(t)
+   if t.typename == "typetype" then
+      fill_field_order(t.def)
+   end
+end
+fill_field_order(OS_DATE_TABLE)
+fill_field_order(DEBUG_GETINFO_TABLE)
+NOMINAL_FILE.found = standard_library["FILE"]
+NOMINAL_METATABLE.found = standard_library["METATABLE"]
+local compat53_code_cache = {}
+local function add_compat53_entries(program, used_set)
+   if not next(used_set) then
+      return
+   end
+   local used_list = {}
+   for name, _ in pairs(used_set) do
+      table.insert(used_list, name)
+   end
+   table.sort(used_list)
+   local compat53_loaded = false
+   local n = 1
+   local function load_code(name, text)
+      local code = compat53_code_cache[name]
+      if not code then
+         local tokens = tl.lex(text)
+         local _
+         _, code = tl.parse_program(tokens, {}, "@internal")
+         tl.type_check(code, { lax = false, skip_compat53 = true })
+         code = code[1]
+         compat53_code_cache[name] = code
+      end
+      table.insert(program, n, code)
+      n = n + 1
+   end
+   for i, name in ipairs(used_list) do
+      local mod, fn = name:match("([^.]*)%.(.*)")
+      local errs = {}
+      local text
+      local code = compat53_code_cache[name]
+      if not code then
+         if name == "table.unpack" then
+            load_code(name, "local _tl_table_unpack = unpack or table.unpack")
+         else
+            if not compat53_loaded then
+               load_code("compat53", "local _tl_compat53 = ((tonumber((_VERSION or ''):match('[%d.]*$')) or 0) < 5.3) and require('compat53.module')")
+               compat53_loaded = true
+            end
+            load_code(name, (("local $NAME = _tl_compat53 and _tl_compat53.$NAME or $NAME"):gsub("$NAME", name)))
+         end
+      end
+   end
+   program.y = 1
+end
+local function get_stdlib_compat53(lax)
+   if lax then
+      return {
+         ["utf8"] = true,
+      }
+   else
+      return {
+         ["io"] = true,
+         ["math"] = true,
+         ["string"] = true,
+         ["table"] = true,
+         ["utf8"] = true,
+         ["coroutine"] = true,
+         ["os"] = true,
+         ["package"] = true,
+         ["debug"] = true,
+         ["load"] = true,
+         ["loadfile"] = true,
+         ["assert"] = true,
+         ["pairs"] = true,
+         ["ipairs"] = true,
+         ["pcall"] = true,
+         ["xpcall"] = true,
+         ["rawlen"] = true,
+      }
+   end
+end
+local function init_globals(lax)
+   local globals = {}
+   local stdlib_compat53 = get_stdlib_compat53(lax)
+   for name, typ in pairs(standard_library) do
+      globals[name] = { t = typ, needs_compat53 = stdlib_compat53[name], is_const = true }
+   end
+   globals["@is_va"] = { t = VARARG_ANY }
+   return globals
+end
+function tl.init_env(lax, skip_compat53)
+   local env = {
+      modules = {},
+      globals = init_globals(lax),
+      skip_compat53 = skip_compat53,
+   }
+   for name, var in pairs(standard_library) do
+      if var.typename == "record" then
+         env.modules[name] = var
+      end
+   end
+   return env
+end
+function tl.type_check(ast, opts)
+   opts = opts or {}
+   opts.env = opts.env or tl.init_env(opts.lax, opts.skip_compat53)
+   local lax = opts.lax
+   local filename = opts.filename
+   local result = opts.result or {
+      syntax_errors = {},
+      type_errors = {},
+      unknowns = {},
+   }
+   local stdlib_compat53 = get_stdlib_compat53(lax)
+   local st = { opts.env.globals }
+   local all_needs_compat53 = {}
+   local errors = result.type_errors or {}
+   local unknowns = result.unknowns or {}
+   local module_type
+   local function find_var(name)
+      if name == "_G" then
+         local globals = {}
+         for k, v in pairs(st[1]) do
+            if k:sub(1, 1) ~= "@" then
+               globals[k] = v.t
+            end
+         end
+         local field_order = {}
+         for k, _ in pairs(globals) do
+            table.insert(field_order, k)
+         end
+         return a_type({
+            typename = "record",
+            field_order = field_order,
+            fields = globals,
+         }), false
+      end
+      for i = #st, 1, -1 do
+         local scope = st[i]
+         if scope[name] then
+            if i == 1 and scope[name].needs_compat53 then
+               all_needs_compat53[name] = true
+            end
+            local typ = scope[name].t
+            return typ, scope[name].is_const
+         end
+      end
+   end
+   local function resolve_typevars(t, seen)
+      seen = seen or {}
+      if seen[t] then
+         return seen[t]
+      end
+      local orig_t = t
+      local clear_tk = false
+      if t.typename == "typevar" then
+         local tv = find_var(t.typevar)
+         if tv then
+            t = tv
+            clear_tk = true
+         else
+            t = UNKNOWN
+         end
+      end
+      local copy = {}
+      seen[orig_t] = copy
+      for k, v in pairs(t) do
+         local cp = copy
+         if type(v) == "table" then
+            cp[k] = resolve_typevars(v, seen)
+         else
+            cp[k] = v
+         end
+      end
+      if clear_tk then
+         copy.tk = nil
+      end
+      return copy
+   end
+   local function find_type(names, accept_typearg)
+      local typ = find_var(names[1])
+      if not typ then
+         return nil
+      end
+      for i = 2, #names do
+         local nested = typ.fields or (typ.def and typ.def.fields)
+         if nested then
+            typ = nested[names[i]]
+            if typ == nil then
+               return nil
+            end
+         else
+            break
+         end
+      end
+      if typ then
+         if accept_typearg and typ.typename == "typearg" then
+            return typ
+         end
+         if is_type(typ) then
+            return typ
+         end
+      end
+      return nil
+   end
+   local function infer_var(emptytable, t, node)
+      local is_global = (emptytable.declared_at and emptytable.declared_at.kind == "global_declaration")
+      local nst = is_global and 1 or #st
+      for i = nst, 1, -1 do
+         local scope = st[i]
+         if scope[emptytable.assigned_to] then
+            scope[emptytable.assigned_to] = {
+               t = t,
+               is_const = false,
+            }
+            t.inferred_at = node
+            t.inferred_at_file = filename
+         end
+      end
+   end
+   local function find_global(name)
+      local scope = st[1]
+      if scope[name] then
+         return scope[name].t, scope[name].is_const
+      end
+   end
+   local function resolve_tuple(t)
+      if t.typename == "tuple" then
+         t = t[1]
+      end
+      if t == nil then
+         return NIL
+      end
+      return t
+   end
+   local function error_in_type(where, msg, ...)
+      local n = select("#", ...)
+      if n > 0 then
+         local showt = {}
+         for i = 1, n do
+            local t = select(i, ...)
+            if t.typename == "invalid" then
+               return nil
+            end
+            showt[i] = show_type(t)
+         end
+         msg = msg:format(_tl_table_unpack(showt))
+      end
+      return {
+         y = where.y,
+         x = where.x,
+         msg = msg,
+         filename = where.filename or filename,
+      }
+   end
+   local function type_error(t, msg, ...)
+      local e = error_in_type(t, msg, ...)
+      if e then
+         table.insert(errors, e)
+         return true
+      else
+         return false
+      end
+   end
+   local function node_error(node, msg, ...)
+      local ok = type_error(node, msg, ...)
+      node.type = INVALID
+      return node.type
+   end
+   local function terr(t, s, ...)
+      return { error_in_type(t, s, ...) }
+   end
+   local function add_unknown(node, name)
+      table.insert(unknowns, { y = node.y, x = node.x, msg = name, filename = filename })
+   end
+   local function add_var(node, var, valtype, is_const, is_narrowing)
+      if lax and node and is_unknown(valtype) and (var ~= "self" and var ~= "...") then
+         add_unknown(node, var)
+      end
+      if st[#st][var] and is_narrowing then
+         if not st[#st][var].is_narrowed then
+            st[#st][var].narrowed_from = st[#st][var].t
+         end
+         st[#st][var].is_narrowed = true
+         st[#st][var].t = valtype
+      else
+         st[#st][var] = { t = valtype, is_const = is_const, is_narrowed = is_narrowing }
+      end
+   end
+   local CompareTypes = {}
+   local function compare_typevars(t1, t2, comp)
+      local tv1 = find_var(t1.typevar)
+      local tv2 = find_var(t2.typevar)
+      if t1.typevar == t2.typevar then
+         local has_t1 = not not tv1
+         local has_t2 = not not tv2
+         if has_t1 == has_t2 then
+            return true
+         end
+      end
+      local function cmp(k, v, a, b)
+         if find_var(k) then
+            return comp(a, b)
+         else
+            add_var(nil, k, resolve_typevars(v))
+            return true
+         end
+      end
+      if t2.typename == "typevar" then
+         return cmp(t2.typevar, t1, t1, tv2)
+      else
+         return cmp(t1.typevar, t2, tv1, t2)
+      end
+   end
+   local function add_errs_prefixing(src, dst, prefix, node)
+      if not src then
+         return
+      end
+      for i, err in ipairs(src) do
+         err.msg = prefix .. err.msg
+         if node and node.y and (
+            (err.filename ~= filename) or
+            (not err.y) or
+            (node.y > err.y or (node.y == err.y and node.x > err.x))) then
+            err.y = node.y
+            err.x = node.x
+            err.filename = filename
+         end
+         table.insert(dst, err)
+      end
+   end
+   local is_a
+   local TypeGetter = {}
+   local function match_record_fields(t1, t2, cmp)
+      cmp = cmp or is_a
+      local fielderrs = {}
+      for _, k in ipairs(t1.field_order) do
+         local f = t1.fields[k]
+         local t2k = t2(k)
+         if t2k == nil then
+            if not lax then
+               table.insert(fielderrs, error_in_type(f, "unknown field " .. k))
+            end
+         else
+            local match, errs = is_a(f, t2k)
+            add_errs_prefixing(errs, fielderrs, "record field doesn't match: " .. k .. ": ")
+         end
+      end
+      if #fielderrs > 0 then
+         return false, fielderrs
+      end
+      return true
+   end
+   local function match_fields_to_record(t1, t2, cmp)
+      return match_record_fields(t1, function(k)          return t2.fields[k] end, cmp)
+   end
+   local function match_fields_to_map(t1, t2)
+      if not match_record_fields(t1, function(_)             return t2.values end) then
+         return false, { error_in_type(t1, "not all fields have type %s", t2.values) }
+      end
+      return true
+   end
+   local function arg_check(cmp, a, b, at, n, errs)
+      local matches, match_errs = cmp(a, b)
+      if not matches then
+         add_errs_prefixing(match_errs, errs, "argument " .. n .. ": ", at)
+         return false
+      end
+      return true
+   end
+   local same_type
+   local function has_all_types_of(t1s, t2s)
+      for _, t1 in ipairs(t1s) do
+         local found = false
+         for _, t2 in ipairs(t2s) do
+            if is_a(t2, t1) then
+               found = true
+               break
+            end
+         end
+         if not found then
+            return false
+         end
+      end
+      return true
+   end
+   local function any_errors(all_errs)
+      if #all_errs == 0 then
+         return true
+      else
+         return false, all_errs
+      end
+   end
+   local function are_same_nominals(t1, t2)
+      local same_names
+      if t1.found and t2.found then
+         same_names = t1.found.typeid == t2.found.typeid
+      else
+         local ft1 = t1.found or find_type(t1.names)
+         local ft2 = t2.found or find_type(t2.names)
+         if ft1 and ft2 then
+            same_names = ft1.typeid == ft2.typeid
+         else
+            if not ft1 then
+               type_error(t1, "unknown type %s", t1)
+            end
+            if not ft2 then
+               type_error(t2, "unknown type %s", t2)
+            end
+            return false, {}
+         end
+      end
+      if same_names then
+         if t1.typevals == nil and t2.typevals == nil then
+            return true
+         elseif t1.typevals and t2.typevals and #t1.typevals == #t2.typevals then
+            local all_errs = {}
+            for i = 1, #t1.typevals do
+               local ok, errs = same_type(t2.typevals[i], t1.typevals[i])
+               add_errs_prefixing(errs, all_errs, "type parameter <" .. show_type(t1.typevals[i]) .. ">: ", t1)
+            end
+            if #all_errs == 0 then
+               return true
+            else
+               return false, all_errs
+            end
+         end
+      else
+         return false, terr(t1, "%s is not a %s", t1, t2)
+      end
+   end
+   same_type = function(t1, t2)
+      assert(type(t1) == "table")
+      assert(type(t2) == "table")
+      if t1.typename == "typevar" or t2.typename == "typevar" then
+         return compare_typevars(t1, t2, same_type)
+      end
+      if t1.typename ~= t2.typename then
+         return false, terr(t1, "got %s, expected %s", t1, t2)
+      end
+      if t1.typename == "array" then
+         return same_type(t1.elements, t2.elements)
+      elseif t1.typename == "map" then
+         local all_errs = {}
+         local k_ok, k_errs = same_type(t1.keys, t2.keys)
+         if not k_ok then
+            add_errs_prefixing(k_errs, all_errs, "keys", t1)
+         end
+         local v_ok, v_errs = same_type(t1.values, t2.values)
+         if not v_ok then
+            add_errs_prefixing(v_errs, all_errs, "values", t1)
+         end
+         return any_errors(all_errs)
+      elseif t1.typename == "union" then
+         if has_all_types_of(t1.types, t2.types) and
+            has_all_types_of(t2.types, t1.types) then
+            return true
+         else
+            return false, terr(t1, "got %s, expected %s", t1, t2)
+         end
+      elseif t1.typename == "nominal" then
+         return are_same_nominals(t1, t2)
+      elseif t1.typename == "record" then
+         return match_fields_to_record(t1, t2, same_type)
+      elseif t1.typename == "function" then
+         if #t1.args ~= #t2.args then
+            return false, terr(t1, "different number of input arguments: got " .. #t1.args .. ", expected " .. #t2.args)
+         end
+         if #t1.rets ~= #t2.rets then
+            return false, terr(t1, "different number of return values: got " .. #t1.args .. ", expected " .. #t2.args)
+         end
+         local all_errs = {}
+         for i = 1, #t1.args do
+            arg_check(same_type, t1.args[i], t2.args[i], t1, i, all_errs)
+         end
+         for i = 1, #t1.rets do
+            local ok, errs = same_type(t1.rets[i], t2.rets[i])
+            add_errs_prefixing(errs, all_errs, "return " .. i, t1)
+         end
+         return any_errors(all_errs)
+      elseif t1.typename == "arrayrecord" then
+         local ok, errs = same_type(t1.elements, t2.elements)
+         if not ok then
+            return ok, errs
+         end
+         return match_fields_to_record(t1, t2, same_type)
+      end
+      return true
+   end
+   local function a_union(types)
+      local ts = {}
+      local stack = {}
+      local i = 1
+      while types[i] or stack[1] do
+         local t
+         if stack[1] then
+            t = table.remove(stack)
+         else
+            t = types[i]
+            i = i + 1
+         end
+         if t.typename == "union" then
+            for _, s in ipairs(t.types) do
+               table.insert(stack, s)
+            end
+         else
+            table.insert(ts, t)
+         end
+      end
+      return a_type({
+         typename = "union",
+         types = ts,
+      })
+   end
+   local function is_vararg(t)
+      return t.args and #t.args > 0 and t.args[#t.args].is_va
+   end
+   local function combine_errs(...)
+      local errs
+      for i = 1, select("#", ...) do
+         local e = select(i, ...)
+         if e then
+            errs = errs or {}
+            for _, err in ipairs(e) do
+               table.insert(errs, err)
+            end
+         end
+      end
+      if not errs then
+         return true
+      else
+         return false, errs
+      end
+   end
+   local resolve_unary = nil
+   local function is_known_table_type(t)
+      return (t.typename == "array" or t.typename == "map" or t.typename == "record" or t.typename == "arrayrecord")
+   end
+   is_a = function(t1, t2, for_equality)
+      assert(type(t1) == "table")
+      assert(type(t2) == "table")
+      if lax and (is_unknown(t1) or is_unknown(t2)) then
+         return true
+      end
+      if t1.typename == "nil" then
+         return true
+      end
+      if t2.typename ~= "tuple" then
+         t1 = resolve_tuple(t1)
+      end
+      if t2.typename == "tuple" and t1.typename ~= "tuple" then
+         t1 = a_type({
+            typename = "tuple",
+            [1] = t1,
+         })
+      end
+      if t1.typename == "typevar" or t2.typename == "typevar" then
+         return compare_typevars(t1, t2, is_a)
+      end
+      if t2.typename == "any" then
+         return true
+      elseif t2.typename == "poly" then
+         for _, t in ipairs(t2.types) do
+            if is_a(t1, t, for_equality) then
+               return true
+            end
+         end
+         return false, terr(t1, "cannot match against any alternatives of the polymorphic type")
+      elseif t1.typename == "union" and t2.typename == "union" then
+         if has_all_types_of(t1.types, t2.types) then
+            return true
+         else
+            return false, terr(t1, "got %s, expected %s", t1, t2)
+         end
+      elseif t2.typename == "union" then
+         for _, t in ipairs(t2.types) do
+            if is_a(t1, t, for_equality) then
+               return true
+            end
+         end
+      elseif t1.typename == "poly" then
+         for _, t in ipairs(t1.types) do
+            if is_a(t, t2, for_equality) then
+               return true
+            end
+         end
+         return false, terr(t1, "cannot match against any alternatives of the polymorphic type")
+      elseif t1.typename == "nominal" and t2.typename == "nominal" and #t2.names == 1 and t2.names[1] == "any" then
+         return true
+      elseif t1.typename == "nominal" and t2.typename == "nominal" then
+         return are_same_nominals(t1, t2)
+      elseif t1.typename == "enum" and t2.typename == "string" then
+         local ok
+         if for_equality then
+            ok = t2.tk and t1.enumset[unquote(t2.tk)]
+         else
+            ok = true
+         end
+         if ok then
+            return true
+         else
+            return false, terr(t1, "enum is incompatible with %s", t2)
+         end
+      elseif t1.typename == "string" and t2.typename == "enum" then
+         local ok = t1.tk and t2.enumset[unquote(t1.tk)]
+         if ok then
+            return true
+         else
+            if t1.tk then
+               return false, terr(t1, "%s is not a member of %s", t1, t2)
+            else
+               return false, terr(t1, "string is not a %s", t2)
+            end
+         end
+      elseif t1.typename == "nominal" or t2.typename == "nominal" then
+         local t1u = resolve_unary(t1)
+         local t2u = resolve_unary(t2)
+         local ok, errs = is_a(t1u, t2u, for_equality)
+         if errs and #errs == 1 then
+            if errs[1].msg:match("^got ") then
+               errs = terr(t1, "got %s, expected %s", t1, t2)
+            end
+         end
+         return ok, errs
+      elseif t1.typename == "emptytable" and is_known_table_type(t2) then
+         return true
+      elseif t2.typename == "array" then
+         if is_array_type(t1) then
+            if is_a(t1.elements, t2.elements) then
+               return true
+            end
+         elseif t1.typename == "map" then
+            local _, errs_keys = is_a(t1.keys, NUMBER)
+            local _, errs_values = is_a(t1.values, t2.elements)
+            return combine_errs(errs_keys, errs_values)
+         end
+      elseif t2.typename == "record" then
+         if is_record_type(t1) then
+            return match_fields_to_record(t1, t2)
+         elseif t1.typename == "typetype" and t1.def.typename == "record" then
+            return is_a(t1.def, t2, for_equality)
+         end
+      elseif t2.typename == "arrayrecord" then
+         if t1.typename == "array" then
+            return is_a(t1.elements, t2.elements)
+         elseif t1.typename == "record" then
+            return match_fields_to_record(t1, t2)
+         elseif t1.typename == "arrayrecord" then
+            if not is_a(t1.elements, t2.elements) then
+               return false, terr(t1, "array parts have incompatible element types")
+            end
+            return match_fields_to_record(t1, t2)
+         end
+      elseif t2.typename == "map" then
+         if t1.typename == "map" then
+            local _, errs_keys = is_a(t1.keys, t2.keys)
+            local _, errs_values = is_a(t2.values, t1.values)
+            if t2.values.typename == "any" then
+               errs_values = {}
+            end
+            return combine_errs(errs_keys, errs_values)
+         elseif t1.typename == "array" then
+            local _, errs_keys = is_a(NUMBER, t2.keys)
+            local _, errs_values = is_a(t1.elements, t2.values)
+            return combine_errs(errs_keys, errs_values)
+         elseif is_record_type(t1) then
+            if not is_a(t2.keys, STRING) then
+               return false, terr(t1, "can't match a record to a map with non-string keys")
+            end
+            if t2.keys.typename == "enum" then
+               for _, k in ipairs(t1.field_order) do
+                  if not t2.keys.enumset[k] then
+                     return false, terr(t1, "key is not an enum value: " .. k)
+                  end
+               end
+            end
+            return match_fields_to_map(t1, t2)
+         end
+      elseif t1.typename == "function" and t2.typename == "function" then
+         local all_errs = {}
+         if (not is_vararg(t2)) and #t1.args > #t2.args then
+            t1.args.typename = "tuple"
+            t2.args.typename = "tuple"
+            table.insert(all_errs, error_in_type(t1, "incompatible number of arguments: got " .. #t1.args .. " %s, expected " .. #t2.args .. " %s", t1.args, t2.args))
+         else
+            for i = (t1.is_method and 2 or 1), #t1.args do
+               arg_check(is_a, t1.args[i], t2.args[i] or ANY, nil, i, all_errs)
+            end
+         end
+         local diff_by_va = #t2.rets - #t1.rets == 1 and t2.rets[#t2.rets].is_va
+         if #t1.rets < #t2.rets and not diff_by_va then
+            t1.rets.typename = "tuple"
+            t2.rets.typename = "tuple"
+            table.insert(all_errs, error_in_type(t1, "incompatible number of returns: got " .. #t1.rets .. " %s, expected " .. #t2.rets .. " %s", t1.rets, t2.rets))
+         else
+            local nrets = #t2.rets
+            if diff_by_va then
+               nrets = nrets - 1
+            end
+            for i = 1, nrets do
+               local ok, errs = is_a(t1.rets[i], t2.rets[i])
+               add_errs_prefixing(errs, all_errs, "return " .. i .. ": ")
+            end
+         end
+         if #all_errs == 0 then
+            return true
+         else
+            return false, all_errs
+         end
+      elseif lax and ((not for_equality) and t2.typename == "boolean") then
+         return true
+      elseif t1.typename == t2.typename then
+         return true
+      end
+      return false, terr(t1, "got %s, expected %s", t1, t2)
+   end
+   local function assert_is_a(node, t1, t2, context, name)
+      t1 = resolve_tuple(t1)
+      t2 = resolve_tuple(t2)
+      if lax and (is_unknown(t1) or is_unknown(t2)) then
+         return
+      end
+      if t2.typename == "unknown_emptytable_value" then
+         if same_type(t2.emptytable_type.keys, NUMBER) then
+            infer_var(t2.emptytable_type, a_type({ typename = "array", elements = t1 }), node)
+         else
+            infer_var(t2.emptytable_type, a_type({ typename = "map", keys = t2.emptytable_type.keys, values = t1 }), node)
+         end
+         return
+      elseif t2.typename == "emptytable" then
+         if is_known_table_type(t1) then
+            infer_var(t2, t1, node)
+         elseif t1.typename ~= "emptytable" then
+            node_error(node, "in " .. context .. ": " .. (name and (name .. ": ") or "") .. "assigning %s to a variable declared with {}", t1)
+         end
+         return
+      end
+      local match, match_errs = is_a(t1, t2)
+      add_errs_prefixing(match_errs, errors, "in " .. context .. ": " .. (name and (name .. ": ") or ""), node)
+   end
+   local function close_types(vars)
+      for name, var in pairs(vars) do
+         if var.t.typename == "typetype" then
+            var.t.closed = true
+         end
+      end
+   end
+   local function begin_scope()
+      table.insert(st, {})
+   end
+   local function end_scope()
+      local unresolved = st[#st]["@unresolved"]
+      if unresolved then
+         local upper = st[#st - 1]["@unresolved"]
+         if upper then
+            for name, nodes in pairs(unresolved.t.labels) do
+               for _, node in ipairs(nodes) do
+                  upper.t.labels[name] = upper.t.labels[name] or {}
+                  table.insert(upper.t.labels[name], node)
+               end
+            end
+            for name, types in pairs(unresolved.t.nominals) do
+               for _, typ in ipairs(types) do
+                  upper.t.nominals[name] = upper.t.nominals[name] or {}
+                  table.insert(upper.t.nominals[name], typ)
+               end
+            end
+         else
+            st[#st - 1]["@unresolved"] = unresolved
+         end
+      end
+      close_types(st[#st])
+      table.remove(st)
+   end
+   local type_check_function_call
+   do
+      local function try_match_func_args(node, f, args, is_method, argdelta)
+         local ok = true
+         local errs = {}
+         if is_method then
+            argdelta = -1
+         elseif not argdelta then
+            argdelta = 0
+         end
+         if f.is_method and not is_method and not (args[1] and is_a(args[1], f.args[1])) then
+            table.insert(errs, { y = node.y, x = node.x, msg = "invoked method as a regular function: use ':' instead of '.'", filename = filename })
+            return nil, errs
+         end
+         local va = is_vararg(f)
+         local nargs = va and
+         math.max(#args, #f.args) or
+         math.min(#args, #f.args)
+         for a = 1, nargs do
+            local arg = args[a]
+            local farg = f.args[a] or (va and f.args[#f.args])
+            if arg == nil then
+               if farg.is_va then
+                  break
+               end
+            else
+               local at = node.e2 and node.e2[a] or node
+               if not arg_check(is_a, arg, farg, at, (a + argdelta), errs) then
+                  ok = false
+                  break
+               end
+            end
+         end
+         if ok == true then
+            f.rets.typename = "tuple"
+            for a = 1, #args do
+               local arg = args[a]
+               local farg = f.args[a] or (va and f.args[#f.args])
+               if arg.typename == "emptytable" then
+                  infer_var(arg, resolve_typevars(farg), node.e2[a])
+               end
+            end
+            return resolve_typevars(f.rets)
+         end
+         return nil, errs
+      end
+      local function revert_typeargs(func)
+         if func.typeargs then
+            for _, arg in ipairs(func.typeargs) do
+               if st[#st][arg.typearg] then
+                  st[#st][arg.typearg] = nil
+               end
+            end
+         end
+      end
+      local function remove_sorted_duplicates(t)
+         local prev = nil
+         for i = #t, 1, -1 do
+            if t[i] == prev then
+               table.remove(t, i)
+            else
+               prev = t[i]
+            end
+         end
+      end
+      local function check_call(node, func, args, is_method, argdelta)
+         assert(type(func) == "table")
+         assert(type(args) == "table")
+         if lax and is_unknown(func) then
+            func = a_type({ typename = "function", args = { VARARG_UNKNOWN }, rets = { VARARG_UNKNOWN } })
+         end
+         func = resolve_unary(func)
+         args = args or {}
+         local poly = func.typename == "poly" and func or { types = { func } }
+         local first_errs
+         local expects = {}
+         local tried = {}
+         for i, f in ipairs(poly.types) do
+            if not tried[i] then
+               if f.typename ~= "function" then
+                  if lax and is_unknown(f) then
+                     return UNKNOWN
+                  end
+                  return node_error(node, "not a function: %s", f)
+               end
+               table.insert(expects, tostring(#f.args or 0))
+               local va = is_vararg(f)
+               if #args == (#f.args or 0) or (va and #args > #f.args) then
+                  tried[i] = true
+                  local matched, errs = try_match_func_args(node, f, args, is_method, argdelta)
+                  if matched then
+                     return matched
+                  else
+                     revert_typeargs(f)
+                  end
+                  first_errs = first_errs or errs
+               end
+            end
+         end
+         for i, f in ipairs(poly.types) do
+            if not tried[i] then
+               tried[i] = true
+               if #args < (#f.args or 0) then
+                  tried[i] = true
+                  local matched, errs = try_match_func_args(node, f, args, is_method, argdelta)
+                  if matched then
+                     return matched
+                  else
+                     revert_typeargs(f)
+                  end
+                  first_errs = first_errs or errs
+               end
+            end
+         end
+         for i, f in ipairs(poly.types) do
+            if not tried[i] then
+               if is_vararg(f) and #args > (#f.args or 0) then
+                  tried[i] = true
+                  local matched, errs = try_match_func_args(node, f, args, is_method, argdelta)
+                  if matched then
+                     return matched
+                  else
+                     revert_typeargs(f)
+                  end
+                  first_errs = first_errs or errs
+               end
+            end
+         end
+         if not first_errs then
+            table.sort(expects)
+            remove_sorted_duplicates(expects)
+            node_error(node, "wrong number of arguments (given " .. #args .. ", expects " .. table.concat(expects, " or ") .. ")")
+         else
+            for _, err in ipairs(first_errs) do
+               table.insert(errors, err)
+            end
+         end
+         poly.types[1].rets.typename = "tuple"
+         return resolve_typevars(poly.types[1].rets)
+      end
+      type_check_function_call = function(node, func, args, is_method, argdelta)
+         begin_scope()
+         local ret = check_call(node, func, args, is_method, argdelta)
+         end_scope()
+         return ret
+      end
+   end
+   local unknown_dots = {}
+   local function add_unknown_dot(node, name)
+      if not unknown_dots[name] then
+         unknown_dots[name] = true
+         add_unknown(node, name)
+      end
+   end
+   local function get_self_type(t)
+      if t.typename == "typetype" then
+         return t.def
+      else
+         return t
+      end
+   end
+   local function match_record_key(node, tbl, key, orig_tbl)
+      assert(type(tbl) == "table")
+      assert(type(key) == "table")
+      tbl = resolve_unary(tbl)
+      local type_description = tbl.typename
+      if tbl.typename == "string" or tbl.typename == "enum" then
+         tbl = find_var("string")
+      end
+      if lax and (is_unknown(tbl) or tbl.typename == "typevar") then
+         if node.e1.kind == "variable" and node.op.op ~= "@funcall" then
+            add_unknown_dot(node, node.e1.tk .. "." .. key.tk)
+         end
+         return UNKNOWN
+      end
+      tbl = get_self_type(tbl)
+      if tbl.typename == "emptytable" then
+      elseif is_record_type(tbl) then
+         assert(tbl.fields, "record has no fields!?")
+         if key.kind == "string" or key.kind == "identifier" then
+            if tbl.fields[key.tk] then
+               return tbl.fields[key.tk]
+            end
+         end
+      else
+         if is_unknown(tbl) then
+            if not lax then
+               node_error(node, "cannot index a value of unknown type")
+            end
+         else
+            node_error(node, "cannot index something that is not a record: %s", tbl)
+         end
+         return INVALID
+      end
+      if lax then
+         if node.e1.kind == "variable" and node.op.op ~= "@funcall" then
+            add_unknown_dot(node, node.e1.tk .. "." .. key.tk)
+         end
+         return UNKNOWN
+      end
+      local description
+      if node.e1.kind == "variable" then
+         description = type_description .. " '" .. node.e1.tk .. "' of type " .. show_type(resolve_tuple(orig_tbl))
+      else
+         description = "type " .. show_type(resolve_tuple(orig_tbl))
+      end
+      return node_error(key, "invalid key '" .. key.tk .. "' in " .. description)
+   end
+   local function widen_in_scope(scope, var)
+      if scope[var].is_narrowed then
+         if scope[var].narrowed_from then
+            scope[var].t = scope[var].narrowed_from
+            scope[var].narrowed_from = nil
+            scope[var].is_narrowed = false
+         else
+            scope[var] = nil
+         end
+         return true
+      end
+      return false
+   end
+   local function widen_back_var(var)
+      local widened = false
+      for i = #st, 1, -1 do
+         if st[i][var] then
+            if widen_in_scope(st[i], var) then
+               widened = true
+            else
+               break
+            end
+         end
+      end
+      return widened
+   end
+   local function widen_all_unions()
+      for i = #st, 1, -1 do
+         for var, _ in pairs(st[i]) do
+            widen_in_scope(st[i], var)
+         end
+      end
+   end
+   local function add_global(node, var, valtype, is_const)
+      if lax and is_unknown(valtype) and (var ~= "self" and var ~= "...") then
+         add_unknown(node, var)
+      end
+      st[1][var] = { t = valtype, is_const = is_const }
+   end
+   local check_typevars
+   local function check_all_typevars(node, ts)
+      if ts ~= nil then
+         for _, arg in ipairs(ts) do
+            check_typevars(node, arg)
+         end
+      end
+   end
+   check_typevars = function(node, t)
+      if t == nil then
+         return
+      end
+      if t.typename == "typevar" then
+         if not find_var(t.typevar) then
+            node_error(node, "unknown type variable " .. t.typevar)
+         end
+         return
+      end
+      check_typevars(node, t.elements)
+      check_typevars(node, t.keys)
+      check_typevars(node, t.values)
+      check_all_typevars(node, t.typeargs)
+      check_all_typevars(node, t.args)
+      check_all_typevars(node, t.rets)
+   end
+   local function get_rets(rets)
+      if lax and (#rets == 0) then
+         return { a_type({ typename = "unknown", is_va = true }) }
+      end
+      return rets
+   end
+   local function begin_function_scope(node, recurse)
+      begin_scope()
+      local args = {}
+      if node.typeargs then
+         for i, arg in ipairs(node.typeargs) do
+            add_var(nil, arg.typearg, arg)
+         end
+      end
+      local is_va = false
+      for i, arg in ipairs(node.args) do
+         local t = arg.decltype
+         if not t then
+            t = a_type({ typename = "unknown" })
+         end
+         if arg.tk == "..." then
+            is_va = true
+            t.is_va = true
+            if i ~= #node.args then
+               node_error(node, "'...' can only be last argument")
+            end
+         end
+         check_typevars(arg, t)
+         table.insert(args, t)
+         add_var(arg, arg.tk, t)
+      end
+      add_var(nil, "@is_va", is_va and VARARG_ANY or NIL)
+      add_var(nil, "@return", node.rets or a_type({ typename = "tuple" }))
+      if recurse then
+         add_var(nil, node.name.tk, a_type({
+            typename = "function",
+            args = args,
+            rets = get_rets(node.rets),
+         }))
+      end
+   end
+   local function fail_unresolved()
+      local unresolved = st[#st]["@unresolved"]
+      if unresolved then
+         st[#st]["@unresolved"] = nil
+         for name, nodes in pairs(unresolved.t.labels) do
+            for _, node in ipairs(nodes) do
+               node_error(node, "no visible label '" .. name .. "' for goto")
+            end
+         end
+         for name, types in pairs(unresolved.t.nominals) do
+            for _, typ in ipairs(types) do
+               assert(typ.x)
+               assert(typ.y)
+               type_error(typ, "unknown type %s", typ)
+            end
+         end
+      end
+   end
+   local function end_function_scope()
+      fail_unresolved()
+      end_scope()
+   end
+   local function match_typevals(t, def)
+      if t.typevals and def.typeargs then
+         if #t.typevals ~= #def.typeargs then
+            type_error(t, "mismatch in number of type arguments")
+            return nil
+         end
+         begin_scope()
+         for i, tt in ipairs(t.typevals) do
+            add_var(nil, def.typeargs[i].typearg, tt)
+         end
+         local ret = resolve_typevars(def)
+         end_scope()
+         return ret
+      elseif t.typevals then
+         type_error(t, "spurious type arguments")
+         return nil
+      elseif def.typeargs then
+         type_error(t, "missing type arguments in %s", def)
+         return nil
+      else
+         return def
+      end
+   end
+   local function resolve_nominal(t)
+      if t.resolved then
+         return t.resolved
+      end
+      local resolved
+      local typetype = t.found or find_type(t.names)
+      if not typetype then
+         type_error(t, "unknown type %s", t)
+      elseif is_type(typetype) then
+         resolved = match_typevals(t, typetype.def)
+      else
+         type_error(t, table.concat(t.names, ".") .. " is not a type")
+      end
+      if not resolved then
+         resolved = a_type({ typename = "bad_nominal", names = t.names })
+      end
+      t.found = typetype
+      t.resolved = resolved
+      return resolved
+   end
+   resolve_unary = function(t)
+      t = resolve_tuple(t)
+      if t.typename == "nominal" then
+         return resolve_nominal(t)
+      end
+      return t
+   end
+   local function flatten_list(list)
+      local exps = {}
+      for i = 1, #list - 1 do
+         table.insert(exps, resolve_unary(list[i]))
+      end
+      if #list > 0 then
+         local last = list[#list]
+         if last.typename == "tuple" then
+            for _, val in ipairs(last) do
+               table.insert(exps, val)
+            end
+         else
+            table.insert(exps, last)
+         end
+      end
+      return exps
+   end
+   local function get_assignment_values(vals, wanted)
+      local ret = {}
+      if vals == nil then
+         return ret
+      end
+      for i = 1, #vals - 1 do
+         ret[i] = vals[i]
+      end
+      local last = vals[#vals]
+      if last.typename == "tuple" then
+         for _, v in ipairs(last) do
+            table.insert(ret, v)
+         end
+      elseif last.is_va and #ret < wanted then
+         while #ret < wanted do
+            table.insert(ret, last)
+         end
+      else
+         table.insert(ret, last)
+      end
+      return ret
+   end
+   local function match_all_record_field_names(node, a, field_names, errmsg)
+      local t
+      for _, k in ipairs(field_names) do
+         local f = a.fields[k]
+         if not t then
+            t = f
+         else
+            if not same_type(f, t) then
+               t = nil
+               break
+            end
+         end
+      end
+      if t then
+         return t
+      else
+         return node_error(node, errmsg)
+      end
+   end
+   local function type_check_index(node, idxnode, a, b)
+      local orig_a = a
+      local orig_b = b
+      a = resolve_unary(a)
+      b = resolve_unary(b)
+      if is_array_type(a) and is_a(b, NUMBER) then
+         return a.elements
+      elseif a.typename == "emptytable" then
+         if a.keys == nil then
+            a.keys = b
+            a.keys_inferred_at = node
+            a.keys_inferred_at_file = filename
+         else
+            if not is_a(b, a.keys) then
+               local inferred = " (type of keys inferred at " .. a.keys_inferred_at_file .. ":" .. a.keys_inferred_at.y .. ":" .. a.keys_inferred_at.x .. ": )"
+               return node_error(idxnode, "inconsistent index type: %s, expected %s" .. inferred, b, a.keys)
+            end
+         end
+         return a_type({ y = node.y, x = node.x, typename = "unknown_emptytable_value", emptytable_type = a })
+      elseif a.typename == "map" then
+         if is_a(b, a.keys) then
+            return a.values
+         else
+            return node_error(idxnode, "wrong index type: %s, expected %s", orig_b, a.keys)
+         end
+      elseif node.e2.kind == "string" or node.e2.kind == "enum_item" then
+         return match_record_key(node, a, { y = node.e2.y, x = node.e2.x, kind = "string", tk = assert(node.e2.conststr) }, orig_a)
+      elseif is_record_type(a) and b.typename == "enum" then
+         local field_names = {}
+         for k, _ in pairs(b.enumset) do
+            table.insert(field_names, k)
+         end
+         table.sort(field_names)
+         for _, k in ipairs(field_names) do
+            if not a.fields[k] then
+               return node_error(idxnode, "enum value '" .. k .. "' is not a field in %s", a)
+            end
+         end
+         return match_all_record_field_names(idxnode, a, field_names,
+"cannot index, not all enum values map to record fields of the same type")
+      elseif lax and is_unknown(a) then
+         return UNKNOWN
+      else
+         if is_a(b, STRING) then
+            return node_error(idxnode, "cannot index object of type %s with a string, consider using an enum", orig_a)
+         end
+         return node_error(idxnode, "cannot index object of type %s with %s", orig_a, orig_b)
+      end
+   end
+   local function expand_type(where, old, new)
+      if not old then
+         return new
+      else
+         if not is_a(new, old) then
+            if old.typename == "map" and is_record_type(new) then
+               if old.keys.typename == "string" then
+                  for _, ftype in pairs(new.fields) do
+                     old.values = expand_type(where, old.values, ftype)
+                  end
+               else
+                  node_error(where, "cannot determine table literal type")
+               end
+            elseif is_record_type(old) and is_record_type(new) then
+               old.typename = "map"
+               old.keys = STRING
+               for _, ftype in pairs(old.fields) do
+                  if not old.values then
+                     old.values = ftype
+                  else
+                     old.values = expand_type(where, old.values, ftype)
+                  end
+               end
+               for _, ftype in pairs(new.fields) do
+                  if not old.values then
+                     new.values = ftype
+                  else
+                     new.values = expand_type(where, old.values, ftype)
+                  end
+               end
+               old.fields = nil
+               old.field_order = nil
+            elseif old.typename == "union" then
+               new.tk = nil
+               table.insert(old.types, new)
+            else
+               old.tk = nil
+               new.tk = nil
+               return a_union({ old, new })
+            end
+         end
+      end
+      return old
+   end
+   local function find_in_scope(exp)
+      if exp.kind == "variable" then
+         local t = find_var(exp.tk)
+         if t.def then
+            if not t.def.closed and not t.closed then
+               return t.def
+            end
+         end
+         if not t.closed then
+            return t
+         end
+      elseif exp.kind == "op" and exp.op.op == "." then
+         local t = find_in_scope(exp.e1)
+         if not t then
+            return nil
+         end
+         while exp.e2.kind == "op" and exp.e2.op.op == "." do
+            t = t.fields[exp.e2.e1.tk]
+            if not t then
+               return nil
+            end
+            exp = exp.e2
+         end
+         t = t.fields[exp.e2.tk]
+         return t
+      end
+   end
+   local facts_and
+   local facts_or
+   local facts_not
+   do
+      local function join_facts(fss)
+         local vars = {}
+         for _, fs in ipairs(fss) do
+            for _, f in ipairs(fs) do
+               if not vars[f.var] then
+                  vars[f.var] = {}
+               end
+               table.insert(vars[f.var], f)
+            end
+         end
+         return vars
+      end
+      local function intersect(xs, ys, same)
+         local rs = {}
+         for i = #xs, 1, -1 do
+            local x = xs[i]
+            for _, y in ipairs(ys) do
+               if same(x, y) then
+                  table.insert(rs, x)
+                  break
+               end
+            end
+         end
+         return rs
+      end
+      local function same_type_for_intersect(t, u)
+         return (same_type(t, u))
+      end
+      local function intersect_facts(fs, errnode)
+         local all_is = true
+         local types = {}
+         for i, f in ipairs(fs) do
+            if f.fact ~= "is" then
+               all_is = false
+               break
+            end
+            if f.typ.typename == "union" then
+               if i == 1 then
+                  types = f.typ.types
+               else
+                  types = intersect(types, f.typ.types, same_type_for_intersect)
+               end
+            else
+               if i == 1 then
+                  types = { f.typ }
+               else
+                  types = intersect(types, { f.typ }, same_type_for_intersect)
+               end
+            end
+         end
+         if #types == 0 then
+            node_error(errnode, "branch is always false")
+            return false
+         end
+         if all_is then
+            if #types == 1 then
+               return true, types[1]
+            else
+               return true, a_union(types)
+            end
+         else
+            return false
+         end
+      end
+      local function sum_facts(fs)
+         local all_is = true
+         local types = {}
+         for _, f in ipairs(fs) do
+            if f.fact ~= "is" then
+               all_is = false
+               break
+            end
+            table.insert(types, f.typ)
+         end
+         if all_is then
+            if #types == 1 then
+               return true, types[1]
+            else
+               return true, a_union(types)
+            end
+         else
+            return false
+         end
+      end
+      local function subtract_types(u1, u2, errt)
+         local types = {}
+         for _, rt in ipairs(u1.types or { u1 }) do
+            local not_present = true
+            for _, ft in ipairs(u2.types or { u2 }) do
+               if same_type(rt, ft) then
+                  not_present = false
+                  break
+               end
+            end
+            if not_present then
+               table.insert(types, rt)
+            end
+         end
+         if #types == 0 then
+            type_error(errt, "branch is always false")
+            return INVALID
+         end
+         if #types == 1 then
+            return types[1]
+         else
+            return a_union(types)
+         end
+      end
+      facts_and = function(f1, f2, errnode)
+         if not f1 then
+            return f2
+         end
+         if not f2 then
+            return f1
+         end
+         local out = {}
+         for v, fs in pairs(join_facts({ f1, f2 })) do
+            local ok, u = intersect_facts(fs, errnode)
+            if ok then
+               table.insert(out, { fact = "is", var = v, typ = u })
+            else
+               for _, f in ipairs(fs) do
+                  table.insert(out, f)
+               end
+            end
+         end
+         return out
+      end
+      facts_or = function(f1, f2)
+         if not f1 or not f2 then
+            return nil
+         end
+         local out = {}
+         for v, fs in pairs(join_facts({ f1, f2 })) do
+            local ok, u = sum_facts(fs)
+            if ok then
+               table.insert(out, { fact = "is", var = v, typ = u })
+            else
+               for _, f in ipairs(fs) do
+                  table.insert(out, f)
+               end
+            end
+         end
+         return out
+      end
+      facts_not = function(f1)
+         if not f1 then
+            return nil
+         end
+         local out = {}
+         for v, fs in pairs(join_facts({ f1 })) do
+            local realtype = find_var(v)
+            if realtype then
+               local ok, u = sum_facts(fs)
+               if ok then
+                  local not_typ = subtract_types(realtype, u, fs[1].typ)
+                  table.insert(out, { fact = "is", var = v, typ = not_typ })
+               end
+            end
+         end
+         return out
+      end
+   end
+   local function apply_facts(where, facts)
+      if not facts then
+         return
+      end
+      for _, f in ipairs(facts) do
+         if f.fact == "is" then
+            local t = resolve_typevars(f.typ)
+            t.inferred_at = where
+            t.inferred_at_file = filename
+            add_var(nil, f.var, t, nil, true)
+         end
+      end
+   end
+   local function dismiss_unresolved(name)
+      local unresolved = st[#st]["@unresolved"]
+      if unresolved then
+         if unresolved.t.nominals[name] then
+            for _, t in ipairs(unresolved.t.nominals[name]) do
+               resolve_nominal(t)
+            end
+         end
+         unresolved.t.nominals[name] = nil
+      end
+   end
+   local function type_check_funcall(node, a, b, argdelta)
+      argdelta = argdelta or 0
+      if node.e1.tk == "rawget" then
+         if #b == 2 then
+            local b1 = resolve_unary(b[1])
+            local b2 = resolve_unary(b[2])
+            local knode = node.e2[2]
+            if is_record_type(b1) and knode.conststr then
+               return match_record_key(node, b1, { y = knode.y, x = knode.x, kind = "string", tk = assert(knode.conststr) }, b1)
+            else
+               return type_check_index(node, knode, b1, b2)
+            end
+         else
+            node_error(node, "rawget expects two arguments")
+         end
+      elseif node.e1.tk == "print_type" then
+         print(show_type(b))
+         return BOOLEAN
+      elseif node.e1.tk == "require" then
+         if #b == 1 then
+            if node.e2[1].kind == "string" then
+               local module_name = assert(node.e2[1].conststr)
+               local t, found = require_module(module_name, lax, opts.env, result)
+               if not found then
+                  node_error(node, "module not found: '" .. module_name .. "'")
+               elseif not lax and is_unknown(t) then
+                  node_error(node, "no type information for required module: '" .. module_name .. "'")
+               end
+               return t
+            else
+               node_error(node, "don't know how to resolve a dynamic require")
+            end
+         else
+            node_error(node, "require expects one literal argument")
+         end
+      elseif node.e1.tk == "pcall" then
+         local ftype = table.remove(b, 1)
+         local fe2 = {}
+         for i = 2, #node.e2 do
+            table.insert(fe2, node.e2[i])
+         end
+         local fnode = {
+            y = node.y,
+            x = node.x,
+            typename = "op",
+            op = { op = "@funcall" },
+            e1 = node.e2[1],
+            e2 = fe2,
+         }
+         local rets = type_check_funcall(fnode, ftype, b, argdelta + 1)
+         if rets.typename ~= "tuple" then
+            rets = a_type({ typename = "tuple", rets })
+         end
+         table.insert(rets, 1, BOOLEAN)
+         return rets
+      elseif node.e1.op and node.e1.op.op == ":" then
+         local func = node.e1.type
+         if func.typename == "function" or func.typename == "poly" then
+            table.insert(b, 1, node.e1.e1.type)
+            return type_check_function_call(node, func, b, true)
+         else
+            if lax and (is_unknown(func)) then
+               if node.e1.e1.kind == "variable" then
+                  add_unknown_dot(node, node.e1.e1.tk .. "." .. node.e1.e2.tk)
+               end
+               return VARARG_UNKNOWN
+            else
+               return INVALID
+            end
+         end
+      else
+         return type_check_function_call(node, a, b, false, argdelta)
+      end
+      return UNKNOWN
+   end
+   local visit_node = {}
+   visit_node.cbs = {
+      ["statements"] = {
+         before = function()
+            begin_scope()
+         end,
+         after = function(node, children)
+            if #st == 2 then
+               fail_unresolved()
+            end
+            if not node.is_repeat then
+               end_scope()
+            end
+            node.type = NONE
+         end,
+      },
+      ["local_type"] = {
+         before = function(node)
+            add_var(node.var, node.var.tk, node.value.newtype, node.var.is_const)
+         end,
+         after = function(node, children)
+            dismiss_unresolved(node.var.tk)
+            node.type = NONE
+         end,
+      },
+      ["global_type"] = {
+         before = function(node)
+            add_global(node.var, node.var.tk, node.value.newtype, node.var.is_const)
+         end,
+         after = function(node, children)
+            local existing, existing_is_const = find_global(node.var.tk)
+            local var = node.var
+            if existing then
+               if existing_is_const == true and not var.is_const then
+                  node_error(var, "global was previously declared as <const>: " .. var.tk)
+               end
+               if existing_is_const == false and var.is_const then
+                  node_error(var, "global was previously declared as not <const>: " .. var.tk)
+               end
+               if not same_type(existing, node.value.newtype) then
+                  node_error(var, "cannot redeclare global with a different type: previous type of " .. var.tk .. " is %s", existing)
+               end
+            end
+            dismiss_unresolved(var.tk)
+            node.type = NONE
+         end,
+      },
+      ["local_declaration"] = {
+         after = function(node, children)
+            local vals = get_assignment_values(children[2], #node.vars)
+            for i, var in ipairs(node.vars) do
+               local decltype = node.decltype and node.decltype[i]
+               local infertype = vals and vals[i]
+               if lax and infertype and infertype.typename == "nil" then
+                  infertype = nil
+               end
+               if decltype and infertype then
+                  assert_is_a(node.vars[i], infertype, decltype, "local declaration", var.tk)
+               end
+               local t = decltype or infertype
+               if t == nil then
+                  t = a_type({ typename = "unknown" })
+                  if not lax then
+                     if node.exps then
+                        node_error(node.vars[i], "assignment in declaration did not produce an initial value for variable '" .. var.tk .. "'")
+                     else
+                        node_error(node.vars[i], "variable '" .. var.tk .. "' has no type or initial value")
+                     end
+                  end
+               elseif t.typename == "emptytable" then
+                  t.declared_at = node
+                  t.assigned_to = var.tk
+               end
+               assert(var)
+               add_var(var, var.tk, t, var.is_const)
+               dismiss_unresolved(var.tk)
+            end
+            node.type = NONE
+         end,
+      },
+      ["global_declaration"] = {
+         after = function(node, children)
+            local vals = get_assignment_values(children[2], #node.vars)
+            for i, var in ipairs(node.vars) do
+               local decltype = node.decltype and node.decltype[i]
+               local infertype = vals and vals[i]
+               if lax and infertype and infertype.typename == "nil" then
+                  infertype = nil
+               end
+               if decltype and infertype then
+                  assert_is_a(node.vars[i], infertype, decltype, "global declaration", var.tk)
+               end
+               local t = decltype or infertype
+               local existing, existing_is_const = find_global(var.tk)
+               if existing then
+                  if infertype and existing_is_const then
+                     node_error(var, "cannot reassign to <const> global: " .. var.tk)
+                  end
+                  if existing_is_const == true and not var.is_const then
+                     node_error(var, "global was previously declared as <const>: " .. var.tk)
+                  end
+                  if existing_is_const == false and var.is_const then
+                     node_error(var, "global was previously declared as not <const>: " .. var.tk)
+                  end
+                  if not same_type(existing, t) then
+                     node_error(var, "cannot redeclare global with a different type: previous type of " .. var.tk .. " is %s", existing)
+                  end
+               else
+                  if t == nil then
+                     t = a_type({ typename = "unknown" })
+                  elseif t.typename == "emptytable" then
+                     t.declared_at = node
+                     t.assigned_to = var.tk
+                  end
+                  add_global(var, var.tk, t, var.is_const)
+                  dismiss_unresolved(var.tk)
+               end
+            end
+            node.type = NONE
+         end,
+      },
+      ["assignment"] = {
+         after = function(node, children)
+            local vals = get_assignment_values(children[2], #children[1])
+            local exps = flatten_list(vals)
+            for i, vartype in ipairs(children[1]) do
+               local varnode = node.vars[i]
+               if varnode.is_const then
+                  node_error(varnode, "cannot assign to <const> variable")
+               end
+               if varnode.kind == "variable" then
+                  if widen_back_var(varnode.tk) then
+                     vartype = find_var(varnode.tk)
+                  end
+               end
+               if vartype then
+                  local val = exps[i]
+                  if resolve_unary(vartype).typename == "typetype" then
+                     node_error(varnode, "cannot reassign a type")
+                  elseif val then
+                     assert_is_a(varnode, val, vartype, "assignment")
+                     if varnode.kind == "variable" and vartype.typename == "union" then
+                        add_var(varnode, varnode.tk, val, false, true)
+                     end
+                  else
+                     node_error(varnode, "variable is not being assigned a value")
+                  end
+               else
+                  node_error(varnode, "unknown variable")
+               end
+            end
+            node.type = NONE
+         end,
+      },
+      ["do"] = {
+         after = function(node, children)
+            node.type = NONE
+         end,
+      },
+      ["if"] = {
+         before_statements = function(node)
+            begin_scope()
+            apply_facts(node.exp, node.exp.facts)
+         end,
+         after = function(node, children)
+            end_scope()
+            node.type = NONE
+         end,
+      },
+      ["elseif"] = {
+         before = function(node)
+            end_scope()
+            begin_scope()
+         end,
+         before_statements = function(node)
+            local f = facts_not(node.parent_if.exp.facts)
+            for e = 1, node.elseif_n - 1 do
+               f = facts_and(f, facts_not(node.parent_if.elseifs[e].exp.facts), node)
+            end
+            f = facts_and(f, node.exp.facts, node)
+            apply_facts(node.exp, f)
+         end,
+         after = function(node, children)
+            node.type = NONE
+         end,
+      },
+      ["else"] = {
+         before = function(node)
+            end_scope()
+            begin_scope()
+            local f = facts_not(node.parent_if.exp.facts)
+            for _, elseifnode in ipairs(node.parent_if.elseifs) do
+               f = facts_and(f, facts_not(elseifnode.exp.facts), node)
+            end
+            apply_facts(node, f)
+         end,
+         after = function(node, children)
+            node.type = NONE
+         end,
+      },
+      ["while"] = {
+         before = function()
+            widen_all_unions()
+         end,
+         before_statements = function(node)
+            begin_scope()
+            apply_facts(node.exp, node.exp.facts)
+         end,
+         after = function(node, children)
+            end_scope()
+            node.type = NONE
+         end,
+      },
+      ["label"] = {
+         before = function(node)
+            widen_all_unions()
+            local label_id = "::" .. node.label .. "::"
+            if st[#st][label_id] then
+               node_error(node, "label '" .. node.label .. "' already defined at " .. filename)
+            end
+            local unresolved = st[#st]["@unresolved"]
+            if unresolved then
+               unresolved.t.labels[node.label] = nil
+            end
+            node.type = a_type({ y = node.y, x = node.x, typename = "none" })
+            add_var(node, label_id, node.type)
+         end,
+      },
+      ["goto"] = {
+         after = function(node, children)
+            if not find_var("::" .. node.label .. "::") then
+               local unresolved = st[#st]["@unresolved"] and st[#st]["@unresolved"].t
+               if not unresolved then
+                  unresolved = { typename = "unresolved", labels = {}, nominals = {} }
+                  add_var(node, "@unresolved", unresolved)
+               end
+               unresolved.labels[node.label] = unresolved.labels[node.label] or {}
+               table.insert(unresolved.labels[node.label], node)
+            end
+            node.type = NONE
+         end,
+      },
+      ["repeat"] = {
+         before = function()
+            widen_all_unions()
+         end,
+         after = function(node, children)
+            end_scope()
+            node.type = NONE
+         end,
+      },
+      ["forin"] = {
+         before = function()
+            begin_scope()
+         end,
+         before_statements = function(node)
+            local exp1 = node.exps[1]
+            local exp1type = resolve_tuple(exp1.type)
+            if exp1type.typename == "function" then
+               if exp1.op and exp1.op.op == "@funcall" then
+                  local t = resolve_unary(exp1.e2.type)
+                  if exp1.e1.tk == "pairs" and not (t.typename == "map" or t.typename == "record") then
+                     if not (lax and is_unknown(t)) then
+                        node_error(exp1, "attempting pairs loop on something that's not a map or record: %s", exp1.e2.type)
+                     end
+                  elseif exp1.e1.tk == "ipairs" and not is_array_type(t) then
+                     if not (lax and (is_unknown(t) or t.typename == "emptytable")) then
+                        node_error(exp1, "attempting ipairs loop on something that's not an array: %s", exp1.e2.type)
+                     end
+                  end
+               end
+               local last
+               for i, v in ipairs(node.vars) do
+                  local r = exp1type.rets[i]
+                  if not r then
+                     if last and last.is_va then
+                        r = last
+                     else
+                        r = UNKNOWN
+                     end
+                  end
+                  add_var(v, v.tk, r)
+                  last = r
+               end
+            else
+               if not (lax and is_unknown(exp1type)) then
+                  node_error(exp1, "expression in for loop does not return an iterator")
+               end
+            end
+         end,
+         after = function(node, children)
+            end_scope()
+            node.type = NONE
+         end,
+      },
+      ["fornum"] = {
+         before = function(node)
+            begin_scope()
+            add_var(nil, node.var.tk, NUMBER)
+         end,
+         after = function(node, children)
+            end_scope()
+            node.type = NONE
+         end,
+      },
+      ["return"] = {
+         after = function(node, children)
+            local rets = assert(find_var("@return"))
+            local nrets = #rets
+            local vatype
+            if nrets > 0 then
+               vatype = rets[nrets].is_va and rets[nrets]
+            end
+            if #children[1] > nrets and (not lax) and not vatype then
+               rets.typename = "tuple"
+               children[1].typename = "tuple"
+               node_error(node, "excess return values, expected " .. #rets .. " %s, got " .. #children[1] .. " %s", rets, children[1])
+            end
+            for i = 1, #children[1] do
+               local expected = rets[i] or vatype
+               if expected then
+                  expected = resolve_unary(expected)
+                  local where = (node.exps[i] and node.exps[i].x) and
+                  node.exps[i] or
+                  node.exps
+                  assert(where and where.x)
+                  assert_is_a(where, children[1][i], expected, "return value")
+               end
+            end
+            if #st == 2 then
+               module_type = resolve_unary(children[1])
+            end
+            node.type = NONE
+         end,
+      },
+      ["variables"] = {
+         after = function(node, children)
+            node.type = children
+            local n = #children
+            if n > 0 and children[n].typename == "tuple" then
+               local tuple = children[n]
+               for i, c in ipairs(tuple) do
+                  children[n + i - 1] = c
+               end
+            end
+            node.type.typename = "tuple"
+         end,
+      },
+      ["table_literal"] = {
+         after = function(node, children)
+            node.type = a_type({
+               y = node.y,
+               x = node.x,
+               typename = "emptytable",
+            })
+            local is_record = false
+            local is_array = false
+            local is_map = false
+            for i, child in ipairs(children) do
+               assert(child.typename == "table_item")
+               if child.kname then
+                  is_record = true
+                  if not node.type.fields then
+                     node.type.fields = {}
+                     node.type.field_order = {}
+                  end
+                  node.type.fields[child.kname] = child.vtype
+                  table.insert(node.type.field_order, child.kname)
+               elseif child.ktype.typename == "number" then
+                  is_array = true
+                  if i == #children and node[i].key_parsed == "implicit" and child.vtype.typename == "tuple" then
+                     for _, c in ipairs(child.vtype) do
+                        node.type.elements = expand_type(node, node.type.elements, c)
+                     end
+                  else
+                     node.type.elements = expand_type(node, node.type.elements, child.vtype)
+                  end
+                  if not node.type.elements then
+                     node_error(node, "cannot determine type of array elements")
+                     is_array = false
+                  end
+               else
+                  is_map = true
+                  node.type.keys = expand_type(node, node.type.keys, child.ktype)
+                  node.type.values = expand_type(node, node.type.values, child.vtype)
+               end
+            end
+            if is_array and is_map then
+               node_error(node, "cannot determine type of table literal")
+            elseif is_record and is_array then
+               node.type.typename = "arrayrecord"
+            elseif is_record and is_map then
+               if node.type.keys.typename == "string" then
+                  node.type.typename = "map"
+                  for _, ftype in pairs(node.type.fields) do
+                     node.type.values = expand_type(node, node.type.values, ftype)
+                  end
+                  node.type.fields = nil
+                  node.type.field_order = nil
+               else
+                  node_error(node, "cannot determine type of table literal")
+               end
+            elseif is_array then
+               node.type.typename = "array"
+            elseif is_record then
+               node.type.typename = "record"
+            elseif is_map then
+               node.type.typename = "map"
+            end
+         end,
+      },
+      ["table_item"] = {
+         after = function(node, children)
+            local kname = node.key.conststr
+            local ktype = children[1]
+            local vtype = children[2]
+            if node.decltype then
+               vtype = node.decltype
+               assert_is_a(node.value, children[2], node.decltype, "table item")
+            end
+            node.type = a_type({
+               y = node.y,
+               x = node.x,
+               typename = "table_item",
+               kname = kname,
+               ktype = ktype,
+               vtype = vtype,
+            })
+         end,
+      },
+      ["local_function"] = {
+         before = function(node)
+            begin_function_scope(node, true)
+         end,
+         after = function(node, children)
+            end_function_scope()
+            local rets = get_rets(children[3])
+            add_var(nil, node.name.tk, a_type({
+               typename = "function",
+               args = children[2],
+               rets = rets,
+            }))
+            node.type = NONE
+         end,
+      },
+      ["global_function"] = {
+         before = function(node)
+            begin_function_scope(node, true)
+         end,
+         after = function(node, children)
+            end_function_scope()
+            add_global(nil, node.name.tk, a_type({
+               typename = "function",
+               args = children[2],
+               rets = get_rets(children[3]),
+            }))
+            node.type = NONE
+         end,
+      },
+      ["record_function"] = {
+         before = function(node)
+            begin_function_scope(node)
+         end,
+         before_statements = function(node, children)
+            if node.is_method then
+               local rtype = get_self_type(children[1])
+               children[3][1] = rtype
+               add_var(nil, "self", rtype)
+            end
+            local rtype = resolve_unary(get_self_type(children[1]))
+            if rtype.typename == "emptytable" then
+               rtype.typename = "record"
+            end
+            if is_record_type(rtype) then
+               local fn_type = a_type({
+                  y = node.y,
+                  x = node.x,
+                  typename = "function",
+                  is_method = node.is_method,
+                  args = children[3],
+                  rets = get_rets(children[4]),
+               })
+               local ok = false
+               if lax then
+                  ok = true
+               elseif rtype.fields and rtype.fields[node.name.tk] and is_a(fn_type, rtype.fields[node.name.tk]) then
+                  ok = true
+               elseif find_in_scope(node.fn_owner) == rtype then
+                  ok = true
+               end
+               if ok then
+                  rtype.fields = rtype.fields or {}
+                  rtype.field_order = rtype.field_order or {}
+                  rtype.fields[node.name.tk] = fn_type
+                  table.insert(rtype.field_order, node.name.tk)
+               else
+                  local name = tl.pretty_print_ast(node.fn_owner, { preserve_indent = true, preserve_newlines = false })
+                  node_error(node, "cannot add undeclared function '" .. node.name.tk .. "' outside of the scope where '" .. name .. "' was originally declared")
+               end
+            else
+               if (not lax) or (rtype.typename ~= "unknown") then
+                  node_error(node, "not a module: %s", rtype)
+               end
+            end
+         end,
+         after = function(node, children)
+            end_function_scope()
+            node.type = NONE
+         end,
+      },
+      ["function"] = {
+         before = function(node)
+            begin_function_scope(node)
+         end,
+         after = function(node, children)
+            end_function_scope()
+            node.type = a_type({
+               y = node.y,
+               x = node.x,
+               typename = "function",
+               args = children[1],
+               rets = children[2],
+            })
+         end,
+      },
+      ["cast"] = {
+         after = function(node, children)
+            node.type = node.casttype
+         end,
+      },
+      ["paren"] = {
+         after = function(node, children)
+            node.type = resolve_unary(children[1])
+         end,
+      },
+      ["op"] = {
+         before = function(node)
+            begin_scope()
+         end,
+         before_e2 = function(node)
+            if node.op.op == "and" then
+               apply_facts(node, node.e1.facts)
+            elseif node.op.op == "or" then
+               apply_facts(node, facts_not(node.e1.facts))
+            end
+         end,
+         after = function(node, children)
+            end_scope()
+            local a = children[1]
+            local b = children[3]
+            local orig_a = a
+            local orig_b = b
+            local ua = a and resolve_unary(a)
+            local ub = b and resolve_unary(b)
+            if node.op.op == "@funcall" then
+               node.type = type_check_funcall(node, a, b)
+            elseif node.op.op == "@index" then
+               node.type = type_check_index(node, node.e2, a, b)
+            elseif node.op.op == "as" then
+               node.type = b
+            elseif node.op.op == "is" then
+               if node.e1.kind == "variable" then
+                  node.facts = { { fact = "is", var = node.e1.tk, typ = b } }
+               else
+                  node_error(node, "can only use 'is' on variables")
+               end
+               node.type = BOOLEAN
+            elseif node.op.op == "." then
+               a = ua
+               if a.typename == "map" then
+                  if is_a(a.keys, STRING) or is_a(a.keys, ANY) then
+                     node.type = a.values
+                  else
+                     node_error(node, "cannot use . index, expects keys of type %s", a.keys)
+                  end
+               else
+                  node.type = match_record_key(node, a, { y = node.e2.y, x = node.e2.x, kind = "string", tk = node.e2.tk }, orig_a)
+                  if node.type.needs_compat53 and not opts.skip_compat53 then
+                     local key = node.e1.tk .. "." .. node.e2.tk
+                     node.kind = "variable"
+                     node.tk = "_tl_" .. node.e1.tk .. "_" .. node.e2.tk
+                     all_needs_compat53[key] = true
+                  end
+               end
+            elseif node.op.op == ":" then
+               node.type = match_record_key(node, node.e1.type, node.e2, orig_a)
+            elseif node.op.op == "not" then
+               node.facts = facts_not(node.e1.facts)
+               node.type = BOOLEAN
+            elseif node.op.op == "and" then
+               node.facts = facts_and(node.e1.facts, node.e2.facts, node)
+               node.type = resolve_tuple(b)
+            elseif node.op.op == "or" and b.typename == "emptytable" then
+               node.facts = nil
+               node.type = resolve_tuple(a)
+            elseif node.op.op == "or" and same_type(ua, ub) then
+               node.facts = facts_or(node.e1.facts, node.e2.facts)
+               node.type = resolve_tuple(a)
+            elseif node.op.op == "or" and b.typename == "nil" then
+               node.facts = nil
+               node.type = resolve_tuple(a)
+            elseif node.op.op == "or" and
+               ((ua.typename == "enum" and ub.typename == "string" and is_a(ub, ua)) or
+               (ua.typename == "string" and ub.typename == "enum" and is_a(ua, ub))) then
+               node.facts = nil
+               node.type = (ua.typename == "enum" and ua or ub)
+            elseif node.op.op == "or" and
+               (a.typename == "nominal" or a.typename == "map") and
+               is_record_type(b) and
+               is_a(b, a) then
+               node.facts = nil
+               node.type = resolve_tuple(a)
+            elseif node.op.op == "==" or node.op.op == "~=" then
+               if is_a(a, b, true) or is_a(b, a, true) then
+                  node.type = BOOLEAN
+               else
+                  if lax and (is_unknown(a) or is_unknown(b)) then
+                     node.type = UNKNOWN
+                  else
+                     node_error(node, "types are not comparable for equality: %s and %s", a, b)
+                  end
+               end
+            elseif node.op.arity == 1 and unop_types[node.op.op] then
+               a = ua
+               local types_op = unop_types[node.op.op]
+               node.type = types_op[a.typename]
+               if not node.type then
+                  if lax and is_unknown(a) then
+                     node.type = UNKNOWN
+                  else
+                     node_error(node, "cannot use operator '" .. node.op.op:gsub("%%", "%%%%") .. "' on type %s", orig_a)
+                  end
+               end
+            elseif node.op.arity == 2 and binop_types[node.op.op] then
+               if node.op.op == "or" then
+                  node.facts = facts_or(node.e1.facts, node.e2.facts)
+               end
+               a = ua
+               b = ub
+               local types_op = binop_types[node.op.op]
+               node.type = types_op[a.typename] and types_op[a.typename][b.typename]
+               if not node.type then
+                  if lax and (is_unknown(a) or is_unknown(b)) then
+                     node.type = UNKNOWN
+                  else
+                     node_error(node, "cannot use operator '" .. node.op.op:gsub("%%", "%%%%") .. "' for types %s and %s", orig_a, orig_b)
+                  end
+               end
+            else
+               error("unknown node op " .. node.op.op)
+            end
+         end,
+      },
+      ["variable"] = {
+         after = function(node, children)
+            if node.tk == "..." then
+               local va_sentinel = find_var("@is_va")
+               if not va_sentinel or va_sentinel.typename == "nil" then
+                  node.type = UNKNOWN
+                  node_error(node, "cannot use '...' outside a vararg function")
+               end
+            end
+            node.type, node.is_const = find_var(node.tk)
+            if node.type == nil then
+               node.type = a_type({ typename = "unknown" })
+               if lax then
+                  add_unknown(node, node.tk)
+               else
+                  node_error(node, "unknown variable: " .. node.tk)
+               end
+            end
+         end,
+      },
+      ["identifier"] = {
+         after = function(node, children)
+            node.type = NONE
+         end,
+      },
+      ["newtype"] = {
+         after = function(node, children)
+            node.type = node.newtype
+         end,
+      },
+   }
+   visit_node.cbs["break"] = visit_node.cbs["do"]
+   visit_node.cbs["values"] = visit_node.cbs["variables"]
+   visit_node.cbs["expression_list"] = visit_node.cbs["variables"]
+   visit_node.cbs["argument_list"] = visit_node.cbs["variables"]
+   visit_node.cbs["argument"] = visit_node.cbs["variable"]
+   visit_node.cbs["string"] = {
+      after = function(node, children)
+         node.type = a_type({
+            y = node.y,
+            x = node.x,
+            typename = node.kind,
+            tk = node.tk,
+         })
+         return node.type
+      end,
+   }
+   visit_node.cbs["number"] = visit_node.cbs["string"]
+   visit_node.cbs["nil"] = visit_node.cbs["string"]
+   visit_node.cbs["boolean"] = visit_node.cbs["string"]
+   visit_node.cbs["..."] = visit_node.cbs["variable"]
+   visit_node.after = {
+      after = function(node, children)
+         assert(type(node.type) == "table", node.kind .. " did not produce a type")
+         assert(type(node.type.typename) == "string", node.kind .. " type does not have a typename")
+         return node.type
+      end,
+   }
+   local visit_type = {
+      cbs = {
+         ["string"] = {
+            after = function(typ, children)
+               return typ
+            end,
+         },
+         ["function"] = {
+            before = function(typ, children)
+               begin_scope()
+            end,
+            after = function(typ, children)
+               end_scope()
+               return typ
+            end,
+         },
+         ["record"] = {
+            before = function(typ, children)
+               begin_scope()
+               for name, typ in pairs(typ.fields) do
+                  if typ.typename == "typetype" then
+                     typ.typename = "nestedtype"
+                     add_var(nil, name, typ)
+                  end
+               end
+            end,
+            after = function(typ, children)
+               end_scope()
+               for name, typ in pairs(typ.fields) do
+                  if typ.typename == "nestedtype" then
+                     typ.typename = "typetype"
+                  end
+               end
+               return typ
+            end,
+         },
+         ["typearg"] = {
+            after = function(typ, children)
+               add_var(nil, typ.typearg, a_type({
+                  y = typ.y,
+                  x = typ.x,
+                  typename = "typearg",
+                  typearg = typ.typearg,
+               }))
+               return typ
+            end,
+         },
+         ["nominal"] = {
+            after = function(typ, children)
+               local t = find_type(typ.names, true)
+               if t then
+                  if t.typename == "typearg" then
+                     typ.names = nil
+                     typ.typename = "typevar"
+                     typ.typevar = t.typearg
+                  else
+                     typ.found = t
+                  end
+               else
+                  local name = typ.names[1]
+                  local unresolved = find_var("@unresolved")
+                  if not unresolved then
+                     unresolved = { typename = "unresolved", labels = {}, nominals = {} }
+                     add_var(nil, "@unresolved", unresolved)
+                  end
+                  unresolved.nominals[name] = unresolved.nominals[name] or {}
+                  table.insert(unresolved.nominals[name], typ)
+               end
+               return typ
+            end,
+         },
+         ["union"] = {
+            after = function(typ, children)
+               local n_table_types = 0
+               local n_function_types = 0
+               local n_string_enum = 0
+               for _, t in ipairs(typ.types) do
+                  t = resolve_unary(t)
+                  if table_types[t.typename] then
+                     n_table_types = n_table_types + 1
+                     if n_table_types > 1 then
+                        type_error(typ, "cannot discriminate a union between multiple table types: %s", typ)
+                        break
+                     end
+                  elseif t.typename == "function" then
+                     n_function_types = n_function_types + 1
+                     if n_function_types > 1 then
+                        type_error(typ, "cannot discriminate a union between multiple function types: %s", typ)
+                        break
+                     end
+                  elseif t.typename == "string" or t.typename == "enum" then
+                     n_string_enum = n_string_enum + 1
+                     if n_string_enum > 1 then
+                        type_error(typ, "cannot discriminate a union between multiple string/enum types: %s", typ)
+                        break
+                     end
+                  end
+               end
+               return typ
+            end,
+         },
+      },
+      after = {
+         after = function(typ, children, ret)
+            assert(type(ret) == "table", typ.typename .. " did not produce a type")
+            assert(type(ret.typename) == "string", "type node does not have a typename")
+            return ret
+         end,
+      },
+   }
+   visit_type.cbs["typetype"] = visit_type.cbs["string"]
+   visit_type.cbs["nestedtype"] = visit_type.cbs["string"]
+   visit_type.cbs["typevar"] = visit_type.cbs["string"]
+   visit_type.cbs["array"] = visit_type.cbs["string"]
+   visit_type.cbs["map"] = visit_type.cbs["string"]
+   visit_type.cbs["arrayrecord"] = visit_type.cbs["string"]
+   visit_type.cbs["enum"] = visit_type.cbs["string"]
+   visit_type.cbs["boolean"] = visit_type.cbs["string"]
+   visit_type.cbs["nil"] = visit_type.cbs["string"]
+   visit_type.cbs["number"] = visit_type.cbs["string"]
+   visit_type.cbs["thread"] = visit_type.cbs["string"]
+   visit_type.cbs["bad_nominal"] = visit_type.cbs["string"]
+   visit_type.cbs["emptytable"] = visit_type.cbs["string"]
+   visit_type.cbs["table_item"] = visit_type.cbs["string"]
+   visit_type.cbs["unknown_emptytable_value"] = visit_type.cbs["string"]
+   visit_type.cbs["tuple"] = visit_type.cbs["string"]
+   visit_type.cbs["poly"] = visit_type.cbs["string"]
+   visit_type.cbs["any"] = visit_type.cbs["string"]
+   visit_type.cbs["unknown"] = visit_type.cbs["string"]
+   visit_type.cbs["invalid"] = visit_type.cbs["string"]
+   visit_type.cbs["unresolved"] = visit_type.cbs["string"]
+   visit_type.cbs["none"] = visit_type.cbs["string"]
+   recurse_node(ast, visit_node, visit_type)
+   close_types(st[1])
+   local redundant = {}
+   local lastx, lasty = 0, 0
+   table.sort(errors, function(a, b)
+      return ((a.filename and b.filename) and a.filename < b.filename) or
+      (a.filename == b.filename and ((a.y < b.y) or (a.y == b.y and a.x < b.x)))
+   end)
+   for i, err in ipairs(errors) do
+      if err.x == lastx and err.y == lasty then
+         table.insert(redundant, i)
+      end
+      lastx, lasty = err.x, err.y
+   end
+   for i = #redundant, 1, -1 do
+      table.remove(errors, redundant[i])
+   end
+   if not opts.skip_compat53 then
+      add_compat53_entries(ast, all_needs_compat53)
+   end
+   return errors, unknowns, module_type
+end
+function tl.process(filename, env, result, preload_modules)
+   local fd, err = io.open(filename, "r")
+   if not fd then
+      return nil, "could not open " .. filename .. ": " .. err
+   end
+   local input, err = fd:read("*a")
+   fd:close()
+   if not input then
+      return nil, "could not read " .. filename .. ": " .. err
+   end
+   local basename, extension = filename:match("(.*)%.([a-z]+)$")
+   extension = extension and extension:lower()
+   local is_lua
+   if extension == "tl" then
+      is_lua = false
+   elseif extension == "lua" then
+      is_lua = true
+   else
+      is_lua = input:match("^#![^\n]*lua[^\n]*\n")
+   end
+   result, err = tl.process_string(input, is_lua, env, result, preload_modules, filename)
+   if err then
+      return nil, err
+   end
+   return result
+end
+function tl.process_string(input, is_lua, env, result, preload_modules,
+filename)
+   env = env or tl.init_env(is_lua)
+   result = result or {
+      syntax_errors = {},
+      type_errors = {},
+      unknowns = {},
+   }
+   preload_modules = preload_modules or {}
+   filename = filename or ""
+   local tokens, errs = tl.lex(input)
+   if errs then
+      for i, err in ipairs(errs) do
+         table.insert(result.syntax_errors, {
+            y = err.y,
+            x = err.x,
+            msg = "invalid token '" .. err.tk .. "'",
+            filename = filename,
+         })
+      end
+   end
+   local i, program = tl.parse_program(tokens, result.syntax_errors, filename)
+   if #result.syntax_errors > 0 then
+      return result
+   end
+   for _, name in ipairs(preload_modules) do
+      local module_type = require_module(name, is_lua, env, result)
+      if module_type == UNKNOWN then
+         return nil, string.format("Error: could not preload module '%s'", name)
+      end
+   end
+   local error, unknown
+   local opts = {
+      lax = is_lua,
+      filename = filename,
+      env = env,
+      result = result,
+      skip_compat53 = env.skip_compat53,
+   }
+   error, unknown, result.type = tl.type_check(program, opts)
+   result.ast = program
+   result.env = env
+   return result
+end
+function tl.gen(input, env)
+   env = env or tl.init_env()
+   local result, err = tl.process_string(input, false, env)
+   if err then
+      return nil, nil
+   end
+   if not result.ast then
+      return nil, result
+   end
+   return tl.pretty_print_ast(result.ast), result
+end
+local function tl_package_loader(module_name)
+   local found_filename, fd, tried = tl.search_module(module_name, false)
+   if found_filename then
+      local input = fd:read("*a")
+      fd:close()
+      local errs = {}
+      local _, program = tl.parse_program(tl.lex(input), errs, module_name)
+      if #errs > 0 then
+         error(module_name .. ":" .. errs[1].y .. ":" .. errs[1].x .. ": " .. errs[1].msg)
+      end
+      local code = tl.pretty_print_ast(program, true)
+      local chunk, err = load(code, module_name, "t")
+      if chunk then
+         return function()
+            local ret = chunk()
+            package.loaded[module_name] = ret
+            return ret
+         end
+      else
+         error("Internal Compiler Error: Teal generator produced invalid Lua. Please report a bug at https://github.com/teal-language/tl")
+      end
+   end
+   return table.concat(tried, "\n\t")
+end
+function tl.loader()
+   if package.searchers then
+      table.insert(package.searchers, 2, tl_package_loader)
+   else
+      table.insert(package.loaders, 2, tl_package_loader)
+   end
+end
+function tl.load(input, chunkname, mode, env)
+   local tokens = tl.lex(input)
+   local errs = {}
+   local i, program = tl.parse_program(tokens, errs, chunkname)
+   if #errs > 0 then
+      return nil, (chunkname or "") .. ":" .. errs[1].y .. ":" .. errs[1].x .. ": " .. errs[1].msg
+   end
+   local code = tl.pretty_print_ast(program, true)
+   return load(code, chunkname, mode, env)
+end
+return tl
author	Li Jin <dragon-fly@qq.com>	2020-10-23 17:32:48 +0800
committer	Li Jin <dragon-fly@qq.com>	2020-10-23 17:32:48 +0800
commit	1c6a9651beffd9cbbb3641179f3a738d5555d3c9 (patch)
tree	31f442c3685bf19e851f62c4b2957d445e313eac /spec
parent	a51a728d847e790329e41c75928a81630200b63f (diff)
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