8 files changed, 98 insertions, 26 deletions

diff --git a/doc/docs/doc/README.md b/doc/docs/doc/README.md
index dac96ee..1142fc3 100755
--- a/doc/docs/doc/README.md
+++ b/doc/docs/doc/README.md
@@ -1513,6 +1513,17 @@ const {:a, :b, c, d} = tb
 </pre>
 </YueDisplay>
 
+You can also declare a global variable to be `const`.
+
+```moonscript
+global const Constant = 123
+```
+<YueDisplay>
+<pre>
+global const Constant = 123
+</pre>
+</YueDisplay>
+
 ## Literals
 
 All of the primitive literals in Lua can be used. This applies to numbers, strings, booleans, and **nil**.
diff --git a/doc/docs/zh/doc/README.md b/doc/docs/zh/doc/README.md
index 850afed..a4e76bb 100755
--- a/doc/docs/zh/doc/README.md
+++ b/doc/docs/zh/doc/README.md
@@ -1512,6 +1512,17 @@ const {:a, :b, c, d} = tb
 </pre>
 </YueDisplay>
 
+你也可以声明全局变量为常量。
+
+```moonscript
+global const Constant = 123
+```
+<YueDisplay>
+<pre>
+global const Constant = 123
+</pre>
+</YueDisplay>
+
 ## 字面量
 
 Lua中的所有基本字面量都可以在月之脚本中使用。包括数字、字符串、布尔值和**nil**。
diff --git a/spec/inputs/global.yue b/spec/inputs/global.yue
index ce1cc15..8316d16 100644
--- a/spec/inputs/global.yue
+++ b/spec/inputs/global.yue
@@ -82,3 +82,8 @@ do
         FooBar = "pascal case"
         FOOBAR = "all uppercase"
 
+do
+        global const class A
+        global const Flag = 1
+        global const const, x, y = "const", 1, 2
+
diff --git a/spec/outputs/global.lua b/spec/outputs/global.lua
index 54a21a9..3918f85 100644
--- a/spec/outputs/global.lua
+++ b/spec/outputs/global.lua
@@ -93,3 +93,28 @@ do
         FooBar = "pascal case"
         FOOBAR = "all uppercase"
 end
+do
+        do
+                local _class_0
+                local _base_0 = { }
+                if _base_0.__index == nil then
+                        _base_0.__index = _base_0
+                end
+                _class_0 = setmetatable({
+                        __init = function() end,
+                        __base = _base_0,
+                        __name = "A"
+                }, {
+                        __index = _base_0,
+                        __call = function(cls, ...)
+                                local _self_0 = setmetatable({ }, _base_0)
+                                cls.__init(_self_0, ...)
+                                return _self_0
+                        end
+                })
+                _base_0.__class = _class_0
+                A = _class_0
+        end
+        Flag = 1
+        const, x, y = "const", 1, 2
+end
diff --git a/src/yuescript/yue_ast.cpp b/src/yuescript/yue_ast.cpp
index 612bdcd..56e3447 100644
--- a/src/yuescript/yue_ast.cpp
+++ b/src/yuescript/yue_ast.cpp
@@ -170,9 +170,8 @@ std::string TableAppendingOp_t::to_string(void*) const {
 std::string PlainItem_t::to_string(void *) const {
         return {};
 }
-std::string GlobalOp_t::to_string(void* ud) const {
-        auto info = reinterpret_cast<YueFormat*>(ud);
-        return info->convert(this);
+std::string GlobalOp_t::to_string(void*) const {
+        return "*"s;
 }
 std::string ExportDefault_t::to_string(void*) const {
         return "default"s;
@@ -1133,7 +1132,7 @@ std::string ClassDecl_t::to_string(void* ud) const {
         return line;
 }
 std::string GlobalValues_t::to_string(void* ud) const {
-        auto line = nameList->to_string(ud);
+        std::string line = nameList->to_string(ud);
         if (valueList) {
                 if (valueList.is<TableBlock_t>()) {
                         line += " =\n"s + valueList->to_string(ud);
@@ -1144,7 +1143,7 @@ std::string GlobalValues_t::to_string(void* ud) const {
         return line;
 }
 std::string Global_t::to_string(void* ud) const {
-        return "global "s + item->to_string(ud);
+        return "global "s + (constAttrib ? "const "s : ""s) + item->to_string(ud);
 }
 std::string Export_t::to_string(void* ud) const {
         auto line = "export"s;
diff --git a/src/yuescript/yue_ast.h b/src/yuescript/yue_ast.h
index 782db5a..8501a19 100644
--- a/src/yuescript/yue_ast.h
+++ b/src/yuescript/yue_ast.h
@@ -727,8 +727,9 @@ AST_LEAF(GlobalOp)
 AST_END(GlobalOp)
 
 AST_NODE(Global)
+        ast_ptr<false, ConstAttrib_t> constAttrib;
         ast_sel<true, ClassDecl_t, GlobalOp_t, GlobalValues_t> item;
-        AST_MEMBER(Global, &item)
+        AST_MEMBER(Global, &constAttrib, &item)
 AST_END(Global)
 
 AST_LEAF(ExportDefault)
diff --git a/src/yuescript/yue_compiler.cpp b/src/yuescript/yue_compiler.cpp
index 1a9387b..452ffbd 100644
--- a/src/yuescript/yue_compiler.cpp
+++ b/src/yuescript/yue_compiler.cpp
@@ -429,8 +429,9 @@ private:
         };
         enum class VarType {
                 Local = 0,
-                Const = 1,
-                Global = 2
+                LocalConst = 1,
+                Global = 2,
+                GlobalConst = 3
         };
         struct Scope {
                 GlobalMode mode = GlobalMode::None;
@@ -558,7 +559,7 @@ private:
                 for (auto it = _scopes.rbegin(); it != _scopes.rend(); ++it) {
                         auto vars = it->vars.get();
                         auto vit = vars->find(name);
-                        if (vit != vars->end() && vit->second != VarType::Global) {
+                        if (vit != vars->end() && (vit->second == VarType::Local || vit->second == VarType::LocalConst)) {
                                 local = true;
                                 break;
                         }
@@ -571,7 +572,7 @@ private:
                 for (auto it = _scopes.rbegin(); it != _scopes.rend(); ++it) {
                         auto vars = it->vars.get();
                         auto vit = vars->find(name);
-                        if (vit != vars->end() && vit->second == VarType::Global) {
+                        if (vit != vars->end() && (vit->second == VarType::Global || vit->second == VarType::GlobalConst)) {
                                 global = true;
                                 break;
                         }
@@ -593,7 +594,7 @@ private:
                         auto vars = it->vars.get();
                         auto vit = vars->find(name);
                         if (vit != vars->end()) {
-                                isConst = (vit->second == VarType::Const);
+                                isConst = (vit->second == VarType::LocalConst || vit->second == VarType::GlobalConst);
                                 break;
                         }
                         if (checkShadowScopeOnly && it->allows) break;
@@ -874,9 +875,9 @@ private:
                 return false;
         }
 
-        void markVarConst(const std::string& name) {
+        void markVarLocalConst(const std::string& name) {
                 auto& scope = _scopes.back();
-                scope.vars->insert_or_assign(name, VarType::Const);
+                scope.vars->insert_or_assign(name, VarType::LocalConst);
         }
 
         void markVarShadowed() {
@@ -895,6 +896,11 @@ private:
                 scope.vars->insert_or_assign(name, VarType::Global);
         }
 
+        void markVarGlobalConst(const std::string& name) {
+                auto& scope = _scopes.back();
+                scope.vars->insert_or_assign(name, VarType::GlobalConst);
+        }
+
         void addToAllowList(const std::string& name) {
                 auto& scope = _scopes.back();
                 scope.allows->insert(name);
@@ -2051,7 +2057,7 @@ private:
                                         if (item.targetVar.empty()) {
                                                 throw CompileError("can only declare variable as const"sv, item.target);
                                         }
-                                        markVarConst(item.targetVar);
+                                        markVarLocalConst(item.targetVar);
                                 }
                         }
                 }
@@ -8064,7 +8070,7 @@ private:
                 pushScope();
                 for (const auto& var : vars) forceAddToScope(var);
                 for (const auto& var : varAfter) addToScope(var);
-                if (!varConstAfter.empty()) markVarConst(varConstAfter);
+                if (!varConstAfter.empty()) markVarLocalConst(varConstAfter);
                 if (!destructPairs.empty()) {
                         temp.clear();
                         for (auto& pair : destructPairs) {
@@ -8149,7 +8155,7 @@ private:
                 _buf << indent() << "for "sv << varName << " = "sv << start << ", "sv << stop << (step.empty() ? Empty : ", "s + step) << " do"sv << nll(var);
                 pushScope();
                 forceAddToScope(varName);
-                markVarConst(varName);
+                markVarLocalConst(varName);
                 out.push_back(clearBuf());
         }
 
@@ -8923,7 +8929,7 @@ private:
                                                 auto names = transformAssignDefs(assignment->expList.get(), DefOp::Get);
                                                 for (const auto& name : names) {
                                                         forceAddToScope(name.first);
-                                                        markVarConst(name.first);
+                                                        markVarLocalConst(name.first);
                                                         varDefs.push_back(name.first);
                                                         classConstVars.push_back(name.first);
                                                 }
@@ -8937,7 +8943,7 @@ private:
                                                                 for (const auto& item : destruct.items) {
                                                                         if (!item.targetVar.empty()) {
                                                                                 forceAddToScope(item.targetVar);
-                                                                                markVarConst(item.targetVar);
+                                                                                markVarLocalConst(item.targetVar);
                                                                                 varDefs.push_back(item.targetVar);
                                                                                 classConstVars.push_back(item.targetVar);
                                                                         }
@@ -9511,12 +9517,18 @@ private:
                 switch (item->get_id()) {
                         case id<ClassDecl_t>(): {
                                 auto classDecl = static_cast<ClassDecl_t*>(item);
+                                std::string varName;
                                 if (classDecl->name) {
                                         if (auto var = classDecl->name->item.as<Variable_t>()) {
-                                                addGlobalVar(variableToString(var), classDecl->name->item);
+                                                varName = variableToString(var);
+                                                addGlobalVar(varName, var);
                                         }
                                 }
+                                if (varName.empty()) {
+                                        throw CompileError("missing name for class", classDecl);
+                                }
                                 transformClassDecl(classDecl, out, ExpUsage::Common);
+                                markVarGlobalConst(varName);
                                 break;
                         }
                         case id<GlobalOp_t>():
@@ -9530,9 +9542,11 @@ private:
                                 auto values = global->item.to<GlobalValues_t>();
                                 if (values->valueList) {
                                         auto expList = x->new_ptr<ExpList_t>();
+                                        str_list varNames;
                                         for (auto name : values->nameList->names.objects()) {
                                                 auto var = static_cast<Variable_t*>(name);
-                                                addGlobalVar(variableToString(var), var);
+                                                varNames.emplace_back(variableToString(var));
+                                                addGlobalVar(varNames.back(), var);
                                                 auto callable = x->new_ptr<Callable_t>();
                                                 callable->item.set(name);
                                                 auto chainValue = x->new_ptr<ChainValue_t>();
@@ -9551,7 +9565,13 @@ private:
                                         }
                                         assignment->action.set(assign);
                                         transformAssignment(assignment, out);
+                                        for (const auto& name : varNames) {
+                                                markVarGlobalConst(name);
+                                        }
                                 } else {
+                                        if (global->constAttrib) {
+                                                throw CompileError("missing initial value for global const", global->constAttrib);
+                                        }
                                         for (auto name : values->nameList->names.objects()) {
                                                 auto var = static_cast<Variable_t*>(name);
                                                 addGlobalVar(variableToString(var), var);
@@ -10216,7 +10236,7 @@ private:
                 out.push_back(join(temp));
                 auto vars = getAssignVars(assignment);
                 for (const auto& var : vars) {
-                        markVarConst(var);
+                        markVarLocalConst(var);
                 }
         }
 
@@ -10444,7 +10464,7 @@ private:
                 transformAssignment(assignment, out);
                 if (auto var = ast_cast<Variable_t>(target)) {
                         auto moduleName = variableToString(var);
-                        markVarConst(moduleName);
+                        markVarLocalConst(moduleName);
                 } else {
                         markDestructureConst(assignment);
                 }
@@ -11028,7 +11048,7 @@ private:
                         }
                         transformAssignment(assignment, temp);
                         for (const auto& name : vars) {
-                                markVarConst(name);
+                                markVarLocalConst(name);
                         }
                         if (localAttrib->attrib.is<CloseAttrib_t>()) {
                                 str_list leftVars, rightVars;
@@ -11100,7 +11120,7 @@ private:
                                 temp.push_back(indent() + "local "s + join(leftVars, ", "sv) + " = "s + join(items, ", "sv) + nll(x));
                         }
                         for (const auto& var : vars) {
-                                markVarConst(var);
+                                markVarLocalConst(var);
                         }
                 }
                 if (!listB->exprs.empty()) {
@@ -11125,7 +11145,7 @@ private:
                         temp.push_back(indent() + "local "s + join(vars, ", "sv) + nll(x));
                         transformAssignment(assignment, temp);
                         for (const auto& name : vars) {
-                                markVarConst(name);
+                                markVarLocalConst(name);
                         }
                 }
                 out.push_back(join(temp));
diff --git a/src/yuescript/yue_parser.cpp b/src/yuescript/yue_parser.cpp
index eaabf0d..045e2c7 100644
--- a/src/yuescript/yue_parser.cpp
+++ b/src/yuescript/yue_parser.cpp
@@ -761,7 +761,7 @@ YueParser::YueParser() {
 
         GlobalValues = NameList >> -(space >> '=' >> space >> (TableBlock | ExpListLow));
         GlobalOp = expr('*') | '^';
-        Global = key("global") >> space >> (ClassDecl | GlobalOp | GlobalValues);
+        Global = key("global") >> space >> (-(ConstAttrib >> space) >> ClassDecl | GlobalOp | -(ConstAttrib >> space) >> GlobalValues);
 
         ExportDefault = key("default");