From 4cd1f4aac01184765818e0cebf02da454ccf6590 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 8 Oct 2018 10:42:07 -0300
Subject: Towards "to closed" local variables

Start of the implementation of "scoped variables" or "to be closed"
variables, local variables whose '__close' (or themselves) are called
when they go out of scope. This commit implements the syntax, the
opcode, and the creation of the corresponding upvalue, but it still
does not call the finalizations when the variable goes out of scope
(the most important part).

Currently, the syntax is 'local scoped name = exp', but that will
probably change.
---
 lparser.c | 34 ++++++++++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 4 deletions(-)

(limited to 'lparser.c')

diff --git a/lparser.c b/lparser.c
index 32500b02..84abeb90 100644
--- a/lparser.c
+++ b/lparser.c
@@ -255,6 +255,7 @@ static void markupval (FuncState *fs, int level) {
   while (bl->nactvar > level)
     bl = bl->previous;
   bl->upval = 1;
+  fs->needclose = 1;
 }
 
 
@@ -547,6 +548,7 @@ static void open_func (LexState *ls, FuncState *fs, BlockCnt *bl) {
   fs->nups = 0;
   fs->nlocvars = 0;
   fs->nactvar = 0;
+  fs->needclose = 0;
   fs->firstlocal = ls->dyd->actvar.n;
   fs->bl = NULL;
   f->source = ls->source;
@@ -1509,15 +1511,16 @@ static void localfunc (LexState *ls) {
 }
 
 
-static void localstat (LexState *ls) {
+static void commonlocalstat (LexState *ls, TString *firstvar) {
   /* stat -> LOCAL NAME {',' NAME} ['=' explist] */
-  int nvars = 0;
+  int nvars = 1;
   int nexps;
   expdesc e;
-  do {
+  new_localvar(ls, firstvar);
+  while (testnext(ls, ',')) {
     new_localvar(ls, str_checkname(ls));
     nvars++;
-  } while (testnext(ls, ','));
+  }
   if (testnext(ls, '='))
     nexps = explist(ls, &e);
   else {
@@ -1529,6 +1532,29 @@ static void localstat (LexState *ls) {
 }
 
 
+static void scopedlocalstat (LexState *ls) {
+  FuncState *fs = ls->fs;
+  new_localvar(ls, str_checkname(ls));
+  checknext(ls, '=');
+  luaK_codeABC(fs, OP_TBC, fs->nactvar, 0, 0);
+  markupval(fs, fs->nactvar);
+  exp1(ls, 0);
+  adjustlocalvars(ls, 1);
+}
+
+
+static void localstat (LexState *ls) {
+  /* stat -> LOCAL NAME {',' NAME} ['=' explist]
+           | LOCAL SCOPED NAME '=' exp */
+  TString *firstvar = str_checkname(ls);
+  if (ls->t.token == TK_NAME &&
+      eqshrstr(firstvar, luaS_newliteral(ls->L, "scoped")))
+    scopedlocalstat(ls);
+  else
+    commonlocalstat(ls, firstvar);
+}
+
+
 static int funcname (LexState *ls, expdesc *v) {
   /* funcname -> NAME {fieldsel} [':' NAME] */
   int ismethod = 0;
-- 
cgit v1.2.3-55-g6feb