From 47cffdc723c2e0c6dfaf62b7775ca1c1d338c0a4 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Wed, 7 Apr 2021 14:59:26 -0300
Subject: Bug: tbc variables in "for" loops don't avoid tail calls

---
 lparser.c         | 21 +++++++++++++++------
 testes/locals.lua | 23 +++++++++++++++++++++++
 2 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/lparser.c b/lparser.c
index 284ef1f0..df9473c2 100644
--- a/lparser.c
+++ b/lparser.c
@@ -416,6 +416,17 @@ static void markupval (FuncState *fs, int level) {
 }
 
 
+/*
+** Mark that current block has a to-be-closed variable.
+*/
+static void marktobeclosed (FuncState *fs) {
+  BlockCnt *bl = fs->bl;
+  bl->upval = 1;
+  bl->insidetbc = 1;
+  fs->needclose = 1;
+}
+
+
 /*
 ** Find a variable with the given name 'n'. If it is an upvalue, add
 ** this upvalue into all intermediate functions. If it is a global, set
@@ -1599,7 +1610,7 @@ static void forlist (LexState *ls, TString *indexname) {
   line = ls->linenumber;
   adjust_assign(ls, 4, explist(ls, &e), &e);
   adjustlocalvars(ls, 4);  /* control variables */
-  markupval(fs, fs->nactvar);  /* last control var. must be closed */
+  marktobeclosed(fs);  /* last control var. must be closed */
   luaK_checkstack(fs, 3);  /* extra space to call generator */
   forbody(ls, base, line, nvars - 4, 1);
 }
@@ -1703,11 +1714,9 @@ static int getlocalattribute (LexState *ls) {
 }
 
 
-static void checktoclose (LexState *ls, int level) {
+static void checktoclose (FuncState *fs, int level) {
   if (level != -1) {  /* is there a to-be-closed variable? */
-    FuncState *fs = ls->fs;
-    markupval(fs, level + 1);
-    fs->bl->insidetbc = 1;  /* in the scope of a to-be-closed variable */
+    marktobeclosed(fs);
     luaK_codeABC(fs, OP_TBC, reglevel(fs, level), 0, 0);
   }
 }
@@ -1751,7 +1760,7 @@ static void localstat (LexState *ls) {
     adjust_assign(ls, nvars, nexps, &e);
     adjustlocalvars(ls, nvars);
   }
-  checktoclose(ls, toclose);
+  checktoclose(fs, toclose);
 }
 
 
diff --git a/testes/locals.lua b/testes/locals.lua
index 2c67edbd..6aad5d25 100644
--- a/testes/locals.lua
+++ b/testes/locals.lua
@@ -335,6 +335,29 @@ do
 end
 
 
+do
+  -- bug in 5.4.3: previous condition (calls cannot be tail in the
+  -- scope of to-be-closed variables) must be valid for tbc variables
+  -- created by 'for' loops.
+
+  local closed = false
+
+  local function foo ()
+    return function () return true end, 0, 0,
+           func2close(function () closed = true end)
+  end
+
+  local function tail() return closed end
+
+  local function foo1 ()
+    for k in foo() do return tail() end
+  end
+
+  assert(foo1() == false)
+  assert(closed == true)
+end
+
+
 do print("testing errors in __close")
 
   -- original error is in __close
-- 
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