[parser] Fix tail calls in for in/of loops

According to the ES6 specification, in "for in/of" loops like:

   for (var v of [1,2,3]) return f(...);

the call to f() should not be considered a tail call.  This was
not working properly, i.e., the case without declarations:

   var v;
   for (v of [1,2,3]) return f(...);

R=adamk@chromium.org, ishell@chromium.org
BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2343823002
Cr-Commit-Position: refs/heads/master@{#39497}

src/parsing/parser.cc

@@ -2609,17 +2609,27 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
 
         Expect(Token::RPAREN, CHECK_OK);
 
-        // For legacy compat reasons, give for loops similar treatment to
-        // if statements in allowing a function declaration for a body
-        Statement* body = ParseScopedStatement(NULL, true, CHECK_OK);
-        Statement* final_loop = InitializeForEachStatement(
-            loop, expression, enumerable, body, each_keyword_position);
+        {
+          ReturnExprScope no_tail_calls(function_state_,
+                                        ReturnExprContext::kInsideForInOfBody);
+          BlockState block_state(&scope_state_);
+          block_state.set_start_position(scanner()->location().beg_pos);
 
-        Scope* for_scope = for_state.FinalizedBlockScope();
-        DCHECK_NULL(for_scope);
-        USE(for_scope);
-        return final_loop;
+          // For legacy compat reasons, give for loops similar treatment to
+          // if statements in allowing a function declaration for a body
+          Statement* body = ParseScopedStatement(NULL, true, CHECK_OK);
+          block_state.set_end_position(scanner()->location().end_pos);
+          Statement* final_loop = InitializeForEachStatement(
+              loop, expression, enumerable, body, each_keyword_position);
 
+          Scope* for_scope = for_state.FinalizedBlockScope();
+          DCHECK_NULL(for_scope);
+          USE(for_scope);
+          Scope* block_scope = block_state.FinalizedBlockScope();
+          DCHECK_NULL(block_scope);
+          USE(block_scope);
+          return final_loop;
+        }
       } else {
         init = factory()->NewExpressionStatement(expression, lhs_beg_pos);
       }

test/mjsunit/es6/tail-call.js

@@ -295,7 +295,7 @@ function f_153(expected_call_stack, a) {
 
   function test() {
     var o = new A();
-    %DebugPrint(o);
+    //%DebugPrint(o);
     assertEquals(153, o.x);
   }
 
@@ -387,18 +387,57 @@ function f_153(expected_call_stack, a) {
     }
   }
 
+  function g1let() {
+    for (let v in {a:0}) {
+      return f_153([f_153, g1let, test]);
+    }
+  }
+
+  function g1nodecl() {
+    var v;
+    for (v in {a:0}) {
+      return f_153([f_153, g1nodecl, test]);
+    }
+  }
+
   function g2() {
     for (var v of [1, 2, 3]) {
       return f_153([f_153, g2, test]);
     }
   }
 
+  function g2let() {
+    for (let v of [1, 2, 3]) {
+      return f_153([f_153, g2let, test]);
+    }
+  }
+
+  function g2nodecl() {
+    var v;
+    for (v of [1, 2, 3]) {
+      return f_153([f_153, g2nodecl, test]);
+    }
+  }
+
   function g3() {
     for (var i = 0; i < 10; i++) {
       return f_153([f_153, test]);
     }
   }
 
+  function g3let() {
+    for (let i = 0; i < 10; i++) {
+      return f_153([f_153, test]);
+    }
+  }
+
+  function g3nodecl() {
+    var i;
+    for (i = 0; i < 10; i++) {
+      return f_153([f_153, test]);
+    }
+  }
+
   function g4() {
     while (true) {
       return f_153([f_153, test]);
@@ -413,8 +452,14 @@ function f_153(expected_call_stack, a) {
 
   function test() {
     assertEquals(153, g1());
+    assertEquals(153, g1let());
+    assertEquals(153, g1nodecl());
     assertEquals(153, g2());
+    assertEquals(153, g2let());
+    assertEquals(153, g2nodecl());
     assertEquals(153, g3());
+    assertEquals(153, g3let());
+    assertEquals(153, g3nodecl());
     assertEquals(153, g4());
     assertEquals(153, g5());
   }