Declare 'this' as DYNAMIC_GLOBAL on the script_scope

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index 59d31f5a73514fd5c8a7f98d8e4be9146f8f433f..29c141257a02c486da32bea216209fbda7618c4c 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -998,6 +998,12 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info) {
   FunctionLiteral* result = NULL;
   {
     Scope* outer = original_scope_;
+    // If there's a chance that there's a reference to global 'this', predeclare

[adamk, 2016/08/11 18:27:17]

What does the "If there's a chance" add to this comment?

[Toon Verwaest, 2016/08/12 04:49:40]

How would you reformulate? I'm just trying to indicate that there's no guarantee
that there's a reference, but that we don't insert it if there can't be a
reference.

[adamk, 2016/08/15 17:39:43]

Makes sense, I missed the fact that the GetReceiverScope() is doing exactly the
"if there's a chance" thing. This is fine on a second reading.

+    // it as a dynamic global on the script scope.
+    if (outer->GetReceiverScope()->is_script_scope()) {
+      info->script_scope()->DeclareDynamicGlobal(
+          ast_value_factory()->this_string(), Variable::THIS);
+    }
     DCHECK(outer);
     if (info->is_eval()) {
       if (!outer->is_script_scope() || is_strict(info->language_mode())) {
@@ -1162,6 +1168,12 @@ FunctionLiteral* Parser::DoParseLazy(ParseInfo* info,
     // Parse the function literal.
     Scope* scope = original_scope_;
     DCHECK(scope);
+    // If there's a chance that there's a reference to global 'this', predeclare
+    // it as a dynamic global on the script scope.
+    if (info->is_arrow() && scope->GetReceiverScope()->is_script_scope()) {
+      info->script_scope()->DeclareDynamicGlobal(
+          ast_value_factory()->this_string(), Variable::THIS);
+    }
     FunctionState function_state(&function_state_, &scope_state_, scope,
                                  info->function_kind());
     DCHECK(is_sloppy(scope->language_mode()) ||