Track usage of "this" and "arguments" in Scope

src/scopes.cc

Index: src/scopes.cc
diff --git a/src/scopes.cc b/src/scopes.cc
index e1297b332ca52bd224bce0129ae3c72d3419ceac..b226be1b573148c23c030ed7cc8294816d73ff2e 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -160,10 +160,14 @@ void Scope::SetDefaults(ScopeType scope_type,
   scope_inside_with_ = false;
   scope_contains_with_ = false;
   scope_calls_eval_ = false;
+  scope_uses_this_ = false;
+  scope_uses_arguments_ = false;
   // Inherit the strict mode from the parent scope.
   strict_mode_ = outer_scope != NULL ? outer_scope->strict_mode_ : SLOPPY;
   outer_scope_calls_sloppy_eval_ = false;
   inner_scope_calls_eval_ = false;
+  inner_scope_uses_this_ = false;
+  inner_scope_uses_arguments_ = false;
   force_eager_compilation_ = false;
   force_context_allocation_ = (outer_scope != NULL && !is_function_scope())
       ? outer_scope->has_forced_context_allocation() : false;
@@ -881,6 +885,12 @@ void Scope::Print(int n) {
   if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n");
   if (scope_contains_with_) Indent(n1, "// scope contains 'with'\n");
   if (scope_calls_eval_) Indent(n1, "// scope calls 'eval'\n");
+  if (scope_uses_this_) Indent(n1, "// scope uses 'this'\n");
+  if (scope_uses_arguments_) Indent(n1, "// scope uses 'arguments'\n");
+  if (inner_scope_uses_this_) Indent(n1, "// inner scope uses 'this'\n");
+  if (inner_scope_uses_arguments_) {
+    Indent(n1, "// inner scope uses 'arguments'\n");
+  }
   if (outer_scope_calls_sloppy_eval_) {
     Indent(n1, "// outer scope calls 'eval' in sloppy context\n");
   }
@@ -1162,6 +1172,12 @@ void Scope::PropagateScopeInfo(bool outer_scope_calls_sloppy_eval ) {
     if (inner->scope_calls_eval_ || inner->inner_scope_calls_eval_) {
       inner_scope_calls_eval_ = true;
     }
+    if (inner->scope_uses_this_ || inner->inner_scope_uses_this_) {

[rossberg, 2014/09/10 06:33:56]

If inner is a function scope and not an arrow function, then both new flags must
not be propagated.

+      inner_scope_uses_this_ = true;
+    }
+    if (inner->scope_uses_arguments_ || inner->inner_scope_uses_arguments_) {
+      inner_scope_uses_arguments_ = true;
+    }
     if (inner->force_eager_compilation_) {
       force_eager_compilation_ = true;
     }