Remove redundant Scope book-keeping

The uses_arguments() bool is not needed for correct
behavior, since that same information is available after scope analysis
based on whether we allocated the Scope::arguments_ var.

BUG=v8:5209

Review-Url: https://codereview.chromium.org/2168293002
Cr-Commit-Position: refs/heads/master@{#37990}

src/ast/scopes.cc

@@ -180,7 +180,6 @@ void Scope::SetDefaults() {
   this_function_ = nullptr;
   scope_inside_with_ = false;
   scope_calls_eval_ = false;
-  scope_uses_arguments_ = false;
   has_arguments_parameter_ = false;
   scope_uses_super_property_ = false;
   asm_module_ = false;
@@ -429,7 +428,6 @@ void Scope::PropagateUsageFlagsToScope(Scope* other) {
   DCHECK_NOT_NULL(other);
   DCHECK(!already_resolved());
   DCHECK(!other->already_resolved());
-  if (uses_arguments()) other->RecordArgumentsUsage();
   if (uses_super_property()) other->RecordSuperPropertyUsage();
   if (calls_eval()) other->RecordEvalCall();
 }
@@ -1030,7 +1028,6 @@ void Scope::Print(int n) {
   if (asm_function_) Indent(n1, "// scope is an asm function\n");
   if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n");
   if (scope_calls_eval_) Indent(n1, "// scope calls 'eval'\n");
-  if (scope_uses_arguments_) Indent(n1, "// scope uses 'arguments'\n");
   if (scope_uses_super_property_)
     Indent(n1, "// scope uses 'super' property\n");
   if (outer_scope_calls_sloppy_eval_) {

src/ast/scopes.h

@@ -270,9 +270,6 @@ class Scope: public ZoneObject {
   // Inform the scope that the corresponding code contains an eval call.
   void RecordEvalCall() { scope_calls_eval_ = true; }
 
-  // Inform the scope that the corresponding code uses "arguments".
-  void RecordArgumentsUsage() { scope_uses_arguments_ = true; }
-
   // Inform the scope that the corresponding code uses "super".
   void RecordSuperPropertyUsage() { scope_uses_super_property_ = true; }
 
@@ -376,8 +373,6 @@ class Scope: public ZoneObject {
   // Is this scope inside a with statement.
   bool inside_with() const { return scope_inside_with_; }
 
-  // Does this scope access "arguments".
-  bool uses_arguments() const { return scope_uses_arguments_; }
   // Does this scope access "super" property (super.foo).
   bool uses_super_property() const { return scope_uses_super_property_; }
   // Does this scope have the potential to execute declarations non-linearly?
@@ -681,8 +676,6 @@ class Scope: public ZoneObject {
   // This scope or a nested catch scope or with scope contain an 'eval' call. At
   // the 'eval' call site this scope is the declaration scope.
   bool scope_calls_eval_;
-  // This scope uses "arguments".
-  bool scope_uses_arguments_;
   // This scope uses "super" property ('super.foo').
   bool scope_uses_super_property_;
   // This scope has a parameter called "arguments".

src/parsing/parser-base.h

@@ -1367,7 +1367,6 @@ ParserBase<Traits>::ParseAndClassifyIdentifier(ExpressionClassifier* classifier,
       }
     }
     if (this->IsArguments(name)) {
-      scope()->RecordArgumentsUsage();
       classifier->RecordStrictModeFormalParameterError(
           scanner()->location(), MessageTemplate::kStrictEvalArguments);
       if (is_strict(language_mode())) {
@@ -1434,9 +1433,7 @@ ParserBase<Traits>::ParseIdentifierOrStrictReservedWord(
     return Traits::EmptyIdentifier();
   }
 
-  IdentifierT name = this->GetSymbol(scanner());
-  if (this->IsArguments(name)) scope()->RecordArgumentsUsage();
-  return name;
+  return this->GetSymbol(scanner());
 }
 
 template <class Traits>
@@ -1454,9 +1451,7 @@ ParserBase<Traits>::ParseIdentifierName(bool* ok) {
     return Traits::EmptyIdentifier();
   }
 
-  IdentifierT name = this->GetSymbol(scanner());
-  if (this->IsArguments(name)) scope()->RecordArgumentsUsage();
-  return name;
+  return this->GetSymbol(scanner());
 }
 
 

test/cctest/test-parsing.cc

@@ -1104,8 +1104,11 @@ TEST(ScopeUsesArgumentsSuperThis) {
         DCHECK_NOT_NULL(scope);
         DCHECK_NULL(scope->sibling());
       }
-      CHECK_EQ((source_data[i].expected & ARGUMENTS) != 0,
-               scope->uses_arguments());
+      // Arrows themselves never get an arguments object.
+      if ((source_data[i].expected & ARGUMENTS) != 0 &&
+          !scope->is_arrow_scope()) {
+        CHECK_NOT_NULL(scope->arguments());
+      }
       CHECK_EQ((source_data[i].expected & SUPER_PROPERTY) != 0,
                scope->uses_super_property());
       if ((source_data[i].expected & THIS) != 0) {