Fix scoping of function declarations in eval inside non-trivial local scope

src/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 523 matching lines @@
 
 // ----------------------------------------------------------------------------
 // Implementation of Parser
 
 Parser::Parser(CompilationInfo* info)
     : isolate_(info->isolate()),
       symbol_cache_(0, info->zone()),
       script_(info->script()),
       scanner_(isolate_->unicode_cache()),
       reusable_preparser_(NULL),
       top_scope_(NULL),

[Michael Starzinger, 2013/08/23 08:56:30]

Missing initialization of original_scope_(NULL) here.

[rossberg, 2013/08/23 09:09:21]

Done.

       current_function_state_(NULL),
       target_stack_(NULL),
       extension_(info->extension()),
       pre_parse_data_(NULL),
       fni_(NULL),
       allow_natives_syntax_(false),
       allow_lazy_(false),
       allow_generators_(false),
       allow_for_of_(false),
       stack_overflow_(false),
@@ skipping 60 matching lines @@
   if (pre_parse_data_ != NULL) pre_parse_data_->Initialize();
 
   Handle<String> no_name = isolate()->factory()->empty_string();
 
   FunctionLiteral* result = NULL;
   { Scope* scope = NewScope(top_scope_, GLOBAL_SCOPE);
     info->SetGlobalScope(scope);
     if (!info->context().is_null()) {
       scope = Scope::DeserializeScopeChain(*info->context(), scope, zone());
     }
+    original_scope_ = scope;
     if (info->is_eval()) {
       if (!scope->is_global_scope() || info->language_mode() != CLASSIC_MODE) {
         scope = NewScope(scope, EVAL_SCOPE);
       }
     } else if (info->is_global()) {
       scope = NewScope(scope, GLOBAL_SCOPE);
     }
     scope->set_start_position(0);
     scope->set_end_position(source->length());
 
@@ skipping 107 matching lines @@
   FunctionLiteral* result = NULL;
 
   {
     // Parse the function literal.
     Scope* scope = NewScope(top_scope_, GLOBAL_SCOPE);
     info()->SetGlobalScope(scope);
     if (!info()->closure().is_null()) {
       scope = Scope::DeserializeScopeChain(info()->closure()->context(), scope,
                                            zone());
     }
+    original_scope_ = scope;
     FunctionState function_state(this, scope, isolate());
     ASSERT(scope->language_mode() != STRICT_MODE || !info()->is_classic_mode());
     ASSERT(scope->language_mode() != EXTENDED_MODE ||
            info()->is_extended_mode());
     ASSERT(info()->language_mode() == shared_info->language_mode());
     scope->SetLanguageMode(shared_info->language_mode());
     FunctionLiteral::FunctionType function_type = shared_info->is_expression()
         ? (shared_info->is_anonymous()
               ? FunctionLiteral::ANONYMOUS_EXPRESSION
               : FunctionLiteral::NAMED_EXPRESSION)
@@ skipping 3510 matching lines @@
 
   // We want a non-null handle as the function name.
   if (should_infer_name) {
     function_name = isolate()->factory()->empty_string();
   }
 
   int num_parameters = 0;
   // Function declarations are function scoped in normal mode, so they are
   // hoisted. In harmony block scoping mode they are block scoped, so they
   // are not hoisted.
+  //
+  // One tricky case are function declarations in a local sloppy-mode eval:
+  // their declaration is hoisted, but they still see the local scope. E.g.,
+  //
+  // function() {
+  //   var x=0
+  //   try {throw 1} catch (x) { eval("function g() { return x }") }

[Michael Starzinger, 2013/08/23 08:56:30]

nit: A few white spaces missing here and in the line above.

[rossberg, 2013/08/23 09:09:21]

Done.

+  //   return g()
+  // }
+  //
+  // needs to return 1. To distinguish such cases, we need to detect
+  // (1) whether a function stems from a sloppy eval, and
+  // (2) whether it actually hoists across the eval.
+  // Unfortunately, we do not represent sloppy eval scopes, so we do not have
+  // either information available directly, especially not when lazily compiling
+  // a function like 'g'. We hence rely on the following invariants:
+  // - (1) is the case iff the innermost scope of the deserialized scope chain
+  //   under which we compile is _not_ a declaration scope. This holds because
+  //   in all normal cases, function declarations are fully hoisted to a
+  //   declaration scope and compiled relative to that.
+  // - (2) is the case iff the current declaration scope is still the original
+  //   one relative to the deserialized scope chain. Otherwise we must be
+  //   compiling a function in an inner declaration scope in the eval, e.g. a
+  //   nested function, and hoisting works normally relative to that.
+  Scope* declaration_scope = top_scope_->DeclarationScope();
+  Scope* original_declaration_scope = original_scope_->DeclarationScope();
   Scope* scope =
-      (function_type == FunctionLiteral::DECLARATION && !is_extended_mode())
-      ? NewScope(top_scope_->DeclarationScope(), FUNCTION_SCOPE)
-      : NewScope(top_scope_, FUNCTION_SCOPE);
+      function_type == FunctionLiteral::DECLARATION && !is_extended_mode() &&
+      (original_scope_ == original_declaration_scope ||
+       declaration_scope != original_declaration_scope)
+          ? NewScope(declaration_scope, FUNCTION_SCOPE)
+          : NewScope(top_scope_, FUNCTION_SCOPE);
   ZoneList<Statement*>* body = NULL;
   int materialized_literal_count = -1;
   int expected_property_count = -1;
   int handler_count = 0;
   FunctionLiteral::ParameterFlag duplicate_parameters =
       FunctionLiteral::kNoDuplicateParameters;
   FunctionLiteral::IsParenthesizedFlag parenthesized = parenthesized_function_
       ? FunctionLiteral::kIsParenthesized
       : FunctionLiteral::kNotParenthesized;
   FunctionLiteral::IsGeneratorFlag generator = is_generator
@@ skipping 1637 matching lines @@
       ASSERT(info()->isolate()->has_pending_exception());
     } else {
       result = ParseProgram();
     }
   }
   info()->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal