Improve strictness of Annex B 3.3 for generators and async functions

src/parsing/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
 #include "src/ast/ast-expression-rewriter.h"
 #include "src/ast/ast-expression-visitor.h"
@@ skipping 785 matching lines @@
                       info->isolate()->is_tail_call_elimination_enabled());
   set_allow_harmony_do_expressions(FLAG_harmony_do_expressions);
   set_allow_harmony_for_in(FLAG_harmony_for_in);
   set_allow_harmony_function_name(FLAG_harmony_function_name);
   set_allow_harmony_function_sent(FLAG_harmony_function_sent);
   set_allow_harmony_restrictive_declarations(
       FLAG_harmony_restrictive_declarations);
   set_allow_harmony_exponentiation_operator(
       FLAG_harmony_exponentiation_operator);
   set_allow_harmony_async_await(FLAG_harmony_async_await);
+  set_allow_harmony_restrictive_generators(FLAG_harmony_restrictive_generators);
   for (int feature = 0; feature < v8::Isolate::kUseCounterFeatureCount;
        ++feature) {
     use_counts_[feature] = 0;
   }
   if (info->ast_value_factory() == NULL) {
     // info takes ownership of AstValueFactory.
     info->set_ast_value_factory(new AstValueFactory(zone(), info->hash_seed()));
     info->set_ast_value_factory_owned();
     ast_value_factory_ = info->ast_value_factory();
   }
@@ skipping 1148 matching lines @@
       // Declare the name.
       Variable::Kind kind = Variable::NORMAL;
       if (is_function_declaration) {
         kind = Variable::FUNCTION;
       }
       var = declaration_scope->DeclareLocal(
           name, mode, declaration->initialization(), kind, kNotAssigned);
     } else if (IsLexicalVariableMode(mode) ||
                IsLexicalVariableMode(var->mode())) {
       // Allow duplicate function decls for web compat, see bug 4693.
+      bool duplicate_allowed = false;
       if (is_sloppy(language_mode()) && is_function_declaration &&
           var->is_function()) {
         DCHECK(IsLexicalVariableMode(mode) &&
                IsLexicalVariableMode(var->mode()));
+        // If the duplication is allowed, then the var will show up
+        // in the SloppyBlockFunctionMap and the new FunctionKind
+        // will be a permitted duplicate.
+        FunctionKind function_kind =
+            declaration->AsFunctionDeclaration()->fun()->kind();
+        duplicate_allowed =
+            scope->DeclarationScope()->sloppy_block_function_map()->Lookup(
+                const_cast<AstRawString*>(name), name->hash()) != nullptr &&
+            !IsAsyncFunction(function_kind) &&
+            !(allow_harmony_restrictive_generators() &&
+              IsGeneratorFunction(function_kind));
+      }
+      if (duplicate_allowed) {
         ++use_counts_[v8::Isolate::kSloppyModeBlockScopedFunctionRedefinition];
       } else {
         // The name was declared in this scope before; check for conflicting
         // re-declarations. We have a conflict if either of the declarations
         // is not a var (in script scope, we also have to ignore legacy const
         // for compatibility). There is similar code in runtime.cc in the
         // Declare functions. The function CheckConflictingVarDeclarations
         // checks for var and let bindings from different scopes whereas this
         // is a check for conflicting declarations within the same scope. This
         // check also covers the special case
@@ skipping 193 matching lines @@
   // a script scope, or the initial scope of eval or another function.
   VariableMode mode =
       (!scope_->is_declaration_scope() || scope_->is_module_scope()) ? LET
                                                                      : VAR;
   VariableProxy* proxy = NewUnresolved(name, mode);
   Declaration* declaration =
       factory()->NewFunctionDeclaration(proxy, mode, fun, scope_, pos);
   Declare(declaration, DeclarationDescriptor::NORMAL, true, CHECK_OK);
   if (names) names->Add(name, zone());
   EmptyStatement* empty = factory()->NewEmptyStatement(RelocInfo::kNoPosition);
-  if (is_sloppy(language_mode()) && !scope_->is_declaration_scope()) {
+  // Async functions don't undergo sloppy mode block scoped hoisting, and don't
+  // allow duplicates in a block. Both are represented by the
+  // sloppy_block_function_map. Don't add them to the map for async functions.
+  // Generators are also supposed to be prohibited; currently doing this behind
+  // a flag and UseCounting violations to assess web compatibility.
+  if (is_sloppy(language_mode()) && !scope_->is_declaration_scope() &&
+      !is_async && !(allow_harmony_restrictive_generators() && is_generator)) {
     SloppyBlockFunctionStatement* delegate =
         factory()->NewSloppyBlockFunctionStatement(empty, scope_);
     scope_->DeclarationScope()->sloppy_block_function_map()->Declare(name,
                                                                      delegate);
     return delegate;
   }
   return empty;
 }
 
 
@@ skipping 4710 matching lines @@
                         try_block, target);
     final_loop = target;
   }
 
   return final_loop;
 }
 
 
 }  // namespace internal
 }  // namespace v8