[async-await] (simpler) fix for Return in try/finally in 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 <memory>
 
 #include "src/api.h"
 #include "src/ast/ast-expression-rewriter.h"
@@ skipping 1597 matching lines @@
     Expression* is_undefined = factory()->NewCompareOperation(
         Token::EQ_STRICT, assign,
         factory()->NewUndefinedLiteral(kNoSourcePosition), pos);
 
     // is_undefined ? this : is_object_conditional
     return_value = factory()->NewConditional(is_undefined, ThisExpression(pos),
                                              is_object_conditional, pos);
   }
   if (is_generator()) {
     return_value = BuildIteratorResult(return_value, true);
-  } else if (is_async_function()) {
-    return_value = BuildResolvePromise(return_value, return_value->position());
   }
   return return_value;
 }
 
 Expression* Parser::RewriteDoExpression(Block* body, int pos, bool* ok) {
   Variable* result = NewTemporary(ast_value_factory()->dot_result_string());
   DoExpression* expr = factory()->NewDoExpression(body, result, pos);
   if (!Rewriter::Rewrite(this, GetClosureScope(), expr, ast_value_factory())) {
     *ok = false;
     return nullptr;
@@ skipping 842 matching lines @@
 void Parser::PrepareGeneratorVariables() {
   // For generators, allocating variables in contexts is currently a win because
   // it minimizes the work needed to suspend and resume an activation.  The
   // code produced for generators relies on this forced context allocation (it
   // does not restore the frame's parameters upon resume).
   function_state_->scope()->ForceContextAllocation();
 
   // Calling a generator returns a generator object.  That object is stored
   // in a temporary variable, a definition that is used by "yield"
   // expressions.
-  Variable* temp =
-      NewTemporary(ast_value_factory()->dot_generator_object_string());
-  function_state_->set_generator_object_variable(temp);
+  Variable* temp = function_state_->scope()->DeclareGeneratorObjectVar(
+      ast_value_factory()->dot_generator_object_string());
+  temp->set_is_used();
 }
 
 FunctionLiteral* Parser::ParseFunctionLiteral(
     const AstRawString* function_name, Scanner::Location function_name_location,
     FunctionNameValidity function_name_validity, FunctionKind kind,
     int function_token_pos, FunctionLiteral::FunctionType function_type,
     LanguageMode language_mode, bool* ok) {
   // Function ::
   //   '(' FormalParameterList? ')' '{' FunctionBody '}'
   //
@@ skipping 593 matching lines @@
       Token::COMMA, call_runtime,
       factory()->NewVariableProxy(PromiseVariable()), pos);
 }
 
 Variable* Parser::PromiseVariable() {
   // Based on the various compilation paths, there are many different code
   // paths which may be the first to access the Promise temporary. Whichever
   // comes first should create it and stash it in the FunctionState.
   Variable* promise = function_state_->promise_variable();
   if (function_state_->promise_variable() == nullptr) {
-    promise = scope()->NewTemporary(ast_value_factory()->empty_string());
-    function_state_->set_promise_variable(promise);
+    promise = function_state_->scope()->DeclarePromiseVar(
+        ast_value_factory()->empty_string());
+    promise->set_is_used();
   }
   return promise;
 }
 
 Expression* Parser::BuildInitialYield(int pos, FunctionKind kind) {
   Assignment* assignment = BuildCreateJSGeneratorObject(pos, kind);
   VariableProxy* generator =
       factory()->NewVariableProxy(function_state_->generator_object_variable());
   // The position of the yield is important for reporting the exception
   // caused by calling the .throw method on a generator suspended at the
@@ skipping 1916 matching lines @@
 
   return final_loop;
 }
 
 #undef CHECK_OK
 #undef CHECK_OK_VOID
 #undef CHECK_FAILED
 
 }  // namespace internal
 }  // namespace v8