Fix scope/context behavior in await transformer.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index e2100454593513ff88c3821fd0702b90c74342f6..dbf903f6aee643c6d249a35cf6d36ac697050c75 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -286,6 +286,7 @@ Parser::Parser(const Script& script, const Library& library, intptr_t token_pos)
       token_kind_(Token::kILLEGAL),
       current_block_(NULL),
       is_top_level_(false),
+      await_is_keyword_(false),
       current_member_(NULL),
       allow_function_literals_(true),
       parsed_function_(NULL),
@@ -312,6 +313,7 @@ Parser::Parser(const Script& script,
       token_kind_(Token::kILLEGAL),
       current_block_(NULL),
       is_top_level_(false),
+      await_is_keyword_(false),
       current_member_(NULL),
       allow_function_literals_(true),
       parsed_function_(parsed_function),
@@ -3053,6 +3055,11 @@ SequenceNode* Parser::ParseFunc(const Function& func,
     OpenAsyncClosure();
   }
 
+  // For async functions and their inner closures parse "await" as a keyword.
+  if (func.IsAsyncFunction() || func.is_async_closure()) {
+    await_is_keyword_ = true;
+  }
+
   intptr_t end_token_pos = 0;
   if (CurrentToken() == Token::kLBRACE) {
     ConsumeToken();
@@ -3121,6 +3128,7 @@ SequenceNode* Parser::ParseFunc(const Function& func,
   current_block_->statements->Add(body);
   innermost_function_ = saved_innermost_function.raw();
   last_used_try_index_ = saved_try_index;
+  await_is_keyword_ = false;
   return CloseBlock();
 }
 
@@ -6351,9 +6359,14 @@ bool Parser::IsSimpleLiteral(const AbstractType& type, Instance* value) {
 }
 
 
-// Returns true if the current token is kIDENT or a pseudo-keyword.
+// Returns true if the current token is
+// * kIDENT,
+// * or a pseudo-keyword,
+// * or is not the literal "await" in an async function.
 bool Parser::IsIdentifier() {
-  return Token::IsIdentifier(CurrentToken());
+  return Token::IsIdentifier(CurrentToken()) &&
+         (!await_is_keyword_ ||
+          (CurrentLiteral()->raw() != Symbols::Await().raw()));
 }
 
 
@@ -8550,11 +8563,12 @@ AstNode* Parser::ParseAwaitableExpr(bool require_compiletime_const,
       // function.
       return expr;
     }
-    SequenceNode* intermediates_block = new(I) SequenceNode(
-        Scanner::kNoSourcePos, current_block_->scope);
-    AwaitTransformer at(intermediates_block, library_, parsed_function());
+    OpenBlock();
+    AwaitTransformer at(current_block_->statements,
+                        library_,
+                        parsed_function());
     AstNode* result = at.Transform(expr);
-    current_block_->statements->Add(intermediates_block);
+    current_block_->statements->Add(CloseBlock());
     parsed_function()->reset_have_seen_await();
     return result;
   }
@@ -10939,7 +10953,7 @@ AstNode* Parser::ParsePrimary() {
     OpenBlock();
     primary = ParseFunctionStatement(true);
     CloseBlock();
-  } else if (IsLiteral("await") &&
+  } else if ((CurrentLiteral()->raw() == Symbols::Await().raw()) &&
              (parsed_function()->function().IsAsyncFunction() ||
               parsed_function()->function().is_async_closure())) {
     // The body of an async function is parsed multiple times. The first time