Set correct token position range for statement block containing moveNext call of

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index 1b7cec334caab0980f4f066e7dbfebee28454909..99b7fcb9831619356059c8bfd5ff7e562ad7de66 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -9028,13 +9028,14 @@ AstNode* Parser::ParseForInStatement(TokenPosition forin_pos,
     loop_var_name = ExpectIdentifier("variable name expected");
   }
   ExpectToken(Token::kIN);
+
+  OpenBlock();  // Implicit block around while loop.

[hausner, 2016/07/29 17:59:35]

Maybe add a comment that explains why we open a block that textually starts in
the middle of the for-in expression. I think you can copy the explanation in the
CL:

Ensure that the block token range contains the call to moveNext and it
also starts the block at a different token position than the following loop
block. Both blocks can allocate contexts and if they have a matching token
position
range, it can be an issue (cf. bug 26941)

[regis, 2016/07/29 21:31:47]

Done.

+
   const TokenPosition collection_pos = TokenPos();
   AstNode* collection_expr =
       ParseAwaitableExpr(kAllowConst, kConsumeCascades, NULL);
   ExpectToken(Token::kRPAREN);
 
-  OpenBlock();  // Implicit block around while loop.
-
   // Generate implicit iterator variable and add to scope.
   // We could set the type of the implicit iterator variable to Iterator<T>
   // where T is the type of the for loop variable. However, the type error