Adjust the column number where a StackOverflow error is reported.

runtime/vm/flow_graph_builder.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #if !defined(DART_PRECOMPILED_RUNTIME)
 
 #include "vm/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
@@ skipping 3863 matching lines @@
   }
 #endif
 
   // This check may be deleted if the generated code is leaf.
   // Native functions don't need a stack check at entry.
   if (is_top_level_sequence && !function.is_native()) {
     // Always allocate CheckOverflowInstr so that deopt-ids match regardless
     // if we inline or not.
     if (!function.IsImplicitGetterFunction() &&
         !function.IsImplicitSetterFunction()) {
+      // We want the stack overlow error to be reported at the opening '{' or
+      // at the '=>' location. So, we get the sequence node corresponding to the
+      // body inside |node| and use its token position.
+      ASSERT(node->length() > 0);
       CheckStackOverflowInstr* check = new (Z) CheckStackOverflowInstr(
-          node->token_pos(), 0, owner()->GetNextDeoptId());
+          node->NodeAt(0)->token_pos(), 0, owner()->GetNextDeoptId());
       // If we are inlining don't actually attach the stack check. We must still
       // create the stack check in order to allocate a deopt id.
       if (!owner()->IsInlining()) {
         AddInstruction(check);
       }
     }
   }
 
   if (Isolate::Current()->type_checks() && is_top_level_sequence) {
     const int num_params = function.NumParameters();
@@ skipping 521 matching lines @@
   // Bail if the type has any type parameters.
   if (type_class.IsGeneric()) return false;
 
   // Finally a simple class for instance of checking.
   return true;
 }
 
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)