Fix issue 18435 (2nd attempt).

runtime/vm/scopes.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.
 
 #include "vm/scopes.h"
 
 #include "vm/object.h"
 #include "vm/stack_frame.h"
 #include "vm/symbols.h"
 
@@ skipping 48 matching lines @@
   variables_.Add(variable);
   if (variable->owner() == NULL) {
     // Variables must be added to their owner scope first. Subsequent calls
     // to 'add' treat the variable as an alias.
     variable->set_owner(this);
   }
   return true;
 }
 
 
+bool LocalScope::InsertParameterAt(intptr_t pos, LocalVariable* parameter) {
+  ASSERT(parameter != NULL);
+  if (LocalLookupVariable(parameter->name()) != NULL) {
+    return false;
+  }
+  variables_.InsertAt(pos, parameter);
+  // InsertParameterAt is not used to add aliases of parameters.
+  ASSERT(parameter->owner() == NULL);
+  parameter->set_owner(this);
+  return true;
+}
+
+
 bool LocalScope::AddLabel(SourceLabel* label) {
   if (LocalLookupLabel(label->name()) != NULL) {
     return false;
   }
   labels_.Add(label);
   if (label->owner() == NULL) {
     // Labels must be added to their owner scope first. Subsequent calls
     // to 'add' treat the label as an alias.
     label->set_owner(this);
   }
@@ skipping 85 matching lines @@
   if (loop_level() > loop_owner->loop_level()) {
     loop_owner = this;
   }
   // Parameters must be listed first and must all appear in the top scope.
   ASSERT(num_parameters <= num_variables());
   int pos = 0;  // Current variable position.
   int frame_index = first_parameter_index;  // Current free frame index.
   while (pos < num_parameters) {
     LocalVariable* parameter = VariableAt(pos);
     pos++;
+    // Parsing formal parameter default values may add local variable aliases
+    // to the local scope before the formal parameters are added. However,
+    // the parameters get inserted in front of the aliases, therefore, no
+    // aliases can be encountered among the first num_parameters variables.
     ASSERT(parameter->owner() == this);
     if (parameter->is_captured()) {
       // A captured parameter has a slot allocated in the frame and one in the
       // context, where it gets copied to. The parameter index reflects the
       // context allocation index.
       frame_index--;
       loop_owner->AllocateContextVariable(parameter, context_owner);
       *found_captured_variables = true;
     } else {
       parameter->set_index(frame_index--);
@@ skipping 447 matching lines @@
     return fixed_parameter_count - (index() - kParamEndSlotFromFp);
   } else {
     // Shift negative indexes so that the lowest one is 0 (they are still
     // non-positive).
     return fixed_parameter_count - (index() - kFirstLocalSlotFromFp);
   }
 }
 
 
 }  // namespace dart