Initializing a final instance is a runtime error

runtime/vm/parser.h

 // 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.
 
 #ifndef VM_PARSER_H_
 #define VM_PARSER_H_
 
 #include "include/dart_api.h"
 
 #include "platform/assert.h"
@@ skipping 452 matching lines @@
                                 bool evaluate_metadata,
                                 ParamList* params);
   void CheckFieldsInitialized(const Class& cls);
   void AddImplicitConstructor(const Class& cls);
   void CheckConstructors(ClassDesc* members);
   AstNode* ParseExternalInitializedField(const Field& field);
   void ParseInitializedInstanceFields(
       const Class& cls,
       LocalVariable* receiver,
       GrowableArray<Field*>* initialized_fields);
-  void CheckDuplicateFieldInit(intptr_t init_pos,
-                               GrowableArray<Field*>* initialized_fields,
-                               Field* field);
+  AstNode* CheckDuplicateFieldInit(
+      intptr_t init_pos,
+      GrowableArray<Field*>* initialized_fields,
+      AstNode* instance,
+      Field* field,
+      AstNode* init_value);
   void GenerateSuperConstructorCall(const Class& cls,
                                     intptr_t supercall_pos,
                                     LocalVariable* receiver,
                                     ArgumentListNode* forwarding_args);
   AstNode* ParseSuperInitializer(const Class& cls, LocalVariable* receiver);
   AstNode* ParseInitializer(const Class& cls,
                             LocalVariable* receiver,
                             GrowableArray<Field*>* initialized_fields);
   void ParseConstructorRedirection(const Class& cls, LocalVariable* receiver);
   void ParseInitializers(const Class& cls,
@@ skipping 322 matching lines @@
   int16_t last_used_try_index_;
 
   bool unregister_pending_function_;
 
   DISALLOW_COPY_AND_ASSIGN(Parser);
 };
 
 }  // namespace dart
 
 #endif  // VM_PARSER_H_