Provide ability to patch external functions in a class that has already been finalized. The follow…

runtime/vm/parser.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/parser.h"
 #include "vm/flags.h"
 
 #ifndef DART_PRECOMPILED_RUNTIME
 
 #include "lib/invocation_mirror.h"
@@ skipping 4547 matching lines @@
   cls.set_super_type(super_type);
 
   if (CurrentToken() == Token::kIMPLEMENTS) {
     ParseInterfaceList(cls);
   }
 
   if (is_patch) {
     cls.set_is_patch();
     // Apply the changes to the patched class looked up above.
     ASSERT(obj.raw() == library_.LookupLocalObject(class_name));
-    // The patched class must not be finalized yet.
-    ASSERT(!Class::Cast(obj).is_finalized());
+    const Class& orig_class = Class::Cast(obj);
+    if (orig_class.is_finalized()) {
+      orig_class.SetRefinalizeAfterPatch();
+      pending_classes.Add(orig_class, Heap::kOld);
+    }
     library_.AddPatchClass(cls);
   }
   pending_classes.Add(cls, Heap::kOld);
 
   if (is_mixin_declaration) {
     ExpectSemicolon();
   } else {
     CheckToken(Token::kLBRACE);
     SkipBlock();
     ExpectToken(Token::kRBRACE);
@@ skipping 47 matching lines @@
     AddImplicitConstructor(cls);
   }
 
   if (cls.is_patch()) {
     // Apply the changes to the patched class looked up above.
     Object& obj = Object::Handle(Z, library_.LookupLocalObject(class_name));
     // The patched class must not be finalized yet.
     const Class& orig_class = Class::Cast(obj);
     ASSERT(!orig_class.is_finalized());
     Error& error = Error::Handle(Z);
+    // Check if this is a case of patching a class after it has already
+    // been finalized.
+    if (orig_class.is_refinalize_after_patch()) {
+      if (!cls.ValidatePostFinalizePatch(orig_class, &error)) {
+        Report::LongJumpF(error, script_, class_pos,
+                          "patch validation failed, not applying patch.\n");
+      }
+    }
     if (!orig_class.ApplyPatch(cls, &error)) {
       Report::LongJumpF(error, script_, class_pos, "applying patch failed");
     }
   }
 }
 
 
 void Parser::ParseEnumDefinition(const Class& cls) {
   TRACE_PARSER("ParseEnumDefinition");
   INC_STAT(thread(), num_classes_parsed, 1);
@@ skipping 9815 matching lines @@
     const ArgumentListNode& function_args,
     const LocalVariable* temp_for_last_arg,
     bool is_super_invocation) {
   UNREACHABLE();
   return NULL;
 }
 
 }  // namespace dart
 
 #endif  // DART_PRECOMPILED_RUNTIME