Clean patch implementation.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

 // 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.
 
 part of resolution;
 
 abstract class TreeElements {
   Element get currentElement;
   Setlet<Node> get superUses;
 
@@ skipping 304 matching lines @@
       redirection = resolver.visitor.resolveConstructorRedirection(redirection);
     }
   }
 
   void checkMatchingPatchParameters(FunctionElement origin,
                                     Link<Element> originParameters,
                                     Link<Element> patchParameters) {
     while (!originParameters.isEmpty) {
       ParameterElementX originParameter = originParameters.head;
       ParameterElementX patchParameter = patchParameters.head;
-      // TODO(johnniwinther): Remove the case for reassignment of
-      // [patch]/[origin] when resolution is ensure to be done only once.
-      assert(invariant(originParameter, originParameter.origin == null));
-      assert(invariant(originParameter,
-          originParameter.patch == null ||
-          originParameter.patch == patchParameter));
-      originParameter.patch = patchParameter;
-      assert(invariant(patchParameter,
-          patchParameter.origin == null ||
-          patchParameter.origin == originParameter));
-      assert(invariant(patchParameter, patchParameter.patch == null));
-      patchParameter.origin = originParameter;
+      originParameter.applyPatch(patchParameter);
       DartType originParameterType = originParameter.computeType(compiler);
       DartType patchParameterType = patchParameter.computeType(compiler);
       if (originParameterType != patchParameterType) {
         compiler.reportError(
             originParameter.parseNode(compiler),
             MessageKind.PATCH_PARAMETER_TYPE_MISMATCH,
             {'methodName': origin.name,
              'parameterName': originParameter.name,
              'originParameterType': originParameterType,
              'patchParameterType': patchParameterType});
@@ skipping 4325 matching lines @@
   TreeElements _treeElements;
 
   bool get hasTreeElements => _treeElements != null;
 
   TreeElements get treeElements {
     assert(invariant(this, _treeElements !=null,
         message: "TreeElements have not been computed for $this."));
     return _treeElements;
   }
 }