Refactor qualified send sets.

pkg/compiler/lib/src/ssa/builder.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 ssa;
 
 class SsaFunctionCompiler implements FunctionCompiler {
   final SsaCodeGeneratorTask generator;
   final SsaBuilderTask builder;
   final SsaOptimizerTask optimizer;
@@ skipping 3610 matching lines @@
     // An erroneous element indicates an unresolved static setter.
     generateThrowNoSuchMethod(
         location, noSuchMethodTargetSymbolString(element, 'set'),
         argumentValues: arguments);
   }
 
   void generateNonInstanceSetter(ast.SendSet send,
                                  Element element,
                                  HInstruction value,
                                  {ast.Node location}) {
-    assert(send == null || !Elements.isInstanceSend(send, elements));
     if (location == null) {
       assert(send != null);
       location = send;
     }
+    assert(invariant(location,
+        send == null || !Elements.isInstanceSend(send, elements),
+        message: "Unexpected non instance setter: $element."));
     if (Elements.isStaticOrTopLevelField(element)) {
       if (element.isSetter) {
         pushInvokeStatic(location, element, <HInstruction>[value]);
         pop();
       } else {
         VariableElement field = element;
         value = potentiallyCheckOrTrustType(value, field.type);
         addWithPosition(new HStaticStore(element, value), location);
       }
       stack.add(value);
@@ skipping 5215 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.findHelper('DynamicRuntimeType');
     builder.push(new HDynamicType(type, new TypeMask.exact(cls, classWorld)));
   }
 }