Use failedAt in more places

pkg/compiler/lib/src/serialization/modelz.dart

 // Copyright (c) 2015, 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.
 
 /// Implementation of the element model used for deserialiation.
 ///
 /// These classes are created by [ElementDeserializer] triggered by the
 /// [Deserializer].
 
 library dart2js.serialization.modelz;
@@ skipping 274 matching lines @@
   bool get hasNode => false;
 
   @override
   bool get hasResolvedAst => _resolvedAst != null;
 
   @override
   get node => _unsupported('node');
 
   @override
   ResolvedAst get resolvedAst {
-    assert(invariant(this, _resolvedAst != null,
-        message: "ResolvedAst has not been set for $this."));
+    assert(_resolvedAst != null,
+        failedAt(this, "ResolvedAst has not been set for $this."));
     return _resolvedAst;
   }
 
   void set resolvedAst(ResolvedAst value) {
-    assert(invariant(this, _resolvedAst == null,
-        message: "ResolvedAst has already been set for $this."));
+    assert(_resolvedAst == null,
+        failedAt(this, "ResolvedAst has already been set for $this."));
     _resolvedAst = value;
   }
 }
 
 abstract class ContainerMixin
     implements DeserializedElementZ, ScopeContainerElement {
   MappedContainer _membersMap = new MappedContainer();
 
   @override
   Element localLookup(String name) {
@@ skipping 1715 matching lines @@
     return visitor.visitTypeVariableElement(this, arg);
   }
 
   @override
   CompilationUnitElement get compilationUnit {
     return typeDeclaration.compilationUnit;
   }
 
   @override
   ResolutionTypeVariableType get type {
-    assert(invariant(this, _type != null,
-        message: "Type variable type has not been set on $this."));
+    assert(_type != null,
+        failedAt(this, "Type variable type has not been set on $this."));
     return _type;
   }
 
   @override
   ResolutionTypeVariableType computeType(Resolution resolution) => type;
 
   @override
   Element get enclosingElement => typeDeclaration;
 
   @override
   Element get enclosingClass => typeDeclaration;
 
   ResolutionDartType get bound {
-    assert(invariant(this, _bound != null,
-        message: "Type variable bound has not been set on $this."));
+    assert(_bound != null,
+        failedAt(this, "Type variable bound has not been set on $this."));
     return _bound;
   }
 
   @override
   LibraryElement get library => typeDeclaration.library;
 
   @override
   int get sourceOffset => typeDeclaration.sourceOffset;
 
   @override
@@ skipping 347 matching lines @@
   }
 
   @override
   Node get node => throw new UnsupportedError('${this}.node');
 
   @override
   bool get hasNode => false;
 
   String toString() => 'MetadataAnnotationZ(${constant.toDartText()})';
 }