Use failedAt in more places

pkg/compiler/lib/src/resolution/signatures.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.resolution.signatures;
 
 import '../common.dart';
 import '../common/resolution.dart';
 import '../elements/resolution_types.dart';
 import '../elements/elements.dart';
@@ skipping 116 matching lines @@
           registry,
           defaultValuesError: MessageKind.FUNCTION_TYPE_FORMAL_WITH_DEFAULT);
       element.functionSignature = functionSignature;
     }
 
     if (currentDefinitions.type != null) {
       element.typeCache = resolveTypeAnnotation(currentDefinitions.type);
     } else {
       // Is node.definitions exactly one FunctionExpression?
       Link<Node> link = currentDefinitions.definitions.nodes;
-      assert(invariant(currentDefinitions, !link.isEmpty));
-      assert(invariant(currentDefinitions, link.tail.isEmpty));
+      assert(!link.isEmpty, failedAt(currentDefinitions));
+      assert(link.tail.isEmpty, failedAt(currentDefinitions));
       if (link.head.asFunctionExpression() != null) {
         // Inline function typed parameter, like `void m(int f(String s))`.
         computeInlineFunctionType(link.head);
       } else if (link.head.asSend() != null &&
           link.head.asSend().selector.asFunctionExpression() != null) {
         // Inline function typed initializing formal or
         // parameter with default value, like `C(int this.f(String s))` or
         // `void m([int f(String s) = null])`.
         computeInlineFunctionType(
             link.head.asSend().selector.asFunctionExpression());
@@ skipping 355 matching lines @@
 /// variables of the function signature itself when its signature is analyzed.
 class FunctionSignatureBuildingScope extends TypeVariablesScope {
   @override
   final List<ResolutionDartType> typeVariables;
 
   FunctionSignatureBuildingScope(Scope parent, this.typeVariables)
       : super(parent);
 
   String toString() => 'FunctionSignatureBuildingScope($typeVariables)';
 }