Use failedAt in more places (constants, universe)

pkg/compiler/lib/src/constants/expressions.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.constants.expressions;
 
 import '../common.dart';
 import '../constants/constant_system.dart';
 import '../common_elements.dart';
 import '../elements/entities.dart';
@@ skipping 542 matching lines @@
       value._createStructuredText(sb);
       delimiter = ',';
     }
     sb.write('])');
   }
 
   Map<FieldEntity, ConstantExpression> computeInstanceFields(
       EvaluationEnvironment environment) {
     ConstantConstructor constantConstructor =
         environment.getConstructorConstant(target);
-    assert(invariant(target, constantConstructor != null,
-        message: "No constant constructor computed for $target."));
+    assert(constantConstructor != null,
+        failedAt(target, "No constant constructor computed for $target."));
     return constantConstructor.computeInstanceFields(
         environment, arguments, callStructure);
   }
 
   InterfaceType computeInstanceType(EvaluationEnvironment environment) {
     return environment
         .getConstructorConstant(target)
         .computeInstanceType(environment, type);
   }
 
@@ skipping 1350 matching lines @@
     visit(exp.name);
     if (exp.defaultValue != null) {
       sb.write(', defaultValue: ');
       visit(exp.defaultValue);
     }
     sb.write(')');
   }
 
   String toString() => sb.toString();
 }