Use failedAt in more places

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

Index: pkg/compiler/lib/src/resolution/signatures.dart
diff --git a/pkg/compiler/lib/src/resolution/signatures.dart b/pkg/compiler/lib/src/resolution/signatures.dart
index 94964fc67f8ea17a443c41576d59299e8d069e9b..d41ca3318f2ca37ecc18b6d4c184b3a37052e4b1 100644
--- a/pkg/compiler/lib/src/resolution/signatures.dart
+++ b/pkg/compiler/lib/src/resolution/signatures.dart
@@ -134,8 +134,8 @@ class SignatureResolver extends MappingVisitor<FormalElementX> {
     } 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);