Use printUnexpected and add location information.

pkg/front_end/lib/src/fasta/errors.dart

Index: pkg/front_end/lib/src/fasta/errors.dart
diff --git a/pkg/front_end/lib/src/fasta/errors.dart b/pkg/front_end/lib/src/fasta/errors.dart
index a053a610a26a961da402757eb3aeb928c105ef28..4a92608b01c4bb33fc14fe6798313b8256c764de 100644
--- a/pkg/front_end/lib/src/fasta/errors.dart
+++ b/pkg/front_end/lib/src/fasta/errors.dart
@@ -65,13 +65,14 @@ dynamic inputError(Uri uri, int charOffset, Object error) {
 }
 
 String printUnexpected(Uri uri, int charOffset, String message) {
+  String formattedMessage = formatUnexpected(uri, charOffset, message);
   if (errorsAreFatal) {
+    print(formattedMessage);
     if (isVerbose) print(StackTrace.current);
     throw new InputError(uri, charOffset, message);
   }
-  message = formatUnexpected(uri, charOffset, message);
-  print(message);
-  return message;
+  print(formattedMessage);
+  return formattedMessage;
 }
 
 String formatUnexpected(Uri uri, int charOffset, String message) {