Improve error messages.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 9cdcbe1f58629274aee5581741b1df02e122905b..c9b20eb823217ccdd2ffaf20fba7e0e4bb25c802 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -2924,7 +2924,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       {bool silent: false}) {
     // TODO(ahe): If constantExpressionRequired is set, set it to false to
     // avoid a long list of errors.
-    return library.addCompileTimeError(charOffset, message, fileUri: uri);
+    return library.addCompileTimeError(charOffset, message,
+        fileUri: uri, silent: silent);
   }
 
   @override