Various constant checks.

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

Index: pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart b/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
index 310d137e0fb19447b6ade38ed1621fb65defea44..a153127b331f9294455892a37f793bc7afccd9ac 100644
--- a/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
@@ -49,6 +49,8 @@ abstract class BuilderHelper {
 
   int get functionNestingLevel;
 
+  bool get constantExpressionRequired;
+
   Constructor lookupConstructor(Name name, {bool isSuper});
 
   Expression toSuperMethodInvocation(MethodInvocation node);