Handle use of constant constructors with default values.

pkg/compiler/lib/src/elements/modelx.dart

Index: pkg/compiler/lib/src/elements/modelx.dart
diff --git a/pkg/compiler/lib/src/elements/modelx.dart b/pkg/compiler/lib/src/elements/modelx.dart
index 9d4a3cfaed923770a25e291e395d15488f687fd0..2381d64022b357abfcc46f8a1b83ca0e81f90309 100644
--- a/pkg/compiler/lib/src/elements/modelx.dart
+++ b/pkg/compiler/lib/src/elements/modelx.dart
@@ -1393,6 +1393,11 @@ class VariableList implements DeclarationSite {
 abstract class ConstantVariableMixin implements VariableElement {
   ConstantExpression constantCache;
 
+  // TODO(johnniwinther): Update the on `constant = ...` when evaluation of
+  // constant expression can handle references to unanalyzed constant variables.
+  @override
+  bool get hasConstant => false;
+
   ConstantExpression get constant {
     if (isPatch) {
       ConstantVariableMixin originVariable = origin;