Fix handling of default formal parameters in DeclarationResolver.

pkg/analyzer/test/src/context/context_test.dart

Index: pkg/analyzer/test/src/context/context_test.dart
diff --git a/pkg/analyzer/test/src/context/context_test.dart b/pkg/analyzer/test/src/context/context_test.dart
index 83de70da6e109140a6e2373f59df78a9d07014d2..19352ab88d4999a1cc3f54b5a073ec3d9338e22d 100644
--- a/pkg/analyzer/test/src/context/context_test.dart
+++ b/pkg/analyzer/test/src/context/context_test.dart
@@ -2475,6 +2475,7 @@ void topLevelFunctionWithLocalFunction() {
 }
 
 void functionWithGenericFunctionTypedParam/*<S>*/(/*=T*/ pf/*<T>*/(/*=T*/ e)) {}
+void functionWithClosureAsDefaultParam([x = () => null]) {}
 ''');
     context.resolveCompilationUnit2(source, source);
     LibraryElement firstElement = context.computeLibraryElement(source);