Calculate default args for local reference completions.

pkg/analysis_server/lib/src/services/completion/dart/local_reference_contributor.dart

Index: pkg/analysis_server/lib/src/services/completion/dart/local_reference_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/local_reference_contributor.dart b/pkg/analysis_server/lib/src/services/completion/dart/local_reference_contributor.dart
index ae669006a4b522b0cfbac074dfaa806fa8e04ae5..bbe9d33a09d48f826ba5f2ab02fee3ee9a8786a6 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/local_reference_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/local_reference_contributor.dart
@@ -470,11 +470,30 @@ class _LocalVisitor extends LocalDeclarationVisitor {
       // TODO(brianwilkerson) Support function types.
       return 'dynamic';
     }).toList();
-    suggestion.requiredParameterCount = paramList
-        .where((FormalParameter param) => param is! DefaultFormalParameter)
-        .length;
-    suggestion.hasNamedParameters = paramList
-        .any((FormalParameter param) => param.kind == ParameterKind.NAMED);
+
+    Iterable<ParameterElement> requiredParameters = paramList
+        .where((FormalParameter param) => param.kind == ParameterKind.REQUIRED)
+        .map((p) => p.element);
+    suggestion.requiredParameterCount = requiredParameters.length;
+
+    Iterable<ParameterElement> namedParameters = paramList
+        .where((FormalParameter param) => param.kind == ParameterKind.NAMED)
+        .map((p) => p.element);
+    suggestion.hasNamedParameters = namedParameters.isNotEmpty;
+
+    suggestion.defaultArgumentListString =
+        _buildDefaultArgList(requiredParameters, namedParameters);
+  }
+
+  String _buildDefaultArgList(Iterable<ParameterElement> requiredParams,
+      Iterable<ParameterElement> namedParams) {
+    List<String> args = requiredParams.map((p) => p.name).toList();
+    List<String> requiredArgs = namedParams
+        .where((p) => p.isRequired)
+        .map((p) => '${p.name}: null')
+        .toList();
+    args.addAll(requiredArgs);
+    return args.join(', ');
   }
 
   bool _isVoid(TypeAnnotation returnType) {