Calculate default args for local reference completions.

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

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library services.completion.contributor.dart.local_ref;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart' as protocol
     show Element, ElementKind;
@@ skipping 452 matching lines @@
       if (type is TypeName) {
         Identifier typeId = type.name;
         if (typeId == null) {
           return 'dynamic';
         }
         return typeId.name;
       }
       // 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) {
     if (returnType is TypeName) {
       Identifier id = returnType.name;
       if (id != null && id.name == 'void') {
         return true;
       }
     }
     return false;
@@ skipping 17 matching lines @@
       String text = documentationComment.tokens
           .map((Token t) => t.toString())
           .join('\n')
           .replaceAll('\r\n', '\n');
       String doc = removeDartDocDelimiters(text);
       suggestion.docComplete = doc;
       suggestion.docSummary = getDartDocSummary(doc);
     }
   }
 }