extract named constructor suggestions from prefixed element contributor

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

Index: pkg/analysis_server/lib/src/services/completion/dart/named_constructor_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/named_constructor_contributor.dart b/pkg/analysis_server/lib/src/services/completion/dart/named_constructor_contributor.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f9dcd4c17897ee1553818c9c77fc5705c5ca0854
--- /dev/null
+++ b/pkg/analysis_server/lib/src/services/completion/dart/named_constructor_contributor.dart
@@ -0,0 +1,85 @@
+// 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.named_constructor;
+
+import 'dart:async';
+
+import 'package:analysis_server/plugin/protocol/protocol.dart' hide Element;
+import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/element.dart';
+import 'package:analysis_server/src/services/completion/dart/suggestion_builder.dart';
+
+/**
+ * A contributor for calculating named constructor suggestions
+ * such as suggesting `bar` in `new Foo.bar()`.
+ */
+class NamedConstructorContributor extends DartCompletionContributor {
+  @override
+  Future<List<CompletionSuggestion>> computeSuggestions(
+      DartCompletionRequest request) async {
+    // Determine if the target looks like a named constructor.
+    AstNode parsedNode = request.target.containingNode;
+    SimpleIdentifier targetId;
+    if (parsedNode is ConstructorName) {
+      TypeName type = parsedNode.type;
+      if (type != null) {
+        targetId = type.name;
+      }
+    } else if (parsedNode is PrefixedIdentifier) {
+      // Some PrefixedIdentifier nodes are transformed into
+      // ConstructorName nodes during the resolution process.
+      targetId = parsedNode.prefix;
+    }
+    if (targetId == null) {
+      return EMPTY_LIST;
+    }
+
+    // Resolve the containing library element
+    LibraryElement libElem = await request.libraryElement;
+    if (libElem == null) {
+      return EMPTY_LIST;
+    }
+
+    // Resolve the target to determine the type
+    await request.resolveIdentifier(targetId);
+
+    // Recompute the target since resolution may have changed it
+    AstNode node = request.target.containingNode;
+
+    // Build the list of suggestions
+    if (node is ConstructorName) {
+      TypeName typeName = node.type;
+      if (typeName != null) {
+        DartType type = typeName.type;
+        if (type != null) {
+          Element classElem = type.element;
+          if (classElem is ClassElement) {
+            return _buildSuggestions(libElem, classElem);
+          }
+        }
+      }
+    }
+    return EMPTY_LIST;
+  }
+
+  List<CompletionSuggestion> _buildSuggestions(
+      LibraryElement libElem, ClassElement classElem) {
+    bool isLocalClassDecl = classElem.library == libElem;
+    List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];
+    for (ConstructorElement elem in classElem.constructors) {
+      if (isLocalClassDecl || !elem.isPrivate) {
+        String name = elem.name;
+        if (name != null) {
+          CompletionSuggestion s = createSuggestion(elem, completion: name);
+          if (s != null) {
+            suggestions.add(s);
+          }
+        }
+      }
+    }
+    return suggestions;
+  }
+}