suggest prefixed constructors - fixes #23210

pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart

 // Copyright (c) 2014, 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 test.services.completion.invocation;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
@@ skipping 223 matching lines @@
   }
 
   test_libraryPrefix2() {
     // SimpleIdentifier  MethodInvocation  ExpressionStatement
     addTestSource('import "dart:async" as bar; foo() {bar.^ print("f")}');
     return computeFull((bool result) {
       assertSuggestClass('Future');
     });
   }
 
+  test_libraryPrefix3() {
+    // SimpleIdentifier  MethodInvocation  ExpressionStatement
+    addTestSource('import "dart:async" as bar; foo() {new bar.F^ print("f")}');
+    return computeFull((bool result) {
+      assertSuggestConstructor('Future');
+      assertSuggestConstructor('Future.delayed');
+    });
+  }
+
   test_libraryPrefix_deferred() {
     // SimpleIdentifier  PrefixedIdentifier  ExpressionStatement
     addTestSource('import "dart:async" deferred as bar; foo() {bar.^}');
     return computeFull((bool result) {
       assertSuggestClass('Future');
       assertSuggestFunction('loadLibrary', 'Future<dynamic>');
     });
   }
 
   test_libraryPrefix_with_exports() {
@@ skipping 403 matching lines @@
       assertNotSuggested('ms2');
       assertSuggestInvocationMethod('m', 'C2', null,
           relevance: DART_RELEVANCE_HIGH);
       assertNotSuggested('fi3');
       assertNotSuggested('fs3');
       assertNotSuggested('mi3');
       assertNotSuggested('ms3');
     });
   }
 }