Issue 21375. Fix for FunctionTypeAliasElement-based FunctionType source.

pkg/analysis_server/lib/src/services/correction/util.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 services.src.correction.util;
 
 import 'dart:math';
 
 import 'package:analysis_server/src/protocol.dart' show SourceChange,
     SourceEdit;
@@ skipping 870 matching lines @@
    */
   String getText(int offset, int length) {
     return _buffer.substring(offset, offset + length);
   }
 
   /**
    * Returns the source to reference [type] in this [CompilationUnit].
    */
   String getTypeSource(DartType type) {
     StringBuffer sb = new StringBuffer();
-    // just some Function, maybe find Function Type Alias later
-    if (type is FunctionType) {
+    // just a Function, not FunctionTypeAliasElement
+    if (type is FunctionType && type.element is! FunctionTypeAliasElement) {
       return "Function";
     }
     // prepare element
     Element element = type.element;
     if (element == null) {
       String source = type.toString();
       source = source.replaceAll('<dynamic>', '');
       source = source.replaceAll('<dynamic, dynamic>', '');
       return source;
     }
     // append prefix
     {
       ImportElement imp = _getImportElement(element);
       if (imp != null && imp.prefix != null) {
         sb.write(imp.prefix.displayName);
         sb.write(".");
       }
     }
     // append simple name
     String name = element.displayName;
     sb.write(name);
     // may be type arguments
-    if (type is InterfaceType) {
-      InterfaceType interfaceType = type;
-      List<DartType> arguments = interfaceType.typeArguments;
+    if (type is ParameterizedType) {
+      List<DartType> arguments = type.typeArguments;
       // check if has arguments
       bool hasArguments = false;
       for (DartType argument in arguments) {
         if (!argument.isDynamic) {
           hasArguments = true;
           break;
         }
       }
       // append type arguments
       if (hasArguments) {
@@ skipping 473 matching lines @@
 
   @override
   Object visitExpression(Expression node) {
     if (node is BinaryExpression && node.operator.type == groupOperatorType) {
       return super.visitNode(node);
     }
     operands.add(node);
     return null;
   }
 }