fix named constructor completion

pkg/analysis_server/lib/src/services/completion/local_computer.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.completion.computer.dart.local;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart' as protocol show Element,
     ElementKind;
@@ skipping 248 matching lines @@
       return finished;
     }
   }
 
   @override
   visitCombinator(Combinator node) {
     // Handled by CombinatorComputer
   }
 
   @override
+  visitConstructorName(ConstructorName node) {
+    // InvocationComputer adds suggestions for prefixed elements
+    // but this computer adds suggestions for the prefix itself
+    Token period = node.period;
+    if (period == null || request.offset <= period.offset) {
+      visitNode(node);
+    }
+  }
+
+  @override
   visitMethodInvocation(MethodInvocation node) {
     // InvocationComputer adds suggestions for method selector
     Token period = node.period;
     if (period != null && period.offset < request.offset) {
       ArgumentList argumentList = node.argumentList;
       if (argumentList == null || request.offset <= argumentList.offset) {
         return;
       }
     }
     visitNode(node);
   }
 
   @override
   bool visitNamespaceDirective(NamespaceDirective node) {
     // No suggestions
     return finished;
   }
 
   @override
   visitPrefixedIdentifier(PrefixedIdentifier node) {
     // InvocationComputer adds suggestions for prefixed elements
     // but this computer adds suggestions for the prefix itself
-    SimpleIdentifier prefix = node.prefix;
-    if (prefix == null || request.offset <= prefix.end) {
+    Token period = node.period;
+    if (period == null || request.offset <= period.offset) {
       visitNode(node);
     }
   }
 
   @override
   visitPropertyAccess(PropertyAccess node) {
     // InvocationComputer adds suggestions for property access selector
   }
 
   @override
@@ skipping 132 matching lines @@
     if (name == null || name.length <= 0) {
       return DYNAMIC;
     }
     TypeArgumentList typeArgs = type.typeArguments;
     if (typeArgs != null) {
       //TODO (danrubel) include type arguments
     }
     return name;
   }
 }