Issue 25252. Stop collecting covering expressions at void invocations.

pkg/analysis_server/lib/src/services/refactoring/extract_local.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.refactoring.extract_local;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analysis_server/src/protocol_server.dart' hide Element;
@@ skipping 214 matching lines @@
     }
     // get covering node
     AstNode coveringNode =
         new NodeLocator(selectionRange.offset, selectionRange.end)
             .searchWithin(unit);
     // compute covering expressions
     for (AstNode node = coveringNode;
         node is Expression || node is ArgumentList;
         node = node.parent) {
       AstNode parent = node.parent;
+      // stop at void method invocations
+      if (node is MethodInvocation) {
+        MethodInvocation invocation = node;
+        Element element = invocation.methodName.bestElement;
+        if (element is ExecutableElement &&
+            element.returnType != null &&
+            element.returnType.isVoid) {
+          if (rootExpression == null) {
+            return new RefactoringStatus.fatal(
+                'Cannot extract the void expression.',
+                newLocation_fromNode(node));
+          }
+          break;
+        }
+      }
       // skip ArgumentList
       if (node is ArgumentList) {
         continue;
       }
       // skip AssignmentExpression
       if (node is AssignmentExpression) {
         continue;
       }
       // cannot extract the name part of a property access
       if (parent is PrefixedIdentifier && parent.identifier == node ||
@@ skipping 416 matching lines @@
 
   _TokenLocalElementVisitor(this.map);
 
   visitSimpleIdentifier(SimpleIdentifier node) {
     Element element = node.staticElement;
     if (element is LocalVariableElement) {
       map[node.token] = element;
     }
   }
 }