Fix infinite loop when there is a cycle in the class hierarchy (issue 28837)

pkg/analyzer/lib/src/generated/error_verifier.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 analyzer.src.generated.error_verifier;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 4890 matching lines @@
         if (hasSuperInitializer) {
           _errorReporter.reportErrorForNode(
               CompileTimeErrorCode.MULTIPLE_SUPER_INITIALIZERS, initializer);
         }
         hasSuperInitializer = true;
       }
     }
   }
 
   void _checkForMustCallSuper(MethodDeclaration node) {
+    if (node.isStatic) {
+      return;
+    }
     MethodElement element = _findOverriddenMemberThatMustCallSuper(node);
     if (element != null) {
       _InvocationCollector collector = new _InvocationCollector();
       node.accept(collector);
       if (!collector.superCalls.contains(element.name)) {
         _errorReporter.reportErrorForNode(HintCode.MUST_CALL_SUPER, node.name,
             [element.enclosingElement.name]);
       }
     }
   }
@@ skipping 1480 matching lines @@
     if (member == null) {
       return null;
     }
     ClassElement classElement =
         member.getAncestor((element) => element is ClassElement);
     if (classElement == null) {
       return null;
     }
     String name = member.name;
     ClassElement superclass = classElement.supertype?.element;
-    while (superclass != null) {
+    Set<ClassElement> visitedClasses = new Set();

[scheglov, 2017/02/20 18:27:02]

Type argument in creation?

[Brian Wilkerson, 2017/02/20 19:46:30]

Done

+    while (superclass != null && visitedClasses.add(superclass)) {
       ExecutableElement member = superclass.getMethod(name) ??
           superclass.getGetter(name) ??
           superclass.getSetter(name);
       if (member != null) {
         return member;
       }
       superclass = superclass.supertype?.element;
     }
     return null;
   }
@@ skipping 655 matching lines @@
 class _InvocationCollector extends RecursiveAstVisitor {
   final List<String> superCalls = <String>[];
 
   @override
   visitMethodInvocation(MethodInvocation node) {
     if (node.target is SuperExpression) {
       superCalls.add(node.methodName.name);
     }
   }
 }