Add debugging for issues 21013 and 21014

pkg/analyzer/lib/src/generated/element.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.element;
 
 import 'dart:collection';
@@ skipping 10018 matching lines @@
    *
    * @param baseAccessor the base property accessor
    * @param definingType the type defining the parameters and arguments to be used in the
    *          substitution
    * @return true if the type is changed by type substitution.
    */
   static bool _isChangedByTypeSubstitution(PropertyAccessorElement baseAccessor, InterfaceType definingType) {
     List<DartType> argumentTypes = definingType.typeArguments;
     if (baseAccessor != null && argumentTypes.length != 0) {
       FunctionType baseType = baseAccessor.type;
+      if (baseType == null) {
+        AnalysisEngine.instance.logger.logInformation(
+            'Type of $baseAccessor is null in PropertyAccessorMember._isChangedByTypeSubstitution');
+        return false;
+      }
       List<DartType> parameterTypes = definingType.element.type.typeArguments;
       FunctionType substitutedType = baseType.substitute2(argumentTypes, parameterTypes);
       if (baseType != substitutedType) {
         return true;
       }
       // If this property accessor is based on a field, that field might have a propagated type.
       // In which case we need to check whether the propagated type of the field needs substitution.
       PropertyInducingElement field = baseAccessor.variable;
       if (!field.isSynthetic) {
         DartType baseFieldType = field.propagatedType;
@@ skipping 623 matching lines @@
   accept(ElementVisitor visitor) => visitor.visitTopLevelVariableElement(this);
 
   @override
   ElementKind get kind => ElementKind.TOP_LEVEL_VARIABLE;
 
   @override
   bool get isStatic => true;
 }
 
 /**
- * The abstract class `TypeImpl` implements the behavior common to objects representing the
- * declared type of elements in the element model.
+ * The abstract class `TypeImpl` implements the behavior common to objects
+ * representing the declared type of elements in the element model.
  */
 abstract class TypeImpl implements DartType {
-  static bool equalArrays(List<DartType> typeArgs1, List<DartType> typeArgs2, Set<ElementPair> visitedElementPairs) {
-    if (typeArgs1.length != typeArgs2.length) {
+  /**
+   * Return `true` if corresponding elements of the [first] and [second] lists
+   * of type arguments are all equal. Use the set of [visitedElementPairs] to
+   * prevent infinite loops when the types are recursively defined.
+   */
+  static bool equalArrays(List<DartType> first, List<DartType> second,
+      Set<ElementPair> visitedElementPairs) {
+    if (first.length != second.length) {
       return false;
     }
-    for (int i = 0; i < typeArgs1.length; i++) {
-      if (!(typeArgs1[i] as TypeImpl).internalEquals(typeArgs2[i], visitedElementPairs)) {
+    for (int i = 0; i < first.length; i++) {
+      if (first[i] == null) {
+        AnalysisEngine.instance.logger.logInformation(
+            'Found null type argument in TypeImpl.equalArrays');
+        return second[i] == null;
+      } else if (second[i] == null) {
+        AnalysisEngine.instance.logger.logInformation(
+            'Found null type argument in TypeImpl.equalArrays');
+        return false;
+      }
+      if (!(first[i] as TypeImpl).internalEquals(second[i], visitedElementPairs)) {
         return false;
       }
     }
     return true;
   }
 
   /**
    * Return an array containing the results of using the given argument types and parameter types to
    * perform a substitution on all of the given types.
    *
@@ skipping 1064 matching lines @@
     if (type is UnionType) {
       return (type as UnionTypeImpl).internalUnionTypeIsSuperTypeOf(this, visitedTypePairs);
     }
     // The only subtype relations that pertain to void are therefore:
     // void <: void (by reflexivity)
     // bottom <: void (as bottom is a subtype of all types).
     // void <: dynamic (as dynamic is a supertype of all types)
     return identical(type, this) || type.isDynamic;
   }
 }