Fix analyzer's treatment of mixin constructors.

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 1013 matching lines @@
   bool get isOrInheritsProxy;
 
   /**
    * Return `true` if this element has an annotation of the form '@proxy'.
    *
    * @return `true` if this element defines a proxy
    */
   bool get isProxy;
 
   /**
+   * Determine whether the given [constructor], which exists in the superclass
+   * of this class, is accessible to constructors in this class.
+   */
+  bool isSuperConstructorAccessible(ConstructorElement constructor);
+
+  /**
    * Return `true` if this class is defined by a typedef construct.
    *
    * @return `true` if this class is defined by a typedef construct
    */
   bool get isTypedef;
 
   /**
    * Return `true` if this class can validly be used as a mixin when defining another class.
    * The behavior of this method is defined by the Dart Language Specification in section 9:
    * <blockquote>It is a compile-time error if a declared or derived mixin refers to super. It is a
@@ skipping 450 matching lines @@
   bool get isProxy {
     for (ElementAnnotation annotation in metadata) {
       if (annotation.isProxy) {
         return true;
       }
     }
     return false;
   }
 
   @override
+  bool isSuperConstructorAccessible(ConstructorElement constructor) {
+    // If this class has no mixins, then all superclass constructors are
+    // accessible.
+    if (mixins.isEmpty) {
+      return true;
+    }
+    // Otherwise only constructors that lack optional parameters are
+    // accessible (see dartbug.com/19576).
+    for (ParameterElement parameter in constructor.parameters) {
+      if (parameter.parameterKind != ParameterKind.REQUIRED) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  @override
   bool get isTypedef => hasModifier(Modifier.TYPEDEF);
 
   @override
   bool get isValidMixin => hasModifier(Modifier.MIXIN);
 
   @override
   MethodElement lookUpConcreteMethod(String methodName, LibraryElement library) => _internalLookUpConcreteMethod(methodName, library, true);
 
   @override
   PropertyAccessorElement lookUpGetter(String getterName, LibraryElement library) => _internalLookUpGetter(getterName, library, true);
@@ skipping 10267 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;
   }
 }