Allow analyzer to distinguish unresolved types from dynamic.

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 2703 matching lines @@
   /**
    * Return `true` if this type is a supertype of the given type. A type <i>S</i> is a
    * supertype of <i>T</i>, written <i>S</i> :> <i>T</i>, iff <i>T</i> is a subtype of <i>S</i>.
    *
    * @param type the type being compared with this type
    * @return `true` if this type is a supertype of the given type
    */
   bool isSupertypeOf(DartType type);
 
   /**
+   * Return `true` if this type represents a typename that couldn't be
+   * resolved.
+   */
+  bool get isUndefined;
+
+  /**
    * Return `true` if this type represents the type 'void'.
    *
    * @return `true` if this type represents the type 'void'
    */
   bool get isVoid;
 
   /**
    * Return the type resulting from substituting the given arguments for the given parameters in
    * this type. The specification defines this operation in section 2: <blockquote> The notation
    * <i>[x<sub>1</sub>, ..., x<sub>n</sub>/y<sub>1</sub>, ..., y<sub>n</sub>]E</i> denotes a copy of
@@ skipping 94 matching lines @@
   ElementKind get kind => ElementKind.DYNAMIC;
 }
 
 /**
  * The unique instance of the class `DynamicTypeImpl` implements the type `dynamic`.
  */
 class DynamicTypeImpl extends TypeImpl {
   /**
    * The unique instance of this class.
    */
-  static DynamicTypeImpl _INSTANCE = new DynamicTypeImpl();
+  static DynamicTypeImpl _INSTANCE = new DynamicTypeImpl._();
 
   /**
    * Return the unique instance of this class.
    *
    * @return the unique instance of this class
    */
   static DynamicTypeImpl get instance => _INSTANCE;
 
   /**
    * Prevent the creation of instances of this class.
    */
-  DynamicTypeImpl() : super(new DynamicElementImpl(), Keyword.DYNAMIC.syntax) {
+  DynamicTypeImpl._() : super(new DynamicElementImpl(), Keyword.DYNAMIC.syntax) {
     (element as DynamicElementImpl).type = this;
   }
 
   @override
   bool operator ==(Object object) => identical(object, this);
 
   @override
   int get hashCode => 1;
 
   @override
@@ skipping 4416 matching lines @@
     return (element == otherType.element) && TypeImpl.equalArrays(typeArguments, otherType.typeArguments, visitedElementPairs);
   }
 
   @override
   bool internalIsMoreSpecificThan(DartType type, bool withDynamic, Set<TypeImpl_TypePair> visitedTypePairs) {
     //
     // S is dynamic.
     // The test to determine whether S is dynamic is done here because dynamic is not an instance of
     // InterfaceType.
     //
-    if (identical(type, DynamicTypeImpl.instance)) {
+    if (type.isDynamic) {
       return true;
     } else if (type is UnionType) {
       return (type as UnionTypeImpl).internalUnionTypeIsLessSpecificThan(this, withDynamic, visitedTypePairs);
     } else if (type is! InterfaceType) {
       return false;
     }
     return _isMoreSpecificThan(type as InterfaceType, new HashSet<ClassElement>(), withDynamic, visitedTypePairs);
   }
 
   @override
@@ skipping 3553 matching lines @@
     }
     bool result = internalIsSubtypeOf(type, visitedTypePairs);
     visitedTypePairs.remove(typePair);
     return result;
   }
 
   @override
   bool isSupertypeOf(DartType type) => type.isSubtypeOf(this);
 
   @override
+  bool get isUndefined => false;
+
+  @override
   bool get isVoid => false;
 
   @override
   String toString() {
     JavaStringBuilder builder = new JavaStringBuilder();
     appendTo(builder);
     return builder.toString();
   }
 
   /**
@@ skipping 260 matching lines @@
 /**
  * The interface `UndefinedElement` defines the behavior of pseudo-elements that represent
  * names that are undefined. This situation is not allowed by the language, so objects implementing
  * this interface always represent an error. As a result, most of the normal operations on elements
  * do not make sense and will return useless results.
  */
 abstract class UndefinedElement implements Element {
 }
 
 /**
+ * The unique instance of the class `UndefinedTypeImpl` implements the type of
+ * typenames that couldn't be resolved.
+ *
+ * This class behaves like DynamicTypeImpl in almost every respect, to reduce
+ * cascading errors.
+ */
+class UndefinedTypeImpl extends TypeImpl {
+  /**
+   * The unique instance of this class.
+   */
+  static UndefinedTypeImpl _INSTANCE = new UndefinedTypeImpl._();
+
+  /**
+   * Return the unique instance of this class.
+   *
+   * @return the unique instance of this class
+   */
+  static UndefinedTypeImpl get instance => _INSTANCE;
+
+  /**
+   * Prevent the creation of instances of this class.
+   */
+  UndefinedTypeImpl._()
+      : super(DynamicElementImpl.instance, Keyword.DYNAMIC.syntax);
+
+  @override
+  bool operator ==(Object object) => identical(object, this);
+
+  @override
+  int get hashCode => 1;
+
+  @override
+  bool get isDynamic => true;
+
+  @override
+  bool isSupertypeOf(DartType type) => true;
+
+  @override
+  bool get isUndefined => true;
+
+  @override
+  DartType substitute2(List<DartType> argumentTypes, List<DartType> parameterTypes) {
+    int length = parameterTypes.length;
+    for (int i = 0; i < length; i++) {
+      if (parameterTypes[i] == this) {
+        return argumentTypes[i];
+      }
+    }
+    return this;
+  }
+
+  @override
+  bool internalEquals(Object object, Set<ElementPair> visitedElementPairs) => identical(object, this);
+
+  @override
+  bool internalIsMoreSpecificThan(DartType type, bool withDynamic, Set<TypeImpl_TypePair> visitedTypePairs) {
+    // T is S
+    if (identical(this, type)) {
+      return true;
+    }
+    // else
+    return withDynamic;
+  }
+
+  @override
+  bool internalIsSubtypeOf(DartType type, Set<TypeImpl_TypePair> visitedTypePairs) => true;
+}
+
+/**
  * A flat immutable union of `Type`s. Here "flat" means a union type never contains another
  * union type.
  */
 abstract class UnionType implements DartType {
   /**
    * @return an immutable view of the types in this union type.
    */
   Set<DartType> get elements;
 }
 
@@ skipping 530 matching lines @@
 
   @override
   bool internalIsSubtypeOf(DartType type, Set<TypeImpl_TypePair> visitedTypePairs) {
     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) || identical(type, DynamicTypeImpl.instance);
+    return identical(type, this) || type.isDynamic;
   }
 }