Add DynamicType, NeverType, and VoidType to API.

R=brianwilkerson@google.com

Change-Id: Icf917d999878b3c4d7b1d9425eb8a3c79921ba6b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153401
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## 0.39.13-dev
 * Added 'dart/sdk/build_sdk_summary.dart' with `buildSdkSummary`.
+* Added `DynamicType`, `NeverType`, and `VoidType` interfaces.
 
 ## 0.39.12
 * Deprecated `canUseSummaries` in `DartSdkManager` constructor.

pkg/analyzer/lib/dart/element/type.dart

@@ -165,6 +165,12 @@ Use ClassElement.instantiate() or FunctionTypeAliasElement.instantiate()
       List<DartType> argumentTypes, List<DartType> parameterTypes);
 }
 
+/// The type `dynamic` is a type which is a supertype of all other types, just
+/// like `Object`, with the difference that the static analysis assumes that
+/// every member access has a corresponding member with a signature that
+/// admits the given access.
+abstract class DynamicType implements DartType {}
+
 /// The type of a function, method, constructor, getter, or setter. Function
 /// types come in three variations:
 ///
@@ -551,6 +557,9 @@ abstract class InterfaceType implements ParameterizedType {
       InterfaceTypeImpl.getSmartLeastUpperBound(first, second);
 }
 
+/// The type `Never` represents the uninhabited bottom type.
+abstract class NeverType implements DartType {}
+
 /// A type that can track substituted type parameters, either for itself after
 /// instantiation, or from a surrounding context.
 ///
@@ -601,3 +610,12 @@ abstract class TypeParameterType implements DartType {
   @override
   TypeParameterElement get element;
 }
+
+/// The special type `void` is used to indicate that the value of an
+/// expression is meaningless, and intended to be discarded.
+abstract class VoidType implements DartType {
+  @override
+  @deprecated
+  VoidType substitute2(
+      List<DartType> argumentTypes, List<DartType> parameterTypes);
+}

pkg/analyzer/lib/dart/element/type_provider.dart

@@ -5,7 +5,6 @@
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/constant/value.dart';
-import 'package:analyzer/src/dart/element/type.dart';
 
 /// The interface `TypeProvider` defines the behavior of objects that provide
 /// access to types defined by the language.

pkg/analyzer/lib/src/dart/constant/potentially_constant.dart

@@ -5,6 +5,7 @@
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:meta/meta.dart';
 

pkg/analyzer/lib/src/dart/element/type.dart

@@ -45,7 +45,7 @@ List<T> _transformOrShare<T>(List<T> list, T Function(T) transform) {
 }
 
 /// The [Type] representing the type `dynamic`.
-class DynamicTypeImpl extends TypeImpl {
+class DynamicTypeImpl extends TypeImpl implements DynamicType {
   /// The unique instance of this class.
   static final DynamicTypeImpl instance = DynamicTypeImpl._();
 
@@ -1629,7 +1629,7 @@ class InterfaceTypeImpl extends TypeImpl implements InterfaceType {
 }
 
 /// The type `Never` represents the uninhabited bottom type.
-class NeverTypeImpl extends TypeImpl {
+class NeverTypeImpl extends TypeImpl implements NeverType {
   /// The unique instance of this class, nullable.
   ///
   /// This behaves equivalently to the `Null` type, but we distinguish it for
@@ -2062,14 +2062,6 @@ class TypeParameterTypeImpl extends TypeImpl implements TypeParameterType {
   }
 }
 
-/// The type `void`.
-abstract class VoidType implements DartType {
-  @override
-  @deprecated
-  VoidType substitute2(
-      List<DartType> argumentTypes, List<DartType> parameterTypes);
-}
-
 /// A concrete implementation of a [VoidType].
 class VoidTypeImpl extends TypeImpl implements VoidType {
   /// The unique instance of this class, with indeterminate nullability.

pkg/analyzer/lib/src/summary2/linking_bundle_context.dart

@@ -7,7 +7,6 @@ import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/member.dart';
-import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/type_algebra.dart';
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/idl.dart';