fix #26141, add support for type arguments to constants

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

Index: pkg/analyzer/lib/src/dart/constant/value.dart
diff --git a/pkg/analyzer/lib/src/dart/constant/value.dart b/pkg/analyzer/lib/src/dart/constant/value.dart
index a26992577fea4e013cc524b7e6ac3fff18a0b632..a0d11629d04247eea94cf6941d2ed8186e3c13a4 100644
--- a/pkg/analyzer/lib/src/dart/constant/value.dart
+++ b/pkg/analyzer/lib/src/dart/constant/value.dart
@@ -720,10 +720,7 @@ class DartObjectImpl implements DartObject {
   DartType toTypeValue() {
     InstanceState state = _state;
     if (state is TypeState) {
-      Element element = state._element;
-      if (element is TypeDefiningElement) {
-        return element.type;
-      }
+      return state._type;
     }
     return null;
   }
@@ -2771,29 +2768,29 @@ class TypeState extends InstanceState {
   /**
    * The element representing the type being modeled.
    */
-  final Element _element;
+  final DartType _type;
 
   /**
    * Initialize a newly created state to represent the given [value].
    */
-  TypeState(this._element);
+  TypeState(this._type);
 
   @override
-  int get hashCode => _element == null ? 0 : _element.hashCode;
+  int get hashCode => _type?.hashCode ?? 0;
 
   @override
   String get typeName => "Type";
 
   @override
   bool operator ==(Object object) =>
-      object is TypeState && (_element == object._element);
+      object is TypeState && (_type == object._type);
 
   @override
   StringState convertToString() {
-    if (_element == null) {
+    if (_type == null) {
       return StringState.UNKNOWN_VALUE;
     }
-    return new StringState(_element.name);
+    return new StringState(_type.displayName);
   }
 
   @override
@@ -2804,15 +2801,15 @@ class TypeState extends InstanceState {
 
   @override
   BoolState isIdentical(InstanceState rightOperand) {
-    if (_element == null) {
+    if (_type == null) {
       return BoolState.UNKNOWN_VALUE;
     }
     if (rightOperand is TypeState) {
-      Element rightElement = rightOperand._element;
-      if (rightElement == null) {
+      DartType rightType = rightOperand._type;
+      if (rightType == null) {
         return BoolState.UNKNOWN_VALUE;
       }
-      return BoolState.from(_element == rightElement);
+      return BoolState.from(_type == rightType);
     } else if (rightOperand is DynamicState) {
       return BoolState.UNKNOWN_VALUE;
     }
@@ -2820,5 +2817,5 @@ class TypeState extends InstanceState {
   }
 
   @override
-  String toString() => _element == null ? "-unknown-" : _element.name;
+  String toString() => _type?.toString() ?? "-unknown-";
 }