treat void as a top type, analyzer fix for #28763

pkg/analyzer/test/generated/type_system_test.dart

Index: pkg/analyzer/test/generated/type_system_test.dart
diff --git a/pkg/analyzer/test/generated/type_system_test.dart b/pkg/analyzer/test/generated/type_system_test.dart
index 0f6ea84d5fb39b618214677aebec14eb79bb185a..a0844fd73111a9deb6d2e99d083bc2eb57c2f262 100644
--- a/pkg/analyzer/test/generated/type_system_test.dart
+++ b/pkg/analyzer/test/generated/type_system_test.dart
@@ -271,7 +271,12 @@ abstract class LeastUpperBoundTestBase extends BoundTestBase {
   }
 
   void test_dynamic_void() {
-    _checkLeastUpperBound(dynamicType, voidType, dynamicType);
+    expect(typeSystem.isSubtypeOf(dynamicType, voidType), isTrue);
+    expect(typeSystem.isSubtypeOf(voidType, dynamicType), isTrue);
+    // TODO(jmesserly): this is sensitive to order, see
+    // https://github.com/dart-lang/sdk/issues/28513
+    expect(typeSystem.getLeastUpperBound(dynamicType, voidType), dynamicType);
+    expect(typeSystem.getLeastUpperBound(voidType, dynamicType), voidType);
   }
 
   void test_functionsDifferentRequiredArity() {
@@ -1199,7 +1204,14 @@ class StrongGreatestLowerBoundTest extends BoundTestBase {
   }
 
   void test_dynamic_void() {
-    _checkGreatestLowerBound(dynamicType, voidType, voidType);
+    expect(typeSystem.isSubtypeOf(dynamicType, voidType), isTrue);
+    expect(typeSystem.isSubtypeOf(voidType, dynamicType), isTrue);
+    // TODO(jmesserly): this is sensitive to order, see
+    // https://github.com/dart-lang/sdk/issues/28513
+    expect(strongTypeSystem.getGreatestLowerBound(dynamicType, voidType),
+        voidType);
+    expect(strongTypeSystem.getGreatestLowerBound(voidType, dynamicType),
+        dynamicType);
   }
 
   void test_functionsDifferentNamedTakeUnion() {