Check for void in rules subtyping (fixes #25069)

pkg/analyzer/test/src/task/strong/checker_test.dart

Index: pkg/analyzer/test/src/task/strong/checker_test.dart
diff --git a/pkg/analyzer/test/src/task/strong/checker_test.dart b/pkg/analyzer/test/src/task/strong/checker_test.dart
index dc4b9c44121d99c11f5f753a1e3f1056286d6d5a..781a91d1702c0fa13f8510db33b02ea4e987a59b 100644
--- a/pkg/analyzer/test/src/task/strong/checker_test.dart
+++ b/pkg/analyzer/test/src/task/strong/checker_test.dart
@@ -276,6 +276,17 @@ void main() {
    '''
   });
 
+  // Regression test for https://github.com/dart-lang/sdk/issues/25069
+  testChecker('Void subtyping', {
+    '/main.dart': '''
+      typedef int Foo();
+      void foo() {}
+      void main () {
+        Foo x = /*severe:StaticTypeError*/foo();
+      }
+   '''
+  });
+
   testChecker('Ground type subtyping: dynamic is top', {
     '/main.dart': '''