Fix a bug where enum variants were not considered properly in type ns resolution

They should be considered just as well as in value ns, for example for struct literals.

crates/ide-diagnostics/src/handlers/generic_args_prohibited.rs

@@ -600,6 +600,25 @@ pub mod __private {
 //- /bar.rs crate:bar deps:foo edition:2018
 fn bar() {
     _ = foo::__private::Result::<(), ()>::Ok;
+}
+        "#,
+        );
+    }
+
+    #[test]
+    fn enum_variant_type_ns() {
+        check_diagnostics(
+            r#"
+enum KvnDeserializerErr<I> {
+    UnexpectedKeyword { found: I, expected: I },
+}
+
+fn foo() {
+    let _x: KvnDeserializerErr<()> =
+        KvnDeserializerErr::<()>::UnexpectedKeyword { found: (), expected: () };
+    let _x: KvnDeserializerErr<()> =
+        KvnDeserializerErr::<()>::UnexpectedKeyword::<()> { found: (), expected: () };
+                                                // ^^^^^^ 💡 error: you can specify generic arguments on either the enum or the variant, but not both
 }
         "#,
         );