Delay a bug when we see SelfCtor in ref pattern

src/test/ui/pattern/issue-95878.rs

@@ -0,0 +1,12 @@
+struct Foo<'a>(&'a ());
+
+impl<'a> Foo<'a> {
+    fn spam(&mut self, baz: &mut Vec<u32>) {
+        match 15 {
+            ref Self => (),
+            //~^ ERROR expected identifier, found keyword `Self`
+        }
+    }
+}
+
+fn main() {}

src/test/ui/pattern/issue-95878.stderr

@@ -0,0 +1,8 @@
+error: expected identifier, found keyword `Self`
+  --> $DIR/issue-95878.rs:6:17
+   |
+LL |             ref Self => (),
+   |                 ^^^^ expected identifier, found keyword
+
+error: aborting due to previous error
+