chore: checkpoint before Python removal

vendor/pin-project/tests/ui/pinned_drop/invalid-self.rs

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// by-ref binding `ref (mut) self` and sub-patterns `@` are not allowed in receivers (rejected by rustc).
+
+use std::pin::Pin;
+
+struct S {}
+
+impl S {
+    fn take_ref_self(ref self: Pin<&mut Self>) {} //~ ERROR expected identifier, found keyword `self`
+    fn take_ref_mut_self(ref mut self: Pin<&mut Self>) {} //~ ERROR expected identifier, found keyword `self`
+
+    fn self_subpat(self @ S {}: Self) {} //~ ERROR expected one of `)`, `,`, or `:`, found `@`
+}
+
+fn main() {}