Rollup merge of #111875 - WaffleLapkin:defer_on_drop, r=Nilstrieb

Don't leak the function that is called on drop

It probably wasn't causing problems anyway, but still, a `// this leaks, please don't pass anything that owns memory` is not sustainable.

I could implement a version which does not require `Option`, but it would require `unsafe`, at which point it's probably not worth it.

compiler/rustc_middle/src/ty/context/tls.rs

@@ -78,7 +78,7 @@ where
 {
     TLV.with(|tlv| {
         let old = tlv.replace(erase(context));
-        let _reset = rustc_data_structures::OnDrop(move || tlv.set(old));
+        let _reset = rustc_data_structures::defer(move || tlv.set(old));
         f()
     })
 }