Rollup merge of rust-lang#94397 - xFrednet:69838-deprecate-pre-expans…

…ion, r=cjgillot

Document that pre-expansion lint passes are softly deprecated

The pre-expansion lint pass has been softly deprecated since rust-lang#69838. Every once in a while I see someone mention it as a possibility, only get the feedback that it's deprecated. This PR officially documents that the method is soft deprecated to have a single point of truth for it.

That's it. Have a great rest of the day 🙃

---

* See [rust#69838](rust-lang#69838)
* See [rust-clippy#5518](rust-lang/rust-clippy#5518)

compiler/rustc_lint/src/context.rs

@@ -166,7 +166,12 @@ impl LintStore {
         self.early_passes.push(Box::new(pass));
     }
 
-    /// Used by clippy.
+    /// This lint pass is softly deprecated. It misses expanded code and has caused a few
+    /// errors in the past. Currently, it is only used in Clippy. New implementations
+    /// should avoid using this interface, as it might be removed in the future.
+    ///
+    /// * See [rust#69838](https://github.com/rust-lang/rust/pull/69838)
+    /// * See [rust-clippy#5518](https://github.com/rust-lang/rust-clippy/pull/5518)
     pub fn register_pre_expansion_pass(
         &mut self,
         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,