Auto merge of #79278 - mark-i-m:stabilize-or-pattern, r=nikomatsakis

Stabilize or_patterns (RFC 2535, 2530, 2175)

closes #54883

This PR stabilizes the or_patterns feature in Rust 1.53.

This is blocked on the following (in order):
- [x] The crater run in https://github.com/rust-lang/rust/pull/78935#issuecomment-731564021
- [x] The resolution of the unresolved questions and a second crater run (https://github.com/rust-lang/rust/pull/78935#issuecomment-735412705)
    - It looks like we will need to pursue some sort of edition-based transition for `:pat`.
- [x] Nomination and discussion by T-lang
- [x] Implement new behavior for `:pat` based on consensus (https://github.com/rust-lang/rust/pull/80100).
- [ ] An FCP on stabilization

EDIT: Stabilization report is in https://github.com/rust-lang/rust/pull/79278#issuecomment-772815177

clippy_lints/src/lib.rs

@@ -5,7 +5,7 @@
 #![feature(drain_filter)]
 #![feature(in_band_lifetimes)]
 #![feature(once_cell)]
-#![feature(or_patterns)]
+#![cfg_attr(bootstrap, feature(or_patterns))]
 #![feature(rustc_private)]
 #![feature(stmt_expr_attributes)]
 #![feature(control_flow_enum)]

clippy_lints/src/unnested_or_patterns.rs

@@ -72,11 +72,6 @@ impl EarlyLintPass for UnnestedOrPatterns {
 }
 
 fn lint_unnested_or_patterns(cx: &EarlyContext<'_>, pat: &Pat) {
-    if !cx.sess.features_untracked().or_patterns {
-        // Do not suggest nesting the patterns if the feature `or_patterns` is not enabled.
-        return;
-    }
-
     if let Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_) = pat.kind {
         // This is a leaf pattern, so cloning is unprofitable.
         return;