Auto merge of #120136 - matthiaskrgr:rollup-3zzb0z9, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #117561 (Stabilize `slice_first_last_chunk`)
 - #117662 ([rustdoc] Allows links in headings)
 - #119815 (Format sources into the error message when loading codegen backends)
 - #119835 (Exhaustiveness: simplify empty pattern logic)
 - #119984 (Change return type of unstable `Waker::noop()` from `Waker` to `&Waker`.)
 - #120009 (never_patterns: typecheck never patterns)
 - #120122 (Don't add needs-triage to A-diagnostics)
 - #120126 (Suggest `.swap()` when encountering conflicting borrows from `mem::swap` on a slice)
 - #120134 (Restrict access to the private field of newtype indexes)

Failed merges:

 - #119968 (Remove unused/unnecessary features)

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 5 insertions, 14 deletions

diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs
index 76098505b79..eba71a23435 100644
--- a/compiler/rustc_pattern_analysis/src/constructor.rs
+++ b/compiler/rustc_pattern_analysis/src/constructor.rs
@@ -861,12 +861,14 @@ impl<Cx: TypeCx> ConstructorSet<Cx> {
     /// any) are missing; 2/ split constructors to handle non-trivial intersections e.g. on ranges
     /// or slices. This can get subtle; see [`SplitConstructorSet`] for details of this operation
     /// and its invariants.
-    #[instrument(level = "debug", skip(self, pcx, ctors), ret)]
+    #[instrument(level = "debug", skip(self, ctors), ret)]
     pub(crate) fn split<'a>(
         &self,
-        pcx: &PlaceCtxt<'a, Cx>,
         ctors: impl Iterator<Item = &'a Constructor<Cx>> + Clone,
-    ) -> SplitConstructorSet<Cx> {
+    ) -> SplitConstructorSet<Cx>
+    where
+        Cx: 'a,
+    {
         let mut present: SmallVec<[_; 1]> = SmallVec::new();
         // Empty constructors found missing.
         let mut missing_empty = Vec::new();
@@ -1006,17 +1008,6 @@ impl<Cx: TypeCx> ConstructorSet<Cx> {
             }
         }
 
-        // We have now grouped all the constructors into 3 buckets: present, missing, missing_empty.
-        // In the absence of the `exhaustive_patterns` feature however, we don't count nested empty
-        // types as empty. Only non-nested `!` or `enum Foo {}` are considered empty.
-        if !pcx.mcx.tycx.is_exhaustive_patterns_feature_on()
-            && !(pcx.is_scrutinee && matches!(self, Self::NoConstructors))
-        {
-            // Treat all missing constructors as nonempty.
-            // This clears `missing_empty`.
-            missing.append(&mut missing_empty);
-        }
-
         SplitConstructorSet { present, missing, missing_empty }
     }
 }