From 02e50f03bf361d987c06cf7033a2d5efece74d20 Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Wed, 22 Nov 2023 02:30:43 +0100
Subject: [PATCH] Add `never_patterns` feature gate

---
 clippy_lints/src/equatable_if_let.rs        | 2 +-
 clippy_lints/src/matches/match_same_arms.rs | 3 +++
 clippy_lints/src/unnested_or_patterns.rs    | 2 +-
 clippy_lints/src/utils/author.rs            | 1 +
 clippy_utils/src/hir_utils.rs               | 1 +
 clippy_utils/src/lib.rs                     | 1 +
 6 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/clippy_lints/src/equatable_if_let.rs b/clippy_lints/src/equatable_if_let.rs
index 575fead5bf3e..630df9a84f58 100644
--- a/clippy_lints/src/equatable_if_let.rs
+++ b/clippy_lints/src/equatable_if_let.rs
@@ -46,7 +46,7 @@ fn unary_pattern(pat: &Pat<'_>) -> bool {
         pats.iter().all(unary_pattern)
     }
     match &pat.kind {
-        PatKind::Slice(_, _, _) | PatKind::Range(_, _, _) | PatKind::Binding(..) | PatKind::Wild | PatKind::Or(_) => {
+        PatKind::Slice(_, _, _) | PatKind::Range(_, _, _) | PatKind::Binding(..) | PatKind::Wild | PatKind::Never | PatKind::Or(_) => {
             false
         },
         PatKind::Struct(_, a, etc) => !etc && a.iter().all(|x| unary_pattern(x.pat)),
diff --git a/clippy_lints/src/matches/match_same_arms.rs b/clippy_lints/src/matches/match_same_arms.rs
index 745be671b86d..cbf478620ec3 100644
--- a/clippy_lints/src/matches/match_same_arms.rs
+++ b/clippy_lints/src/matches/match_same_arms.rs
@@ -150,6 +150,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
 #[derive(Clone, Copy)]
 enum NormalizedPat<'a> {
     Wild,
+    Never,
     Struct(Option<DefId>, &'a [(Symbol, Self)]),
     Tuple(Option<DefId>, &'a [Self]),
     Or(&'a [Self]),
@@ -229,6 +230,7 @@ impl<'a> NormalizedPat<'a> {
             PatKind::Binding(.., Some(pat)) | PatKind::Box(pat) | PatKind::Ref(pat, _) => {
                 Self::from_pat(cx, arena, pat)
             },
+            PatKind::Never => Self::Never,
             PatKind::Struct(ref path, fields, _) => {
                 let fields =
                     arena.alloc_from_iter(fields.iter().map(|f| (f.ident.name, Self::from_pat(cx, arena, f.pat))));
@@ -333,6 +335,7 @@ impl<'a> NormalizedPat<'a> {
     fn has_overlapping_values(&self, other: &Self) -> bool {
         match (*self, *other) {
             (Self::Wild, _) | (_, Self::Wild) => true,
+            (Self::Never, Self::Never) => true,
             (Self::Or(pats), ref other) | (ref other, Self::Or(pats)) => {
                 pats.iter().any(|pat| pat.has_overlapping_values(other))
             },
diff --git a/clippy_lints/src/unnested_or_patterns.rs b/clippy_lints/src/unnested_or_patterns.rs
index 8ff088a208f2..952c0dc72b19 100644
--- a/clippy_lints/src/unnested_or_patterns.rs
+++ b/clippy_lints/src/unnested_or_patterns.rs
@@ -226,7 +226,7 @@ fn transform_with_focus_on_idx(alternatives: &mut ThinVec<P<Pat>>, focus_idx: us
         // Therefore they are not some form of constructor `C`,
         // with which a pattern `C(p_0)` may be formed,
         // which we would want to join with other `C(p_j)`s.
-        Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_)
+        Ident(.., None) | Lit(_) | Wild | Never | Path(..) | Range(..) | Rest | MacCall(_)
         // Skip immutable refs, as grouping them saves few characters,
         // and almost always requires adding parens (increasing noisiness).
         // In the case of only two patterns, replacement adds net characters.
diff --git a/clippy_lints/src/utils/author.rs b/clippy_lints/src/utils/author.rs
index e8842ce10f8a..e83c04eda207 100644
--- a/clippy_lints/src/utils/author.rs
+++ b/clippy_lints/src/utils/author.rs
@@ -629,6 +629,7 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
 
         match pat.value.kind {
             PatKind::Wild => kind!("Wild"),
+            PatKind::Never => kind!("Never"),
             PatKind::Binding(ann, _, name, sub) => {
                 bind!(self, name);
                 opt_bind!(self, sub);
diff --git a/clippy_utils/src/hir_utils.rs b/clippy_utils/src/hir_utils.rs
index 8031e6faa745..34ec83709ffd 100644
--- a/clippy_utils/src/hir_utils.rs
+++ b/clippy_utils/src/hir_utils.rs
@@ -1017,6 +1017,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                 }
                 e.hash(&mut self.s);
             },
+            PatKind::Never => {},
             PatKind::Wild => {},
         }
     }
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 172b063df315..fd37713fc605 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -1707,6 +1707,7 @@ pub fn is_refutable(cx: &LateContext<'_>, pat: &Pat<'_>) -> bool {
 
     match pat.kind {
         PatKind::Wild => false,
+        PatKind::Never => false, // If `!` typechecked then the type is empty, so not refutable.
         PatKind::Binding(_, _, _, pat) => pat.map_or(false, |pat| is_refutable(cx, pat)),
         PatKind::Box(pat) | PatKind::Ref(pat, _) => is_refutable(cx, pat),
         PatKind::Lit(..) | PatKind::Range(..) => true,