Rollup merge of #119967 - ShE3py:patkind-err, r=WaffleLapkin

Add `PatKind::Err` to AST/HIR

#116715 added `thir::PatKind::Error`; this PR adds `hir::PatKind::Err` and `ast::PatKind::Err` (see https://github.com/rust-lang/rust/pull/118625#discussion_r1446587901.)

---

``@rustbot`` label +A-patterns
r? WaffleLapkin

src/tools/clippy/clippy_lints/src/equatable_if_let.rs

@@ -51,7 +51,8 @@ fn unary_pattern(pat: &Pat<'_>) -> bool {
         | PatKind::Binding(..)
         | PatKind::Wild
         | PatKind::Never
-        | PatKind::Or(_) => false,
+        | PatKind::Or(_)
+        | PatKind::Err(_) => false,
         PatKind::Struct(_, a, etc) => !etc && a.iter().all(|x| unary_pattern(x.pat)),
         PatKind::Tuple(a, etc) | PatKind::TupleStruct(_, a, etc) => etc.as_opt_usize().is_none() && array_rec(a),
         PatKind::Ref(x, _) | PatKind::Box(x) => unary_pattern(x),

src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs

@@ -11,7 +11,7 @@ use rustc_hir::{Arm, Expr, ExprKind, HirId, HirIdMap, HirIdMapEntry, HirIdSet, P
 use rustc_lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
 use rustc_lint::LateContext;
 use rustc_middle::ty;
-use rustc_span::Symbol;
+use rustc_span::{ErrorGuaranteed, Symbol};
 
 use super::MATCH_SAME_ARMS;
 
@@ -167,6 +167,8 @@ enum NormalizedPat<'a> {
     /// contains everything afterwards. Note that either side, or both sides, may contain zero
     /// patterns.
     Slice(&'a [Self], Option<&'a [Self]>),
+    /// A placeholder for a pattern that wasn't well formed in some way.
+    Err(ErrorGuaranteed),
 }
 
 #[derive(Clone, Copy)]
@@ -329,6 +331,7 @@ impl<'a> NormalizedPat<'a> {
                 arena.alloc_from_iter(front.iter().map(|pat| Self::from_pat(cx, arena, pat))),
                 wild_pat.map(|_| &*arena.alloc_from_iter(back.iter().map(|pat| Self::from_pat(cx, arena, pat)))),
             ),
+            PatKind::Err(guar) => Self::Err(guar),
         }
     }
 

src/tools/clippy/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 | Never | Path(..) | Range(..) | Rest | MacCall(_)
+        Ident(.., None) | Lit(_) | Wild | Err(_) | 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.

src/tools/clippy/clippy_lints/src/utils/author.rs

@@ -710,6 +710,7 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
                 self.slice(start, |pat| self.pat(pat));
                 self.slice(end, |pat| self.pat(pat));
             },
+            PatKind::Err(_) => kind!("Err"),
         }
     }
 

src/tools/clippy/clippy_utils/src/hir_utils.rs

@@ -1007,7 +1007,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                 }
                 e.hash(&mut self.s);
             },
-            PatKind::Never | PatKind::Wild => {},
+            PatKind::Never | PatKind::Wild | PatKind::Err(_) => {},
         }
     }
 

src/tools/clippy/clippy_utils/src/lib.rs

@@ -1733,6 +1733,7 @@ pub fn is_refutable(cx: &LateContext<'_>, pat: &Pat<'_>) -> bool {
                 },
             }
         },
+        PatKind::Err(_) => true,
     }
 }
 

src/tools/rustfmt/src/patterns.rs

@@ -40,9 +40,11 @@ pub(crate) fn is_short_pattern(pat: &ast::Pat, pat_str: &str) -> bool {
 
 fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
     match pat.kind {
-        ast::PatKind::Rest | ast::PatKind::Never | ast::PatKind::Wild | ast::PatKind::Lit(_) => {
-            true
-        }
+        ast::PatKind::Rest
+        | ast::PatKind::Never
+        | ast::PatKind::Wild
+        | ast::PatKind::Err(_)
+        | ast::PatKind::Lit(_) => true,
         ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
         ast::PatKind::Struct(..)
         | ast::PatKind::MacCall(..)
@@ -274,6 +276,7 @@ impl Rewrite for Pat {
             PatKind::Paren(ref pat) => pat
                 .rewrite(context, shape.offset_left(1)?.sub_width(1)?)
                 .map(|inner_pat| format!("({})", inner_pat)),
+            PatKind::Err(_) => None,
         }
     }
 }