Rollup merge of rust-lang#119307 - compiler-errors:pat-lifetimes, r=Nadrieril

Clean up some lifetimes in `rustc_pattern_analysis`

This PR removes some redundant lifetimes. I figured out that we were shortening the lifetime of an arena-allocated `&'p DeconstructedPat<'p>` to `'a DeconstructedPat<'p>`, which forced us to carry both lifetimes when we could otherwise carry just one.

This PR also removes and elides some unnecessary lifetimes.

I also cherry-picked 0292eb9, and then simplified more lifetimes in `MatchVisitor`, which should make rust-lang#119233 a very simple PR!

r? Nadrieril

Author: compiler-errors

compiler/rustc_middle/src/thir/visit.rs

@@ -3,26 +3,26 @@ use super::{
     PatKind, Stmt, StmtKind, Thir,
 };
 
-pub trait Visitor<'a, 'tcx: 'a>: Sized {
-    fn thir(&self) -> &'a Thir<'tcx>;
+pub trait Visitor<'thir, 'tcx: 'thir>: Sized {
+    fn thir(&self) -> &'thir Thir<'tcx>;
 
-    fn visit_expr(&mut self, expr: &Expr<'tcx>) {
+    fn visit_expr(&mut self, expr: &'thir Expr<'tcx>) {
         walk_expr(self, expr);
     }
 
-    fn visit_stmt(&mut self, stmt: &Stmt<'tcx>) {
+    fn visit_stmt(&mut self, stmt: &'thir Stmt<'tcx>) {
         walk_stmt(self, stmt);
     }
 
-    fn visit_block(&mut self, block: &Block) {
+    fn visit_block(&mut self, block: &'thir Block) {
         walk_block(self, block);
     }
 
-    fn visit_arm(&mut self, arm: &Arm<'tcx>) {
+    fn visit_arm(&mut self, arm: &'thir Arm<'tcx>) {
         walk_arm(self, arm);
     }
 
-    fn visit_pat(&mut self, pat: &Pat<'tcx>) {
+    fn visit_pat(&mut self, pat: &'thir Pat<'tcx>) {
         walk_pat(self, pat);
     }
 
@@ -36,7 +36,10 @@ pub trait Visitor<'a, 'tcx: 'a>: Sized {
     // other `visit*` functions.
 }
 
-pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Expr<'tcx>) {
+pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
+    visitor: &mut V,
+    expr: &'thir Expr<'tcx>,
+) {
     use ExprKind::*;
     match expr.kind {
         Scope { value, region_scope: _, lint_level: _ } => {
@@ -168,7 +171,10 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
     }
 }
 
-pub fn walk_stmt<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, stmt: &Stmt<'tcx>) {
+pub fn walk_stmt<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
+    visitor: &mut V,
+    stmt: &'thir Stmt<'tcx>,
+) {
     match &stmt.kind {
         StmtKind::Expr { expr, scope: _ } => visitor.visit_expr(&visitor.thir()[*expr]),
         StmtKind::Let {
@@ -191,7 +197,10 @@ pub fn walk_stmt<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, stmt: &Stm
     }
 }
 
-pub fn walk_block<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, block: &Block) {
+pub fn walk_block<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
+    visitor: &mut V,
+    block: &'thir Block,
+) {
     for &stmt in &*block.stmts {
         visitor.visit_stmt(&visitor.thir()[stmt]);
     }
@@ -200,7 +209,10 @@ pub fn walk_block<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, block: &B
     }
 }
 
-pub fn walk_arm<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, arm: &Arm<'tcx>) {
+pub fn walk_arm<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
+    visitor: &mut V,
+    arm: &'thir Arm<'tcx>,
+) {
     match arm.guard {
         Some(Guard::If(expr)) => visitor.visit_expr(&visitor.thir()[expr]),
         Some(Guard::IfLet(ref pat, expr)) => {
@@ -213,7 +225,10 @@ pub fn walk_arm<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, arm: &Arm<'
     visitor.visit_expr(&visitor.thir()[arm.body]);
 }
 
-pub fn walk_pat<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, pat: &Pat<'tcx>) {
+pub fn walk_pat<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
+    visitor: &mut V,
+    pat: &'thir Pat<'tcx>,
+) {
     use PatKind::*;
     match &pat.kind {
         AscribeUserType { subpattern, ascription: _ }

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -175,7 +175,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for LayoutConstrainedPlaceVisitor<'a, 'tcx> {
         self.thir
     }
 
-    fn visit_expr(&mut self, expr: &Expr<'tcx>) {
+    fn visit_expr(&mut self, expr: &'a Expr<'tcx>) {
         match expr.kind {
             ExprKind::Field { lhs, .. } => {
                 if let ty::Adt(adt_def, _) = self.thir[lhs].ty.kind() {
@@ -206,7 +206,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
         self.thir
     }
 
-    fn visit_block(&mut self, block: &Block) {
+    fn visit_block(&mut self, block: &'a Block) {
         match block.safety_mode {
             // compiler-generated unsafe code should not count towards the usefulness of
             // an outer unsafe block
@@ -234,7 +234,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
         }
     }
 
-    fn visit_pat(&mut self, pat: &Pat<'tcx>) {
+    fn visit_pat(&mut self, pat: &'a Pat<'tcx>) {
         if self.in_union_destructure {
             match pat.kind {
                 // binding to a variable allows getting stuff out of variable
@@ -319,7 +319,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
         }
     }
 
-    fn visit_expr(&mut self, expr: &Expr<'tcx>) {
+    fn visit_expr(&mut self, expr: &'a Expr<'tcx>) {
         // could we be in the LHS of an assignment to a field?
         match expr.kind {
             ExprKind::Field { .. }

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -75,11 +75,11 @@ enum LetSource {
     WhileLet,
 }
 
-struct MatchVisitor<'thir, 'p, 'tcx> {
+struct MatchVisitor<'p, 'tcx> {
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     typeck_results: &'tcx ty::TypeckResults<'tcx>,
-    thir: &'thir Thir<'tcx>,
+    thir: &'p Thir<'tcx>,
     lint_level: HirId,
     let_source: LetSource,
     pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
@@ -92,13 +92,13 @@ struct MatchVisitor<'thir, 'p, 'tcx> {
 
 // Visitor for a thir body. This calls `check_match`, `check_let` and `check_let_chain` as
 // appropriate.
-impl<'thir, 'tcx> Visitor<'thir, 'tcx> for MatchVisitor<'thir, '_, 'tcx> {
-    fn thir(&self) -> &'thir Thir<'tcx> {
+impl<'p, 'tcx> Visitor<'p, 'tcx> for MatchVisitor<'p, 'tcx> {
+    fn thir(&self) -> &'p Thir<'tcx> {
         self.thir
     }
 
     #[instrument(level = "trace", skip(self))]
-    fn visit_arm(&mut self, arm: &Arm<'tcx>) {
+    fn visit_arm(&mut self, arm: &'p Arm<'tcx>) {
         self.with_lint_level(arm.lint_level, |this| {
             match arm.guard {
                 Some(Guard::If(expr)) => {
@@ -121,7 +121,7 @@ impl<'thir, 'tcx> Visitor<'thir, 'tcx> for MatchVisitor<'thir, '_, 'tcx> {
     }
 
     #[instrument(level = "trace", skip(self))]
-    fn visit_expr(&mut self, ex: &Expr<'tcx>) {
+    fn visit_expr(&mut self, ex: &'p Expr<'tcx>) {
         match ex.kind {
             ExprKind::Scope { value, lint_level, .. } => {
                 self.with_lint_level(lint_level, |this| {
@@ -174,7 +174,7 @@ impl<'thir, 'tcx> Visitor<'thir, 'tcx> for MatchVisitor<'thir, '_, 'tcx> {
         self.with_let_source(LetSource::None, |this| visit::walk_expr(this, ex));
     }
 
-    fn visit_stmt(&mut self, stmt: &Stmt<'tcx>) {
+    fn visit_stmt(&mut self, stmt: &'p Stmt<'tcx>) {
         match stmt.kind {
             StmtKind::Let {
                 box ref pattern, initializer, else_block, lint_level, span, ..
@@ -195,7 +195,7 @@ impl<'thir, 'tcx> Visitor<'thir, 'tcx> for MatchVisitor<'thir, '_, 'tcx> {
     }
 }
 
-impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
+impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
     #[instrument(level = "trace", skip(self, f))]
     fn with_let_source(&mut self, let_source: LetSource, f: impl FnOnce(&mut Self)) {
         let old_let_source = self.let_source;
@@ -224,7 +224,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
     /// subexpressions we are not handling ourselves.
     fn visit_land(
         &mut self,
-        ex: &Expr<'tcx>,
+        ex: &'p Expr<'tcx>,
         accumulator: &mut Vec<Option<(Span, RefutableFlag)>>,
     ) -> Result<(), ErrorGuaranteed> {
         match ex.kind {
@@ -251,7 +251,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
     /// expression. This must call `visit_expr` on the subexpressions we are not handling ourselves.
     fn visit_land_rhs(
         &mut self,
-        ex: &Expr<'tcx>,
+        ex: &'p Expr<'tcx>,
     ) -> Result<Option<(Span, RefutableFlag)>, ErrorGuaranteed> {
         match ex.kind {
             ExprKind::Scope { value, lint_level, .. } => {
@@ -276,7 +276,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
     fn lower_pattern(
         &mut self,
         cx: &MatchCheckCtxt<'p, 'tcx>,
-        pat: &Pat<'tcx>,
+        pat: &'p Pat<'tcx>,
     ) -> Result<&'p DeconstructedPat<'p, 'tcx>, ErrorGuaranteed> {
         if let Err(err) = pat.pat_error_reported() {
             self.error = Err(err);
@@ -395,7 +395,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
     }
 
     #[instrument(level = "trace", skip(self))]
-    fn check_let(&mut self, pat: &Pat<'tcx>, scrutinee: Option<ExprId>, span: Span) {
+    fn check_let(&mut self, pat: &'p Pat<'tcx>, scrutinee: Option<ExprId>, span: Span) {
         assert!(self.let_source != LetSource::None);
         let scrut = scrutinee.map(|id| &self.thir[id]);
         if let LetSource::PlainLet = self.let_source {
@@ -547,7 +547,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
 
     fn analyze_binding(
         &mut self,
-        pat: &Pat<'tcx>,
+        pat: &'p Pat<'tcx>,
         refutability: RefutableFlag,
         scrut: Option<&Expr<'tcx>>,
     ) -> Result<(MatchCheckCtxt<'p, 'tcx>, UsefulnessReport<'p, 'tcx>), ErrorGuaranteed> {
@@ -560,7 +560,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
 
     fn is_let_irrefutable(
         &mut self,
-        pat: &Pat<'tcx>,
+        pat: &'p Pat<'tcx>,
         scrut: Option<&Expr<'tcx>>,
     ) -> Result<RefutableFlag, ErrorGuaranteed> {
         let (cx, report) = self.analyze_binding(pat, Refutable, scrut)?;
@@ -575,7 +575,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
     #[instrument(level = "trace", skip(self))]
     fn check_binding_is_irrefutable(
         &mut self,
-        pat: &Pat<'tcx>,
+        pat: &'p Pat<'tcx>,
         origin: &str,
         scrut: Option<&Expr<'tcx>>,
         sp: Option<Span>,
@@ -677,7 +677,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
 /// - `x @ Some(ref mut? y)`.
 ///
 /// This analysis is *not* subsumed by NLL.
-fn check_borrow_conflicts_in_at_patterns<'tcx>(cx: &MatchVisitor<'_, '_, 'tcx>, pat: &Pat<'tcx>) {
+fn check_borrow_conflicts_in_at_patterns<'tcx>(cx: &MatchVisitor<'_, 'tcx>, pat: &Pat<'tcx>) {
     // Extract `sub` in `binding @ sub`.
     let PatKind::Binding { name, mode, ty, subpattern: Some(box ref sub), .. } = pat.kind else {
         return;
@@ -772,7 +772,7 @@ fn check_borrow_conflicts_in_at_patterns<'tcx>(cx: &MatchVisitor<'_, '_, 'tcx>,
 }
 
 fn check_for_bindings_named_same_as_variants(
-    cx: &MatchVisitor<'_, '_, '_>,
+    cx: &MatchVisitor<'_, '_>,
     pat: &Pat<'_>,
     rf: RefutableFlag,
 ) {

compiler/rustc_pattern_analysis/src/constructor.rs

@@ -861,12 +861,9 @@ impl<Cx: TypeCx> ConstructorSet<Cx> {
     #[instrument(level = "debug", skip(self, pcx, ctors), ret)]
     pub(crate) fn split<'a>(
         &self,
-        pcx: &PlaceCtxt<'_, '_, Cx>,
+        pcx: &PlaceCtxt<'a, '_, Cx>,
         ctors: impl Iterator<Item = &'a Constructor<Cx>> + Clone,
-    ) -> SplitConstructorSet<Cx>
-    where
-        Cx: 'a,
-    {
+    ) -> SplitConstructorSet<Cx> {
         let mut present: SmallVec<[_; 1]> = SmallVec::new();
         // Empty constructors found missing.
         let mut missing_empty = Vec::new();

compiler/rustc_pattern_analysis/src/lib.rs

@@ -91,7 +91,7 @@ pub struct MatchCtxt<'a, 'p, Cx: TypeCx> {
     /// The context for type information.
     pub tycx: &'a Cx,
     /// An arena to store the wildcards we produce during analysis.
-    pub wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
+    pub wildcard_arena: &'p TypedArena<DeconstructedPat<'p, Cx>>,
 }
 
 /// The arm of a match expression.

compiler/rustc_pattern_analysis/src/lints.rs

@@ -28,11 +28,11 @@ use crate::TypeCx;
 ///
 /// This is not used in the main algorithm; only in lints.
 #[derive(Debug)]
-pub(crate) struct PatternColumn<'a, 'p, 'tcx> {
-    patterns: Vec<&'a DeconstructedPat<'p, 'tcx>>,
+pub(crate) struct PatternColumn<'p, 'tcx> {
+    patterns: Vec<&'p DeconstructedPat<'p, 'tcx>>,
 }
 
-impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
+impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
     pub(crate) fn new(arms: &[MatchArm<'p, 'tcx>]) -> Self {
         let mut patterns = Vec::with_capacity(arms.len());
         for arm in arms {
@@ -48,7 +48,7 @@ impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
     fn is_empty(&self) -> bool {
         self.patterns.is_empty()
     }
-    fn head_ty(&self, cx: MatchCtxt<'a, 'p, 'tcx>) -> Option<Ty<'tcx>> {
+    fn head_ty(&self, cx: MatchCtxt<'_, 'p, 'tcx>) -> Option<Ty<'tcx>> {
         if self.patterns.len() == 0 {
             return None;
         }
@@ -64,7 +64,7 @@ impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
         pcx.ctors_for_ty().split(pcx, column_ctors)
     }
 
-    fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, 'tcx>> + Captures<'b> {
+    fn iter(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p, 'tcx>> + Captures<'_> {
         self.patterns.iter().copied()
     }
 
@@ -75,9 +75,9 @@ impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
     /// which may change the lengths.
     fn specialize(
         &self,
-        pcx: &PlaceCtxt<'a, 'p, 'tcx>,
+        pcx: &PlaceCtxt<'_, 'p, 'tcx>,
         ctor: &Constructor<'p, 'tcx>,
-    ) -> Vec<PatternColumn<'a, 'p, 'tcx>> {
+    ) -> Vec<PatternColumn<'p, 'tcx>> {
         let arity = ctor.arity(pcx);
         if arity == 0 {
             return Vec::new();
@@ -115,7 +115,7 @@ impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
 #[instrument(level = "debug", skip(cx), ret)]
 fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     cx: MatchCtxt<'a, 'p, 'tcx>,
-    column: &PatternColumn<'a, 'p, 'tcx>,
+    column: &PatternColumn<'p, 'tcx>,
 ) -> Vec<WitnessPat<'p, 'tcx>> {
     let Some(ty) = column.head_ty(cx) else {
         return Vec::new();
@@ -163,7 +163,7 @@ fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
 pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     cx: MatchCtxt<'a, 'p, 'tcx>,
     arms: &[MatchArm<'p, 'tcx>],
-    pat_column: &PatternColumn<'a, 'p, 'tcx>,
+    pat_column: &PatternColumn<'p, 'tcx>,
     scrut_ty: Ty<'tcx>,
 ) {
     let rcx: &RustcMatchCheckCtxt<'_, '_> = cx.tycx;
@@ -216,7 +216,7 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
 #[instrument(level = "debug", skip(cx))]
 pub(crate) fn lint_overlapping_range_endpoints<'a, 'p, 'tcx>(
     cx: MatchCtxt<'a, 'p, 'tcx>,
-    column: &PatternColumn<'a, 'p, 'tcx>,
+    column: &PatternColumn<'p, 'tcx>,
 ) {
     let Some(ty) = column.head_ty(cx) else {
         return;

compiler/rustc_pattern_analysis/src/pat.rs

@@ -71,19 +71,17 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
         self.data.as_ref()
     }
 
-    pub fn iter_fields<'a>(
-        &'a self,
-    ) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'a> {
+    pub fn iter_fields(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'_> {
         self.fields.iter()
     }
 
     /// Specialize this pattern with a constructor.
     /// `other_ctor` can be different from `self.ctor`, but must be covered by it.
-    pub(crate) fn specialize<'a>(
+    pub(crate) fn specialize(
         &self,
-        pcx: &PlaceCtxt<'a, 'p, Cx>,
+        pcx: &PlaceCtxt<'_, 'p, Cx>,
         other_ctor: &Constructor<Cx>,
-    ) -> SmallVec<[&'a DeconstructedPat<'p, Cx>; 2]> {
+    ) -> SmallVec<[&'p DeconstructedPat<'p, Cx>; 2]> {
         let wildcard_sub_tys = || {
             let tys = pcx.ctor_sub_tys(other_ctor);
             tys.iter()
@@ -196,7 +194,7 @@ impl<Cx: TypeCx> WitnessPat<Cx> {
         self.ty
     }
 
-    pub fn iter_fields<'a>(&'a self) -> impl Iterator<Item = &'a WitnessPat<Cx>> {
+    pub fn iter_fields(&self) -> impl Iterator<Item = &WitnessPat<Cx>> {
         self.fields.iter()
     }
 }

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -128,11 +128,11 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
     // In the cases of either a `#[non_exhaustive]` field list or a non-public field, we hide
     // uninhabited fields in order not to reveal the uninhabitedness of the whole variant.
     // This lists the fields we keep along with their types.
-    pub(crate) fn list_variant_nonhidden_fields<'a>(
-        &'a self,
+    pub(crate) fn list_variant_nonhidden_fields(
+        &self,
         ty: Ty<'tcx>,
-        variant: &'a VariantDef,
-    ) -> impl Iterator<Item = (FieldIdx, Ty<'tcx>)> + Captures<'p> + Captures<'a> {
+        variant: &'tcx VariantDef,
+    ) -> impl Iterator<Item = (FieldIdx, Ty<'tcx>)> + Captures<'p> + Captures<'_> {
         let cx = self;
         let ty::Adt(adt, args) = ty.kind() else { bug!() };
         // Whether we must not match the fields of this variant exhaustively.
@@ -399,7 +399,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
 
     /// Note: the input patterns must have been lowered through
     /// `rustc_mir_build::thir::pattern::check_match::MatchVisitor::lower_pattern`.
-    pub fn lower_pat(&self, pat: &Pat<'tcx>) -> DeconstructedPat<'p, 'tcx> {
+    pub fn lower_pat(&self, pat: &'p Pat<'tcx>) -> DeconstructedPat<'p, 'tcx> {
         let singleton = |pat| std::slice::from_ref(self.pattern_arena.alloc(pat));
         let cx = self;
         let ctor;

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -821,22 +821,21 @@ impl fmt::Display for ValidityConstraint {
 
 /// Represents a pattern-tuple under investigation.
 // The three lifetimes are:
-// - 'a allocated by us
 // - 'p coming from the input
 // - Cx global compilation context
 #[derive(derivative::Derivative)]
 #[derivative(Clone(bound = ""))]
-struct PatStack<'a, 'p, Cx: TypeCx> {
+struct PatStack<'p, Cx: TypeCx> {
     // Rows of len 1 are very common, which is why `SmallVec[_; 2]` works well.
-    pats: SmallVec<[&'a DeconstructedPat<'p, Cx>; 2]>,
+    pats: SmallVec<[&'p DeconstructedPat<'p, Cx>; 2]>,
     /// Sometimes we know that as far as this row is concerned, the current case is already handled
     /// by a different, more general, case. When the case is irrelevant for all rows this allows us
     /// to skip a case entirely. This is purely an optimization. See at the top for details.
     relevant: bool,
 }
 
-impl<'a, 'p, Cx: TypeCx> PatStack<'a, 'p, Cx> {
-    fn from_pattern(pat: &'a DeconstructedPat<'p, Cx>) -> Self {
+impl<'p, Cx: TypeCx> PatStack<'p, Cx> {
+    fn from_pattern(pat: &'p DeconstructedPat<'p, Cx>) -> Self {
         PatStack { pats: smallvec![pat], relevant: true }
     }
 
@@ -848,17 +847,17 @@ impl<'a, 'p, Cx: TypeCx> PatStack<'a, 'p, Cx> {
         self.pats.len()
     }
 
-    fn head(&self) -> &'a DeconstructedPat<'p, Cx> {
+    fn head(&self) -> &'p DeconstructedPat<'p, Cx> {
         self.pats[0]
     }
 
-    fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, Cx>> + Captures<'b> {
+    fn iter(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'_> {
         self.pats.iter().copied()
     }
 
     // Recursively expand the first or-pattern into its subpatterns. Only useful if the pattern is
     // an or-pattern. Panics if `self` is empty.
-    fn expand_or_pat<'b>(&'b self) -> impl Iterator<Item = PatStack<'a, 'p, Cx>> + Captures<'b> {
+    fn expand_or_pat(&self) -> impl Iterator<Item = PatStack<'p, Cx>> + Captures<'_> {
         self.head().flatten_or_pat().into_iter().map(move |pat| {
             let mut new = self.clone();
             new.pats[0] = pat;
@@ -870,10 +869,10 @@ impl<'a, 'p, Cx: TypeCx> PatStack<'a, 'p, Cx> {
     /// Only call if `ctor.is_covered_by(self.head().ctor())` is true.
     fn pop_head_constructor(
         &self,
-        pcx: &PlaceCtxt<'a, 'p, Cx>,
+        pcx: &PlaceCtxt<'_, 'p, Cx>,
         ctor: &Constructor<Cx>,
         ctor_is_relevant: bool,
-    ) -> PatStack<'a, 'p, Cx> {
+    ) -> PatStack<'p, Cx> {
         // We pop the head pattern and push the new fields extracted from the arguments of
         // `self.head()`.
         let mut new_pats = self.head().specialize(pcx, ctor);
@@ -886,7 +885,7 @@ impl<'a, 'p, Cx: TypeCx> PatStack<'a, 'p, Cx> {
     }
 }
 
-impl<'a, 'p, Cx: TypeCx> fmt::Debug for PatStack<'a, 'p, Cx> {
+impl<'p, Cx: TypeCx> fmt::Debug for PatStack<'p, Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // We pretty-print similarly to the `Debug` impl of `Matrix`.
         write!(f, "+")?;
@@ -899,9 +898,9 @@ impl<'a, 'p, Cx: TypeCx> fmt::Debug for PatStack<'a, 'p, Cx> {
 
 /// A row of the matrix.
 #[derive(Clone)]
-struct MatrixRow<'a, 'p, Cx: TypeCx> {
+struct MatrixRow<'p, Cx: TypeCx> {
     // The patterns in the row.
-    pats: PatStack<'a, 'p, Cx>,
+    pats: PatStack<'p, Cx>,
     /// Whether the original arm had a guard. This is inherited when specializing.
     is_under_guard: bool,
     /// When we specialize, we remember which row of the original matrix produced a given row of the
@@ -914,7 +913,7 @@ struct MatrixRow<'a, 'p, Cx: TypeCx> {
     useful: bool,
 }
 
-impl<'a, 'p, Cx: TypeCx> MatrixRow<'a, 'p, Cx> {
+impl<'p, Cx: TypeCx> MatrixRow<'p, Cx> {
     fn is_empty(&self) -> bool {
         self.pats.is_empty()
     }
@@ -923,17 +922,17 @@ impl<'a, 'p, Cx: TypeCx> MatrixRow<'a, 'p, Cx> {
         self.pats.len()
     }
 
-    fn head(&self) -> &'a DeconstructedPat<'p, Cx> {
+    fn head(&self) -> &'p DeconstructedPat<'p, Cx> {
         self.pats.head()
     }
 
-    fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, Cx>> + Captures<'b> {
+    fn iter(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'_> {
         self.pats.iter()
     }
 
     // Recursively expand the first or-pattern into its subpatterns. Only useful if the pattern is
     // an or-pattern. Panics if `self` is empty.
-    fn expand_or_pat<'b>(&'b self) -> impl Iterator<Item = MatrixRow<'a, 'p, Cx>> + Captures<'b> {
+    fn expand_or_pat(&self) -> impl Iterator<Item = MatrixRow<'p, Cx>> + Captures<'_> {
         self.pats.expand_or_pat().map(|patstack| MatrixRow {
             pats: patstack,
             parent_row: self.parent_row,
@@ -946,11 +945,11 @@ impl<'a, 'p, Cx: TypeCx> MatrixRow<'a, 'p, Cx> {
     /// Only call if `ctor.is_covered_by(self.head().ctor())` is true.
     fn pop_head_constructor(
         &self,
-        pcx: &PlaceCtxt<'a, 'p, Cx>,
+        pcx: &PlaceCtxt<'_, 'p, Cx>,
         ctor: &Constructor<Cx>,
         ctor_is_relevant: bool,
         parent_row: usize,
-    ) -> MatrixRow<'a, 'p, Cx> {
+    ) -> MatrixRow<'p, Cx> {
         MatrixRow {
             pats: self.pats.pop_head_constructor(pcx, ctor, ctor_is_relevant),
             parent_row,
@@ -960,7 +959,7 @@ impl<'a, 'p, Cx: TypeCx> MatrixRow<'a, 'p, Cx> {
     }
 }
 
-impl<'a, 'p, Cx: TypeCx> fmt::Debug for MatrixRow<'a, 'p, Cx> {
+impl<'p, Cx: TypeCx> fmt::Debug for MatrixRow<'p, Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.pats.fmt(f)
     }
@@ -977,22 +976,22 @@ impl<'a, 'p, Cx: TypeCx> fmt::Debug for MatrixRow<'a, 'p, Cx> {
 /// specializing `(,)` and `Some` on a pattern of type `(Option<u32>, bool)`, the first column of
 /// the matrix will correspond to `scrutinee.0.Some.0` and the second column to `scrutinee.1`.
 #[derive(Clone)]
-struct Matrix<'a, 'p, Cx: TypeCx> {
+struct Matrix<'p, Cx: TypeCx> {
     /// Vector of rows. The rows must form a rectangular 2D array. Moreover, all the patterns of
     /// each column must have the same type. Each column corresponds to a place within the
     /// scrutinee.
-    rows: Vec<MatrixRow<'a, 'p, Cx>>,
+    rows: Vec<MatrixRow<'p, Cx>>,
     /// Stores an extra fictitious row full of wildcards. Mostly used to keep track of the type of
     /// each column. This must obey the same invariants as the real rows.
-    wildcard_row: PatStack<'a, 'p, Cx>,
+    wildcard_row: PatStack<'p, Cx>,
     /// Track for each column/place whether it contains a known valid value.
     place_validity: SmallVec<[ValidityConstraint; 2]>,
 }
 
-impl<'a, 'p, Cx: TypeCx> Matrix<'a, 'p, Cx> {
+impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
     /// Pushes a new row to the matrix. If the row starts with an or-pattern, this recursively
     /// expands it. Internal method, prefer [`Matrix::new`].
-    fn expand_and_push(&mut self, row: MatrixRow<'a, 'p, Cx>) {
+    fn expand_and_push(&mut self, row: MatrixRow<'p, Cx>) {
         if !row.is_empty() && row.head().is_or_pat() {
             // Expand nested or-patterns.
             for new_row in row.expand_or_pat() {
@@ -1005,8 +1004,8 @@ impl<'a, 'p, Cx: TypeCx> Matrix<'a, 'p, Cx> {
 
     /// Build a new matrix from an iterator of `MatchArm`s.
     fn new(
-        wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
-        arms: &'a [MatchArm<'p, Cx>],
+        wildcard_arena: &'p TypedArena<DeconstructedPat<'p, Cx>>,
+        arms: &[MatchArm<'p, Cx>],
         scrut_ty: Cx::Ty,
         scrut_validity: ValidityConstraint,
     ) -> Self {
@@ -1029,7 +1028,7 @@ impl<'a, 'p, Cx: TypeCx> Matrix<'a, 'p, Cx> {
         matrix
     }
 
-    fn head_ty(&self, mcx: MatchCtxt<'a, 'p, Cx>) -> Option<Cx::Ty> {
+    fn head_ty(&self, mcx: MatchCtxt<'_, 'p, Cx>) -> Option<Cx::Ty> {
         if self.column_count() == 0 {
             return None;
         }
@@ -1042,33 +1041,31 @@ impl<'a, 'p, Cx: TypeCx> Matrix<'a, 'p, Cx> {
         self.wildcard_row.len()
     }
 
-    fn rows<'b>(
-        &'b self,
-    ) -> impl Iterator<Item = &'b MatrixRow<'a, 'p, Cx>> + Clone + DoubleEndedIterator + ExactSizeIterator
+    fn rows(
+        &self,
+    ) -> impl Iterator<Item = &MatrixRow<'p, Cx>> + Clone + DoubleEndedIterator + ExactSizeIterator
     {
         self.rows.iter()
     }
-    fn rows_mut<'b>(
-        &'b mut self,
-    ) -> impl Iterator<Item = &'b mut MatrixRow<'a, 'p, Cx>> + DoubleEndedIterator + ExactSizeIterator
+    fn rows_mut(
+        &mut self,
+    ) -> impl Iterator<Item = &mut MatrixRow<'p, Cx>> + DoubleEndedIterator + ExactSizeIterator
     {
         self.rows.iter_mut()
     }
 
     /// Iterate over the first pattern of each row.
-    fn heads<'b>(
-        &'b self,
-    ) -> impl Iterator<Item = &'b DeconstructedPat<'p, Cx>> + Clone + Captures<'a> {
+    fn heads(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Clone + Captures<'_> {
         self.rows().map(|r| r.head())
     }
 
     /// This computes `specialize(ctor, self)`. See top of the file for explanations.
     fn specialize_constructor(
         &self,
-        pcx: &PlaceCtxt<'a, 'p, Cx>,
+        pcx: &PlaceCtxt<'_, 'p, Cx>,
         ctor: &Constructor<Cx>,
         ctor_is_relevant: bool,
-    ) -> Matrix<'a, 'p, Cx> {
+    ) -> Matrix<'p, Cx> {
         let wildcard_row = self.wildcard_row.pop_head_constructor(pcx, ctor, ctor_is_relevant);
         let new_validity = self.place_validity[0].specialize(ctor);
         let new_place_validity = std::iter::repeat(new_validity)
@@ -1097,7 +1094,7 @@ impl<'a, 'p, Cx: TypeCx> Matrix<'a, 'p, Cx> {
 /// + _     + [_, _, tail @ ..] +
 /// | ✓     | ?                 | // column validity
 /// ```
-impl<'a, 'p, Cx: TypeCx> fmt::Debug for Matrix<'a, 'p, Cx> {
+impl<'p, Cx: TypeCx> fmt::Debug for Matrix<'p, Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "\n")?;
 
@@ -1336,7 +1333,7 @@ impl<Cx: TypeCx> WitnessMatrix<Cx> {
 #[instrument(level = "debug", skip(mcx, is_top_level), ret)]
 fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     mcx: MatchCtxt<'a, 'p, Cx>,
-    matrix: &mut Matrix<'a, 'p, Cx>,
+    matrix: &mut Matrix<'p, Cx>,
     is_top_level: bool,
 ) -> WitnessMatrix<Cx> {
     debug_assert!(matrix.rows().all(|r| r.len() == matrix.column_count()));

compiler/rustc_ty_utils/src/consts.rs

@@ -379,15 +379,15 @@ impl<'a, 'tcx> visit::Visitor<'a, 'tcx> for IsThirPolymorphic<'a, 'tcx> {
     }
 
     #[instrument(skip(self), level = "debug")]
-    fn visit_expr(&mut self, expr: &thir::Expr<'tcx>) {
+    fn visit_expr(&mut self, expr: &'a thir::Expr<'tcx>) {
         self.is_poly |= self.expr_is_poly(expr);
         if !self.is_poly {
             visit::walk_expr(self, expr)
         }
     }
 
     #[instrument(skip(self), level = "debug")]
-    fn visit_pat(&mut self, pat: &thir::Pat<'tcx>) {
+    fn visit_pat(&mut self, pat: &'a thir::Pat<'tcx>) {
         self.is_poly |= self.pat_is_poly(pat);
         if !self.is_poly {
             visit::walk_pat(self, pat);