From db36304102fd86305b0319d5a3d8f440aa4b139d Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Wed, 3 Jan 2024 01:34:38 +0100
Subject: rustc_pattern_analysis no longer needs to be passed an arena

---
 compiler/rustc_pattern_analysis/src/constructor.rs |  6 +++---
 compiler/rustc_pattern_analysis/src/lib.rs         | 15 ++-------------
 compiler/rustc_pattern_analysis/src/pat.rs         |  2 +-
 compiler/rustc_pattern_analysis/src/rustc.rs       |  6 ++++--
 compiler/rustc_pattern_analysis/src/usefulness.rs  | 18 +++++++++---------
 5 files changed, 19 insertions(+), 28 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs
index 15ff4ceb5b3..c1042d5b66e 100644
--- a/compiler/rustc_pattern_analysis/src/constructor.rs
+++ b/compiler/rustc_pattern_analysis/src/constructor.rs
@@ -718,7 +718,7 @@ impl<Cx: TypeCx> Constructor<Cx> {
 
     /// The number of fields for this constructor. This must be kept in sync with
     /// `Fields::wildcards`.
-    pub(crate) fn arity(&self, pcx: &PlaceCtxt<'_, '_, Cx>) -> usize {
+    pub(crate) fn arity(&self, pcx: &PlaceCtxt<'_, Cx>) -> usize {
         pcx.ctor_arity(self)
     }
 
@@ -727,7 +727,7 @@ impl<Cx: TypeCx> Constructor<Cx> {
     /// this checks for inclusion.
     // We inline because this has a single call site in `Matrix::specialize_constructor`.
     #[inline]
-    pub(crate) fn is_covered_by<'p>(&self, pcx: &PlaceCtxt<'_, 'p, Cx>, other: &Self) -> bool {
+    pub(crate) fn is_covered_by(&self, pcx: &PlaceCtxt<'_, Cx>, other: &Self) -> bool {
         match (self, other) {
             (Wildcard, _) => pcx
                 .mcx
@@ -861,7 +861,7 @@ impl<Cx: TypeCx> ConstructorSet<Cx> {
     #[instrument(level = "debug", skip(self, pcx, ctors), ret)]
     pub(crate) fn split<'a>(
         &self,
-        pcx: &PlaceCtxt<'a, '_, Cx>,
+        pcx: &PlaceCtxt<'a, Cx>,
         ctors: impl Iterator<Item = &'a Constructor<Cx>> + Clone,
     ) -> SplitConstructorSet<Cx> {
         let mut present: SmallVec<[_; 1]> = SmallVec::new();
diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs
index 374914055d8..ed10a515508 100644
--- a/compiler/rustc_pattern_analysis/src/lib.rs
+++ b/compiler/rustc_pattern_analysis/src/lib.rs
@@ -38,13 +38,6 @@ use crate::rustc::RustcMatchCheckCtxt;
 #[cfg(feature = "rustc")]
 use crate::usefulness::{compute_match_usefulness, ValidityConstraint};
 
-// It's not possible to only enable the `typed_arena` dependency when the `rustc` feature is off, so
-// we use another feature instead. The crate won't compile if one of these isn't enabled.
-#[cfg(feature = "rustc")]
-pub(crate) use rustc_arena::TypedArena;
-#[cfg(feature = "stable")]
-pub(crate) use typed_arena::Arena as TypedArena;
-
 pub trait Captures<'a> {}
 impl<'a, T: ?Sized> Captures<'a> for T {}
 
@@ -89,11 +82,9 @@ pub trait TypeCx: Sized + fmt::Debug {
 /// Context that provides information global to a match.
 #[derive(derivative::Derivative)]
 #[derivative(Clone(bound = ""), Copy(bound = ""))]
-pub struct MatchCtxt<'a, 'p, Cx: TypeCx> {
+pub struct MatchCtxt<'a, Cx: TypeCx> {
     /// The context for type information.
     pub tycx: &'a Cx,
-    /// An arena to store the wildcards we produce during analysis.
-    pub wildcard_arena: &'p TypedArena<DeconstructedPat<'p, Cx>>,
 }
 
 /// The arm of a match expression.
@@ -114,11 +105,9 @@ pub fn analyze_match<'p, 'tcx>(
     arms: &[rustc::MatchArm<'p, 'tcx>],
     scrut_ty: Ty<'tcx>,
 ) -> Result<rustc::UsefulnessReport<'p, 'tcx>, ErrorGuaranteed> {
-    // Arena to store the extra wildcards we construct during analysis.
-    let wildcard_arena = tycx.pattern_arena;
     let scrut_ty = tycx.reveal_opaque_ty(scrut_ty);
     let scrut_validity = ValidityConstraint::from_bool(tycx.known_valid_scrutinee);
-    let cx = MatchCtxt { tycx, wildcard_arena };
+    let cx = MatchCtxt { tycx };
 
     let report = compute_match_usefulness(cx, arms, scrut_ty, scrut_validity)?;
 
diff --git a/compiler/rustc_pattern_analysis/src/pat.rs b/compiler/rustc_pattern_analysis/src/pat.rs
index 2f5dc241cb7..75fe59edf88 100644
--- a/compiler/rustc_pattern_analysis/src/pat.rs
+++ b/compiler/rustc_pattern_analysis/src/pat.rs
@@ -240,7 +240,7 @@ impl<Cx: TypeCx> WitnessPat<Cx> {
     /// Construct a pattern that matches everything that starts with this constructor.
     /// For example, if `ctor` is a `Constructor::Variant` for `Option::Some`, we get the pattern
     /// `Some(_)`.
-    pub(crate) fn wild_from_ctor(pcx: &PlaceCtxt<'_, '_, Cx>, ctor: Constructor<Cx>) -> Self {
+    pub(crate) fn wild_from_ctor(pcx: &PlaceCtxt<'_, Cx>, ctor: Constructor<Cx>) -> Self {
         let field_tys = pcx.ctor_sub_tys(&ctor);
         let fields = field_tys.iter().map(|ty| Self::wildcard(*ty)).collect();
         Self::new(ctor, fields, pcx.ty)
diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index a17cd2c81b9..e82d6666b1a 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -33,11 +33,11 @@ pub type ConstructorSet<'p, 'tcx> =
 pub type DeconstructedPat<'p, 'tcx> =
     crate::pat::DeconstructedPat<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type MatchArm<'p, 'tcx> = crate::MatchArm<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
-pub type MatchCtxt<'a, 'p, 'tcx> = crate::MatchCtxt<'a, 'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type MatchCtxt<'a, 'p, 'tcx> = crate::MatchCtxt<'a, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type OverlappingRanges<'p, 'tcx> =
     crate::usefulness::OverlappingRanges<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub(crate) type PlaceCtxt<'a, 'p, 'tcx> =
-    crate::usefulness::PlaceCtxt<'a, 'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+    crate::usefulness::PlaceCtxt<'a, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub(crate) type SplitConstructorSet<'p, 'tcx> =
     crate::constructor::SplitConstructorSet<RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type Usefulness<'p, 'tcx> = crate::usefulness::Usefulness<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
@@ -80,7 +80,9 @@ pub struct RustcMatchCheckCtxt<'p, 'tcx> {
     /// outside its module and should not be matchable with an empty match statement.
     pub module: DefId,
     pub param_env: ty::ParamEnv<'tcx>,
+    /// To allocate lowered patterns
     pub pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
+    /// To allocate the result of `self.ctor_sub_tys()`
     pub dropless_arena: &'p DroplessArena,
     /// Lint level at the match.
     pub match_lint_level: HirId,
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index 85b6a6a3b6c..6244cf0ff7d 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -732,19 +732,19 @@ pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R {
 /// Context that provides information local to a place under investigation.
 #[derive(derivative::Derivative)]
 #[derivative(Debug(bound = ""), Clone(bound = ""), Copy(bound = ""))]
-pub(crate) struct PlaceCtxt<'a, 'p, Cx: TypeCx> {
+pub(crate) struct PlaceCtxt<'a, Cx: TypeCx> {
     #[derivative(Debug = "ignore")]
-    pub(crate) mcx: MatchCtxt<'a, 'p, Cx>,
+    pub(crate) mcx: MatchCtxt<'a, Cx>,
     /// Type of the place under investigation.
     pub(crate) ty: Cx::Ty,
     /// Whether the place is the original scrutinee place, as opposed to a subplace of it.
     pub(crate) is_scrutinee: bool,
 }
 
-impl<'a, 'p, Cx: TypeCx> PlaceCtxt<'a, 'p, Cx> {
+impl<'a, Cx: TypeCx> PlaceCtxt<'a, Cx> {
     /// A `PlaceCtxt` when code other than `is_useful` needs one.
     #[cfg_attr(not(feature = "rustc"), allow(dead_code))]
-    pub(crate) fn new_dummy(mcx: MatchCtxt<'a, 'p, Cx>, ty: Cx::Ty) -> Self {
+    pub(crate) fn new_dummy(mcx: MatchCtxt<'a, Cx>, ty: Cx::Ty) -> Self {
         PlaceCtxt { mcx, ty, is_scrutinee: false }
     }
 
@@ -1067,7 +1067,7 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
     /// This computes `specialize(ctor, self)`. See top of the file for explanations.
     fn specialize_constructor(
         &self,
-        pcx: &PlaceCtxt<'_, 'p, Cx>,
+        pcx: &PlaceCtxt<'_, Cx>,
         ctor: &Constructor<Cx>,
         ctor_is_relevant: bool,
     ) -> Matrix<'p, Cx> {
@@ -1226,7 +1226,7 @@ impl<Cx: TypeCx> WitnessStack<Cx> {
     /// pats: [(false, "foo"), _, true]
     /// result: [Enum::Variant { a: (false, "foo"), b: _ }, true]
     /// ```
-    fn apply_constructor(&mut self, pcx: &PlaceCtxt<'_, '_, Cx>, ctor: &Constructor<Cx>) {
+    fn apply_constructor(&mut self, pcx: &PlaceCtxt<'_, Cx>, ctor: &Constructor<Cx>) {
         let len = self.0.len();
         let arity = ctor.arity(pcx);
         let fields = self.0.drain((len - arity)..).rev().collect();
@@ -1277,7 +1277,7 @@ impl<Cx: TypeCx> WitnessMatrix<Cx> {
     /// Reverses specialization by `ctor`. See the section on `unspecialize` at the top of the file.
     fn apply_constructor(
         &mut self,
-        pcx: &PlaceCtxt<'_, '_, Cx>,
+        pcx: &PlaceCtxt<'_, Cx>,
         missing_ctors: &[Constructor<Cx>],
         ctor: &Constructor<Cx>,
         report_individual_missing_ctors: bool,
@@ -1421,7 +1421,7 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
 /// This is all explained at the top of the file.
 #[instrument(level = "debug", skip(mcx, is_top_level), ret)]
 fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
-    mcx: MatchCtxt<'a, 'p, Cx>,
+    mcx: MatchCtxt<'a, Cx>,
     matrix: &mut Matrix<'p, Cx>,
     overlapping_range_endpoints: &mut Vec<OverlappingRanges<'p, Cx>>,
     is_top_level: bool,
@@ -1591,7 +1591,7 @@ pub struct UsefulnessReport<'p, Cx: TypeCx> {
 /// Computes whether a match is exhaustive and which of its arms are useful.
 #[instrument(skip(cx, arms), level = "debug")]
 pub fn compute_match_usefulness<'p, Cx: TypeCx>(
-    cx: MatchCtxt<'_, 'p, Cx>,
+    cx: MatchCtxt<'_, Cx>,
     arms: &[MatchArm<'p, Cx>],
     scrut_ty: Cx::Ty,
     scrut_validity: ValidityConstraint,
-- 
cgit 1.4.1-3-g733a5


From bf913ad0aee7e97b93f50824e9b2292414670954 Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Wed, 10 Jan 2024 22:42:23 +0100
Subject: Simplify use of `ValidityConstraint`

We had reached a point where the shenanigans about omitting empty arms
are unnecessary.
---
 compiler/rustc_pattern_analysis/src/usefulness.rs | 27 ++++-------------------
 1 file changed, 4 insertions(+), 23 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index 6244cf0ff7d..72459582113 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -768,9 +768,6 @@ impl<'a, Cx: TypeCx> PlaceCtxt<'a, Cx> {
 pub enum ValidityConstraint {
     ValidOnly,
     MaybeInvalid,
-    /// Option for backwards compatibility: the place is not known to be valid but we allow omitting
-    /// `useful && !reachable` arms anyway.
-    MaybeInvalidButAllowOmittingArms,
 }
 
 impl ValidityConstraint {
@@ -778,20 +775,9 @@ impl ValidityConstraint {
         if is_valid_only { ValidOnly } else { MaybeInvalid }
     }
 
-    fn allow_omitting_side_effecting_arms(self) -> Self {
-        match self {
-            MaybeInvalid | MaybeInvalidButAllowOmittingArms => MaybeInvalidButAllowOmittingArms,
-            // There are no side-effecting empty arms here, nothing to do.
-            ValidOnly => ValidOnly,
-        }
-    }
-
     fn is_known_valid(self) -> bool {
         matches!(self, ValidOnly)
     }
-    fn allows_omitting_empty_arms(self) -> bool {
-        matches!(self, ValidOnly | MaybeInvalidButAllowOmittingArms)
-    }
 
     /// If the place has validity given by `self` and we read that the value at the place has
     /// constructor `ctor`, this computes what we can assume about the validity of the constructor
@@ -814,7 +800,7 @@ impl fmt::Display for ValidityConstraint {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let s = match self {
             ValidOnly => "✓",
-            MaybeInvalid | MaybeInvalidButAllowOmittingArms => "?",
+            MaybeInvalid => "?",
         };
         write!(f, "{s}")
     }
@@ -1460,8 +1446,6 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
 
     // Whether the place/column we are inspecting is known to contain valid data.
     let place_validity = matrix.place_validity[0];
-    // For backwards compability we allow omitting some empty arms that we ideally shouldn't.
-    let place_validity = place_validity.allow_omitting_side_effecting_arms();
 
     // Analyze the constructors present in this column.
     let ctors = matrix.heads().map(|p| p.ctor());
@@ -1486,12 +1470,9 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     // Whether we should report "Enum::A and Enum::C are missing" or "_ is missing".
     let report_individual_missing_ctors = always_report_all || !all_missing;
     // Which constructors are considered missing. We ensure that `!missing_ctors.is_empty() =>
-    // split_ctors.contains(Missing)`. The converse usually holds except in the
-    // `MaybeInvalidButAllowOmittingArms` backwards-compatibility case.
-    let mut missing_ctors = split_set.missing;
-    if !place_validity.allows_omitting_empty_arms() {
-        missing_ctors.extend(split_set.missing_empty);
-    }
+    // split_ctors.contains(Missing)`. The converse usually holds except when
+    // `!place_validity.is_known_valid()`.
+    let missing_ctors = split_set.missing;
 
     let mut ret = WitnessMatrix::empty();
     for ctor in split_ctors {
-- 
cgit 1.4.1-3-g733a5


From edb27a306a29b5b3e9f63da3e74e985736905bc2 Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Wed, 10 Jan 2024 22:23:21 +0100
Subject: Make all the empty pattern decisions in `usefulness`

---
 compiler/rustc_pattern_analysis/src/constructor.rs | 19 +++++--------------
 compiler/rustc_pattern_analysis/src/lints.rs       |  2 +-
 compiler/rustc_pattern_analysis/src/usefulness.rs  | 18 +++++++++++++-----
 3 files changed, 19 insertions(+), 20 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs
index c1042d5b66e..af553840898 100644
--- a/compiler/rustc_pattern_analysis/src/constructor.rs
+++ b/compiler/rustc_pattern_analysis/src/constructor.rs
@@ -858,12 +858,14 @@ 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();
@@ -1003,17 +1005,6 @@ 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 }
     }
 }
diff --git a/compiler/rustc_pattern_analysis/src/lints.rs b/compiler/rustc_pattern_analysis/src/lints.rs
index cfe4ca3ce93..cf3dddfafeb 100644
--- a/compiler/rustc_pattern_analysis/src/lints.rs
+++ b/compiler/rustc_pattern_analysis/src/lints.rs
@@ -59,7 +59,7 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
     ) -> Result<SplitConstructorSet<'p, 'tcx>, ErrorGuaranteed> {
         let column_ctors = self.patterns.iter().map(|p| p.ctor());
         let ctors_for_ty = &pcx.ctors_for_ty()?;
-        Ok(ctors_for_ty.split(pcx, column_ctors))
+        Ok(ctors_for_ty.split(column_ctors))
     }
 
     /// Does specialization: given a constructor, this takes the patterns from the column that match
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index 72459582113..490a84c65db 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -737,15 +737,13 @@ pub(crate) struct PlaceCtxt<'a, Cx: TypeCx> {
     pub(crate) mcx: MatchCtxt<'a, Cx>,
     /// Type of the place under investigation.
     pub(crate) ty: Cx::Ty,
-    /// Whether the place is the original scrutinee place, as opposed to a subplace of it.
-    pub(crate) is_scrutinee: bool,
 }
 
 impl<'a, Cx: TypeCx> PlaceCtxt<'a, Cx> {
     /// A `PlaceCtxt` when code other than `is_useful` needs one.
     #[cfg_attr(not(feature = "rustc"), allow(dead_code))]
     pub(crate) fn new_dummy(mcx: MatchCtxt<'a, Cx>, ty: Cx::Ty) -> Self {
-        PlaceCtxt { mcx, ty, is_scrutinee: false }
+        PlaceCtxt { mcx, ty }
     }
 
     pub(crate) fn ctor_arity(&self, ctor: &Constructor<Cx>) -> usize {
@@ -1442,7 +1440,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     };
 
     debug!("ty: {ty:?}");
-    let pcx = &PlaceCtxt { mcx, ty, is_scrutinee: is_top_level };
+    let pcx = &PlaceCtxt { mcx, ty };
 
     // Whether the place/column we are inspecting is known to contain valid data.
     let place_validity = matrix.place_validity[0];
@@ -1451,7 +1449,17 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     let ctors = matrix.heads().map(|p| p.ctor());
     let ctors_for_ty = pcx.ctors_for_ty()?;
     let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. }); // For diagnostics.
-    let split_set = ctors_for_ty.split(pcx, ctors);
+    let mut split_set = ctors_for_ty.split(ctors);
+    // 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()
+        && !(is_top_level && matches!(ctors_for_ty, ConstructorSet::NoConstructors))
+    {
+        // Treat all missing constructors as nonempty.
+        // This clears `missing_empty`.
+        split_set.missing.append(&mut split_set.missing_empty);
+    }
     let all_missing = split_set.present.is_empty();
 
     // Build the set of constructors we will specialize with. It must cover the whole type.
-- 
cgit 1.4.1-3-g733a5


From de77f1a86ef732d3cbffd284bb32c5908a535748 Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Wed, 10 Jan 2024 22:47:52 +0100
Subject: Simplify empty pattern logic a bit

---
 compiler/rustc_pattern_analysis/src/usefulness.rs | 27 +++++++++++------------
 1 file changed, 13 insertions(+), 14 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index 490a84c65db..ec9cbeb4fef 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -1441,21 +1441,20 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
 
     debug!("ty: {ty:?}");
     let pcx = &PlaceCtxt { mcx, ty };
+    let ctors_for_ty = pcx.ctors_for_ty()?;
 
     // Whether the place/column we are inspecting is known to contain valid data.
     let place_validity = matrix.place_validity[0];
+    // We treat match scrutinees of type `!` or `EmptyEnum` differently.
+    let is_toplevel_exception =
+        is_top_level && matches!(ctors_for_ty, ConstructorSet::NoConstructors);
+    // Whether empty patterns can be omitted for exhaustiveness.
+    let can_omit_empty_arms = is_toplevel_exception || mcx.tycx.is_exhaustive_patterns_feature_on();
 
     // Analyze the constructors present in this column.
     let ctors = matrix.heads().map(|p| p.ctor());
-    let ctors_for_ty = pcx.ctors_for_ty()?;
-    let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. }); // For diagnostics.
     let mut split_set = ctors_for_ty.split(ctors);
-    // 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()
-        && !(is_top_level && matches!(ctors_for_ty, ConstructorSet::NoConstructors))
-    {
+    if !can_omit_empty_arms {
         // Treat all missing constructors as nonempty.
         // This clears `missing_empty`.
         split_set.missing.append(&mut split_set.missing_empty);
@@ -1463,17 +1462,17 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     let all_missing = split_set.present.is_empty();
 
     // Build the set of constructors we will specialize with. It must cover the whole type.
+    // We need to iterate over a full set of constructors, so we add `Missing` to represent the
+    // missing ones. This is explained under "Constructor Splitting" at the top of this file.
     let mut split_ctors = split_set.present;
-    if !split_set.missing.is_empty() {
-        // We need to iterate over a full set of constructors, so we add `Missing` to represent the
-        // missing ones. This is explained under "Constructor Splitting" at the top of this file.
-        split_ctors.push(Constructor::Missing);
-    } else if !split_set.missing_empty.is_empty() && !place_validity.is_known_valid() {
-        // The missing empty constructors are reachable if the place can contain invalid data.
+    if !(split_set.missing.is_empty()
+        && (split_set.missing_empty.is_empty() || place_validity.is_known_valid()))
+    {
         split_ctors.push(Constructor::Missing);
     }
 
     // Decide what constructors to report.
+    let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. });
     let always_report_all = is_top_level && !is_integers;
     // Whether we should report "Enum::A and Enum::C are missing" or "_ is missing".
     let report_individual_missing_ctors = always_report_all || !all_missing;
-- 
cgit 1.4.1-3-g733a5


From d95644d3ae276ba787cdf9214a97f27b82c1348e Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Wed, 10 Jan 2024 23:08:31 +0100
Subject: Simplify empty pattern logic some more

---
 compiler/rustc_pattern_analysis/src/usefulness.rs | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index ec9cbeb4fef..d8c63e0571d 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -1450,23 +1450,19 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
         is_top_level && matches!(ctors_for_ty, ConstructorSet::NoConstructors);
     // Whether empty patterns can be omitted for exhaustiveness.
     let can_omit_empty_arms = is_toplevel_exception || mcx.tycx.is_exhaustive_patterns_feature_on();
+    // Whether empty patterns are counted as useful or not.
+    let empty_arms_are_unreachable = place_validity.is_known_valid() && can_omit_empty_arms;
 
     // Analyze the constructors present in this column.
     let ctors = matrix.heads().map(|p| p.ctor());
     let mut split_set = ctors_for_ty.split(ctors);
-    if !can_omit_empty_arms {
-        // Treat all missing constructors as nonempty.
-        // This clears `missing_empty`.
-        split_set.missing.append(&mut split_set.missing_empty);
-    }
     let all_missing = split_set.present.is_empty();
-
     // Build the set of constructors we will specialize with. It must cover the whole type.
     // We need to iterate over a full set of constructors, so we add `Missing` to represent the
     // missing ones. This is explained under "Constructor Splitting" at the top of this file.
     let mut split_ctors = split_set.present;
     if !(split_set.missing.is_empty()
-        && (split_set.missing_empty.is_empty() || place_validity.is_known_valid()))
+        && (split_set.missing_empty.is_empty() || empty_arms_are_unreachable))
     {
         split_ctors.push(Constructor::Missing);
     }
@@ -1479,7 +1475,10 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     // Which constructors are considered missing. We ensure that `!missing_ctors.is_empty() =>
     // split_ctors.contains(Missing)`. The converse usually holds except when
     // `!place_validity.is_known_valid()`.
-    let missing_ctors = split_set.missing;
+    let mut missing_ctors = split_set.missing;
+    if !can_omit_empty_arms {
+        missing_ctors.append(&mut split_set.missing_empty);
+    }
 
     let mut ret = WitnessMatrix::empty();
     for ctor in split_ctors {
-- 
cgit 1.4.1-3-g733a5


From 8b66f497ebe3458226dbcc91501b5dd1c1728b45 Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Mon, 15 Jan 2024 19:17:28 +0100
Subject: Lint overlapping ranges directly from exhaustiveness

---
 compiler/rustc_pattern_analysis/src/lib.rs        | 25 +++++++++-------
 compiler/rustc_pattern_analysis/src/lints.rs      | 32 ++-------------------
 compiler/rustc_pattern_analysis/src/rustc.rs      | 35 +++++++++++++++++------
 compiler/rustc_pattern_analysis/src/usefulness.rs | 16 ++++-------
 4 files changed, 49 insertions(+), 59 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs
index ed10a515508..0bc432fa6f0 100644
--- a/compiler/rustc_pattern_analysis/src/lib.rs
+++ b/compiler/rustc_pattern_analysis/src/lib.rs
@@ -27,11 +27,9 @@ use rustc_middle::ty::Ty;
 #[cfg(feature = "rustc")]
 use rustc_span::ErrorGuaranteed;
 
-use crate::constructor::{Constructor, ConstructorSet};
+use crate::constructor::{Constructor, ConstructorSet, IntRange};
 #[cfg(feature = "rustc")]
-use crate::lints::{
-    lint_nonexhaustive_missing_variants, lint_overlapping_range_endpoints, PatternColumn,
-};
+use crate::lints::{lint_nonexhaustive_missing_variants, PatternColumn};
 use crate::pat::DeconstructedPat;
 #[cfg(feature = "rustc")]
 use crate::rustc::RustcMatchCheckCtxt;
@@ -77,6 +75,17 @@ pub trait TypeCx: Sized + fmt::Debug {
 
     /// Raise a bug.
     fn bug(&self, fmt: fmt::Arguments<'_>) -> !;
+
+    /// Lint that the range `pat` overlapped with all the ranges in `overlaps_with`, where the range
+    /// they overlapped over is `overlaps_on`. We only detect singleton overlaps.
+    /// The default implementation does nothing.
+    fn lint_overlapping_range_endpoints(
+        &self,
+        _pat: &DeconstructedPat<'_, Self>,
+        _overlaps_on: IntRange,
+        _overlaps_with: &[&DeconstructedPat<'_, Self>],
+    ) {
+    }
 }
 
 /// Context that provides information global to a match.
@@ -111,16 +120,10 @@ pub fn analyze_match<'p, 'tcx>(
 
     let report = compute_match_usefulness(cx, arms, scrut_ty, scrut_validity)?;
 
-    let pat_column = PatternColumn::new(arms);
-
-    // Lint ranges that overlap on their endpoints, which is likely a mistake.
-    if !report.overlapping_range_endpoints.is_empty() {
-        lint_overlapping_range_endpoints(cx, &report.overlapping_range_endpoints);
-    }
-
     // Run the non_exhaustive_omitted_patterns lint. Only run on refutable patterns to avoid hitting
     // `if let`s. Only run if the match is exhaustive otherwise the error is redundant.
     if tycx.refutable && report.non_exhaustiveness_witnesses.is_empty() {
+        let pat_column = PatternColumn::new(arms);
         lint_nonexhaustive_missing_variants(cx, arms, &pat_column, scrut_ty)?;
     }
 
diff --git a/compiler/rustc_pattern_analysis/src/lints.rs b/compiler/rustc_pattern_analysis/src/lints.rs
index cfe4ca3ce93..4266e2a405e 100644
--- a/compiler/rustc_pattern_analysis/src/lints.rs
+++ b/compiler/rustc_pattern_analysis/src/lints.rs
@@ -1,14 +1,11 @@
-use rustc_session::lint;
 use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
 use rustc_span::ErrorGuaranteed;
 
-use crate::errors::{
-    self, NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Uncovered,
-};
+use crate::errors::{NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Uncovered};
 use crate::pat::PatOrWild;
 use crate::rustc::{
-    self, Constructor, DeconstructedPat, MatchArm, MatchCtxt, PlaceCtxt, RevealedTy,
-    RustcMatchCheckCtxt, SplitConstructorSet, WitnessPat,
+    Constructor, DeconstructedPat, MatchArm, MatchCtxt, PlaceCtxt, RevealedTy, RustcMatchCheckCtxt,
+    SplitConstructorSet, WitnessPat,
 };
 
 /// A column of patterns in the matrix, where a column is the intuitive notion of "subpatterns that
@@ -196,26 +193,3 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     }
     Ok(())
 }
-
-pub(crate) fn lint_overlapping_range_endpoints<'a, 'p, 'tcx>(
-    cx: MatchCtxt<'a, 'p, 'tcx>,
-    overlapping_range_endpoints: &[rustc::OverlappingRanges<'p, 'tcx>],
-) {
-    let rcx = cx.tycx;
-    for overlap in overlapping_range_endpoints {
-        let overlap_as_pat = rcx.hoist_pat_range(&overlap.overlaps_on, overlap.pat.ty());
-        let overlaps: Vec<_> = overlap
-            .overlaps_with
-            .iter()
-            .map(|pat| pat.data().unwrap().span)
-            .map(|span| errors::Overlap { range: overlap_as_pat.clone(), span })
-            .collect();
-        let pat_span = overlap.pat.data().unwrap().span;
-        rcx.tcx.emit_spanned_lint(
-            lint::builtin::OVERLAPPING_RANGE_ENDPOINTS,
-            rcx.match_lint_level,
-            pat_span,
-            errors::OverlappingRangeEndpoints { overlap: overlaps, range: pat_span },
-        );
-    }
-}
diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index e82d6666b1a..dbb2bf4a4cb 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -1,3 +1,4 @@
+use smallvec::SmallVec;
 use std::fmt;
 use std::iter::once;
 
@@ -5,24 +6,21 @@ use rustc_arena::{DroplessArena, TypedArena};
 use rustc_data_structures::captures::Captures;
 use rustc_hir::def_id::DefId;
 use rustc_hir::HirId;
-use rustc_index::Idx;
-use rustc_index::IndexVec;
+use rustc_index::{Idx, IndexVec};
 use rustc_middle::middle::stability::EvalResult;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::{self, Const};
 use rustc_middle::thir::{FieldPat, Pat, PatKind, PatRange, PatRangeBoundary};
 use rustc_middle::ty::layout::IntegerExt;
-use rustc_middle::ty::TypeVisitableExt;
-use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, VariantDef};
-use rustc_span::ErrorGuaranteed;
-use rustc_span::{Span, DUMMY_SP};
+use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, TypeVisitableExt, VariantDef};
+use rustc_session::lint;
+use rustc_span::{ErrorGuaranteed, Span, DUMMY_SP};
 use rustc_target::abi::{FieldIdx, Integer, VariantIdx, FIRST_VARIANT};
-use smallvec::SmallVec;
 
 use crate::constructor::{
     IntRange, MaybeInfiniteInt, OpaqueId, RangeEnd, Slice, SliceKind, VariantVisibility,
 };
-use crate::TypeCx;
+use crate::{errors, TypeCx};
 
 use crate::constructor::Constructor::*;
 
@@ -991,6 +989,27 @@ impl<'p, 'tcx> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
     fn bug(&self, fmt: fmt::Arguments<'_>) -> ! {
         span_bug!(self.scrut_span, "{}", fmt)
     }
+
+    fn lint_overlapping_range_endpoints(
+        &self,
+        pat: &crate::pat::DeconstructedPat<'_, Self>,
+        overlaps_on: IntRange,
+        overlaps_with: &[&crate::pat::DeconstructedPat<'_, Self>],
+    ) {
+        let overlap_as_pat = self.hoist_pat_range(&overlaps_on, pat.ty());
+        let overlaps: Vec<_> = overlaps_with
+            .iter()
+            .map(|pat| pat.data().unwrap().span)
+            .map(|span| errors::Overlap { range: overlap_as_pat.clone(), span })
+            .collect();
+        let pat_span = pat.data().unwrap().span;
+        self.tcx.emit_spanned_lint(
+            lint::builtin::OVERLAPPING_RANGE_ENDPOINTS,
+            self.match_lint_level,
+            pat_span,
+            errors::OverlappingRangeEndpoints { overlap: overlaps, range: pat_span },
+        );
+    }
 }
 
 /// Recursively expand this pattern into its subpatterns. Only useful for or-patterns.
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index 6244cf0ff7d..1d505f0c1cd 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -1340,10 +1340,11 @@ impl<Cx: TypeCx> WitnessMatrix<Cx> {
 /// We can however get false negatives because exhaustiveness does not explore all cases. See the
 /// section on relevancy at the top of the file.
 fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
+    mcx: MatchCtxt<'_, Cx>,
     overlap_range: IntRange,
     matrix: &Matrix<'p, Cx>,
     specialized_matrix: &Matrix<'p, Cx>,
-    overlapping_range_endpoints: &mut Vec<OverlappingRanges<'p, Cx>>,
+    _overlapping_range_endpoints: &mut Vec<OverlappingRanges<'p, Cx>>,
 ) {
     let overlap = overlap_range.lo;
     // Ranges that look like `lo..=overlap`.
@@ -1373,11 +1374,7 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
                     .map(|&(_, pat)| pat)
                     .collect();
                 if !overlaps_with.is_empty() {
-                    overlapping_range_endpoints.push(OverlappingRanges {
-                        pat,
-                        overlaps_on: overlap_range,
-                        overlaps_with,
-                    });
+                    mcx.tycx.lint_overlapping_range_endpoints(pat, overlap_range, &overlaps_with);
                 }
             }
             suffixes.push((child_row_id, pat))
@@ -1393,11 +1390,7 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
                     .map(|&(_, pat)| pat)
                     .collect();
                 if !overlaps_with.is_empty() {
-                    overlapping_range_endpoints.push(OverlappingRanges {
-                        pat,
-                        overlaps_on: overlap_range,
-                        overlaps_with,
-                    });
+                    mcx.tycx.lint_overlapping_range_endpoints(pat, overlap_range, &overlaps_with);
                 }
             }
             prefixes.push((child_row_id, pat))
@@ -1538,6 +1531,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
                 && spec_matrix.rows.iter().any(|row| !row.intersects.is_empty())
             {
                 collect_overlapping_range_endpoints(
+                    mcx,
                     overlap_range,
                     matrix,
                     &spec_matrix,
-- 
cgit 1.4.1-3-g733a5


From 448c4a4efb689f5d7d1479a1c3d1cac0d3a1fc82 Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Mon, 15 Jan 2024 19:26:55 +0100
Subject: Remove the unused `overlapping_range_endpoints` Vec

---
 compiler/rustc_pattern_analysis/src/rustc.rs      |  2 --
 compiler/rustc_pattern_analysis/src/usefulness.rs | 42 +++--------------------
 2 files changed, 5 insertions(+), 39 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index dbb2bf4a4cb..87e70d68c1b 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -32,8 +32,6 @@ pub type DeconstructedPat<'p, 'tcx> =
     crate::pat::DeconstructedPat<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type MatchArm<'p, 'tcx> = crate::MatchArm<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type MatchCtxt<'a, 'p, 'tcx> = crate::MatchCtxt<'a, RustcMatchCheckCtxt<'p, 'tcx>>;
-pub type OverlappingRanges<'p, 'tcx> =
-    crate::usefulness::OverlappingRanges<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub(crate) type PlaceCtxt<'a, 'p, 'tcx> =
     crate::usefulness::PlaceCtxt<'a, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub(crate) type SplitConstructorSet<'p, 'tcx> =
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index 1d505f0c1cd..c7894994213 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -1344,7 +1344,6 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
     overlap_range: IntRange,
     matrix: &Matrix<'p, Cx>,
     specialized_matrix: &Matrix<'p, Cx>,
-    _overlapping_range_endpoints: &mut Vec<OverlappingRanges<'p, Cx>>,
 ) {
     let overlap = overlap_range.lo;
     // Ranges that look like `lo..=overlap`.
@@ -1416,7 +1415,6 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
 fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     mcx: MatchCtxt<'a, Cx>,
     matrix: &mut Matrix<'p, Cx>,
-    overlapping_range_endpoints: &mut Vec<OverlappingRanges<'p, Cx>>,
     is_top_level: bool,
 ) -> Result<WitnessMatrix<Cx>, Cx::Error> {
     debug_assert!(matrix.rows().all(|r| r.len() == matrix.column_count()));
@@ -1496,12 +1494,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
         let ctor_is_relevant = matches!(ctor, Constructor::Missing) || missing_ctors.is_empty();
         let mut spec_matrix = matrix.specialize_constructor(pcx, &ctor, ctor_is_relevant);
         let mut witnesses = ensure_sufficient_stack(|| {
-            compute_exhaustiveness_and_usefulness(
-                mcx,
-                &mut spec_matrix,
-                overlapping_range_endpoints,
-                false,
-            )
+            compute_exhaustiveness_and_usefulness(mcx, &mut spec_matrix, false)
         })?;
 
         // Transform witnesses for `spec_matrix` into witnesses for `matrix`.
@@ -1530,13 +1523,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
                 && spec_matrix.rows.len() >= 2
                 && spec_matrix.rows.iter().any(|row| !row.intersects.is_empty())
             {
-                collect_overlapping_range_endpoints(
-                    mcx,
-                    overlap_range,
-                    matrix,
-                    &spec_matrix,
-                    overlapping_range_endpoints,
-                );
+                collect_overlapping_range_endpoints(mcx, overlap_range, matrix, &spec_matrix);
             }
         }
     }
@@ -1563,15 +1550,6 @@ pub enum Usefulness<'p, Cx: TypeCx> {
     Redundant,
 }
 
-/// Indicates that the range `pat` overlapped with all the ranges in `overlaps_with`, where the
-/// range they overlapped over is `overlaps_on`. We only detect singleton overlaps.
-#[derive(Clone, Debug)]
-pub struct OverlappingRanges<'p, Cx: TypeCx> {
-    pub pat: &'p DeconstructedPat<'p, Cx>,
-    pub overlaps_on: IntRange,
-    pub overlaps_with: Vec<&'p DeconstructedPat<'p, Cx>>,
-}
-
 /// The output of checking a match for exhaustiveness and arm usefulness.
 pub struct UsefulnessReport<'p, Cx: TypeCx> {
     /// For each arm of the input, whether that arm is useful after the arms above it.
@@ -1579,7 +1557,6 @@ pub struct UsefulnessReport<'p, Cx: TypeCx> {
     /// If the match is exhaustive, this is empty. If not, this contains witnesses for the lack of
     /// exhaustiveness.
     pub non_exhaustiveness_witnesses: Vec<WitnessPat<Cx>>,
-    pub overlapping_range_endpoints: Vec<OverlappingRanges<'p, Cx>>,
 }
 
 /// Computes whether a match is exhaustive and which of its arms are useful.
@@ -1590,14 +1567,9 @@ pub fn compute_match_usefulness<'p, Cx: TypeCx>(
     scrut_ty: Cx::Ty,
     scrut_validity: ValidityConstraint,
 ) -> Result<UsefulnessReport<'p, Cx>, Cx::Error> {
-    let mut overlapping_range_endpoints = Vec::new();
     let mut matrix = Matrix::new(arms, scrut_ty, scrut_validity);
-    let non_exhaustiveness_witnesses = compute_exhaustiveness_and_usefulness(
-        cx,
-        &mut matrix,
-        &mut overlapping_range_endpoints,
-        true,
-    )?;
+    let non_exhaustiveness_witnesses =
+        compute_exhaustiveness_and_usefulness(cx, &mut matrix, true)?;
 
     let non_exhaustiveness_witnesses: Vec<_> = non_exhaustiveness_witnesses.single_column();
     let arm_usefulness: Vec<_> = arms
@@ -1615,9 +1587,5 @@ pub fn compute_match_usefulness<'p, Cx: TypeCx>(
         })
         .collect();
 
-    Ok(UsefulnessReport {
-        arm_usefulness,
-        non_exhaustiveness_witnesses,
-        overlapping_range_endpoints,
-    })
+    Ok(UsefulnessReport { arm_usefulness, non_exhaustiveness_witnesses })
 }
-- 
cgit 1.4.1-3-g733a5


From 19d6f068ee75d258a5f14d609894af49943f907e Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Wed, 17 Jan 2024 02:59:47 +0100
Subject: Don't rely on contiguous `VariantId`s outside of rustc

---
 Cargo.lock                                         |  1 +
 compiler/rustc_pattern_analysis/Cargo.toml         |  1 +
 compiler/rustc_pattern_analysis/src/constructor.rs | 11 +++---
 compiler/rustc_pattern_analysis/src/lib.rs         | 42 ++++++++++++++++++++--
 4 files changed, 49 insertions(+), 6 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/Cargo.lock b/Cargo.lock
index f85d523fc1b..0df01e5e29a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4355,6 +4355,7 @@ name = "rustc_pattern_analysis"
 version = "0.0.0"
 dependencies = [
  "derivative",
+ "rustc-hash",
  "rustc_apfloat",
  "rustc_arena",
  "rustc_data_structures",
diff --git a/compiler/rustc_pattern_analysis/Cargo.toml b/compiler/rustc_pattern_analysis/Cargo.toml
index 7cc585bea3a..1d0e1cb7e6a 100644
--- a/compiler/rustc_pattern_analysis/Cargo.toml
+++ b/compiler/rustc_pattern_analysis/Cargo.toml
@@ -6,6 +6,7 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 derivative = "2.2.0"
+rustc-hash = "1.1.0"
 rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena", optional = true }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs
index c1042d5b66e..76098505b79 100644
--- a/compiler/rustc_pattern_analysis/src/constructor.rs
+++ b/compiler/rustc_pattern_analysis/src/constructor.rs
@@ -155,13 +155,13 @@ use std::iter::once;
 use smallvec::SmallVec;
 
 use rustc_apfloat::ieee::{DoubleS, IeeeFloat, SingleS};
-use rustc_index::bit_set::{BitSet, GrowableBitSet};
-use rustc_index::IndexVec;
+use rustc_index::bit_set::GrowableBitSet;
 
 use self::Constructor::*;
 use self::MaybeInfiniteInt::*;
 use self::SliceKind::*;
 
+use crate::index;
 use crate::usefulness::PlaceCtxt;
 use crate::TypeCx;
 
@@ -804,7 +804,10 @@ pub enum ConstructorSet<Cx: TypeCx> {
     Struct { empty: bool },
     /// This type has the following list of constructors. If `variants` is empty and
     /// `non_exhaustive` is false, don't use this; use `NoConstructors` instead.
-    Variants { variants: IndexVec<Cx::VariantIdx, VariantVisibility>, non_exhaustive: bool },
+    Variants {
+        variants: index::IdxContainer<Cx::VariantIdx, VariantVisibility>,
+        non_exhaustive: bool,
+    },
     /// The type is `&T`.
     Ref,
     /// The type is a union.
@@ -904,7 +907,7 @@ impl<Cx: TypeCx> ConstructorSet<Cx> {
                 }
             }
             ConstructorSet::Variants { variants, non_exhaustive } => {
-                let mut seen_set: BitSet<_> = BitSet::new_empty(variants.len());
+                let mut seen_set = index::IdxSet::new_empty(variants.len());
                 for idx in seen.iter().map(|c| c.as_variant().unwrap()) {
                     seen_set.insert(idx);
                 }
diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs
index ed10a515508..867924180dd 100644
--- a/compiler/rustc_pattern_analysis/src/lib.rs
+++ b/compiler/rustc_pattern_analysis/src/lib.rs
@@ -21,7 +21,45 @@ rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 use std::fmt;
 
-use rustc_index::Idx;
+#[cfg(feature = "rustc")]
+pub mod index {
+    // Faster version when the indices of variants are `0..variants.len()`.
+    pub use rustc_index::bit_set::BitSet as IdxSet;
+    pub use rustc_index::Idx;
+    pub use rustc_index::IndexVec as IdxContainer;
+}
+#[cfg(not(feature = "rustc"))]
+pub mod index {
+    // Slower version when the indices of variants are something else.
+    pub trait Idx: Copy + PartialEq + Eq + std::hash::Hash {}
+    impl<T: Copy + PartialEq + Eq + std::hash::Hash> Idx for T {}
+
+    #[derive(Debug)]
+    pub struct IdxContainer<K, V>(pub rustc_hash::FxHashMap<K, V>);
+    impl<K: Idx, V> IdxContainer<K, V> {
+        pub fn len(&self) -> usize {
+            self.0.len()
+        }
+        pub fn iter_enumerated(&self) -> impl Iterator<Item = (K, &V)> {
+            self.0.iter().map(|(k, v)| (*k, v))
+        }
+    }
+
+    #[derive(Debug)]
+    pub struct IdxSet<T>(pub rustc_hash::FxHashSet<T>);
+    impl<T: Idx> IdxSet<T> {
+        pub fn new_empty(_len: usize) -> Self {
+            Self(Default::default())
+        }
+        pub fn contains(&self, elem: T) -> bool {
+            self.0.contains(&elem)
+        }
+        pub fn insert(&mut self, elem: T) {
+            self.0.insert(elem);
+        }
+    }
+}
+
 #[cfg(feature = "rustc")]
 use rustc_middle::ty::Ty;
 #[cfg(feature = "rustc")]
@@ -50,7 +88,7 @@ pub trait TypeCx: Sized + fmt::Debug {
     /// Errors that can abort analysis.
     type Error: fmt::Debug;
     /// The index of an enum variant.
-    type VariantIdx: Clone + Idx;
+    type VariantIdx: Clone + index::Idx + fmt::Debug;
     /// A string literal
     type StrLit: Clone + PartialEq + fmt::Debug;
     /// Extra data to store in a match arm.
-- 
cgit 1.4.1-3-g733a5


From 796cdc590c0f6badb9629feb2a2b55873408cc0f Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Sat, 23 Dec 2023 00:21:27 +0100
Subject: Remove Ty: Copy bound

---
 .../rustc_mir_build/src/thir/pattern/check_match.rs  |  2 +-
 compiler/rustc_pattern_analysis/src/lib.rs           |  8 ++++----
 compiler/rustc_pattern_analysis/src/lints.rs         |  4 ++--
 compiler/rustc_pattern_analysis/src/pat.rs           | 12 ++++++------
 compiler/rustc_pattern_analysis/src/rustc.rs         | 20 ++++++++++----------
 compiler/rustc_pattern_analysis/src/usefulness.rs    | 17 +++++++++--------
 6 files changed, 32 insertions(+), 31 deletions(-)

(limited to 'compiler/rustc_pattern_analysis/src')

diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index e8ba83a5527..693dc49c6e8 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -1130,7 +1130,7 @@ fn collect_non_exhaustive_tys<'tcx>(
         non_exhaustive_tys.insert(pat.ty().inner());
     }
     if let Constructor::IntRange(range) = pat.ctor() {
-        if cx.is_range_beyond_boundaries(range, pat.ty()) {
+        if cx.is_range_beyond_boundaries(range, *pat.ty()) {
             // The range denotes the values before `isize::MIN` or the values after `usize::MAX`/`isize::MAX`.
             non_exhaustive_tys.insert(pat.ty().inner());
         }
diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs
index 21fa8e68d82..4fd01b5e638 100644
--- a/compiler/rustc_pattern_analysis/src/lib.rs
+++ b/compiler/rustc_pattern_analysis/src/lib.rs
@@ -82,7 +82,7 @@ impl<'a, T: ?Sized> Captures<'a> for T {}
 /// Most of the crate is parameterized on a type that implements this trait.
 pub trait TypeCx: Sized + fmt::Debug {
     /// The type of a pattern.
-    type Ty: Copy + Clone + fmt::Debug; // FIXME: remove Copy
+    type Ty: Clone + fmt::Debug;
     /// Errors that can abort analysis.
     type Error: fmt::Debug;
     /// The index of an enum variant.
@@ -97,16 +97,16 @@ pub trait TypeCx: Sized + fmt::Debug {
     fn is_exhaustive_patterns_feature_on(&self) -> bool;
 
     /// The number of fields for this constructor.
-    fn ctor_arity(&self, ctor: &Constructor<Self>, ty: Self::Ty) -> usize;
+    fn ctor_arity(&self, ctor: &Constructor<Self>, ty: &Self::Ty) -> usize;
 
     /// The types of the fields for this constructor. The result must have a length of
     /// `ctor_arity()`.
-    fn ctor_sub_tys(&self, ctor: &Constructor<Self>, ty: Self::Ty) -> &[Self::Ty];
+    fn ctor_sub_tys(&self, ctor: &Constructor<Self>, ty: &Self::Ty) -> &[Self::Ty];
 
     /// The set of all the constructors for `ty`.
     ///
     /// This must follow the invariants of `ConstructorSet`
-    fn ctors_for_ty(&self, ty: Self::Ty) -> Result<ConstructorSet<Self>, Self::Error>;
+    fn ctors_for_ty(&self, ty: &Self::Ty) -> Result<ConstructorSet<Self>, Self::Error>;
 
     /// Best-effort `Debug` implementation.
     fn debug_pat(f: &mut fmt::Formatter<'_>, pat: &DeconstructedPat<'_, Self>) -> fmt::Result;
diff --git a/compiler/rustc_pattern_analysis/src/lints.rs b/compiler/rustc_pattern_analysis/src/lints.rs
index d9dbd8250ef..f9f065fbe8b 100644
--- a/compiler/rustc_pattern_analysis/src/lints.rs
+++ b/compiler/rustc_pattern_analysis/src/lints.rs
@@ -46,7 +46,7 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
     }
 
     fn head_ty(&self) -> Option<RevealedTy<'tcx>> {
-        self.patterns.first().map(|pat| pat.ty())
+        self.patterns.first().map(|pat| *pat.ty())
     }
 
     /// Do constructor splitting on the constructors of the column.
@@ -101,7 +101,7 @@ fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     let Some(ty) = column.head_ty() else {
         return Ok(Vec::new());
     };
-    let pcx = &PlaceCtxt::new_dummy(cx, ty);
+    let pcx = &PlaceCtxt::new_dummy(cx, &ty);
 
     let set = column.analyze_ctors(pcx)?;
     if set.present.is_empty() {
diff --git a/compiler/rustc_pattern_analysis/src/pat.rs b/compiler/rustc_pattern_analysis/src/pat.rs
index 75fe59edf88..8cd0ecb073c 100644
--- a/compiler/rustc_pattern_analysis/src/pat.rs
+++ b/compiler/rustc_pattern_analysis/src/pat.rs
@@ -54,8 +54,8 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
     pub fn ctor(&self) -> &Constructor<Cx> {
         &self.ctor
     }
-    pub fn ty(&self) -> Cx::Ty {
-        self.ty
+    pub fn ty(&self) -> &Cx::Ty {
+        &self.ty
     }
     /// Returns the extra data stored in a pattern. Returns `None` if the pattern is a wildcard that
     /// does not correspond to a user-supplied pattern.
@@ -242,15 +242,15 @@ impl<Cx: TypeCx> WitnessPat<Cx> {
     /// `Some(_)`.
     pub(crate) fn wild_from_ctor(pcx: &PlaceCtxt<'_, Cx>, ctor: Constructor<Cx>) -> Self {
         let field_tys = pcx.ctor_sub_tys(&ctor);
-        let fields = field_tys.iter().map(|ty| Self::wildcard(*ty)).collect();
-        Self::new(ctor, fields, pcx.ty)
+        let fields = field_tys.iter().cloned().map(|ty| Self::wildcard(ty)).collect();
+        Self::new(ctor, fields, pcx.ty.clone())
     }
 
     pub fn ctor(&self) -> &Constructor<Cx> {
         &self.ctor
     }
-    pub fn ty(&self) -> Cx::Ty {
-        self.ty
+    pub fn ty(&self) -> &Cx::Ty {
+        &self.ty
     }
 
     pub fn iter_fields(&self) -> impl Iterator<Item = &WitnessPat<Cx>> {
diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index 87e70d68c1b..27b25802427 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -766,7 +766,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
         let mut subpatterns = pat.iter_fields().map(|p| Box::new(cx.hoist_witness_pat(p)));
         let kind = match pat.ctor() {
             Bool(b) => PatKind::Constant { value: mir::Const::from_bool(cx.tcx, *b) },
-            IntRange(range) => return self.hoist_pat_range(range, pat.ty()),
+            IntRange(range) => return self.hoist_pat_range(range, *pat.ty()),
             Struct | Variant(_) | UnionField => match pat.ty().kind() {
                 ty::Tuple(..) => PatKind::Leaf {
                     subpatterns: subpatterns
@@ -785,7 +785,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                         RustcMatchCheckCtxt::variant_index_for_adt(&pat.ctor(), *adt_def);
                     let variant = &adt_def.variant(variant_index);
                     let subpatterns = cx
-                        .list_variant_nonhidden_fields(pat.ty(), variant)
+                        .list_variant_nonhidden_fields(*pat.ty(), variant)
                         .zip(subpatterns)
                         .map(|((field, _ty), pattern)| FieldPat { field, pattern })
                         .collect();
@@ -796,7 +796,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                         PatKind::Leaf { subpatterns }
                     }
                 }
-                _ => bug!("unexpected ctor for type {:?} {:?}", pat.ctor(), pat.ty()),
+                _ => bug!("unexpected ctor for type {:?} {:?}", pat.ctor(), *pat.ty()),
             },
             // Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
             // be careful to reconstruct the correct constant pattern here. However a string
@@ -961,21 +961,21 @@ impl<'p, 'tcx> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
         self.tcx.features().exhaustive_patterns
     }
 
-    fn ctor_arity(&self, ctor: &crate::constructor::Constructor<Self>, ty: Self::Ty) -> usize {
-        self.ctor_arity(ctor, ty)
+    fn ctor_arity(&self, ctor: &crate::constructor::Constructor<Self>, ty: &Self::Ty) -> usize {
+        self.ctor_arity(ctor, *ty)
     }
     fn ctor_sub_tys(
         &self,
         ctor: &crate::constructor::Constructor<Self>,
-        ty: Self::Ty,
+        ty: &Self::Ty,
     ) -> &[Self::Ty] {
-        self.ctor_sub_tys(ctor, ty)
+        self.ctor_sub_tys(ctor, *ty)
     }
     fn ctors_for_ty(
         &self,
-        ty: Self::Ty,
+        ty: &Self::Ty,
     ) -> Result<crate::constructor::ConstructorSet<Self>, Self::Error> {
-        self.ctors_for_ty(ty)
+        self.ctors_for_ty(*ty)
     }
 
     fn debug_pat(
@@ -994,7 +994,7 @@ impl<'p, 'tcx> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
         overlaps_on: IntRange,
         overlaps_with: &[&crate::pat::DeconstructedPat<'_, Self>],
     ) {
-        let overlap_as_pat = self.hoist_pat_range(&overlaps_on, pat.ty());
+        let overlap_as_pat = self.hoist_pat_range(&overlaps_on, *pat.ty());
         let overlaps: Vec<_> = overlaps_with
             .iter()
             .map(|pat| pat.data().unwrap().span)
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index dac354a1c52..d7852a2b2cb 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -736,13 +736,14 @@ pub(crate) struct PlaceCtxt<'a, Cx: TypeCx> {
     #[derivative(Debug = "ignore")]
     pub(crate) mcx: MatchCtxt<'a, Cx>,
     /// Type of the place under investigation.
-    pub(crate) ty: Cx::Ty,
+    #[derivative(Clone(clone_with = "Clone::clone"))] // See rust-derivative#90
+    pub(crate) ty: &'a Cx::Ty,
 }
 
 impl<'a, Cx: TypeCx> PlaceCtxt<'a, Cx> {
     /// A `PlaceCtxt` when code other than `is_useful` needs one.
     #[cfg_attr(not(feature = "rustc"), allow(dead_code))]
-    pub(crate) fn new_dummy(mcx: MatchCtxt<'a, Cx>, ty: Cx::Ty) -> Self {
+    pub(crate) fn new_dummy(mcx: MatchCtxt<'a, Cx>, ty: &'a Cx::Ty) -> Self {
         PlaceCtxt { mcx, ty }
     }
 
@@ -1023,8 +1024,8 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
         matrix
     }
 
-    fn head_ty(&self) -> Option<Cx::Ty> {
-        self.place_ty.first().copied()
+    fn head_ty(&self) -> Option<&Cx::Ty> {
+        self.place_ty.first()
     }
     fn column_count(&self) -> usize {
         self.place_ty.len()
@@ -1058,7 +1059,7 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
         let ctor_sub_tys = pcx.ctor_sub_tys(ctor);
         let arity = ctor_sub_tys.len();
         let specialized_place_ty =
-            ctor_sub_tys.iter().chain(self.place_ty[1..].iter()).copied().collect();
+            ctor_sub_tys.iter().chain(self.place_ty[1..].iter()).cloned().collect();
         let ctor_sub_validity = self.place_validity[0].specialize(ctor);
         let specialized_place_validity = std::iter::repeat(ctor_sub_validity)
             .take(arity)
@@ -1214,7 +1215,7 @@ impl<Cx: TypeCx> WitnessStack<Cx> {
         let len = self.0.len();
         let arity = ctor.arity(pcx);
         let fields = self.0.drain((len - arity)..).rev().collect();
-        let pat = WitnessPat::new(ctor.clone(), fields, pcx.ty);
+        let pat = WitnessPat::new(ctor.clone(), fields, pcx.ty.clone());
         self.0.push(pat);
     }
 }
@@ -1410,7 +1411,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
         return Ok(WitnessMatrix::empty());
     }
 
-    let Some(ty) = matrix.head_ty() else {
+    let Some(ty) = matrix.head_ty().cloned() else {
         // The base case: there are no columns in the matrix. We are morally pattern-matching on ().
         // A row is useful iff it has no (unguarded) rows above it.
         let mut useful = true; // Whether the next row is useful.
@@ -1431,7 +1432,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     };
 
     debug!("ty: {ty:?}");
-    let pcx = &PlaceCtxt { mcx, ty };
+    let pcx = &PlaceCtxt { mcx, ty: &ty };
     let ctors_for_ty = pcx.ctors_for_ty()?;
 
     // Whether the place/column we are inspecting is known to contain valid data.
-- 
cgit 1.4.1-3-g733a5