diff options
Diffstat (limited to 'compiler/rustc_pattern_analysis/src')
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/constructor.rs | 34 | ||||
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/lib.rs | 82 | ||||
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/lints.rs | 34 | ||||
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/pat.rs | 2 | ||||
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/rustc.rs | 43 | ||||
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/usefulness.rs | 129 |
6 files changed, 145 insertions, 179 deletions
diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs index 15ff4ceb5b3..eba71a23435 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; @@ -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 @@ -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. @@ -858,12 +861,14 @@ impl<Cx: TypeCx> ConstructorSet<Cx> { /// any) are missing; 2/ split constructors to handle non-trivial intersections e.g. on ranges /// or slices. This can get subtle; see [`SplitConstructorSet`] for details of this operation /// and its invariants. - #[instrument(level = "debug", skip(self, pcx, ctors), ret)] + #[instrument(level = "debug", skip(self, ctors), ret)] pub(crate) fn split<'a>( &self, - pcx: &PlaceCtxt<'a, '_, Cx>, ctors: impl Iterator<Item = &'a Constructor<Cx>> + Clone, - ) -> SplitConstructorSet<Cx> { + ) -> SplitConstructorSet<Cx> + where + Cx: 'a, + { let mut present: SmallVec<[_; 1]> = SmallVec::new(); // Empty constructors found missing. let mut missing_empty = Vec::new(); @@ -904,7 +909,7 @@ 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); } @@ -1003,17 +1008,6 @@ impl<Cx: TypeCx> ConstructorSet<Cx> { } } - // We have now grouped all the constructors into 3 buckets: present, missing, missing_empty. - // In the absence of the `exhaustive_patterns` feature however, we don't count nested empty - // types as empty. Only non-nested `!` or `enum Foo {}` are considered empty. - if !pcx.mcx.tycx.is_exhaustive_patterns_feature_on() - && !(pcx.is_scrutinee && matches!(self, Self::NoConstructors)) - { - // Treat all missing constructors as nonempty. - // This clears `missing_empty`. - missing.append(&mut missing_empty); - } - SplitConstructorSet { present, missing, missing_empty } } } diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs index 374914055d8..21fa8e68d82 100644 --- a/compiler/rustc_pattern_analysis/src/lib.rs +++ b/compiler/rustc_pattern_analysis/src/lib.rs @@ -21,30 +21,59 @@ 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")] 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; #[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 {} @@ -57,7 +86,7 @@ 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. @@ -84,16 +113,25 @@ 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. #[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. @@ -114,24 +152,16 @@ 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)?; - 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..d9dbd8250ef 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 @@ -59,7 +56,7 @@ 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 @@ -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/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..87e70d68c1b 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::*; @@ -33,11 +31,9 @@ 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 OverlappingRanges<'p, 'tcx> = - crate::usefulness::OverlappingRanges<'p, RustcMatchCheckCtxt<'p, 'tcx>>; +pub type MatchCtxt<'a, 'p, 'tcx> = crate::MatchCtxt<'a, 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 +76,9 @@ 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, @@ -989,6 +987,27 @@ 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 85b6a6a3b6c..dac354a1c52 100644 --- a/compiler/rustc_pattern_analysis/src/usefulness.rs +++ b/compiler/rustc_pattern_analysis/src/usefulness.rs @@ -732,20 +732,18 @@ 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 { - PlaceCtxt { mcx, ty, is_scrutinee: false } + pub(crate) fn new_dummy(mcx: MatchCtxt<'a, Cx>, ty: Cx::Ty) -> Self { + PlaceCtxt { mcx, ty } } pub(crate) fn ctor_arity(&self, ctor: &Constructor<Cx>) -> usize { @@ -768,9 +766,6 @@ impl<'a, 'p, Cx: TypeCx> PlaceCtxt<'a, 'p, 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 +773,9 @@ 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 +798,7 @@ 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}") } @@ -1067,7 +1051,7 @@ 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 +1210,7 @@ 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 +1261,7 @@ 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, @@ -1340,10 +1324,10 @@ 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>>, ) { let overlap = overlap_range.lo; // Ranges that look like `lo..=overlap`. @@ -1373,11 +1357,7 @@ 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 +1373,7 @@ 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)) @@ -1421,9 +1397,8 @@ 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, ) -> Result<WitnessMatrix<Cx>, Cx::Error> { debug_assert!(matrix.rows().all(|r| r.len() == matrix.column_count())); @@ -1456,41 +1431,44 @@ 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 }; + 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]; - // For backwards compability we allow omitting some empty arms that we ideally shouldn't. - let place_validity = place_validity.allow_omitting_side_effecting_arms(); + // 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(); + // 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 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); 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() || empty_arms_are_unreachable)) + { 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; // 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. + // split_ctors.contains(Missing)`. The converse usually holds except when + // `!place_validity.is_known_valid()`. let mut missing_ctors = split_set.missing; - if !place_validity.allows_omitting_empty_arms() { - missing_ctors.extend(split_set.missing_empty); + if !can_omit_empty_arms { + missing_ctors.append(&mut split_set.missing_empty); } let mut ret = WitnessMatrix::empty(); @@ -1503,12 +1481,7 @@ 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`. @@ -1537,12 +1510,7 @@ 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( - overlap_range, - matrix, - &spec_matrix, - overlapping_range_endpoints, - ); + collect_overlapping_range_endpoints(mcx, overlap_range, matrix, &spec_matrix); } } } @@ -1569,15 +1537,6 @@ 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. @@ -1585,25 +1544,19 @@ 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. #[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, ) -> 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 @@ -1621,9 +1574,5 @@ 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 }) } |