diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs index df5bf3111ad..4be564b1d7b 100644 --- a/compiler/rustc_pattern_analysis/src/constructor.rs +++ b/compiler/rustc_pattern_analysis/src/constructor.rs @@ -948,10 +948,10 @@ pub enum ConstructorSet { /// of the `ConstructorSet` for the type, yet if we forgot to include them in `present` we would be /// ignoring any row with `Opaque`s in the algorithm. Hence the importance of point 4. #[derive(Debug)] -pub(crate) struct SplitConstructorSet { - pub(crate) present: SmallVec<[Constructor; 1]>, - pub(crate) missing: Vec>, - pub(crate) missing_empty: Vec>, +pub struct SplitConstructorSet { + pub present: SmallVec<[Constructor; 1]>, + pub missing: Vec>, + pub missing_empty: Vec>, } impl ConstructorSet { @@ -960,7 +960,7 @@ impl ConstructorSet { /// or slices. This can get subtle; see [`SplitConstructorSet`] for details of this operation /// and its invariants. #[instrument(level = "debug", skip(self, ctors), ret)] - pub(crate) fn split<'a>( + pub fn split<'a>( &self, ctors: impl Iterator> + Clone, ) -> SplitConstructorSet diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs index 99c32de7482..3d0eb117d17 100644 --- a/compiler/rustc_pattern_analysis/src/lib.rs +++ b/compiler/rustc_pattern_analysis/src/lib.rs @@ -6,6 +6,7 @@ pub mod errors; #[cfg(feature = "rustc")] pub(crate) mod lints; pub mod pat; +pub mod pat_column; #[cfg(feature = "rustc")] pub mod rustc; pub mod usefulness; @@ -67,8 +68,9 @@ use rustc_span::ErrorGuaranteed; use crate::constructor::{Constructor, ConstructorSet, IntRange}; #[cfg(feature = "rustc")] -use crate::lints::{lint_nonexhaustive_missing_variants, PatternColumn}; +use crate::lints::lint_nonexhaustive_missing_variants; use crate::pat::DeconstructedPat; +use crate::pat_column::PatternColumn; #[cfg(feature = "rustc")] use crate::rustc::RustcMatchCheckCtxt; #[cfg(feature = "rustc")] diff --git a/compiler/rustc_pattern_analysis/src/lints.rs b/compiler/rustc_pattern_analysis/src/lints.rs index 4cbd5e70189..3f1497540d2 100644 --- a/compiler/rustc_pattern_analysis/src/lints.rs +++ b/compiler/rustc_pattern_analysis/src/lints.rs @@ -1,92 +1,11 @@ use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS; use rustc_span::ErrorGuaranteed; -use crate::constructor::{Constructor, SplitConstructorSet}; +use crate::constructor::Constructor; use crate::errors::{NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Uncovered}; -use crate::pat::{DeconstructedPat, PatOrWild}; +use crate::pat_column::PatternColumn; use crate::rustc::{RevealedTy, RustcMatchCheckCtxt, WitnessPat}; -use crate::{MatchArm, TypeCx}; - -/// A column of patterns in the matrix, where a column is the intuitive notion of "subpatterns that -/// inspect the same subvalue/place". -/// This is used to traverse patterns column-by-column for lints. Despite similarities with the -/// algorithm in [`crate::usefulness`], this does a different traversal. Notably this is linear in -/// the depth of patterns, whereas `compute_exhaustiveness_and_usefulness` is worst-case exponential -/// (exhaustiveness is NP-complete). The core difference is that we treat sub-columns separately. -/// -/// This must not contain an or-pattern. `expand_and_push` takes care to expand them. -/// -/// This is not used in the usefulness algorithm; only in lints. -#[derive(Debug)] -pub(crate) struct PatternColumn<'p, Cx: TypeCx> { - patterns: Vec<&'p DeconstructedPat<'p, Cx>>, -} - -impl<'p, Cx: TypeCx> PatternColumn<'p, Cx> { - pub(crate) fn new(arms: &[MatchArm<'p, Cx>]) -> Self { - let patterns = Vec::with_capacity(arms.len()); - let mut column = PatternColumn { patterns }; - for arm in arms { - column.expand_and_push(PatOrWild::Pat(arm.pat)); - } - column - } - /// Pushes a pattern onto the column, expanding any or-patterns into its subpatterns. - /// Internal method, prefer [`PatternColumn::new`]. - fn expand_and_push(&mut self, pat: PatOrWild<'p, Cx>) { - // We flatten or-patterns and skip algorithm-generated wildcards. - if pat.is_or_pat() { - self.patterns.extend( - pat.flatten_or_pat().into_iter().filter_map(|pat_or_wild| pat_or_wild.as_pat()), - ) - } else if let Some(pat) = pat.as_pat() { - self.patterns.push(pat) - } - } - - fn head_ty(&self) -> Option<&Cx::Ty> { - self.patterns.first().map(|pat| pat.ty()) - } - - /// Do constructor splitting on the constructors of the column. - fn analyze_ctors(&self, cx: &Cx, ty: &Cx::Ty) -> Result, Cx::Error> { - let column_ctors = self.patterns.iter().map(|p| p.ctor()); - let ctors_for_ty = cx.ctors_for_ty(ty)?; - Ok(ctors_for_ty.split(column_ctors)) - } - - /// Does specialization: given a constructor, this takes the patterns from the column that match - /// the constructor, and outputs their fields. - /// This returns one column per field of the constructor. They usually all have the same length - /// (the number of patterns in `self` that matched `ctor`), except that we expand or-patterns - /// which may change the lengths. - fn specialize( - &self, - cx: &Cx, - ty: &Cx::Ty, - ctor: &Constructor, - ) -> Vec> { - let arity = ctor.arity(cx, ty); - if arity == 0 { - return Vec::new(); - } - - // We specialize the column by `ctor`. This gives us `arity`-many columns of patterns. These - // columns may have different lengths in the presence of or-patterns (this is why we can't - // reuse `Matrix`). - let mut specialized_columns: Vec<_> = - (0..arity).map(|_| Self { patterns: Vec::new() }).collect(); - let relevant_patterns = - self.patterns.iter().filter(|pat| ctor.is_covered_by(cx, pat.ctor())); - for pat in relevant_patterns { - let specialized = pat.specialize(ctor, arity); - for (subpat, column) in specialized.into_iter().zip(&mut specialized_columns) { - column.expand_and_push(subpat); - } - } - specialized_columns - } -} +use crate::MatchArm; /// Traverse the patterns to collect any variants of a non_exhaustive enum that fail to be mentioned /// in a given column. diff --git a/compiler/rustc_pattern_analysis/src/pat_column.rs b/compiler/rustc_pattern_analysis/src/pat_column.rs new file mode 100644 index 00000000000..3cacfc491b9 --- /dev/null +++ b/compiler/rustc_pattern_analysis/src/pat_column.rs @@ -0,0 +1,90 @@ +use crate::constructor::{Constructor, SplitConstructorSet}; +use crate::pat::{DeconstructedPat, PatOrWild}; +use crate::{Captures, MatchArm, TypeCx}; + +/// A column of patterns in a match, where a column is the intuitive notion of "subpatterns that +/// inspect the same subvalue/place". +/// This is used to traverse patterns column-by-column for lints. Despite similarities with the +/// algorithm in [`crate::usefulness`], this does a different traversal. Notably this is linear in +/// the depth of patterns, whereas `compute_exhaustiveness_and_usefulness` is worst-case exponential +/// (exhaustiveness is NP-complete). The core difference is that we treat sub-columns separately. +/// +/// This is not used in the usefulness algorithm; only in lints. +#[derive(Debug)] +pub struct PatternColumn<'p, Cx: TypeCx> { + /// This must not contain an or-pattern. `expand_and_push` takes care to expand them. + patterns: Vec<&'p DeconstructedPat<'p, Cx>>, +} + +impl<'p, Cx: TypeCx> PatternColumn<'p, Cx> { + pub fn new(arms: &[MatchArm<'p, Cx>]) -> Self { + let patterns = Vec::with_capacity(arms.len()); + let mut column = PatternColumn { patterns }; + for arm in arms { + column.expand_and_push(PatOrWild::Pat(arm.pat)); + } + column + } + /// Pushes a pattern onto the column, expanding any or-patterns into its subpatterns. + /// Internal method, prefer [`PatternColumn::new`]. + fn expand_and_push(&mut self, pat: PatOrWild<'p, Cx>) { + // We flatten or-patterns and skip algorithm-generated wildcards. + if pat.is_or_pat() { + self.patterns.extend( + pat.flatten_or_pat().into_iter().filter_map(|pat_or_wild| pat_or_wild.as_pat()), + ) + } else if let Some(pat) = pat.as_pat() { + self.patterns.push(pat) + } + } + + pub fn head_ty(&self) -> Option<&Cx::Ty> { + self.patterns.first().map(|pat| pat.ty()) + } + pub fn iter<'a>(&'a self) -> impl Iterator> + Captures<'a> { + self.patterns.iter().copied() + } + + /// Do constructor splitting on the constructors of the column. + pub fn analyze_ctors( + &self, + cx: &Cx, + ty: &Cx::Ty, + ) -> Result, Cx::Error> { + let column_ctors = self.patterns.iter().map(|p| p.ctor()); + let ctors_for_ty = cx.ctors_for_ty(ty)?; + Ok(ctors_for_ty.split(column_ctors)) + } + + /// Does specialization: given a constructor, this takes the patterns from the column that match + /// the constructor, and outputs their fields. + /// This returns one column per field of the constructor. They usually all have the same length + /// (the number of patterns in `self` that matched `ctor`), except that we expand or-patterns + /// which may change the lengths. + pub fn specialize( + &self, + cx: &Cx, + ty: &Cx::Ty, + ctor: &Constructor, + ) -> Vec> { + let arity = ctor.arity(cx, ty); + if arity == 0 { + return Vec::new(); + } + + // We specialize the column by `ctor`. This gives us `arity`-many columns of patterns. These + // columns may have different lengths in the presence of or-patterns (this is why we can't + // reuse `Matrix`). + let mut specialized_columns: Vec<_> = + (0..arity).map(|_| Self { patterns: Vec::new() }).collect(); + let relevant_patterns = + self.patterns.iter().filter(|pat| ctor.is_covered_by(cx, pat.ctor())); + for pat in relevant_patterns { + let specialized = pat.specialize(ctor, arity); + for (subpat, column) in specialized.into_iter().zip(&mut specialized_columns) { + column.expand_and_push(subpat); + } + } + specialized_columns + } +}