diff options
Diffstat (limited to 'compiler/rustc_pattern_analysis/src/pat.rs')
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/pat.rs | 162 |
1 files changed, 77 insertions, 85 deletions
diff --git a/compiler/rustc_pattern_analysis/src/pat.rs b/compiler/rustc_pattern_analysis/src/pat.rs index 404651124ad..0cc8477b7cd 100644 --- a/compiler/rustc_pattern_analysis/src/pat.rs +++ b/compiler/rustc_pattern_analysis/src/pat.rs @@ -5,16 +5,11 @@ use std::fmt; use smallvec::{smallvec, SmallVec}; -use rustc_data_structures::captures::Captures; -use rustc_middle::ty::{self, Ty}; -use rustc_span::{Span, DUMMY_SP}; +use crate::constructor::{Constructor, Slice, SliceKind}; +use crate::usefulness::PlaceCtxt; +use crate::{Captures, TypeCx}; use self::Constructor::*; -use self::SliceKind::*; - -use crate::constructor::{Constructor, SliceKind}; -use crate::cx::MatchCheckCtxt; -use crate::usefulness::PatCtxt; /// Values and patterns can be represented as a constructor applied to some fields. This represents /// a pattern in this form. @@ -27,34 +22,34 @@ use crate::usefulness::PatCtxt; /// This happens if a private or `non_exhaustive` field is uninhabited, because the code mustn't /// observe that it is uninhabited. In that case that field is not included in `fields`. Care must /// be taken when converting to/from `thir::Pat`. -pub struct DeconstructedPat<'p, 'tcx> { - ctor: Constructor<'tcx>, - fields: &'p [DeconstructedPat<'p, 'tcx>], - ty: Ty<'tcx>, - span: Span, +pub struct DeconstructedPat<'p, Cx: TypeCx> { + ctor: Constructor<Cx>, + fields: &'p [DeconstructedPat<'p, Cx>], + ty: Cx::Ty, + data: Cx::PatData, /// Whether removing this arm would change the behavior of the match expression. useful: Cell<bool>, } -impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> { - pub fn wildcard(ty: Ty<'tcx>, span: Span) -> Self { - Self::new(Wildcard, &[], ty, span) +impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> { + pub fn wildcard(ty: Cx::Ty, data: Cx::PatData) -> Self { + Self::new(Wildcard, &[], ty, data) } pub fn new( - ctor: Constructor<'tcx>, - fields: &'p [DeconstructedPat<'p, 'tcx>], - ty: Ty<'tcx>, - span: Span, + ctor: Constructor<Cx>, + fields: &'p [DeconstructedPat<'p, Cx>], + ty: Cx::Ty, + data: Cx::PatData, ) -> Self { - DeconstructedPat { ctor, fields, ty, span, useful: Cell::new(false) } + DeconstructedPat { ctor, fields, ty, data, useful: Cell::new(false) } } pub(crate) fn is_or_pat(&self) -> bool { matches!(self.ctor, Or) } /// Expand this (possibly-nested) or-pattern into its alternatives. - pub(crate) fn flatten_or_pat(&'p self) -> SmallVec<[&'p Self; 1]> { + pub(crate) fn flatten_or_pat(&self) -> SmallVec<[&Self; 1]> { if self.is_or_pat() { self.iter_fields().flat_map(|p| p.flatten_or_pat()).collect() } else { @@ -62,66 +57,64 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> { } } - pub fn ctor(&self) -> &Constructor<'tcx> { + pub fn ctor(&self) -> &Constructor<Cx> { &self.ctor } - pub fn ty(&self) -> Ty<'tcx> { + pub fn ty(&self) -> Cx::Ty { self.ty } - pub fn span(&self) -> Span { - self.span + pub fn data(&self) -> &Cx::PatData { + &self.data } pub fn iter_fields<'a>( &'a self, - ) -> impl Iterator<Item = &'p DeconstructedPat<'p, 'tcx>> + Captures<'a> { + ) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'a> { self.fields.iter() } /// Specialize this pattern with a constructor. /// `other_ctor` can be different from `self.ctor`, but must be covered by it. pub(crate) fn specialize<'a>( - &'a self, - pcx: &PatCtxt<'_, 'p, 'tcx>, - other_ctor: &Constructor<'tcx>, - ) -> SmallVec<[&'p DeconstructedPat<'p, 'tcx>; 2]> { + &self, + pcx: &PlaceCtxt<'a, 'p, Cx>, + other_ctor: &Constructor<Cx>, + ) -> SmallVec<[&'a DeconstructedPat<'p, Cx>; 2]> { + let wildcard_sub_tys = || { + let tys = pcx.ctor_sub_tys(other_ctor); + tys.iter() + .map(|ty| DeconstructedPat::wildcard(*ty, Cx::PatData::default())) + .map(|pat| pcx.mcx.wildcard_arena.alloc(pat) as &_) + .collect() + }; match (&self.ctor, other_ctor) { - (Wildcard, _) => { - // We return a wildcard for each field of `other_ctor`. - pcx.cx.ctor_wildcard_fields(other_ctor, pcx.ty).iter().collect() - } - (Slice(self_slice), Slice(other_slice)) - if self_slice.arity() != other_slice.arity() => - { - // The only tricky case: two slices of different arity. Since `self_slice` covers - // `other_slice`, `self_slice` must be `VarLen`, i.e. of the form - // `[prefix, .., suffix]`. Moreover `other_slice` is guaranteed to have a larger - // arity. So we fill the middle part with enough wildcards to reach the length of - // the new, larger slice. - match self_slice.kind { - FixedLen(_) => bug!("{:?} doesn't cover {:?}", self_slice, other_slice), - VarLen(prefix, suffix) => { - let (ty::Slice(inner_ty) | ty::Array(inner_ty, _)) = *self.ty.kind() else { - bug!("bad slice pattern {:?} {:?}", self.ctor, self.ty); - }; - let prefix = &self.fields[..prefix]; - let suffix = &self.fields[self_slice.arity() - suffix..]; - let wildcard: &_ = pcx - .cx - .pattern_arena - .alloc(DeconstructedPat::wildcard(inner_ty, DUMMY_SP)); - let extra_wildcards = other_slice.arity() - self_slice.arity(); - let extra_wildcards = (0..extra_wildcards).map(|_| wildcard); - prefix.iter().chain(extra_wildcards).chain(suffix).collect() - } + // Return a wildcard for each field of `other_ctor`. + (Wildcard, _) => wildcard_sub_tys(), + // The only non-trivial case: two slices of different arity. `other_slice` is + // guaranteed to have a larger arity, so we fill the middle part with enough + // wildcards to reach the length of the new, larger slice. + ( + &Slice(self_slice @ Slice { kind: SliceKind::VarLen(prefix, suffix), .. }), + &Slice(other_slice), + ) if self_slice.arity() != other_slice.arity() => { + // Start with a slice of wildcards of the appropriate length. + let mut fields: SmallVec<[_; 2]> = wildcard_sub_tys(); + // Fill in the fields from both ends. + let new_arity = fields.len(); + for i in 0..prefix { + fields[i] = &self.fields[i]; + } + for i in 0..suffix { + fields[new_arity - 1 - i] = &self.fields[self.fields.len() - 1 - i]; } + fields } _ => self.fields.iter().collect(), } } - /// We keep track for each pattern if it was ever useful during the analysis. This is used - /// with `redundant_spans` to report redundant subpatterns arising from or patterns. + /// We keep track for each pattern if it was ever useful during the analysis. This is used with + /// `redundant_subpatterns` to report redundant subpatterns arising from or patterns. pub(crate) fn set_useful(&self) { self.useful.set(true) } @@ -139,19 +132,19 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> { } } - /// Report the spans of subpatterns that were not useful, if any. - pub(crate) fn redundant_spans(&self) -> Vec<Span> { - let mut spans = Vec::new(); - self.collect_redundant_spans(&mut spans); - spans + /// Report the subpatterns that were not useful, if any. + pub(crate) fn redundant_subpatterns(&self) -> Vec<&Self> { + let mut subpats = Vec::new(); + self.collect_redundant_subpatterns(&mut subpats); + subpats } - fn collect_redundant_spans(&self, spans: &mut Vec<Span>) { + fn collect_redundant_subpatterns<'a>(&'a self, subpats: &mut Vec<&'a Self>) { // We don't look at subpatterns if we already reported the whole pattern as redundant. if !self.is_useful() { - spans.push(self.span); + subpats.push(self); } else { for p in self.iter_fields() { - p.collect_redundant_spans(spans); + p.collect_redundant_subpatterns(subpats); } } } @@ -159,47 +152,46 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> { /// This is mostly copied from the `Pat` impl. This is best effort and not good enough for a /// `Display` impl. -impl<'p, 'tcx> fmt::Debug for DeconstructedPat<'p, 'tcx> { +impl<'p, Cx: TypeCx> fmt::Debug for DeconstructedPat<'p, Cx> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - MatchCheckCtxt::debug_pat(f, self) + Cx::debug_pat(f, self) } } /// Same idea as `DeconstructedPat`, except this is a fictitious pattern built up for diagnostics /// purposes. As such they don't use interning and can be cloned. #[derive(Debug, Clone)] -pub struct WitnessPat<'tcx> { - ctor: Constructor<'tcx>, - pub(crate) fields: Vec<WitnessPat<'tcx>>, - ty: Ty<'tcx>, +pub struct WitnessPat<Cx: TypeCx> { + ctor: Constructor<Cx>, + pub(crate) fields: Vec<WitnessPat<Cx>>, + ty: Cx::Ty, } -impl<'tcx> WitnessPat<'tcx> { - pub(crate) fn new(ctor: Constructor<'tcx>, fields: Vec<Self>, ty: Ty<'tcx>) -> Self { +impl<Cx: TypeCx> WitnessPat<Cx> { + pub(crate) fn new(ctor: Constructor<Cx>, fields: Vec<Self>, ty: Cx::Ty) -> Self { Self { ctor, fields, ty } } - pub(crate) fn wildcard(ty: Ty<'tcx>) -> Self { + pub(crate) fn wildcard(ty: Cx::Ty) -> Self { Self::new(Wildcard, Vec::new(), ty) } /// 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: &PatCtxt<'_, '_, 'tcx>, ctor: Constructor<'tcx>) -> Self { - let field_tys = - pcx.cx.ctor_wildcard_fields(&ctor, pcx.ty).iter().map(|deco_pat| deco_pat.ty()); - let fields = field_tys.map(|ty| Self::wildcard(ty)).collect(); + 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) } - pub fn ctor(&self) -> &Constructor<'tcx> { + pub fn ctor(&self) -> &Constructor<Cx> { &self.ctor } - pub fn ty(&self) -> Ty<'tcx> { + pub fn ty(&self) -> Cx::Ty { self.ty } - pub fn iter_fields<'a>(&'a self) -> impl Iterator<Item = &'a WitnessPat<'tcx>> { + pub fn iter_fields<'a>(&'a self) -> impl Iterator<Item = &'a WitnessPat<Cx>> { self.fields.iter() } } |