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Abstract `MatchCheckCtxt` into a trait

This commit is contained in:
Nadrieril 2023-12-11 20:01:02 +01:00
parent 3ad76f9325
commit 3d7c4df326
8 changed files with 313 additions and 239 deletions
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40
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View File

@ -1,8 +1,7 @@
use rustc_pattern_analysis::constructor::Constructor;
use rustc_pattern_analysis::cx::MatchCheckCtxt;
use rustc_pattern_analysis::cx::{
Constructor, DeconstructedPat, MatchCheckCtxt, Usefulness, UsefulnessReport, WitnessPat,
};
use rustc_pattern_analysis::errors::Uncovered;
use rustc_pattern_analysis::pat::{DeconstructedPat, WitnessPat};
use rustc_pattern_analysis::usefulness::{Usefulness, UsefulnessReport};
use rustc_pattern_analysis::{analyze_match, MatchArm};
use crate::errors::*;
@ -851,14 +850,15 @@ fn report_arm_reachability<'p, 'tcx>(
);
};
use Usefulness::*;
let mut catchall = None;
for (arm, is_useful) in report.arm_usefulness.iter() {
match is_useful {
Redundant => report_unreachable_pattern(arm.pat.span(), arm.hir_id, catchall),
Useful(redundant_spans) if redundant_spans.is_empty() => {}
Usefulness::Redundant => {
report_unreachable_pattern(*arm.pat.span(), arm.hir_id, catchall)
}
Usefulness::Useful(redundant_spans) if redundant_spans.is_empty() => {}
// The arm is reachable, but contains redundant subpatterns (from or-patterns).
Useful(redundant_spans) => {
Usefulness::Useful(redundant_spans) => {
let mut redundant_spans = redundant_spans.clone();
// Emit lints in the order in which they occur in the file.
redundant_spans.sort_unstable();
@ -868,17 +868,16 @@ fn report_arm_reachability<'p, 'tcx>(
}
}
if !arm.has_guard && catchall.is_none() && pat_is_catchall(arm.pat) {
catchall = Some(arm.pat.span());
catchall = Some(*arm.pat.span());
}
}
}
/// Checks for common cases of "catchall" patterns that may not be intended as such.
fn pat_is_catchall(pat: &DeconstructedPat<'_, '_>) -> bool {
use Constructor::*;
match pat.ctor() {
Wildcard => true,
Struct | Ref => pat.iter_fields().all(|pat| pat_is_catchall(pat)),
Constructor::Wildcard => true,
Constructor::Struct | Constructor::Ref => pat.iter_fields().all(|pat| pat_is_catchall(pat)),
_ => false,
}
}
@ -889,7 +888,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
thir: &Thir<'tcx>,
scrut_ty: Ty<'tcx>,
sp: Span,
witnesses: Vec<WitnessPat<'tcx>>,
witnesses: Vec<WitnessPat<'p, 'tcx>>,
arms: &[ArmId],
expr_span: Span,
) -> ErrorGuaranteed {
@ -1086,10 +1085,10 @@ fn report_non_exhaustive_match<'p, 'tcx>(
fn joined_uncovered_patterns<'p, 'tcx>(
cx: &MatchCheckCtxt<'p, 'tcx>,
witnesses: &[WitnessPat<'tcx>],
witnesses: &[WitnessPat<'p, 'tcx>],
) -> String {
const LIMIT: usize = 3;
let pat_to_str = |pat: &WitnessPat<'tcx>| cx.hoist_witness_pat(pat).to_string();
let pat_to_str = |pat: &WitnessPat<'p, 'tcx>| cx.hoist_witness_pat(pat).to_string();
match witnesses {
[] => bug!(),
[witness] => format!("`{}`", cx.hoist_witness_pat(witness)),
@ -1107,7 +1106,7 @@ fn joined_uncovered_patterns<'p, 'tcx>(
fn collect_non_exhaustive_tys<'tcx>(
cx: &MatchCheckCtxt<'_, 'tcx>,
pat: &WitnessPat<'tcx>,
pat: &WitnessPat<'_, 'tcx>,
non_exhaustive_tys: &mut FxIndexSet<Ty<'tcx>>,
) {
if matches!(pat.ctor(), Constructor::NonExhaustive) {
@ -1126,7 +1125,7 @@ fn collect_non_exhaustive_tys<'tcx>(
fn report_adt_defined_here<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
witnesses: &[WitnessPat<'tcx>],
witnesses: &[WitnessPat<'_, 'tcx>],
point_at_non_local_ty: bool,
) -> Option<AdtDefinedHere<'tcx>> {
let ty = ty.peel_refs();
@ -1148,15 +1147,14 @@ fn report_adt_defined_here<'tcx>(
Some(AdtDefinedHere { adt_def_span, ty, variants })
}
fn maybe_point_at_variant<'a, 'tcx: 'a>(
fn maybe_point_at_variant<'a, 'p: 'a, 'tcx: 'p>(
tcx: TyCtxt<'tcx>,
def: AdtDef<'tcx>,
patterns: impl Iterator<Item = &'a WitnessPat<'tcx>>,
patterns: impl Iterator<Item = &'a WitnessPat<'p, 'tcx>>,
) -> Vec<Span> {
use Constructor::*;
let mut covered = vec![];
for pattern in patterns {
if let Variant(variant_index) = pattern.ctor() {
if let Constructor::Variant(variant_index) = pattern.ctor() {
if let ty::Adt(this_def, _) = pattern.ty().kind()
&& this_def.did() != def.did()
{

65
compiler/rustc_pattern_analysis/src/constructor.rs
View File

@ -40,7 +40,7 @@
//! - That have no non-trivial intersection with any of the constructors in the column (i.e. they're
//! each either disjoint with or covered by any given column constructor).
//!
//! We compute this in two steps: first [`crate::cx::MatchCheckCtxt::ctors_for_ty`] determines the
//! We compute this in two steps: first [`MatchCx::ctors_for_ty`] determines the
//! set of all possible constructors for the type. Then [`ConstructorSet::split`] looks at the
//! column of constructors and splits the set into groups accordingly. The precise invariants of
//! [`ConstructorSet::split`] is described in [`SplitConstructorSet`].
@ -136,7 +136,7 @@
//! the algorithm can't distinguish them from a nonempty constructor. The only known case where this
//! could happen is the `[..]` pattern on `[!; N]` with `N > 0` so we must take care to not emit it.
//!
//! This is all handled by [`crate::cx::MatchCheckCtxt::ctors_for_ty`] and
//! This is all handled by [`MatchCx::ctors_for_ty`] and
//! [`ConstructorSet::split`]. The invariants of [`SplitConstructorSet`] are also of interest.
//!
//!
@ -158,14 +158,13 @@ use rustc_apfloat::ieee::{DoubleS, IeeeFloat, SingleS};
use rustc_data_structures::fx::FxHashSet;
use rustc_hir::RangeEnd;
use rustc_index::IndexVec;
use rustc_middle::mir::Const;
use rustc_target::abi::VariantIdx;
use self::Constructor::*;
use self::MaybeInfiniteInt::*;
use self::SliceKind::*;
use crate::usefulness::PatCtxt;
use crate::MatchCx;
/// Whether we have seen a constructor in the column or not.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
@ -630,11 +629,11 @@ impl OpaqueId {
/// constructor. `Constructor::apply` reconstructs the pattern from a pair of `Constructor` and
/// `Fields`.
#[derive(Clone, Debug, PartialEq)]
pub enum Constructor<'tcx> {
pub enum Constructor<Cx: MatchCx> {
/// Tuples and structs.
Struct,
/// Enum variants.
Variant(VariantIdx),
Variant(Cx::VariantIdx),
/// References
Ref,
/// Array and slice patterns.
@ -649,7 +648,7 @@ pub enum Constructor<'tcx> {
F32Range(IeeeFloat<SingleS>, IeeeFloat<SingleS>, RangeEnd),
F64Range(IeeeFloat<DoubleS>, IeeeFloat<DoubleS>, RangeEnd),
/// String literals. Strings are not quite the same as `&[u8]` so we treat them separately.
Str(Const<'tcx>),
Str(Cx::StrLit),
/// Constants that must not be matched structurally. They are treated as black boxes for the
/// purposes of exhaustiveness: we must not inspect them, and they don't count towards making a
/// match exhaustive.
@ -672,12 +671,12 @@ pub enum Constructor<'tcx> {
Missing,
}
impl<'tcx> Constructor<'tcx> {
impl<Cx: MatchCx> Constructor<Cx> {
pub(crate) fn is_non_exhaustive(&self) -> bool {
matches!(self, NonExhaustive)
}
pub(crate) fn as_variant(&self) -> Option<VariantIdx> {
pub(crate) fn as_variant(&self) -> Option<Cx::VariantIdx> {
match self {
Variant(i) => Some(*i),
_ => None,
@ -704,7 +703,7 @@ impl<'tcx> Constructor<'tcx> {
/// The number of fields for this constructor. This must be kept in sync with
/// `Fields::wildcards`.
pub(crate) fn arity(&self, pcx: &PatCtxt<'_, '_, 'tcx>) -> usize {
pub(crate) fn arity(&self, pcx: &PatCtxt<'_, '_, Cx>) -> usize {
pcx.cx.ctor_arity(self, pcx.ty)
}
@ -713,14 +712,11 @@ impl<'tcx> Constructor<'tcx> {
/// 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: &PatCtxt<'_, 'p, 'tcx>, other: &Self) -> bool {
pub(crate) fn is_covered_by<'p>(&self, pcx: &PatCtxt<'_, 'p, Cx>, other: &Self) -> bool {
match (self, other) {
(Wildcard, _) => {
span_bug!(
pcx.cx.scrut_span,
"Constructor splitting should not have returned `Wildcard`"
)
}
(Wildcard, _) => pcx
.cx
.bug(format_args!("Constructor splitting should not have returned `Wildcard`")),
// Wildcards cover anything
(_, Wildcard) => true,
// Only a wildcard pattern can match these special constructors.
@ -761,12 +757,9 @@ impl<'tcx> Constructor<'tcx> {
(Opaque(self_id), Opaque(other_id)) => self_id == other_id,
(Opaque(..), _) | (_, Opaque(..)) => false,
_ => span_bug!(
pcx.cx.scrut_span,
"trying to compare incompatible constructors {:?} and {:?}",
self,
other
),
_ => pcx.cx.bug(format_args!(
"trying to compare incompatible constructors {self:?} and {other:?}"
)),
}
}
}
@ -790,12 +783,12 @@ pub enum VariantVisibility {
/// In terms of division of responsibility, [`ConstructorSet::split`] handles all of the
/// `exhaustive_patterns` feature.
#[derive(Debug)]
pub enum ConstructorSet {
pub enum ConstructorSet<Cx: MatchCx> {
/// The type is a tuple or struct. `empty` tracks whether the type is empty.
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<VariantIdx, VariantVisibility>, non_exhaustive: bool },
Variants { variants: IndexVec<Cx::VariantIdx, VariantVisibility>, non_exhaustive: bool },
/// The type is `&T`.
Ref,
/// The type is a union.
@ -838,25 +831,25 @@ 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<'tcx> {
pub(crate) present: SmallVec<[Constructor<'tcx>; 1]>,
pub(crate) missing: Vec<Constructor<'tcx>>,
pub(crate) missing_empty: Vec<Constructor<'tcx>>,
pub(crate) struct SplitConstructorSet<Cx: MatchCx> {
pub(crate) present: SmallVec<[Constructor<Cx>; 1]>,
pub(crate) missing: Vec<Constructor<Cx>>,
pub(crate) missing_empty: Vec<Constructor<Cx>>,
}
impl ConstructorSet {
impl<Cx: MatchCx> ConstructorSet<Cx> {
/// This analyzes a column of constructors to 1/ determine which constructors of the type (if
/// 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)]
pub(crate) fn split<'a, 'tcx>(
pub(crate) fn split<'a>(
&self,
pcx: &PatCtxt<'_, '_, 'tcx>,
ctors: impl Iterator<Item = &'a Constructor<'tcx>> + Clone,
) -> SplitConstructorSet<'tcx>
pcx: &PatCtxt<'_, '_, Cx>,
ctors: impl Iterator<Item = &'a Constructor<Cx>> + Clone,
) -> SplitConstructorSet<Cx>
where
'tcx: 'a,
Cx: 'a,
{
let mut present: SmallVec<[_; 1]> = SmallVec::new();
// Empty constructors found missing.
@ -997,7 +990,7 @@ impl ConstructorSet {
// 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.cx.tcx.features().exhaustive_patterns
if !pcx.cx.is_exhaustive_patterns_feature_on()
&& !(pcx.is_top_level && matches!(self, Self::NoConstructors))
{
// Treat all missing constructors as nonempty.

114
compiler/rustc_pattern_analysis/src/cx.rs
View File

@ -9,7 +9,7 @@ use rustc_index::Idx;
use rustc_index::IndexVec;
use rustc_middle::middle::stability::EvalResult;
use rustc_middle::mir::interpret::Scalar;
use rustc_middle::mir::{self};
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::{self, Ty, TyCtxt, VariantDef};
@ -18,13 +18,26 @@ use rustc_target::abi::{FieldIdx, Integer, VariantIdx, FIRST_VARIANT};
use smallvec::SmallVec;
use crate::constructor::{
Constructor, ConstructorSet, IntRange, MaybeInfiniteInt, OpaqueId, Slice, SliceKind,
VariantVisibility,
IntRange, MaybeInfiniteInt, OpaqueId, Slice, SliceKind, VariantVisibility,
};
use crate::pat::{DeconstructedPat, WitnessPat};
use crate::MatchCx;
use Constructor::*;
use crate::constructor::Constructor::*;
pub type Constructor<'p, 'tcx> = crate::constructor::Constructor<MatchCheckCtxt<'p, 'tcx>>;
pub type ConstructorSet<'p, 'tcx> = crate::constructor::ConstructorSet<MatchCheckCtxt<'p, 'tcx>>;
pub type DeconstructedPat<'p, 'tcx> = crate::pat::DeconstructedPat<'p, MatchCheckCtxt<'p, 'tcx>>;
pub type MatchArm<'p, 'tcx> = crate::MatchArm<'p, MatchCheckCtxt<'p, 'tcx>>;
pub(crate) type PatCtxt<'a, 'p, 'tcx> =
crate::usefulness::PatCtxt<'a, 'p, MatchCheckCtxt<'p, 'tcx>>;
pub(crate) type SplitConstructorSet<'p, 'tcx> =
crate::constructor::SplitConstructorSet<MatchCheckCtxt<'p, 'tcx>>;
pub type Usefulness = crate::usefulness::Usefulness<Span>;
pub type UsefulnessReport<'p, 'tcx> =
crate::usefulness::UsefulnessReport<'p, MatchCheckCtxt<'p, 'tcx>>;
pub type WitnessPat<'p, 'tcx> = crate::pat::WitnessPat<MatchCheckCtxt<'p, 'tcx>>;
#[derive(Clone)]
pub struct MatchCheckCtxt<'p, 'tcx> {
pub tcx: TyCtxt<'tcx>,
/// The module in which the match occurs. This is necessary for
@ -49,15 +62,17 @@ pub struct MatchCheckCtxt<'p, 'tcx> {
pub known_valid_scrutinee: bool,
}
impl<'p, 'tcx> fmt::Debug for MatchCheckCtxt<'p, 'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("MatchCheckCtxt").finish()
}
}
impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
pub(crate) fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
!ty.is_inhabited_from(self.tcx, self.module, self.param_env)
}
pub(crate) fn is_opaque(ty: Ty<'tcx>) -> bool {
matches!(ty.kind(), ty::Alias(ty::Opaque, ..))
}
/// Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`.
pub fn is_foreign_non_exhaustive_enum(&self, ty: Ty<'tcx>) -> bool {
match ty.kind() {
@ -68,6 +83,20 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
}
}
/// Whether the range denotes the fictitious values before `isize::MIN` or after
/// `usize::MAX`/`isize::MAX` (see doc of [`IntRange::split`] for why these exist).
pub fn is_range_beyond_boundaries(&self, range: &IntRange, ty: Ty<'tcx>) -> bool {
ty.is_ptr_sized_integral() && {
// The two invalid ranges are `NegInfinity..isize::MIN` (represented as
// `NegInfinity..0`), and `{u,i}size::MAX+1..PosInfinity`. `hoist_pat_range_bdy`
// converts `MAX+1` to `PosInfinity`, and we couldn't have `PosInfinity` in `range.lo`
// otherwise.
let lo = self.hoist_pat_range_bdy(range.lo, ty);
matches!(lo, PatRangeBoundary::PosInfinity)
|| matches!(range.hi, MaybeInfiniteInt::Finite(0))
}
}
// In the cases of either a `#[non_exhaustive]` field list or a non-public field, we hide
// uninhabited fields in order not to reveal the uninhabitedness of the whole variant.
// This lists the fields we keep along with their types.
@ -97,7 +126,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
}
pub(crate) fn variant_index_for_adt(
ctor: &Constructor<'tcx>,
ctor: &Constructor<'p, 'tcx>,
adt: ty::AdtDef<'tcx>,
) -> VariantIdx {
match *ctor {
@ -113,7 +142,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
/// Returns the types of the fields for a given constructor. The result must have a length of
/// `ctor.arity()`.
#[instrument(level = "trace", skip(self))]
pub(crate) fn ctor_sub_tys(&self, ctor: &Constructor<'tcx>, ty: Ty<'tcx>) -> &[Ty<'tcx>] {
pub(crate) fn ctor_sub_tys(&self, ctor: &Constructor<'p, 'tcx>, ty: Ty<'tcx>) -> &[Ty<'tcx>] {
let cx = self;
match ctor {
Struct | Variant(_) | UnionField => match ty.kind() {
@ -159,9 +188,8 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
}
}
/// The number of fields for this constructor. This must be kept in sync with
/// `Fields::wildcards`.
pub(crate) fn ctor_arity(&self, ctor: &Constructor<'tcx>, ty: Ty<'tcx>) -> usize {
/// The number of fields for this constructor.
pub(crate) fn ctor_arity(&self, ctor: &Constructor<'p, 'tcx>, ty: Ty<'tcx>) -> usize {
match ctor {
Struct | Variant(_) | UnionField => match ty.kind() {
ty::Tuple(fs) => fs.len(),
@ -198,7 +226,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
///
/// See [`crate::constructor`] for considerations of emptiness.
#[instrument(level = "debug", skip(self), ret)]
pub fn ctors_for_ty(&self, ty: Ty<'tcx>) -> ConstructorSet {
pub fn ctors_for_ty(&self, ty: Ty<'tcx>) -> ConstructorSet<'p, 'tcx> {
let cx = self;
let make_uint_range = |start, end| {
IntRange::from_range(
@ -599,20 +627,6 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
}
}
/// Whether the range denotes the fictitious values before `isize::MIN` or after
/// `usize::MAX`/`isize::MAX` (see doc of [`IntRange::split`] for why these exist).
pub fn is_range_beyond_boundaries(&self, range: &IntRange, ty: Ty<'tcx>) -> bool {
ty.is_ptr_sized_integral() && {
// The two invalid ranges are `NegInfinity..isize::MIN` (represented as
// `NegInfinity..0`), and `{u,i}size::MAX+1..PosInfinity`. `hoist_pat_range_bdy`
// converts `MAX+1` to `PosInfinity`, and we couldn't have `PosInfinity` in `range.lo`
// otherwise.
let lo = self.hoist_pat_range_bdy(range.lo, ty);
matches!(lo, PatRangeBoundary::PosInfinity)
|| matches!(range.hi, MaybeInfiniteInt::Finite(0))
}
}
/// Convert back to a `thir::Pat` for diagnostic purposes.
pub(crate) fn hoist_pat_range(&self, range: &IntRange, ty: Ty<'tcx>) -> Pat<'tcx> {
use MaybeInfiniteInt::*;
@ -652,7 +666,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
}
/// Convert back to a `thir::Pat` for diagnostic purposes. This panics for patterns that don't
/// appear in diagnostics, like float ranges.
pub fn hoist_witness_pat(&self, pat: &WitnessPat<'tcx>) -> Pat<'tcx> {
pub fn hoist_witness_pat(&self, pat: &WitnessPat<'p, 'tcx>) -> Pat<'tcx> {
let cx = self;
let is_wildcard = |pat: &Pat<'_>| matches!(pat.kind, PatKind::Wild);
let mut subpatterns = pat.iter_fields().map(|p| Box::new(cx.hoist_witness_pat(p)));
@ -746,7 +760,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
/// Best-effort `Debug` implementation.
pub(crate) fn debug_pat(
f: &mut fmt::Formatter<'_>,
pat: &DeconstructedPat<'p, 'tcx>,
pat: &crate::pat::DeconstructedPat<'_, Self>,
) -> fmt::Result {
let mut first = true;
let mut start_or_continue = |s| {
@ -840,6 +854,44 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
}
}
impl<'p, 'tcx> MatchCx for MatchCheckCtxt<'p, 'tcx> {
type Ty = Ty<'tcx>;
type Span = Span;
type VariantIdx = VariantIdx;
type StrLit = Const<'tcx>;
fn is_exhaustive_patterns_feature_on(&self) -> bool {
self.tcx.features().exhaustive_patterns
}
fn is_opaque_ty(ty: Self::Ty) -> bool {
matches!(ty.kind(), ty::Alias(ty::Opaque, ..))
}
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,
) -> &[Self::Ty] {
self.ctor_sub_tys(ctor, ty)
}
fn ctors_for_ty(&self, ty: Self::Ty) -> crate::constructor::ConstructorSet<Self> {
self.ctors_for_ty(ty)
}
fn debug_pat(
f: &mut fmt::Formatter<'_>,
pat: &crate::pat::DeconstructedPat<'_, Self>,
) -> fmt::Result {
Self::debug_pat(f, pat)
}
fn bug(&self, fmt: fmt::Arguments<'_>) -> ! {
span_bug!(self.scrut_span, "{}", fmt)
}
}
/// Recursively expand this pattern into its subpatterns. Only useful for or-patterns.
fn expand_or_pat<'p, 'tcx>(pat: &'p Pat<'tcx>) -> Vec<&'p Pat<'tcx>> {
fn expand<'p, 'tcx>(pat: &'p Pat<'tcx>, vec: &mut Vec<&'p Pat<'tcx>>) {

6
compiler/rustc_pattern_analysis/src/errors.rs
View File

@ -1,11 +1,11 @@
use crate::{cx::MatchCheckCtxt, pat::WitnessPat};
use rustc_errors::{AddToDiagnostic, Diagnostic, SubdiagnosticMessage};
use rustc_macros::{LintDiagnostic, Subdiagnostic};
use rustc_middle::thir::Pat;
use rustc_middle::ty::Ty;
use rustc_span::Span;
use crate::cx::{MatchCheckCtxt, WitnessPat};
#[derive(Subdiagnostic)]
#[label(pattern_analysis_uncovered)]
pub struct Uncovered<'tcx> {
@ -22,7 +22,7 @@ impl<'tcx> Uncovered<'tcx> {
pub fn new<'p>(
span: Span,
cx: &MatchCheckCtxt<'p, 'tcx>,
witnesses: Vec<WitnessPat<'tcx>>,
witnesses: Vec<WitnessPat<'p, 'tcx>>,
) -> Self {
let witness_1 = cx.hoist_witness_pat(witnesses.get(0).unwrap());
Self {

49
compiler/rustc_pattern_analysis/src/lib.rs
View File

@ -14,36 +14,71 @@ extern crate rustc_middle;
rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
use std::fmt;
use constructor::{Constructor, ConstructorSet};
use lints::PatternColumn;
use rustc_hir::HirId;
use rustc_index::Idx;
use rustc_middle::ty::Ty;
use usefulness::{compute_match_usefulness, UsefulnessReport};
use usefulness::{compute_match_usefulness, UsefulnessReport, ValidityConstraint};
use crate::cx::MatchCheckCtxt;
use crate::lints::{lint_nonexhaustive_missing_variants, lint_overlapping_range_endpoints};
use crate::pat::DeconstructedPat;
pub trait MatchCx: Sized + Clone + fmt::Debug {
type Ty: Copy + Clone + fmt::Debug; // FIXME: remove Copy
type Span: Clone + Default;
type VariantIdx: Clone + Idx;
type StrLit: Clone + PartialEq + fmt::Debug;
fn is_opaque_ty(ty: Self::Ty) -> bool;
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;
/// 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];
/// The set of all the constructors for `ty`.
///
/// This must follow the invariants of `ConstructorSet`
fn ctors_for_ty(&self, ty: Self::Ty) -> ConstructorSet<Self>;
/// Best-effort `Debug` implementation.
fn debug_pat(f: &mut fmt::Formatter<'_>, pat: &DeconstructedPat<'_, Self>) -> fmt::Result;
/// Raise a bug.
fn bug(&self, fmt: fmt::Arguments<'_>) -> !;
}
/// The arm of a match expression.
#[derive(Clone, Copy, Debug)]
pub struct MatchArm<'p, 'tcx> {
#[derive(Clone, Debug)]
pub struct MatchArm<'p, Cx: MatchCx> {
/// The pattern must have been lowered through `check_match::MatchVisitor::lower_pattern`.
pub pat: &'p DeconstructedPat<'p, 'tcx>,
pub pat: &'p DeconstructedPat<'p, Cx>,
pub hir_id: HirId,
pub has_guard: bool,
}
impl<'p, Cx: MatchCx> Copy for MatchArm<'p, Cx> {}
/// The entrypoint for this crate. Computes whether a match is exhaustive and which of its arms are
/// useful, and runs some lints.
pub fn analyze_match<'p, 'tcx>(
cx: &MatchCheckCtxt<'p, 'tcx>,
arms: &[MatchArm<'p, 'tcx>],
arms: &[MatchArm<'p, MatchCheckCtxt<'p, 'tcx>>],
scrut_ty: Ty<'tcx>,
) -> UsefulnessReport<'p, 'tcx> {
) -> UsefulnessReport<'p, MatchCheckCtxt<'p, 'tcx>> {
// Arena to store the extra wildcards we construct during analysis.
let wildcard_arena = cx.pattern_arena;
let pat_column = PatternColumn::new(arms);
let report = compute_match_usefulness(cx, arms, scrut_ty, wildcard_arena);
let scrut_validity = ValidityConstraint::from_bool(cx.known_valid_scrutinee);
let report = compute_match_usefulness(cx, arms, scrut_ty, scrut_validity, wildcard_arena);
// Lint on ranges that overlap on their endpoints, which is likely a mistake.
lint_overlapping_range_endpoints(cx, &pat_column, wildcard_arena);

25
compiler/rustc_pattern_analysis/src/lints.rs
View File

@ -7,15 +7,16 @@ use rustc_session::lint;
use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
use rustc_span::Span;
use crate::constructor::{Constructor, IntRange, MaybeInfiniteInt, SplitConstructorSet};
use crate::cx::MatchCheckCtxt;
use crate::constructor::{IntRange, MaybeInfiniteInt};
use crate::cx::{
Constructor, DeconstructedPat, MatchArm, MatchCheckCtxt, PatCtxt, SplitConstructorSet,
WitnessPat,
};
use crate::errors::{
NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Overlap,
OverlappingRangeEndpoints, Uncovered,
};
use crate::pat::{DeconstructedPat, WitnessPat};
use crate::usefulness::PatCtxt;
use crate::MatchArm;
use crate::MatchCx;
/// A column of patterns in the matrix, where a column is the intuitive notion of "subpatterns that
/// inspect the same subvalue/place".
@ -55,10 +56,10 @@ impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
// If the type is opaque and it is revealed anywhere in the column, we take the revealed
// version. Otherwise we could encounter constructors for the revealed type and crash.
let first_ty = self.patterns[0].ty();
if MatchCheckCtxt::is_opaque(first_ty) {
if MatchCheckCtxt::is_opaque_ty(first_ty) {
for pat in &self.patterns {
let ty = pat.ty();
if !MatchCheckCtxt::is_opaque(ty) {
if !MatchCheckCtxt::is_opaque_ty(ty) {
return Some(ty);
}
}
@ -67,7 +68,7 @@ impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
}
/// Do constructor splitting on the constructors of the column.
fn analyze_ctors(&self, pcx: &PatCtxt<'_, 'p, 'tcx>) -> SplitConstructorSet<'tcx> {
fn analyze_ctors(&self, pcx: &PatCtxt<'_, 'p, 'tcx>) -> SplitConstructorSet<'p, 'tcx> {
let column_ctors = self.patterns.iter().map(|p| p.ctor());
pcx.cx.ctors_for_ty(pcx.ty).split(pcx, column_ctors)
}
@ -84,7 +85,7 @@ impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
fn specialize<'b>(
&self,
pcx: &'b PatCtxt<'_, 'p, 'tcx>,
ctor: &Constructor<'tcx>,
ctor: &Constructor<'p, 'tcx>,
) -> Vec<PatternColumn<'b, 'p, 'tcx>>
where
'a: 'b,
@ -128,7 +129,7 @@ fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
cx: &MatchCheckCtxt<'p, 'tcx>,
column: &PatternColumn<'a, 'p, 'tcx>,
wildcard_arena: &TypedArena<DeconstructedPat<'p, 'tcx>>,
) -> Vec<WitnessPat<'tcx>> {
) -> Vec<WitnessPat<'p, 'tcx>> {
let Some(ty) = column.head_ty() else {
return Vec::new();
};
@ -215,7 +216,7 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
};
use rustc_errors::DecorateLint;
let mut err = cx.tcx.sess.struct_span_warn(arm.pat.span(), "");
let mut err = cx.tcx.sess.struct_span_warn(*arm.pat.span(), "");
err.set_primary_message(decorator.msg());
decorator.decorate_lint(&mut err);
err.emit();
@ -265,7 +266,7 @@ pub(crate) fn lint_overlapping_range_endpoints<'a, 'p, 'tcx>(
let mut suffixes: SmallVec<[_; 1]> = Default::default();
// Iterate on patterns that contained `overlap`.
for pat in column.iter() {
let this_span = pat.span();
let this_span = *pat.span();
let Constructor::IntRange(this_range) = pat.ctor() else { continue };
if this_range.is_singleton() {
// Don't lint when one of the ranges is a singleton.

76
compiler/rustc_pattern_analysis/src/pat.rs
View File

@ -6,14 +6,12 @@ use std::fmt;
use smallvec::{smallvec, SmallVec};
use rustc_data_structures::captures::Captures;
use rustc_middle::ty::Ty;
use rustc_span::Span;
use self::Constructor::*;
use crate::constructor::{Constructor, Slice, SliceKind};
use crate::cx::MatchCheckCtxt;
use crate::usefulness::PatCtxt;
use crate::MatchCx;
/// Values and patterns can be represented as a constructor applied to some fields. This represents
/// a pattern in this form.
@ -26,25 +24,25 @@ 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: MatchCx> {
ctor: Constructor<Cx>,
fields: &'p [DeconstructedPat<'p, Cx>],
ty: Cx::Ty,
span: Cx::Span,
/// 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 {
impl<'p, Cx: MatchCx> DeconstructedPat<'p, Cx> {
pub fn wildcard(ty: Cx::Ty, span: Cx::Span) -> Self {
Self::new(Wildcard, &[], ty, span)
}
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,
span: Cx::Span,
) -> Self {
DeconstructedPat { ctor, fields, ty, span, useful: Cell::new(false) }
}
@ -61,19 +59,19 @@ 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 span(&self) -> &Cx::Span {
&self.span
}
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()
}
@ -81,13 +79,13 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
/// `other_ctor` can be different from `self.ctor`, but must be covered by it.
pub(crate) fn specialize<'a>(
&self,
pcx: &PatCtxt<'a, 'p, 'tcx>,
other_ctor: &Constructor<'tcx>,
) -> SmallVec<[&'a DeconstructedPat<'p, 'tcx>; 2]> {
pcx: &PatCtxt<'a, 'p, Cx>,
other_ctor: &Constructor<Cx>,
) -> SmallVec<[&'a DeconstructedPat<'p, Cx>; 2]> {
let wildcard_sub_tys = || {
let tys = pcx.cx.ctor_sub_tys(other_ctor, pcx.ty);
tys.iter()
.map(|ty| DeconstructedPat::wildcard(*ty, Span::default()))
.map(|ty| DeconstructedPat::wildcard(*ty, Cx::Span::default()))
.map(|pat| pcx.wildcard_arena.alloc(pat) as &_)
.collect()
};
@ -137,15 +135,15 @@ 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> {
pub(crate) fn redundant_spans(&self) -> Vec<Cx::Span> {
let mut spans = Vec::new();
self.collect_redundant_spans(&mut spans);
spans
}
fn collect_redundant_spans(&self, spans: &mut Vec<Span>) {
fn collect_redundant_spans(&self, spans: &mut Vec<Cx::Span>) {
// We don't look at subpatterns if we already reported the whole pattern as redundant.
if !self.is_useful() {
spans.push(self.span);
spans.push(self.span.clone());
} else {
for p in self.iter_fields() {
p.collect_redundant_spans(spans);
@ -156,46 +154,46 @@ 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: MatchCx> 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: MatchCx> {
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: MatchCx> 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 {
pub(crate) fn wild_from_ctor(pcx: &PatCtxt<'_, '_, Cx>, ctor: Constructor<Cx>) -> Self {
let field_tys = pcx.cx.ctor_sub_tys(&ctor, pcx.ty);
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()
}
}

177
compiler/rustc_pattern_analysis/src/usefulness.rs
View File

@ -242,7 +242,7 @@
//! Therefore `usefulness(tp_1, tp_2, tq)` returns the single witness-tuple `[Variant2(Some(true), 0)]`.
//!
//!
//! Computing the set of constructors for a type is done in [`MatchCheckCtxt::ctors_for_ty`]. See
//! Computing the set of constructors for a type is done in [`MatchCx::ctors_for_ty`]. See
//! the following sections for more accurate versions of the algorithm and corresponding links.
//!
//!
@ -557,40 +557,39 @@ use std::fmt;
use rustc_arena::TypedArena;
use rustc_data_structures::{captures::Captures, stack::ensure_sufficient_stack};
use rustc_middle::ty::Ty;
use rustc_span::Span;
use crate::constructor::{Constructor, ConstructorSet};
use crate::cx::MatchCheckCtxt;
use crate::pat::{DeconstructedPat, WitnessPat};
use crate::MatchArm;
use crate::{MatchArm, MatchCx};
use self::ValidityConstraint::*;
#[derive(Copy, Clone)]
pub(crate) struct PatCtxt<'a, 'p, 'tcx> {
pub(crate) cx: &'a MatchCheckCtxt<'p, 'tcx>,
#[derive(Clone)]
pub(crate) struct PatCtxt<'a, 'p, Cx: MatchCx> {
pub(crate) cx: &'a Cx,
/// Type of the current column under investigation.
pub(crate) ty: Ty<'tcx>,
pub(crate) ty: Cx::Ty,
/// Whether the current pattern is the whole pattern as found in a match arm, or if it's a
/// subpattern.
pub(crate) is_top_level: bool,
/// An arena to store the wildcards we produce during analysis.
pub(crate) wildcard_arena: &'a TypedArena<DeconstructedPat<'p, 'tcx>>,
pub(crate) wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
}
impl<'a, 'p, 'tcx> PatCtxt<'a, 'p, 'tcx> {
impl<'a, 'p, Cx: MatchCx> PatCtxt<'a, 'p, Cx> {
/// A `PatCtxt` when code other than `is_useful` needs one.
pub(crate) fn new_dummy(
cx: &'a MatchCheckCtxt<'p, 'tcx>,
ty: Ty<'tcx>,
wildcard_arena: &'a TypedArena<DeconstructedPat<'p, 'tcx>>,
cx: &'a Cx,
ty: Cx::Ty,
wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
) -> Self {
PatCtxt { cx, ty, is_top_level: false, wildcard_arena }
}
}
impl<'a, 'p, 'tcx> fmt::Debug for PatCtxt<'a, 'p, 'tcx> {
impl<'a, 'p, Cx: MatchCx> Copy for PatCtxt<'a, 'p, Cx> {}
impl<'a, 'p, Cx: MatchCx> fmt::Debug for PatCtxt<'a, 'p, Cx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("PatCtxt").field("ty", &self.ty).finish()
}
@ -602,7 +601,7 @@ impl<'a, 'p, 'tcx> fmt::Debug for PatCtxt<'a, 'p, 'tcx> {
/// - in the matrix, track whether a given place (aka column) is known to contain a valid value or
/// not.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum ValidityConstraint {
pub(crate) enum ValidityConstraint {
ValidOnly,
MaybeInvalid,
/// Option for backwards compatibility: the place is not known to be valid but we allow omitting
@ -611,7 +610,7 @@ enum ValidityConstraint {
}
impl ValidityConstraint {
fn from_bool(is_valid_only: bool) -> Self {
pub(crate) fn from_bool(is_valid_only: bool) -> Self {
if is_valid_only { ValidOnly } else { MaybeInvalid }
}
@ -636,7 +635,7 @@ impl ValidityConstraint {
///
/// Pending further opsem decisions, the current behavior is: validity is preserved, except
/// inside `&` and union fields where validity is reset to `MaybeInvalid`.
fn specialize(self, ctor: &Constructor<'_>) -> Self {
fn specialize<Cx: MatchCx>(self, ctor: &Constructor<Cx>) -> Self {
// We preserve validity except when we go inside a reference or a union field.
if matches!(ctor, Constructor::Ref | Constructor::UnionField) {
// Validity of `x: &T` does not imply validity of `*x: T`.
@ -661,15 +660,15 @@ impl fmt::Display for ValidityConstraint {
// The three lifetimes are:
// - 'a allocated by us
// - 'p coming from the input
// - 'tcx global compilation context
// - Cx global compilation context
#[derive(Clone)]
struct PatStack<'a, 'p, 'tcx> {
struct PatStack<'a, 'p, Cx: MatchCx> {
// Rows of len 1 are very common, which is why `SmallVec[_; 2]` works well.
pats: SmallVec<[&'a DeconstructedPat<'p, 'tcx>; 2]>,
pats: SmallVec<[&'a DeconstructedPat<'p, Cx>; 2]>,
}
impl<'a, 'p, 'tcx> PatStack<'a, 'p, 'tcx> {
fn from_pattern(pat: &'a DeconstructedPat<'p, 'tcx>) -> Self {
impl<'a, 'p, Cx: MatchCx> PatStack<'a, 'p, Cx> {
fn from_pattern(pat: &'a DeconstructedPat<'p, Cx>) -> Self {
PatStack { pats: smallvec![pat] }
}
@ -681,17 +680,17 @@ impl<'a, 'p, 'tcx> PatStack<'a, 'p, 'tcx> {
self.pats.len()
}
fn head(&self) -> &'a DeconstructedPat<'p, 'tcx> {
fn head(&self) -> &'a DeconstructedPat<'p, Cx> {
self.pats[0]
}
fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, 'tcx>> + Captures<'b> {
fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, Cx>> + Captures<'b> {
self.pats.iter().copied()
}
// Recursively expand the first or-pattern into its subpatterns. Only useful if the pattern is
// an or-pattern. Panics if `self` is empty.
fn expand_or_pat<'b>(&'b self) -> impl Iterator<Item = PatStack<'a, 'p, 'tcx>> + Captures<'b> {
fn expand_or_pat<'b>(&'b self) -> impl Iterator<Item = PatStack<'a, 'p, Cx>> + Captures<'b> {
self.head().flatten_or_pat().into_iter().map(move |pat| {
let mut new = self.clone();
new.pats[0] = pat;
@ -703,9 +702,9 @@ impl<'a, 'p, 'tcx> PatStack<'a, 'p, 'tcx> {
/// Only call if `ctor.is_covered_by(self.head().ctor())` is true.
fn pop_head_constructor(
&self,
pcx: &PatCtxt<'a, 'p, 'tcx>,
ctor: &Constructor<'tcx>,
) -> PatStack<'a, 'p, 'tcx> {
pcx: &PatCtxt<'a, 'p, Cx>,
ctor: &Constructor<Cx>,
) -> PatStack<'a, 'p, Cx> {
// We pop the head pattern and push the new fields extracted from the arguments of
// `self.head()`.
let mut new_pats = self.head().specialize(pcx, ctor);
@ -714,7 +713,7 @@ impl<'a, 'p, 'tcx> PatStack<'a, 'p, 'tcx> {
}
}
impl<'a, 'p, 'tcx> fmt::Debug for PatStack<'a, 'p, 'tcx> {
impl<'a, 'p, Cx: MatchCx> fmt::Debug for PatStack<'a, 'p, Cx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// We pretty-print similarly to the `Debug` impl of `Matrix`.
write!(f, "+")?;
@ -727,9 +726,9 @@ impl<'a, 'p, 'tcx> fmt::Debug for PatStack<'a, 'p, 'tcx> {
/// A row of the matrix.
#[derive(Clone)]
struct MatrixRow<'a, 'p, 'tcx> {
struct MatrixRow<'a, 'p, Cx: MatchCx> {
// The patterns in the row.
pats: PatStack<'a, 'p, 'tcx>,
pats: PatStack<'a, 'p, Cx>,
/// Whether the original arm had a guard. This is inherited when specializing.
is_under_guard: bool,
/// When we specialize, we remember which row of the original matrix produced a given row of the
@ -742,7 +741,7 @@ struct MatrixRow<'a, 'p, 'tcx> {
useful: bool,
}
impl<'a, 'p, 'tcx> MatrixRow<'a, 'p, 'tcx> {
impl<'a, 'p, Cx: MatchCx> MatrixRow<'a, 'p, Cx> {
fn is_empty(&self) -> bool {
self.pats.is_empty()
}
@ -751,17 +750,17 @@ impl<'a, 'p, 'tcx> MatrixRow<'a, 'p, 'tcx> {
self.pats.len()
}
fn head(&self) -> &'a DeconstructedPat<'p, 'tcx> {
fn head(&self) -> &'a DeconstructedPat<'p, Cx> {
self.pats.head()
}
fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, 'tcx>> + Captures<'b> {
fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, Cx>> + Captures<'b> {
self.pats.iter()
}
// Recursively expand the first or-pattern into its subpatterns. Only useful if the pattern is
// an or-pattern. Panics if `self` is empty.
fn expand_or_pat<'b>(&'b self) -> impl Iterator<Item = MatrixRow<'a, 'p, 'tcx>> + Captures<'b> {
fn expand_or_pat<'b>(&'b self) -> impl Iterator<Item = MatrixRow<'a, 'p, Cx>> + Captures<'b> {
self.pats.expand_or_pat().map(|patstack| MatrixRow {
pats: patstack,
parent_row: self.parent_row,
@ -774,10 +773,10 @@ impl<'a, 'p, 'tcx> MatrixRow<'a, 'p, 'tcx> {
/// Only call if `ctor.is_covered_by(self.head().ctor())` is true.
fn pop_head_constructor(
&self,
pcx: &PatCtxt<'a, 'p, 'tcx>,
ctor: &Constructor<'tcx>,
pcx: &PatCtxt<'a, 'p, Cx>,
ctor: &Constructor<Cx>,
parent_row: usize,
) -> MatrixRow<'a, 'p, 'tcx> {
) -> MatrixRow<'a, 'p, Cx> {
MatrixRow {
pats: self.pats.pop_head_constructor(pcx, ctor),
parent_row,
@ -787,7 +786,7 @@ impl<'a, 'p, 'tcx> MatrixRow<'a, 'p, 'tcx> {
}
}
impl<'a, 'p, 'tcx> fmt::Debug for MatrixRow<'a, 'p, 'tcx> {
impl<'a, 'p, Cx: MatchCx> fmt::Debug for MatrixRow<'a, 'p, Cx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.pats.fmt(f)
}
@ -804,22 +803,22 @@ impl<'a, 'p, 'tcx> fmt::Debug for MatrixRow<'a, 'p, 'tcx> {
/// specializing `(,)` and `Some` on a pattern of type `(Option<u32>, bool)`, the first column of
/// the matrix will correspond to `scrutinee.0.Some.0` and the second column to `scrutinee.1`.
#[derive(Clone)]
struct Matrix<'a, 'p, 'tcx> {
struct Matrix<'a, 'p, Cx: MatchCx> {
/// Vector of rows. The rows must form a rectangular 2D array. Moreover, all the patterns of
/// each column must have the same type. Each column corresponds to a place within the
/// scrutinee.
rows: Vec<MatrixRow<'a, 'p, 'tcx>>,
rows: Vec<MatrixRow<'a, 'p, Cx>>,
/// Stores an extra fictitious row full of wildcards. Mostly used to keep track of the type of
/// each column. This must obey the same invariants as the real rows.
wildcard_row: PatStack<'a, 'p, 'tcx>,
wildcard_row: PatStack<'a, 'p, Cx>,
/// Track for each column/place whether it contains a known valid value.
place_validity: SmallVec<[ValidityConstraint; 2]>,
}
impl<'a, 'p, 'tcx> Matrix<'a, 'p, 'tcx> {
impl<'a, 'p, Cx: MatchCx> Matrix<'a, 'p, Cx> {
/// Pushes a new row to the matrix. If the row starts with an or-pattern, this recursively
/// expands it. Internal method, prefer [`Matrix::new`].
fn expand_and_push(&mut self, row: MatrixRow<'a, 'p, 'tcx>) {
fn expand_and_push(&mut self, row: MatrixRow<'a, 'p, Cx>) {
if !row.is_empty() && row.head().is_or_pat() {
// Expand nested or-patterns.
for new_row in row.expand_or_pat() {
@ -832,13 +831,13 @@ impl<'a, 'p, 'tcx> Matrix<'a, 'p, 'tcx> {
/// Build a new matrix from an iterator of `MatchArm`s.
fn new(
wildcard_arena: &'a TypedArena<DeconstructedPat<'p, 'tcx>>,
arms: &'a [MatchArm<'p, 'tcx>],
scrut_ty: Ty<'tcx>,
wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
arms: &'a [MatchArm<'p, Cx>],
scrut_ty: Cx::Ty,
scrut_validity: ValidityConstraint,
) -> Self {
let wild_pattern =
wildcard_arena.alloc(DeconstructedPat::wildcard(scrut_ty, Span::default()));
wildcard_arena.alloc(DeconstructedPat::wildcard(scrut_ty, Cx::Span::default()));
let wildcard_row = PatStack::from_pattern(wild_pattern);
let mut matrix = Matrix {
rows: Vec::with_capacity(arms.len()),
@ -857,7 +856,7 @@ impl<'a, 'p, 'tcx> Matrix<'a, 'p, 'tcx> {
matrix
}
fn head_ty(&self) -> Option<Ty<'tcx>> {
fn head_ty(&self) -> Option<Cx::Ty> {
if self.column_count() == 0 {
return None;
}
@ -865,10 +864,10 @@ impl<'a, 'p, 'tcx> Matrix<'a, 'p, 'tcx> {
let mut ty = self.wildcard_row.head().ty();
// If the type is opaque and it is revealed anywhere in the column, we take the revealed
// version. Otherwise we could encounter constructors for the revealed type and crash.
if MatchCheckCtxt::is_opaque(ty) {
if Cx::is_opaque_ty(ty) {
for pat in self.heads() {
let pat_ty = pat.ty();
if !MatchCheckCtxt::is_opaque(pat_ty) {
if !Cx::is_opaque_ty(pat_ty) {
ty = pat_ty;
break;
}
@ -882,15 +881,13 @@ impl<'a, 'p, 'tcx> Matrix<'a, 'p, 'tcx> {
fn rows<'b>(
&'b self,
) -> impl Iterator<Item = &'b MatrixRow<'a, 'p, 'tcx>>
+ Clone
+ DoubleEndedIterator
+ ExactSizeIterator {
) -> impl Iterator<Item = &'b MatrixRow<'a, 'p, Cx>> + Clone + DoubleEndedIterator + ExactSizeIterator
{
self.rows.iter()
}
fn rows_mut<'b>(
&'b mut self,
) -> impl Iterator<Item = &'b mut MatrixRow<'a, 'p, 'tcx>> + DoubleEndedIterator + ExactSizeIterator
) -> impl Iterator<Item = &'b mut MatrixRow<'a, 'p, Cx>> + DoubleEndedIterator + ExactSizeIterator
{
self.rows.iter_mut()
}
@ -898,16 +895,16 @@ impl<'a, 'p, 'tcx> Matrix<'a, 'p, 'tcx> {
/// Iterate over the first pattern of each row.
fn heads<'b>(
&'b self,
) -> impl Iterator<Item = &'b DeconstructedPat<'p, 'tcx>> + Clone + Captures<'a> {
) -> impl Iterator<Item = &'b DeconstructedPat<'p, Cx>> + Clone + Captures<'a> {
self.rows().map(|r| r.head())
}
/// This computes `specialize(ctor, self)`. See top of the file for explanations.
fn specialize_constructor(
&self,
pcx: &PatCtxt<'a, 'p, 'tcx>,
ctor: &Constructor<'tcx>,
) -> Matrix<'a, 'p, 'tcx> {
pcx: &PatCtxt<'a, 'p, Cx>,
ctor: &Constructor<Cx>,
) -> Matrix<'a, 'p, Cx> {
let wildcard_row = self.wildcard_row.pop_head_constructor(pcx, ctor);
let new_validity = self.place_validity[0].specialize(ctor);
let new_place_validity = std::iter::repeat(new_validity)
@ -936,7 +933,7 @@ impl<'a, 'p, 'tcx> Matrix<'a, 'p, 'tcx> {
/// + _ + [_, _, tail @ ..] +
/// | ✓ | ? | // column validity
/// ```
impl<'a, 'p, 'tcx> fmt::Debug for Matrix<'a, 'p, 'tcx> {
impl<'a, 'p, Cx: MatchCx> fmt::Debug for Matrix<'a, 'p, Cx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "\n")?;
@ -1027,17 +1024,17 @@ impl<'a, 'p, 'tcx> fmt::Debug for Matrix<'a, 'p, 'tcx> {
///
/// See the top of the file for more detailed explanations and examples.
#[derive(Debug, Clone)]
struct WitnessStack<'tcx>(Vec<WitnessPat<'tcx>>);
struct WitnessStack<Cx: MatchCx>(Vec<WitnessPat<Cx>>);
impl<'tcx> WitnessStack<'tcx> {
impl<Cx: MatchCx> WitnessStack<Cx> {
/// Asserts that the witness contains a single pattern, and returns it.
fn single_pattern(self) -> WitnessPat<'tcx> {
fn single_pattern(self) -> WitnessPat<Cx> {
assert_eq!(self.0.len(), 1);
self.0.into_iter().next().unwrap()
}
/// Reverses specialization by the `Missing` constructor by pushing a whole new pattern.
fn push_pattern(&mut self, pat: WitnessPat<'tcx>) {
fn push_pattern(&mut self, pat: WitnessPat<Cx>) {
self.0.push(pat);
}
@ -1055,7 +1052,7 @@ impl<'tcx> WitnessStack<'tcx> {
/// pats: [(false, "foo"), _, true]
/// result: [Enum::Variant { a: (false, "foo"), b: _ }, true]
/// ```
fn apply_constructor(&mut self, pcx: &PatCtxt<'_, '_, 'tcx>, ctor: &Constructor<'tcx>) {
fn apply_constructor(&mut self, pcx: &PatCtxt<'_, '_, Cx>, ctor: &Constructor<Cx>) {
let len = self.0.len();
let arity = ctor.arity(pcx);
let fields = self.0.drain((len - arity)..).rev().collect();
@ -1074,9 +1071,9 @@ impl<'tcx> WitnessStack<'tcx> {
/// Just as the `Matrix` starts with a single column, by the end of the algorithm, this has a single
/// column, which contains the patterns that are missing for the match to be exhaustive.
#[derive(Debug, Clone)]
struct WitnessMatrix<'tcx>(Vec<WitnessStack<'tcx>>);
struct WitnessMatrix<Cx: MatchCx>(Vec<WitnessStack<Cx>>);
impl<'tcx> WitnessMatrix<'tcx> {
impl<Cx: MatchCx> WitnessMatrix<Cx> {
/// New matrix with no witnesses.
fn empty() -> Self {
WitnessMatrix(vec![])
@ -1091,12 +1088,12 @@ impl<'tcx> WitnessMatrix<'tcx> {
self.0.is_empty()
}
/// Asserts that there is a single column and returns the patterns in it.
fn single_column(self) -> Vec<WitnessPat<'tcx>> {
fn single_column(self) -> Vec<WitnessPat<Cx>> {
self.0.into_iter().map(|w| w.single_pattern()).collect()
}
/// Reverses specialization by the `Missing` constructor by pushing a whole new pattern.
fn push_pattern(&mut self, pat: WitnessPat<'tcx>) {
fn push_pattern(&mut self, pat: WitnessPat<Cx>) {
for witness in self.0.iter_mut() {
witness.push_pattern(pat.clone())
}
@ -1105,9 +1102,9 @@ impl<'tcx> WitnessMatrix<'tcx> {
/// Reverses specialization by `ctor`. See the section on `unspecialize` at the top of the file.
fn apply_constructor(
&mut self,
pcx: &PatCtxt<'_, '_, 'tcx>,
missing_ctors: &[Constructor<'tcx>],
ctor: &Constructor<'tcx>,
pcx: &PatCtxt<'_, '_, Cx>,
missing_ctors: &[Constructor<Cx>],
ctor: &Constructor<Cx>,
report_individual_missing_ctors: bool,
) {
if self.is_empty() {
@ -1168,12 +1165,12 @@ impl<'tcx> WitnessMatrix<'tcx> {
/// (using `apply_constructor` and by updating `row.useful` for each parent row).
/// This is all explained at the top of the file.
#[instrument(level = "debug", skip(cx, is_top_level, wildcard_arena), ret)]
fn compute_exhaustiveness_and_usefulness<'a, 'p, 'tcx>(
cx: &'a MatchCheckCtxt<'p, 'tcx>,
matrix: &mut Matrix<'a, 'p, 'tcx>,
wildcard_arena: &'a TypedArena<DeconstructedPat<'p, 'tcx>>,
fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: MatchCx>(
cx: &'a Cx,
matrix: &mut Matrix<'a, 'p, Cx>,
wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
is_top_level: bool,
) -> WitnessMatrix<'tcx> {
) -> WitnessMatrix<Cx> {
debug_assert!(matrix.rows().all(|r| r.len() == matrix.column_count()));
let Some(ty) = matrix.head_ty() else {
@ -1278,7 +1275,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, 'tcx>(
/// Indicates whether or not a given arm is useful.
#[derive(Clone, Debug)]
pub enum Usefulness {
pub enum Usefulness<Span> {
/// The arm is useful. This additionally carries a set of or-pattern branches that have been
/// found to be redundant despite the overall arm being useful. Used only in the presence of
/// or-patterns, otherwise it stays empty.
@ -1289,23 +1286,23 @@ pub enum Usefulness {
}
/// The output of checking a match for exhaustiveness and arm usefulness.
pub struct UsefulnessReport<'p, 'tcx> {
pub struct UsefulnessReport<'p, Cx: MatchCx> {
/// For each arm of the input, whether that arm is useful after the arms above it.
pub arm_usefulness: Vec<(MatchArm<'p, 'tcx>, Usefulness)>,
pub arm_usefulness: Vec<(MatchArm<'p, Cx>, Usefulness<Cx::Span>)>,
/// If the match is exhaustive, this is empty. If not, this contains witnesses for the lack of
/// exhaustiveness.
pub non_exhaustiveness_witnesses: Vec<WitnessPat<'tcx>>,
pub non_exhaustiveness_witnesses: Vec<WitnessPat<Cx>>,
}
/// Computes whether a match is exhaustive and which of its arms are useful.
#[instrument(skip(cx, arms, wildcard_arena), level = "debug")]
pub(crate) fn compute_match_usefulness<'p, 'tcx>(
cx: &MatchCheckCtxt<'p, 'tcx>,
arms: &[MatchArm<'p, 'tcx>],
scrut_ty: Ty<'tcx>,
wildcard_arena: &TypedArena<DeconstructedPat<'p, 'tcx>>,
) -> UsefulnessReport<'p, 'tcx> {
let scrut_validity = ValidityConstraint::from_bool(cx.known_valid_scrutinee);
pub(crate) fn compute_match_usefulness<'p, Cx: MatchCx>(
cx: &Cx,
arms: &[MatchArm<'p, Cx>],
scrut_ty: Cx::Ty,
scrut_validity: ValidityConstraint,
wildcard_arena: &TypedArena<DeconstructedPat<'p, Cx>>,
) -> UsefulnessReport<'p, Cx> {
let mut matrix = Matrix::new(wildcard_arena, arms, scrut_ty, scrut_validity);
let non_exhaustiveness_witnesses =
compute_exhaustiveness_and_usefulness(cx, &mut matrix, wildcard_arena, true);