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Gather rustc-specific functions around MatchCheckCtxt

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This commit is contained in:
Nadrieril 2023-12-10 22:14:00 +01:00
parent 281002d42c
commit 3691a0aee5
8 changed files with 903 additions and 900 deletions
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2
compiler/rustc_mir_build/src/errors.rs
View file

@ -6,7 +6,7 @@ use rustc_errors::{
};
use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
use rustc_middle::ty::{self, Ty};
use rustc_pattern_analysis::{errors::Uncovered, usefulness::MatchCheckCtxt};
use rustc_pattern_analysis::{cx::MatchCheckCtxt, errors::Uncovered};
use rustc_span::symbol::Symbol;
use rustc_span::Span;

21
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View file

@ -1,8 +1,9 @@
use rustc_pattern_analysis::constructor::Constructor;
use rustc_pattern_analysis::cx::MatchCheckCtxt;
use rustc_pattern_analysis::errors::Uncovered;
use rustc_pattern_analysis::pat::{DeconstructedPat, WitnessPat};
use rustc_pattern_analysis::usefulness::{
compute_match_usefulness, MatchArm, MatchCheckCtxt, Usefulness, UsefulnessReport,
compute_match_usefulness, MatchArm, Usefulness, UsefulnessReport,
};
use crate::errors::*;
@ -286,7 +287,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
check_borrow_conflicts_in_at_patterns(self, pat);
check_for_bindings_named_same_as_variants(self, pat, refutable);
});
Ok(cx.pattern_arena.alloc(DeconstructedPat::from_pat(cx, pat)))
Ok(cx.pattern_arena.alloc(cx.lower_pat(pat)))
}
}
@ -926,7 +927,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
pattern = if witnesses.len() < 4 {
witnesses
.iter()
.map(|witness| witness.to_diagnostic_pat(cx).to_string())
.map(|witness| cx.hoist_witness_pat(witness).to_string())
.collect::<Vec<String>>()
.join(" | ")
} else {
@ -950,7 +951,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
if !is_empty_match {
let mut non_exhaustive_tys = FxHashSet::default();
// Look at the first witness.
collect_non_exhaustive_tys(cx.tcx, &witnesses[0], &mut non_exhaustive_tys);
collect_non_exhaustive_tys(cx, &witnesses[0], &mut non_exhaustive_tys);
for ty in non_exhaustive_tys {
if ty.is_ptr_sized_integral() {
@ -1085,13 +1086,13 @@ fn joined_uncovered_patterns<'p, 'tcx>(
witnesses: &[WitnessPat<'tcx>],
) -> String {
const LIMIT: usize = 3;
let pat_to_str = |pat: &WitnessPat<'tcx>| pat.to_diagnostic_pat(cx).to_string();
let pat_to_str = |pat: &WitnessPat<'tcx>| cx.hoist_witness_pat(pat).to_string();
match witnesses {
[] => bug!(),
[witness] => format!("`{}`", witness.to_diagnostic_pat(cx)),
[witness] => format!("`{}`", cx.hoist_witness_pat(witness)),
[head @ .., tail] if head.len() < LIMIT => {
let head: Vec<_> = head.iter().map(pat_to_str).collect();
format!("`{}` and `{}`", head.join("`, `"), tail.to_diagnostic_pat(cx))
format!("`{}` and `{}`", head.join("`, `"), cx.hoist_witness_pat(tail))
}
_ => {
let (head, tail) = witnesses.split_at(LIMIT);
@ -1102,7 +1103,7 @@ fn joined_uncovered_patterns<'p, 'tcx>(
}
fn collect_non_exhaustive_tys<'tcx>(
tcx: TyCtxt<'tcx>,
cx: &MatchCheckCtxt<'_, 'tcx>,
pat: &WitnessPat<'tcx>,
non_exhaustive_tys: &mut FxHashSet<Ty<'tcx>>,
) {
@ -1110,13 +1111,13 @@ fn collect_non_exhaustive_tys<'tcx>(
non_exhaustive_tys.insert(pat.ty());
}
if let Constructor::IntRange(range) = pat.ctor() {
if range.is_beyond_boundaries(pat.ty(), tcx) {
if cx.is_range_beyond_boundaries(range, pat.ty()) {
// The range denotes the values before `isize::MIN` or the values after `usize::MAX`/`isize::MAX`.
non_exhaustive_tys.insert(pat.ty());
}
}
pat.iter_fields()
.for_each(|field_pat| collect_non_exhaustive_tys(tcx, field_pat, non_exhaustive_tys))
.for_each(|field_pat| collect_non_exhaustive_tys(cx, field_pat, non_exhaustive_tys))
}
fn report_adt_defined_here<'tcx>(

278
compiler/rustc_pattern_analysis/src/constructor.rs
View file

@ -158,21 +158,16 @@ use rustc_apfloat::ieee::{DoubleS, IeeeFloat, SingleS};
use rustc_data_structures::fx::FxHashSet;
use rustc_hir::RangeEnd;
use rustc_index::IndexVec;
use rustc_middle::middle::stability::EvalResult;
use rustc_middle::mir;
use rustc_middle::mir::interpret::Scalar;
use rustc_middle::thir::{Pat, PatKind, PatRange, PatRangeBoundary};
use rustc_middle::mir::Const;
use rustc_middle::ty::layout::IntegerExt;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::DUMMY_SP;
use rustc_target::abi::{Integer, VariantIdx, FIRST_VARIANT};
use rustc_target::abi::{Integer, VariantIdx};
use self::Constructor::*;
use self::MaybeInfiniteInt::*;
use self::SliceKind::*;
use crate::pat::Fields;
use crate::usefulness::{MatchCheckCtxt, PatCtxt};
use crate::usefulness::PatCtxt;
/// Whether we have seen a constructor in the column or not.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
@ -196,7 +191,7 @@ pub enum MaybeInfiniteInt {
impl MaybeInfiniteInt {
// The return value of `signed_bias` should be XORed with a value to encode/decode it.
fn signed_bias(tcx: TyCtxt<'_>, ty: Ty<'_>) -> u128 {
pub(crate) fn signed_bias(tcx: TyCtxt<'_>, ty: Ty<'_>) -> u128 {
match *ty.kind() {
ty::Int(ity) => {
let bits = Integer::from_int_ty(&tcx, ity).size().bits() as u128;
@ -206,58 +201,13 @@ impl MaybeInfiniteInt {
}
}
fn new_finite(tcx: TyCtxt<'_>, ty: Ty<'_>, bits: u128) -> Self {
pub fn new_finite(tcx: TyCtxt<'_>, ty: Ty<'_>, bits: u128) -> Self {
let bias = Self::signed_bias(tcx, ty);
// Perform a shift if the underlying types are signed, which makes the interval arithmetic
// type-independent.
let x = bits ^ bias;
Finite(x)
}
pub(crate) fn from_pat_range_bdy<'tcx>(
bdy: PatRangeBoundary<'tcx>,
ty: Ty<'tcx>,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Self {
match bdy {
PatRangeBoundary::NegInfinity => NegInfinity,
PatRangeBoundary::Finite(value) => {
let bits = value.eval_bits(tcx, param_env);
Self::new_finite(tcx, ty, bits)
}
PatRangeBoundary::PosInfinity => PosInfinity,
}
}
/// Used only for diagnostics.
/// Note: it is possible to get `isize/usize::MAX+1` here, as explained in the doc for
/// [`IntRange::split`]. This cannot be represented as a `Const`, so we represent it with
/// `PosInfinity`.
fn to_diagnostic_pat_range_bdy<'tcx>(
self,
ty: Ty<'tcx>,
tcx: TyCtxt<'tcx>,
) -> PatRangeBoundary<'tcx> {
match self {
NegInfinity => PatRangeBoundary::NegInfinity,
Finite(x) => {
let bias = Self::signed_bias(tcx, ty);
let bits = x ^ bias;
let size = ty.primitive_size(tcx);
match Scalar::try_from_uint(bits, size) {
Some(scalar) => {
let value = mir::Const::from_scalar(tcx, scalar, ty);
PatRangeBoundary::Finite(value)
}
// The value doesn't fit. Since `x >= 0` and 0 always encodes the minimum value
// for a type, the problem isn't that the value is too small. So it must be too
// large.
None => PatRangeBoundary::PosInfinity,
}
}
JustAfterMax | PosInfinity => PatRangeBoundary::PosInfinity,
}
}
/// Note: this will not turn a finite value into an infinite one or vice-versa.
pub fn minus_one(self) -> Self {
@ -290,16 +240,11 @@ impl MaybeInfiniteInt {
/// space: i.e., `range.lo < range.hi`.
#[derive(Clone, Copy, PartialEq, Eq)]
pub struct IntRange {
pub(crate) lo: MaybeInfiniteInt, // Must not be `PosInfinity`.
pub(crate) hi: MaybeInfiniteInt, // Must not be `NegInfinity`.
pub lo: MaybeInfiniteInt, // Must not be `PosInfinity`.
pub hi: MaybeInfiniteInt, // Must not be `NegInfinity`.
}
impl IntRange {
#[inline]
pub(super) fn is_integral(ty: Ty<'_>) -> bool {
matches!(ty.kind(), ty::Char | ty::Int(_) | ty::Uint(_))
}
/// Best effort; will not know that e.g. `255u8..` is a singleton.
pub fn is_singleton(&self) -> bool {
// Since `lo` and `hi` can't be the same `Infinity` and `plus_one` never changes from finite
@ -421,55 +366,6 @@ impl IntRange {
(presence, range)
})
}
/// 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_beyond_boundaries<'tcx>(&self, ty: Ty<'tcx>, tcx: TyCtxt<'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`. `to_diagnostic_pat_range_bdy`
// converts `MAX+1` to `PosInfinity`, and we couldn't have `PosInfinity` in `self.lo`
// otherwise.
let lo = self.lo.to_diagnostic_pat_range_bdy(ty, tcx);
matches!(lo, PatRangeBoundary::PosInfinity)
|| matches!(self.hi, MaybeInfiniteInt::Finite(0))
}
}
/// Only used for displaying the range.
pub(super) fn to_diagnostic_pat<'tcx>(&self, ty: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Pat<'tcx> {
let kind = if matches!((self.lo, self.hi), (NegInfinity, PosInfinity)) {
PatKind::Wild
} else if self.is_singleton() {
let lo = self.lo.to_diagnostic_pat_range_bdy(ty, tcx);
let value = lo.as_finite().unwrap();
PatKind::Constant { value }
} else {
// We convert to an inclusive range for diagnostics.
let mut end = RangeEnd::Included;
let mut lo = self.lo.to_diagnostic_pat_range_bdy(ty, tcx);
if matches!(lo, PatRangeBoundary::PosInfinity) {
// The only reason to get `PosInfinity` here is the special case where
// `to_diagnostic_pat_range_bdy` found `{u,i}size::MAX+1`. So the range denotes the
// fictitious values after `{u,i}size::MAX` (see [`IntRange::split`] for why we do
// this). We show this to the user as `usize::MAX..` which is slightly incorrect but
// probably clear enough.
let c = ty.numeric_max_val(tcx).unwrap();
let value = mir::Const::from_ty_const(c, tcx);
lo = PatRangeBoundary::Finite(value);
}
let hi = if matches!(self.hi, MaybeInfiniteInt::Finite(0)) {
// The range encodes `..ty::MIN`, so we can't convert it to an inclusive range.
end = RangeEnd::Excluded;
self.hi
} else {
self.hi.minus_one()
};
let hi = hi.to_diagnostic_pat_range_bdy(ty, tcx);
PatKind::Range(Box::new(PatRange { lo, hi, end, ty }))
};
Pat { ty, span: DUMMY_SP, kind }
}
}
/// Note: this will render signed ranges incorrectly. To render properly, convert to a pattern
@ -742,7 +638,7 @@ 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(mir::Const<'tcx>),
Str(Const<'tcx>),
/// Array and slice patterns.
Slice(Slice),
/// Constants that must not be matched structurally. They are treated as black boxes for the
@ -797,49 +693,10 @@ impl<'tcx> Constructor<'tcx> {
}
}
pub(crate) fn variant_index_for_adt(&self, adt: ty::AdtDef<'tcx>) -> VariantIdx {
match *self {
Variant(idx) => idx,
Single => {
assert!(!adt.is_enum());
FIRST_VARIANT
}
_ => bug!("bad constructor {:?} for adt {:?}", self, adt),
}
}
/// 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 {
match self {
Single | Variant(_) => match pcx.ty.kind() {
ty::Tuple(fs) => fs.len(),
ty::Ref(..) => 1,
ty::Adt(adt, ..) => {
if adt.is_box() {
// The only legal patterns of type `Box` (outside `std`) are `_` and box
// patterns. If we're here we can assume this is a box pattern.
1
} else {
let variant = &adt.variant(self.variant_index_for_adt(*adt));
Fields::list_variant_nonhidden_fields(pcx.cx, pcx.ty, variant).count()
}
}
_ => bug!("Unexpected type for `Single` constructor: {:?}", pcx.ty),
},
Slice(slice) => slice.arity(),
Bool(..)
| IntRange(..)
| F32Range(..)
| F64Range(..)
| Str(..)
| Opaque(..)
| NonExhaustive
| Hidden
| Missing { .. }
| Wildcard => 0,
Or => bug!("The `Or` constructor doesn't have a fixed arity"),
}
pcx.cx.ctor_arity(self, pcx.ty)
}
/// Returns whether `self` is covered by `other`, i.e. whether `self` is a subset of `other`.
@ -974,123 +831,6 @@ pub(super) struct SplitConstructorSet<'tcx> {
}
impl ConstructorSet {
/// Creates a set that represents all the constructors of `ty`.
///
/// See at the top of the file for considerations of emptiness.
#[instrument(level = "debug", skip(cx), ret)]
pub fn for_ty<'p, 'tcx>(cx: &MatchCheckCtxt<'p, 'tcx>, ty: Ty<'tcx>) -> Self {
let make_range = |start, end| {
IntRange::from_range(
MaybeInfiniteInt::new_finite(cx.tcx, ty, start),
MaybeInfiniteInt::new_finite(cx.tcx, ty, end),
RangeEnd::Included,
)
};
// This determines the set of all possible constructors for the type `ty`. For numbers,
// arrays and slices we use ranges and variable-length slices when appropriate.
match ty.kind() {
ty::Bool => Self::Bool,
ty::Char => {
// The valid Unicode Scalar Value ranges.
Self::Integers {
range_1: make_range('\u{0000}' as u128, '\u{D7FF}' as u128),
range_2: Some(make_range('\u{E000}' as u128, '\u{10FFFF}' as u128)),
}
}
&ty::Int(ity) => {
let range = if ty.is_ptr_sized_integral() {
// The min/max values of `isize` are not allowed to be observed.
IntRange { lo: NegInfinity, hi: PosInfinity }
} else {
let bits = Integer::from_int_ty(&cx.tcx, ity).size().bits() as u128;
let min = 1u128 << (bits - 1);
let max = min - 1;
make_range(min, max)
};
Self::Integers { range_1: range, range_2: None }
}
&ty::Uint(uty) => {
let range = if ty.is_ptr_sized_integral() {
// The max value of `usize` is not allowed to be observed.
let lo = MaybeInfiniteInt::new_finite(cx.tcx, ty, 0);
IntRange { lo, hi: PosInfinity }
} else {
let size = Integer::from_uint_ty(&cx.tcx, uty).size();
let max = size.truncate(u128::MAX);
make_range(0, max)
};
Self::Integers { range_1: range, range_2: None }
}
ty::Slice(sub_ty) => {
Self::Slice { array_len: None, subtype_is_empty: cx.is_uninhabited(*sub_ty) }
}
ty::Array(sub_ty, len) => {
// We treat arrays of a constant but unknown length like slices.
Self::Slice {
array_len: len.try_eval_target_usize(cx.tcx, cx.param_env).map(|l| l as usize),
subtype_is_empty: cx.is_uninhabited(*sub_ty),
}
}
ty::Adt(def, args) if def.is_enum() => {
let is_declared_nonexhaustive = cx.is_foreign_non_exhaustive_enum(ty);
if def.variants().is_empty() && !is_declared_nonexhaustive {
Self::NoConstructors
} else {
let mut variants =
IndexVec::from_elem(VariantVisibility::Visible, def.variants());
for (idx, v) in def.variants().iter_enumerated() {
let variant_def_id = def.variant(idx).def_id;
// Visibly uninhabited variants.
let is_inhabited = v
.inhabited_predicate(cx.tcx, *def)
.instantiate(cx.tcx, args)
.apply(cx.tcx, cx.param_env, cx.module);
// Variants that depend on a disabled unstable feature.
let is_unstable = matches!(
cx.tcx.eval_stability(variant_def_id, None, DUMMY_SP, None),
EvalResult::Deny { .. }
);
// Foreign `#[doc(hidden)]` variants.
let is_doc_hidden =
cx.tcx.is_doc_hidden(variant_def_id) && !variant_def_id.is_local();
let visibility = if !is_inhabited {
// FIXME: handle empty+hidden
VariantVisibility::Empty
} else if is_unstable || is_doc_hidden {
VariantVisibility::Hidden
} else {
VariantVisibility::Visible
};
variants[idx] = visibility;
}
Self::Variants { variants, non_exhaustive: is_declared_nonexhaustive }
}
}
ty::Adt(..) | ty::Tuple(..) | ty::Ref(..) => {
Self::Single { empty: cx.is_uninhabited(ty) }
}
ty::Never => Self::NoConstructors,
// This type is one for which we cannot list constructors, like `str` or `f64`.
// FIXME(Nadrieril): which of these are actually allowed?
ty::Float(_)
| ty::Str
| ty::Foreign(_)
| ty::RawPtr(_)
| ty::FnDef(_, _)
| ty::FnPtr(_)
| ty::Dynamic(_, _, _)
| ty::Closure(_, _)
| ty::Coroutine(_, _, _)
| ty::Alias(_, _)
| ty::Param(_)
| ty::Error(_) => Self::Unlistable,
ty::CoroutineWitness(_, _) | ty::Bound(_, _) | ty::Placeholder(_) | ty::Infer(_) => {
bug!("Encountered unexpected type in `ConstructorSet::for_ty`: {ty:?}")
}
}
}
/// 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

837
compiler/rustc_pattern_analysis/src/cx.rs Normal file
View file

@ -0,0 +1,837 @@
use std::fmt;
use std::iter::once;
use rustc_arena::TypedArena;
use rustc_data_structures::captures::Captures;
use rustc_hir::def_id::DefId;
use rustc_hir::{HirId, RangeEnd};
use rustc_index::Idx;
use rustc_index::IndexVec;
use rustc_middle::middle::stability::EvalResult;
use rustc_middle::mir;
use rustc_middle::mir::interpret::Scalar;
use rustc_middle::thir::{FieldPat, Pat, PatKind, PatRange, PatRangeBoundary};
use rustc_middle::ty::layout::IntegerExt;
use rustc_middle::ty::{self, Ty, TyCtxt, VariantDef};
use rustc_span::{Span, DUMMY_SP};
use rustc_target::abi::{FieldIdx, Integer, VariantIdx, FIRST_VARIANT};
use smallvec::SmallVec;
use crate::constructor::{
Constructor, ConstructorSet, IntRange, MaybeInfiniteInt, OpaqueId, Slice, SliceKind,
VariantVisibility,
};
use crate::pat::{DeconstructedPat, WitnessPat};
use Constructor::*;
pub struct MatchCheckCtxt<'p, 'tcx> {
pub tcx: TyCtxt<'tcx>,
/// The module in which the match occurs. This is necessary for
/// checking inhabited-ness of types because whether a type is (visibly)
/// inhabited can depend on whether it was defined in the current module or
/// not. E.g., `struct Foo { _private: ! }` cannot be seen to be empty
/// outside its module and should not be matchable with an empty match statement.
pub module: DefId,
pub param_env: ty::ParamEnv<'tcx>,
pub pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
/// Lint level at the match.
pub match_lint_level: HirId,
/// The span of the whole match, if applicable.
pub whole_match_span: Option<Span>,
/// Span of the scrutinee.
pub scrut_span: Span,
/// Only produce `NON_EXHAUSTIVE_OMITTED_PATTERNS` lint on refutable patterns.
pub refutable: bool,
/// Whether the data at the scrutinee is known to be valid. This is false if the scrutinee comes
/// from a union field, a pointer deref, or a reference deref (pending opsem decisions).
pub known_valid_scrutinee: bool,
}
impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
pub(super) fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
!ty.is_inhabited_from(self.tcx, self.module, self.param_env)
}
/// 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() {
ty::Adt(def, ..) => {
def.is_enum() && def.is_variant_list_non_exhaustive() && !def.did().is_local()
}
_ => false,
}
}
pub(crate) fn alloc_wildcard_slice(
&self,
tys: impl IntoIterator<Item = Ty<'tcx>>,
) -> &'p [DeconstructedPat<'p, 'tcx>] {
self.pattern_arena
.alloc_from_iter(tys.into_iter().map(|ty| DeconstructedPat::wildcard(ty, DUMMY_SP)))
}
// 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.
pub(crate) fn list_variant_nonhidden_fields<'a>(
&'a self,
ty: Ty<'tcx>,
variant: &'a VariantDef,
) -> impl Iterator<Item = (FieldIdx, Ty<'tcx>)> + Captures<'p> + Captures<'a> {
let cx = self;
let ty::Adt(adt, args) = ty.kind() else { bug!() };
// Whether we must not match the fields of this variant exhaustively.
let is_non_exhaustive = variant.is_field_list_non_exhaustive() && !adt.did().is_local();
variant.fields.iter().enumerate().filter_map(move |(i, field)| {
let ty = field.ty(cx.tcx, args);
// `field.ty()` doesn't normalize after substituting.
let ty = cx.tcx.normalize_erasing_regions(cx.param_env, ty);
let is_visible = adt.is_enum() || field.vis.is_accessible_from(cx.module, cx.tcx);
let is_uninhabited = cx.tcx.features().exhaustive_patterns && cx.is_uninhabited(ty);
if is_uninhabited && (!is_visible || is_non_exhaustive) {
None
} else {
Some((FieldIdx::new(i), ty))
}
})
}
pub(crate) fn variant_index_for_adt(
ctor: &Constructor<'tcx>,
adt: ty::AdtDef<'tcx>,
) -> VariantIdx {
match *ctor {
Variant(idx) => idx,
Single => {
assert!(!adt.is_enum());
FIRST_VARIANT
}
_ => bug!("bad constructor {:?} for adt {:?}", ctor, adt),
}
}
/// Creates a new list of wildcard fields for a given constructor. The result must have a length
/// of `ctor.arity()`.
#[instrument(level = "trace", skip(self))]
pub(crate) fn ctor_wildcard_fields(
&self,
ctor: &Constructor<'tcx>,
ty: Ty<'tcx>,
) -> &'p [DeconstructedPat<'p, 'tcx>] {
let cx = self;
match ctor {
Single | Variant(_) => match ty.kind() {
ty::Tuple(fs) => cx.alloc_wildcard_slice(fs.iter()),
ty::Ref(_, rty, _) => cx.alloc_wildcard_slice(once(*rty)),
ty::Adt(adt, args) => {
if adt.is_box() {
// The only legal patterns of type `Box` (outside `std`) are `_` and box
// patterns. If we're here we can assume this is a box pattern.
cx.alloc_wildcard_slice(once(args.type_at(0)))
} else {
let variant =
&adt.variant(MatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
let tys = cx.list_variant_nonhidden_fields(ty, variant).map(|(_, ty)| ty);
cx.alloc_wildcard_slice(tys)
}
}
_ => bug!("Unexpected type for `Single` constructor: {:?}", ty),
},
Slice(slice) => match *ty.kind() {
ty::Slice(ty) | ty::Array(ty, _) => {
let arity = slice.arity();
cx.alloc_wildcard_slice((0..arity).map(|_| ty))
}
_ => bug!("bad slice pattern {:?} {:?}", ctor, ty),
},
Bool(..)
| IntRange(..)
| F32Range(..)
| F64Range(..)
| Str(..)
| Opaque(..)
| NonExhaustive
| Hidden
| Missing { .. }
| Wildcard => &[],
Or => {
bug!("called `Fields::wildcards` on an `Or` ctor")
}
}
}
/// 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 {
match ctor {
Single | Variant(_) => match ty.kind() {
ty::Tuple(fs) => fs.len(),
ty::Ref(..) => 1,
ty::Adt(adt, ..) => {
if adt.is_box() {
// The only legal patterns of type `Box` (outside `std`) are `_` and box
// patterns. If we're here we can assume this is a box pattern.
1
} else {
let variant =
&adt.variant(MatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
self.list_variant_nonhidden_fields(ty, variant).count()
}
}
_ => bug!("Unexpected type for `Single` constructor: {:?}", ty),
},
Slice(slice) => slice.arity(),
Bool(..)
| IntRange(..)
| F32Range(..)
| F64Range(..)
| Str(..)
| Opaque(..)
| NonExhaustive
| Hidden
| Missing { .. }
| Wildcard => 0,
Or => bug!("The `Or` constructor doesn't have a fixed arity"),
}
}
/// Creates a set that represents all the constructors of `ty`.
///
/// See [`crate::constructor`] for considerations of emptiness.
#[instrument(level = "debug", skip(self), ret)]
pub fn ctors_for_ty(&self, ty: Ty<'tcx>) -> ConstructorSet {
let cx = self;
let make_range = |start, end| {
IntRange::from_range(
MaybeInfiniteInt::new_finite(cx.tcx, ty, start),
MaybeInfiniteInt::new_finite(cx.tcx, ty, end),
RangeEnd::Included,
)
};
// This determines the set of all possible constructors for the type `ty`. For numbers,
// arrays and slices we use ranges and variable-length slices when appropriate.
match ty.kind() {
ty::Bool => ConstructorSet::Bool,
ty::Char => {
// The valid Unicode Scalar Value ranges.
ConstructorSet::Integers {
range_1: make_range('\u{0000}' as u128, '\u{D7FF}' as u128),
range_2: Some(make_range('\u{E000}' as u128, '\u{10FFFF}' as u128)),
}
}
&ty::Int(ity) => {
let range = if ty.is_ptr_sized_integral() {
// The min/max values of `isize` are not allowed to be observed.
IntRange {
lo: MaybeInfiniteInt::NegInfinity,
hi: MaybeInfiniteInt::PosInfinity,
}
} else {
let bits = Integer::from_int_ty(&cx.tcx, ity).size().bits() as u128;
let min = 1u128 << (bits - 1);
let max = min - 1;
make_range(min, max)
};
ConstructorSet::Integers { range_1: range, range_2: None }
}
&ty::Uint(uty) => {
let range = if ty.is_ptr_sized_integral() {
// The max value of `usize` is not allowed to be observed.
let lo = MaybeInfiniteInt::new_finite(cx.tcx, ty, 0);
IntRange { lo, hi: MaybeInfiniteInt::PosInfinity }
} else {
let size = Integer::from_uint_ty(&cx.tcx, uty).size();
let max = size.truncate(u128::MAX);
make_range(0, max)
};
ConstructorSet::Integers { range_1: range, range_2: None }
}
ty::Slice(sub_ty) => ConstructorSet::Slice {
array_len: None,
subtype_is_empty: cx.is_uninhabited(*sub_ty),
},
ty::Array(sub_ty, len) => {
// We treat arrays of a constant but unknown length like slices.
ConstructorSet::Slice {
array_len: len.try_eval_target_usize(cx.tcx, cx.param_env).map(|l| l as usize),
subtype_is_empty: cx.is_uninhabited(*sub_ty),
}
}
ty::Adt(def, args) if def.is_enum() => {
let is_declared_nonexhaustive = cx.is_foreign_non_exhaustive_enum(ty);
if def.variants().is_empty() && !is_declared_nonexhaustive {
ConstructorSet::NoConstructors
} else {
let mut variants =
IndexVec::from_elem(VariantVisibility::Visible, def.variants());
for (idx, v) in def.variants().iter_enumerated() {
let variant_def_id = def.variant(idx).def_id;
// Visibly uninhabited variants.
let is_inhabited = v
.inhabited_predicate(cx.tcx, *def)
.instantiate(cx.tcx, args)
.apply(cx.tcx, cx.param_env, cx.module);
// Variants that depend on a disabled unstable feature.
let is_unstable = matches!(
cx.tcx.eval_stability(variant_def_id, None, DUMMY_SP, None),
EvalResult::Deny { .. }
);
// Foreign `#[doc(hidden)]` variants.
let is_doc_hidden =
cx.tcx.is_doc_hidden(variant_def_id) && !variant_def_id.is_local();
let visibility = if !is_inhabited {
// FIXME: handle empty+hidden
VariantVisibility::Empty
} else if is_unstable || is_doc_hidden {
VariantVisibility::Hidden
} else {
VariantVisibility::Visible
};
variants[idx] = visibility;
}
ConstructorSet::Variants { variants, non_exhaustive: is_declared_nonexhaustive }
}
}
ty::Adt(..) | ty::Tuple(..) | ty::Ref(..) => {
ConstructorSet::Single { empty: cx.is_uninhabited(ty) }
}
ty::Never => ConstructorSet::NoConstructors,
// This type is one for which we cannot list constructors, like `str` or `f64`.
// FIXME(Nadrieril): which of these are actually allowed?
ty::Float(_)
| ty::Str
| ty::Foreign(_)
| ty::RawPtr(_)
| ty::FnDef(_, _)
| ty::FnPtr(_)
| ty::Dynamic(_, _, _)
| ty::Closure(_, _)
| ty::Coroutine(_, _, _)
| ty::Alias(_, _)
| ty::Param(_)
| ty::Error(_) => ConstructorSet::Unlistable,
ty::CoroutineWitness(_, _) | ty::Bound(_, _) | ty::Placeholder(_) | ty::Infer(_) => {
bug!("Encountered unexpected type in `ConstructorSet::for_ty`: {ty:?}")
}
}
}
pub(crate) fn lower_pat_range_bdy(
&self,
bdy: PatRangeBoundary<'tcx>,
ty: Ty<'tcx>,
) -> MaybeInfiniteInt {
match bdy {
PatRangeBoundary::NegInfinity => MaybeInfiniteInt::NegInfinity,
PatRangeBoundary::Finite(value) => {
let bits = value.eval_bits(self.tcx, self.param_env);
MaybeInfiniteInt::new_finite(self.tcx, ty, bits)
}
PatRangeBoundary::PosInfinity => MaybeInfiniteInt::PosInfinity,
}
}
/// Note: the input patterns must have been lowered through
/// `rustc_mir_build::thir::pattern::check_match::MatchVisitor::lower_pattern`.
pub fn lower_pat(&self, pat: &Pat<'tcx>) -> DeconstructedPat<'p, 'tcx> {
let singleton = |pat| std::slice::from_ref(self.pattern_arena.alloc(pat));
let cx = self;
let ctor;
let fields: &[_];
match &pat.kind {
PatKind::AscribeUserType { subpattern, .. }
| PatKind::InlineConstant { subpattern, .. } => return self.lower_pat(subpattern),
PatKind::Binding { subpattern: Some(subpat), .. } => return self.lower_pat(subpat),
PatKind::Binding { subpattern: None, .. } | PatKind::Wild => {
ctor = Wildcard;
fields = &[];
}
PatKind::Deref { subpattern } => {
ctor = Single;
fields = singleton(self.lower_pat(subpattern));
}
PatKind::Leaf { subpatterns } | PatKind::Variant { subpatterns, .. } => {
match pat.ty.kind() {
ty::Tuple(fs) => {
ctor = Single;
let mut wilds: SmallVec<[_; 2]> =
fs.iter().map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
for pat in subpatterns {
wilds[pat.field.index()] = self.lower_pat(&pat.pattern);
}
fields = cx.pattern_arena.alloc_from_iter(wilds);
}
ty::Adt(adt, args) if adt.is_box() => {
// The only legal patterns of type `Box` (outside `std`) are `_` and box
// patterns. If we're here we can assume this is a box pattern.
// FIXME(Nadrieril): A `Box` can in theory be matched either with `Box(_,
// _)` or a box pattern. As a hack to avoid an ICE with the former, we
// ignore other fields than the first one. This will trigger an error later
// anyway.
// See https://github.com/rust-lang/rust/issues/82772 ,
// explanation: https://github.com/rust-lang/rust/pull/82789#issuecomment-796921977
// The problem is that we can't know from the type whether we'll match
// normally or through box-patterns. We'll have to figure out a proper
// solution when we introduce generalized deref patterns. Also need to
// prevent mixing of those two options.
let pattern = subpatterns.into_iter().find(|pat| pat.field.index() == 0);
let pat = if let Some(pat) = pattern {
self.lower_pat(&pat.pattern)
} else {
DeconstructedPat::wildcard(args.type_at(0), pat.span)
};
ctor = Single;
fields = singleton(pat);
}
ty::Adt(adt, _) => {
ctor = match pat.kind {
PatKind::Leaf { .. } => Single,
PatKind::Variant { variant_index, .. } => Variant(variant_index),
_ => bug!(),
};
let variant =
&adt.variant(MatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
// For each field in the variant, we store the relevant index into `self.fields` if any.
let mut field_id_to_id: Vec<Option<usize>> =
(0..variant.fields.len()).map(|_| None).collect();
let tys = cx
.list_variant_nonhidden_fields(pat.ty, variant)
.enumerate()
.map(|(i, (field, ty))| {
field_id_to_id[field.index()] = Some(i);
ty
});
let mut wilds: SmallVec<[_; 2]> =
tys.map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
for pat in subpatterns {
if let Some(i) = field_id_to_id[pat.field.index()] {
wilds[i] = self.lower_pat(&pat.pattern);
}
}
fields = cx.pattern_arena.alloc_from_iter(wilds);
}
_ => bug!("pattern has unexpected type: pat: {:?}, ty: {:?}", pat, pat.ty),
}
}
PatKind::Constant { value } => {
match pat.ty.kind() {
ty::Bool => {
ctor = match value.try_eval_bool(cx.tcx, cx.param_env) {
Some(b) => Bool(b),
None => Opaque(OpaqueId::new()),
};
fields = &[];
}
ty::Char | ty::Int(_) | ty::Uint(_) => {
ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
Some(bits) => IntRange(IntRange::from_bits(cx.tcx, pat.ty, bits)),
None => Opaque(OpaqueId::new()),
};
fields = &[];
}
ty::Float(ty::FloatTy::F32) => {
ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
Some(bits) => {
use rustc_apfloat::Float;
let value = rustc_apfloat::ieee::Single::from_bits(bits);
F32Range(value, value, RangeEnd::Included)
}
None => Opaque(OpaqueId::new()),
};
fields = &[];
}
ty::Float(ty::FloatTy::F64) => {
ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
Some(bits) => {
use rustc_apfloat::Float;
let value = rustc_apfloat::ieee::Double::from_bits(bits);
F64Range(value, value, RangeEnd::Included)
}
None => Opaque(OpaqueId::new()),
};
fields = &[];
}
ty::Ref(_, t, _) if t.is_str() => {
// We want a `&str` constant to behave like a `Deref` pattern, to be compatible
// with other `Deref` patterns. This could have been done in `const_to_pat`,
// but that causes issues with the rest of the matching code.
// So here, the constructor for a `"foo"` pattern is `&` (represented by
// `Single`), and has one field. That field has constructor `Str(value)` and no
// fields.
// Note: `t` is `str`, not `&str`.
let subpattern = DeconstructedPat::new(Str(*value), &[], *t, pat.span);
ctor = Single;
fields = singleton(subpattern)
}
// All constants that can be structurally matched have already been expanded
// into the corresponding `Pat`s by `const_to_pat`. Constants that remain are
// opaque.
_ => {
ctor = Opaque(OpaqueId::new());
fields = &[];
}
}
}
PatKind::Range(patrange) => {
let PatRange { lo, hi, end, .. } = patrange.as_ref();
let ty = pat.ty;
ctor = match ty.kind() {
ty::Char | ty::Int(_) | ty::Uint(_) => {
let lo = cx.lower_pat_range_bdy(*lo, ty);
let hi = cx.lower_pat_range_bdy(*hi, ty);
IntRange(IntRange::from_range(lo, hi, *end))
}
ty::Float(fty) => {
use rustc_apfloat::Float;
let lo = lo.as_finite().map(|c| c.eval_bits(cx.tcx, cx.param_env));
let hi = hi.as_finite().map(|c| c.eval_bits(cx.tcx, cx.param_env));
match fty {
ty::FloatTy::F32 => {
use rustc_apfloat::ieee::Single;
let lo = lo.map(Single::from_bits).unwrap_or(-Single::INFINITY);
let hi = hi.map(Single::from_bits).unwrap_or(Single::INFINITY);
F32Range(lo, hi, *end)
}
ty::FloatTy::F64 => {
use rustc_apfloat::ieee::Double;
let lo = lo.map(Double::from_bits).unwrap_or(-Double::INFINITY);
let hi = hi.map(Double::from_bits).unwrap_or(Double::INFINITY);
F64Range(lo, hi, *end)
}
}
}
_ => bug!("invalid type for range pattern: {}", ty),
};
fields = &[];
}
PatKind::Array { prefix, slice, suffix } | PatKind::Slice { prefix, slice, suffix } => {
let array_len = match pat.ty.kind() {
ty::Array(_, length) => {
Some(length.eval_target_usize(cx.tcx, cx.param_env) as usize)
}
ty::Slice(_) => None,
_ => span_bug!(pat.span, "bad ty {:?} for slice pattern", pat.ty),
};
let kind = if slice.is_some() {
SliceKind::VarLen(prefix.len(), suffix.len())
} else {
SliceKind::FixedLen(prefix.len() + suffix.len())
};
ctor = Slice(Slice::new(array_len, kind));
fields = cx.pattern_arena.alloc_from_iter(
prefix.iter().chain(suffix.iter()).map(|p| self.lower_pat(&*p)),
)
}
PatKind::Or { .. } => {
ctor = Or;
let pats = expand_or_pat(pat);
fields =
cx.pattern_arena.alloc_from_iter(pats.into_iter().map(|p| self.lower_pat(p)))
}
PatKind::Never => {
// FIXME(never_patterns): handle `!` in exhaustiveness. This is a sane default
// in the meantime.
ctor = Wildcard;
fields = &[];
}
PatKind::Error(_) => {
ctor = Opaque(OpaqueId::new());
fields = &[];
}
}
DeconstructedPat::new(ctor, fields, pat.ty, pat.span)
}
/// Convert back to a `thir::PatRangeBoundary` for diagnostic purposes.
/// Note: it is possible to get `isize/usize::MAX+1` here, as explained in the doc for
/// [`IntRange::split`]. This cannot be represented as a `Const`, so we represent it with
/// `PosInfinity`.
pub(crate) fn hoist_pat_range_bdy(
&self,
miint: MaybeInfiniteInt,
ty: Ty<'tcx>,
) -> PatRangeBoundary<'tcx> {
use MaybeInfiniteInt::*;
let tcx = self.tcx;
match miint {
NegInfinity => PatRangeBoundary::NegInfinity,
Finite(x) => {
let bias = MaybeInfiniteInt::signed_bias(tcx, ty);
let bits = x ^ bias;
let size = ty.primitive_size(tcx);
match Scalar::try_from_uint(bits, size) {
Some(scalar) => {
let value = mir::Const::from_scalar(tcx, scalar, ty);
PatRangeBoundary::Finite(value)
}
// The value doesn't fit. Since `x >= 0` and 0 always encodes the minimum value
// for a type, the problem isn't that the value is too small. So it must be too
// large.
None => PatRangeBoundary::PosInfinity,
}
}
JustAfterMax | PosInfinity => PatRangeBoundary::PosInfinity,
}
}
/// 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::*;
let cx = self;
let kind = if matches!((range.lo, range.hi), (NegInfinity, PosInfinity)) {
PatKind::Wild
} else if range.is_singleton() {
let lo = cx.hoist_pat_range_bdy(range.lo, ty);
let value = lo.as_finite().unwrap();
PatKind::Constant { value }
} else {
// We convert to an inclusive range for diagnostics.
let mut end = RangeEnd::Included;
let mut lo = cx.hoist_pat_range_bdy(range.lo, ty);
if matches!(lo, PatRangeBoundary::PosInfinity) {
// The only reason to get `PosInfinity` here is the special case where
// `hoist_pat_range_bdy` found `{u,i}size::MAX+1`. So the range denotes the
// fictitious values after `{u,i}size::MAX` (see [`IntRange::split`] for why we do
// this). We show this to the user as `usize::MAX..` which is slightly incorrect but
// probably clear enough.
let c = ty.numeric_max_val(cx.tcx).unwrap();
let value = mir::Const::from_ty_const(c, cx.tcx);
lo = PatRangeBoundary::Finite(value);
}
let hi = if matches!(range.hi, Finite(0)) {
// The range encodes `..ty::MIN`, so we can't convert it to an inclusive range.
end = RangeEnd::Excluded;
range.hi
} else {
range.hi.minus_one()
};
let hi = cx.hoist_pat_range_bdy(hi, ty);
PatKind::Range(Box::new(PatRange { lo, hi, end, ty }))
};
Pat { ty, span: DUMMY_SP, kind }
}
/// 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> {
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)));
let kind = match pat.ctor() {
Bool(b) => PatKind::Constant { value: mir::Const::from_bool(cx.tcx, *b) },
IntRange(range) => return self.hoist_pat_range(range, pat.ty()),
Single | Variant(_) => match pat.ty().kind() {
ty::Tuple(..) => PatKind::Leaf {
subpatterns: subpatterns
.enumerate()
.map(|(i, pattern)| FieldPat { field: FieldIdx::new(i), pattern })
.collect(),
},
ty::Adt(adt_def, _) if adt_def.is_box() => {
// Without `box_patterns`, the only legal pattern of type `Box` is `_` (outside
// of `std`). So this branch is only reachable when the feature is enabled and
// the pattern is a box pattern.
PatKind::Deref { subpattern: subpatterns.next().unwrap() }
}
ty::Adt(adt_def, args) => {
let variant_index =
MatchCheckCtxt::variant_index_for_adt(&pat.ctor(), *adt_def);
let variant = &adt_def.variant(variant_index);
let subpatterns = cx
.list_variant_nonhidden_fields(pat.ty(), variant)
.zip(subpatterns)
.map(|((field, _ty), pattern)| FieldPat { field, pattern })
.collect();
if adt_def.is_enum() {
PatKind::Variant { adt_def: *adt_def, args, variant_index, subpatterns }
} else {
PatKind::Leaf { subpatterns }
}
}
// Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
// be careful to reconstruct the correct constant pattern here. However a string
// literal pattern will never be reported as a non-exhaustiveness witness, so we
// ignore this issue.
ty::Ref(..) => PatKind::Deref { subpattern: subpatterns.next().unwrap() },
_ => bug!("unexpected ctor for type {:?} {:?}", pat.ctor(), pat.ty()),
},
Slice(slice) => {
match slice.kind {
SliceKind::FixedLen(_) => PatKind::Slice {
prefix: subpatterns.collect(),
slice: None,
suffix: Box::new([]),
},
SliceKind::VarLen(prefix, _) => {
let mut subpatterns = subpatterns.peekable();
let mut prefix: Vec<_> = subpatterns.by_ref().take(prefix).collect();
if slice.array_len.is_some() {
// Improves diagnostics a bit: if the type is a known-size array, instead
// of reporting `[x, _, .., _, y]`, we prefer to report `[x, .., y]`.
// This is incorrect if the size is not known, since `[_, ..]` captures
// arrays of lengths `>= 1` whereas `[..]` captures any length.
while !prefix.is_empty() && is_wildcard(prefix.last().unwrap()) {
prefix.pop();
}
while subpatterns.peek().is_some()
&& is_wildcard(subpatterns.peek().unwrap())
{
subpatterns.next();
}
}
let suffix: Box<[_]> = subpatterns.collect();
let wild = Pat::wildcard_from_ty(pat.ty());
PatKind::Slice {
prefix: prefix.into_boxed_slice(),
slice: Some(Box::new(wild)),
suffix,
}
}
}
}
&Str(value) => PatKind::Constant { value },
Wildcard | NonExhaustive | Hidden => PatKind::Wild,
Missing { .. } => bug!(
"trying to convert a `Missing` constructor into a `Pat`; this is probably a bug,
`Missing` should have been processed in `apply_constructors`"
),
F32Range(..) | F64Range(..) | Opaque(..) | Or => {
bug!("can't convert to pattern: {:?}", pat)
}
};
Pat { ty: pat.ty(), span: DUMMY_SP, kind }
}
/// Best-effort `Debug` implementation.
pub(crate) fn debug_pat(
f: &mut fmt::Formatter<'_>,
pat: &DeconstructedPat<'p, 'tcx>,
) -> fmt::Result {
let mut first = true;
let mut start_or_continue = |s| {
if first {
first = false;
""
} else {
s
}
};
let mut start_or_comma = || start_or_continue(", ");
match pat.ctor() {
Single | Variant(_) => match pat.ty().kind() {
ty::Adt(def, _) if def.is_box() => {
// Without `box_patterns`, the only legal pattern of type `Box` is `_` (outside
// of `std`). So this branch is only reachable when the feature is enabled and
// the pattern is a box pattern.
let subpattern = pat.iter_fields().next().unwrap();
write!(f, "box {subpattern:?}")
}
ty::Adt(..) | ty::Tuple(..) => {
let variant = match pat.ty().kind() {
ty::Adt(adt, _) => Some(
adt.variant(MatchCheckCtxt::variant_index_for_adt(pat.ctor(), *adt)),
),
ty::Tuple(_) => None,
_ => unreachable!(),
};
if let Some(variant) = variant {
write!(f, "{}", variant.name)?;
}
// Without `cx`, we can't know which field corresponds to which, so we can't
// get the names of the fields. Instead we just display everything as a tuple
// struct, which should be good enough.
write!(f, "(")?;
for p in pat.iter_fields() {
write!(f, "{}", start_or_comma())?;
write!(f, "{p:?}")?;
}
write!(f, ")")
}
// Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
// be careful to detect strings here. However a string literal pattern will never
// be reported as a non-exhaustiveness witness, so we can ignore this issue.
ty::Ref(_, _, mutbl) => {
let subpattern = pat.iter_fields().next().unwrap();
write!(f, "&{}{:?}", mutbl.prefix_str(), subpattern)
}
_ => write!(f, "_"),
},
Slice(slice) => {
let mut subpatterns = pat.iter_fields();
write!(f, "[")?;
match slice.kind {
SliceKind::FixedLen(_) => {
for p in subpatterns {
write!(f, "{}{:?}", start_or_comma(), p)?;
}
}
SliceKind::VarLen(prefix_len, _) => {
for p in subpatterns.by_ref().take(prefix_len) {
write!(f, "{}{:?}", start_or_comma(), p)?;
}
write!(f, "{}", start_or_comma())?;
write!(f, "..")?;
for p in subpatterns {
write!(f, "{}{:?}", start_or_comma(), p)?;
}
}
}
write!(f, "]")
}
Bool(b) => write!(f, "{b}"),
// Best-effort, will render signed ranges incorrectly
IntRange(range) => write!(f, "{range:?}"),
F32Range(lo, hi, end) => write!(f, "{lo}{end}{hi}"),
F64Range(lo, hi, end) => write!(f, "{lo}{end}{hi}"),
Str(value) => write!(f, "{value}"),
Opaque(..) => write!(f, "<constant pattern>"),
Or => {
for pat in pat.iter_fields() {
write!(f, "{}{:?}", start_or_continue(" | "), pat)?;
}
Ok(())
}
Wildcard | Missing { .. } | NonExhaustive | Hidden => write!(f, "_ : {:?}", pat.ty()),
}
}
}
/// 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>>) {
if let PatKind::Or { pats } = &pat.kind {
for pat in pats.iter() {
expand(pat, vec);
}
} else {
vec.push(pat)
}
}
let mut pats = Vec::new();
expand(pat, &mut pats);
pats
}

8
compiler/rustc_pattern_analysis/src/errors.rs
View file

@ -1,4 +1,4 @@
use crate::{pat::WitnessPat, usefulness::MatchCheckCtxt};
use crate::{cx::MatchCheckCtxt, pat::WitnessPat};
use rustc_errors::{AddToDiagnostic, Diagnostic, SubdiagnosticMessage};
use rustc_macros::{LintDiagnostic, Subdiagnostic};
@ -24,18 +24,18 @@ impl<'tcx> Uncovered<'tcx> {
cx: &MatchCheckCtxt<'p, 'tcx>,
witnesses: Vec<WitnessPat<'tcx>>,
) -> Self {
let witness_1 = witnesses.get(0).unwrap().to_diagnostic_pat(cx);
let witness_1 = cx.hoist_witness_pat(witnesses.get(0).unwrap());
Self {
span,
count: witnesses.len(),
// Substitute dummy values if witnesses is smaller than 3. These will never be read.
witness_2: witnesses
.get(1)
.map(|w| w.to_diagnostic_pat(cx))
.map(|w| cx.hoist_witness_pat(w))
.unwrap_or_else(|| witness_1.clone()),
witness_3: witnesses
.get(2)
.map(|w| w.to_diagnostic_pat(cx))
.map(|w| cx.hoist_witness_pat(w))
.unwrap_or_else(|| witness_1.clone()),
witness_1,
remainder: witnesses.len().saturating_sub(3),

1
compiler/rustc_pattern_analysis/src/lib.rs
View file

@ -1,6 +1,7 @@
//! Analysis of patterns, notably match exhaustiveness checking.
pub mod constructor;
pub mod cx;
pub mod errors;
pub mod pat;
pub mod usefulness;

581
compiler/rustc_pattern_analysis/src/pat.rs
View file

@ -2,175 +2,19 @@
//! fields. This file defines types that represent patterns in this way.
use std::cell::Cell;
use std::fmt;
use std::iter::once;
use smallvec::{smallvec, SmallVec};
use rustc_data_structures::captures::Captures;
use rustc_hir::RangeEnd;
use rustc_index::Idx;
use rustc_middle::mir;
use rustc_middle::thir::{FieldPat, Pat, PatKind, PatRange};
use rustc_middle::ty::{self, Ty, VariantDef};
use rustc_middle::ty::{self, Ty};
use rustc_span::{Span, DUMMY_SP};
use rustc_target::abi::FieldIdx;
use self::Constructor::*;
use self::SliceKind::*;
use crate::constructor::{Constructor, IntRange, MaybeInfiniteInt, OpaqueId, Slice, SliceKind};
use crate::usefulness::{MatchCheckCtxt, PatCtxt};
/// A value can be decomposed into a constructor applied to some fields. This struct represents
/// those fields, generalized to allow patterns in each field. See also `Constructor`.
///
/// This is constructed for a constructor using [`Fields::wildcards()`]. The idea is that
/// [`Fields::wildcards()`] constructs a list of fields where all entries are wildcards, and then
/// given a pattern we fill some of the fields with its subpatterns.
/// In the following example `Fields::wildcards` returns `[_, _, _, _]`. Then in
/// `extract_pattern_arguments` we fill some of the entries, and the result is
/// `[Some(0), _, _, _]`.
/// ```compile_fail,E0004
/// # fn foo() -> [Option<u8>; 4] { [None; 4] }
/// let x: [Option<u8>; 4] = foo();
/// match x {
/// [Some(0), ..] => {}
/// }
/// ```
///
/// Note that the number of fields of a constructor may not match the fields declared in the
/// original struct/variant. 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`. For that reason, when you have a `FieldIdx` you must use
/// `index_with_declared_idx`.
#[derive(Debug, Clone, Copy)]
pub struct Fields<'p, 'tcx> {
fields: &'p [DeconstructedPat<'p, 'tcx>],
}
impl<'p, 'tcx> Fields<'p, 'tcx> {
fn empty() -> Self {
Fields { fields: &[] }
}
fn singleton(cx: &MatchCheckCtxt<'p, 'tcx>, field: DeconstructedPat<'p, 'tcx>) -> Self {
let field: &_ = cx.pattern_arena.alloc(field);
Fields { fields: std::slice::from_ref(field) }
}
pub fn from_iter(
cx: &MatchCheckCtxt<'p, 'tcx>,
fields: impl IntoIterator<Item = DeconstructedPat<'p, 'tcx>>,
) -> Self {
let fields: &[_] = cx.pattern_arena.alloc_from_iter(fields);
Fields { fields }
}
fn wildcards_from_tys(
cx: &MatchCheckCtxt<'p, 'tcx>,
tys: impl IntoIterator<Item = Ty<'tcx>>,
) -> Self {
Fields::from_iter(cx, tys.into_iter().map(|ty| DeconstructedPat::wildcard(ty, DUMMY_SP)))
}
// 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.
pub(crate) fn list_variant_nonhidden_fields<'a>(
cx: &'a MatchCheckCtxt<'p, 'tcx>,
ty: Ty<'tcx>,
variant: &'a VariantDef,
) -> impl Iterator<Item = (FieldIdx, Ty<'tcx>)> + Captures<'a> + Captures<'p> {
let ty::Adt(adt, args) = ty.kind() else { bug!() };
// Whether we must not match the fields of this variant exhaustively.
let is_non_exhaustive = variant.is_field_list_non_exhaustive() && !adt.did().is_local();
variant.fields.iter().enumerate().filter_map(move |(i, field)| {
let ty = field.ty(cx.tcx, args);
// `field.ty()` doesn't normalize after substituting.
let ty = cx.tcx.normalize_erasing_regions(cx.param_env, ty);
let is_visible = adt.is_enum() || field.vis.is_accessible_from(cx.module, cx.tcx);
let is_uninhabited = cx.tcx.features().exhaustive_patterns && cx.is_uninhabited(ty);
if is_uninhabited && (!is_visible || is_non_exhaustive) {
None
} else {
Some((FieldIdx::new(i), ty))
}
})
}
/// Creates a new list of wildcard fields for a given constructor. The result must have a
/// length of `constructor.arity()`.
#[instrument(level = "trace")]
pub(super) fn wildcards(pcx: &PatCtxt<'_, 'p, 'tcx>, constructor: &Constructor<'tcx>) -> Self {
let ret = match constructor {
Single | Variant(_) => match pcx.ty.kind() {
ty::Tuple(fs) => Fields::wildcards_from_tys(pcx.cx, fs.iter()),
ty::Ref(_, rty, _) => Fields::wildcards_from_tys(pcx.cx, once(*rty)),
ty::Adt(adt, args) => {
if adt.is_box() {
// The only legal patterns of type `Box` (outside `std`) are `_` and box
// patterns. If we're here we can assume this is a box pattern.
Fields::wildcards_from_tys(pcx.cx, once(args.type_at(0)))
} else {
let variant = &adt.variant(constructor.variant_index_for_adt(*adt));
let tys = Fields::list_variant_nonhidden_fields(pcx.cx, pcx.ty, variant)
.map(|(_, ty)| ty);
Fields::wildcards_from_tys(pcx.cx, tys)
}
}
_ => bug!("Unexpected type for `Single` constructor: {:?}", pcx),
},
Slice(slice) => match *pcx.ty.kind() {
ty::Slice(ty) | ty::Array(ty, _) => {
let arity = slice.arity();
Fields::wildcards_from_tys(pcx.cx, (0..arity).map(|_| ty))
}
_ => bug!("bad slice pattern {:?} {:?}", constructor, pcx),
},
Bool(..)
| IntRange(..)
| F32Range(..)
| F64Range(..)
| Str(..)
| Opaque(..)
| NonExhaustive
| Hidden
| Missing { .. }
| Wildcard => Fields::empty(),
Or => {
bug!("called `Fields::wildcards` on an `Or` ctor")
}
};
debug!(?ret);
ret
}
/// Returns the list of patterns.
pub(super) fn iter_patterns<'a>(
&'a self,
) -> impl Iterator<Item = &'p DeconstructedPat<'p, 'tcx>> + Captures<'a> {
self.fields.iter()
}
}
/// 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>>) {
if let PatKind::Or { pats } = &pat.kind {
for pat in pats.iter() {
expand(pat, vec);
}
} else {
vec.push(pat)
}
}
let mut pats = Vec::new();
expand(pat, &mut pats);
pats
}
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.
@ -178,9 +22,14 @@ fn expand_or_pat<'p, 'tcx>(pat: &'p Pat<'tcx>) -> Vec<&'p Pat<'tcx>> {
/// during analysis. For this reason they cannot be cloned.
/// A `DeconstructedPat` will almost always come from user input; the only exception are some
/// `Wildcard`s introduced during specialization.
///
/// Note that the number of fields may not match the fields declared in the original struct/variant.
/// 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: Fields<'p, 'tcx>,
fields: &'p [DeconstructedPat<'p, 'tcx>],
ty: Ty<'tcx>,
span: Span,
/// Whether removing this arm would change the behavior of the match expression.
@ -189,227 +38,18 @@ pub struct DeconstructedPat<'p, 'tcx> {
impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
pub(super) fn wildcard(ty: Ty<'tcx>, span: Span) -> Self {
Self::new(Wildcard, Fields::empty(), ty, span)
Self::new(Wildcard, &[], ty, span)
}
pub(super) fn new(
ctor: Constructor<'tcx>,
fields: Fields<'p, 'tcx>,
fields: &'p [DeconstructedPat<'p, 'tcx>],
ty: Ty<'tcx>,
span: Span,
) -> Self {
DeconstructedPat { ctor, fields, ty, span, useful: Cell::new(false) }
}
/// Note: the input patterns must have been lowered through
/// `rustc_mir_build::thir::pattern::check_match::MatchVisitor::lower_pattern`.
pub fn from_pat(cx: &MatchCheckCtxt<'p, 'tcx>, pat: &Pat<'tcx>) -> Self {
let mkpat = |pat| DeconstructedPat::from_pat(cx, pat);
let ctor;
let fields;
match &pat.kind {
PatKind::AscribeUserType { subpattern, .. }
| PatKind::InlineConstant { subpattern, .. } => return mkpat(subpattern),
PatKind::Binding { subpattern: Some(subpat), .. } => return mkpat(subpat),
PatKind::Binding { subpattern: None, .. } | PatKind::Wild => {
ctor = Wildcard;
fields = Fields::empty();
}
PatKind::Deref { subpattern } => {
ctor = Single;
fields = Fields::singleton(cx, mkpat(subpattern));
}
PatKind::Leaf { subpatterns } | PatKind::Variant { subpatterns, .. } => {
match pat.ty.kind() {
ty::Tuple(fs) => {
ctor = Single;
let mut wilds: SmallVec<[_; 2]> =
fs.iter().map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
for pat in subpatterns {
wilds[pat.field.index()] = mkpat(&pat.pattern);
}
fields = Fields::from_iter(cx, wilds);
}
ty::Adt(adt, args) if adt.is_box() => {
// The only legal patterns of type `Box` (outside `std`) are `_` and box
// patterns. If we're here we can assume this is a box pattern.
// FIXME(Nadrieril): A `Box` can in theory be matched either with `Box(_,
// _)` or a box pattern. As a hack to avoid an ICE with the former, we
// ignore other fields than the first one. This will trigger an error later
// anyway.
// See https://github.com/rust-lang/rust/issues/82772 ,
// explanation: https://github.com/rust-lang/rust/pull/82789#issuecomment-796921977
// The problem is that we can't know from the type whether we'll match
// normally or through box-patterns. We'll have to figure out a proper
// solution when we introduce generalized deref patterns. Also need to
// prevent mixing of those two options.
let pattern = subpatterns.into_iter().find(|pat| pat.field.index() == 0);
let pat = if let Some(pat) = pattern {
mkpat(&pat.pattern)
} else {
DeconstructedPat::wildcard(args.type_at(0), pat.span)
};
ctor = Single;
fields = Fields::singleton(cx, pat);
}
ty::Adt(adt, _) => {
ctor = match pat.kind {
PatKind::Leaf { .. } => Single,
PatKind::Variant { variant_index, .. } => Variant(variant_index),
_ => bug!(),
};
let variant = &adt.variant(ctor.variant_index_for_adt(*adt));
// For each field in the variant, we store the relevant index into `self.fields` if any.
let mut field_id_to_id: Vec<Option<usize>> =
(0..variant.fields.len()).map(|_| None).collect();
let tys = Fields::list_variant_nonhidden_fields(cx, pat.ty, variant)
.enumerate()
.map(|(i, (field, ty))| {
field_id_to_id[field.index()] = Some(i);
ty
});
let mut wilds: SmallVec<[_; 2]> =
tys.map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
for pat in subpatterns {
if let Some(i) = field_id_to_id[pat.field.index()] {
wilds[i] = mkpat(&pat.pattern);
}
}
fields = Fields::from_iter(cx, wilds);
}
_ => bug!("pattern has unexpected type: pat: {:?}, ty: {:?}", pat, pat.ty),
}
}
PatKind::Constant { value } => {
match pat.ty.kind() {
ty::Bool => {
ctor = match value.try_eval_bool(cx.tcx, cx.param_env) {
Some(b) => Bool(b),
None => Opaque(OpaqueId::new()),
};
fields = Fields::empty();
}
ty::Char | ty::Int(_) | ty::Uint(_) => {
ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
Some(bits) => IntRange(IntRange::from_bits(cx.tcx, pat.ty, bits)),
None => Opaque(OpaqueId::new()),
};
fields = Fields::empty();
}
ty::Float(ty::FloatTy::F32) => {
ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
Some(bits) => {
use rustc_apfloat::Float;
let value = rustc_apfloat::ieee::Single::from_bits(bits);
F32Range(value, value, RangeEnd::Included)
}
None => Opaque(OpaqueId::new()),
};
fields = Fields::empty();
}
ty::Float(ty::FloatTy::F64) => {
ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
Some(bits) => {
use rustc_apfloat::Float;
let value = rustc_apfloat::ieee::Double::from_bits(bits);
F64Range(value, value, RangeEnd::Included)
}
None => Opaque(OpaqueId::new()),
};
fields = Fields::empty();
}
ty::Ref(_, t, _) if t.is_str() => {
// We want a `&str` constant to behave like a `Deref` pattern, to be compatible
// with other `Deref` patterns. This could have been done in `const_to_pat`,
// but that causes issues with the rest of the matching code.
// So here, the constructor for a `"foo"` pattern is `&` (represented by
// `Single`), and has one field. That field has constructor `Str(value)` and no
// fields.
// Note: `t` is `str`, not `&str`.
let subpattern =
DeconstructedPat::new(Str(*value), Fields::empty(), *t, pat.span);
ctor = Single;
fields = Fields::singleton(cx, subpattern)
}
// All constants that can be structurally matched have already been expanded
// into the corresponding `Pat`s by `const_to_pat`. Constants that remain are
// opaque.
_ => {
ctor = Opaque(OpaqueId::new());
fields = Fields::empty();
}
}
}
PatKind::Range(patrange) => {
let PatRange { lo, hi, end, .. } = patrange.as_ref();
let ty = pat.ty;
ctor = match ty.kind() {
ty::Char | ty::Int(_) | ty::Uint(_) => {
let lo =
MaybeInfiniteInt::from_pat_range_bdy(*lo, ty, cx.tcx, cx.param_env);
let hi =
MaybeInfiniteInt::from_pat_range_bdy(*hi, ty, cx.tcx, cx.param_env);
IntRange(IntRange::from_range(lo, hi, *end))
}
ty::Float(fty) => {
use rustc_apfloat::Float;
let lo = lo.as_finite().map(|c| c.eval_bits(cx.tcx, cx.param_env));
let hi = hi.as_finite().map(|c| c.eval_bits(cx.tcx, cx.param_env));
match fty {
ty::FloatTy::F32 => {
use rustc_apfloat::ieee::Single;
let lo = lo.map(Single::from_bits).unwrap_or(-Single::INFINITY);
let hi = hi.map(Single::from_bits).unwrap_or(Single::INFINITY);
F32Range(lo, hi, *end)
}
ty::FloatTy::F64 => {
use rustc_apfloat::ieee::Double;
let lo = lo.map(Double::from_bits).unwrap_or(-Double::INFINITY);
let hi = hi.map(Double::from_bits).unwrap_or(Double::INFINITY);
F64Range(lo, hi, *end)
}
}
}
_ => bug!("invalid type for range pattern: {}", ty),
};
fields = Fields::empty();
}
PatKind::Array { prefix, slice, suffix } | PatKind::Slice { prefix, slice, suffix } => {
let array_len = match pat.ty.kind() {
ty::Array(_, length) => {
Some(length.eval_target_usize(cx.tcx, cx.param_env) as usize)
}
ty::Slice(_) => None,
_ => span_bug!(pat.span, "bad ty {:?} for slice pattern", pat.ty),
};
let kind = if slice.is_some() {
VarLen(prefix.len(), suffix.len())
} else {
FixedLen(prefix.len() + suffix.len())
};
ctor = Slice(Slice::new(array_len, kind));
fields =
Fields::from_iter(cx, prefix.iter().chain(suffix.iter()).map(|p| mkpat(&*p)));
}
PatKind::Or { .. } => {
ctor = Or;
let pats = expand_or_pat(pat);
fields = Fields::from_iter(cx, pats.into_iter().map(mkpat));
}
PatKind::Never => {
// FIXME(never_patterns): handle `!` in exhaustiveness. This is a sane default
// in the meantime.
ctor = Wildcard;
fields = Fields::empty();
}
PatKind::Error(_) => {
ctor = Opaque(OpaqueId::new());
fields = Fields::empty();
}
}
DeconstructedPat::new(ctor, fields, pat.ty, pat.span)
}
pub(super) fn is_or_pat(&self) -> bool {
matches!(self.ctor, Or)
}
@ -435,7 +75,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
pub fn iter_fields<'a>(
&'a self,
) -> impl Iterator<Item = &'p DeconstructedPat<'p, 'tcx>> + Captures<'a> {
self.fields.iter_patterns()
self.fields.iter()
}
/// Specialize this pattern with a constructor.
@ -448,7 +88,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
match (&self.ctor, other_ctor) {
(Wildcard, _) => {
// We return a wildcard for each field of `other_ctor`.
Fields::wildcards(pcx, other_ctor).iter_patterns().collect()
pcx.cx.ctor_wildcard_fields(other_ctor, pcx.ty).iter().collect()
}
(Slice(self_slice), Slice(other_slice))
if self_slice.arity() != other_slice.arity() =>
@ -464,8 +104,8 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
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.fields[..prefix];
let suffix = &self.fields.fields[self_slice.arity() - suffix..];
let prefix = &self.fields[..prefix];
let suffix = &self.fields[self_slice.arity() - suffix..];
let wildcard: &_ = pcx
.cx
.pattern_arena
@ -476,7 +116,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
}
}
}
_ => self.fields.iter_patterns().collect(),
_ => self.fields.iter().collect(),
}
}
@ -521,94 +161,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
/// `Display` impl.
impl<'p, 'tcx> fmt::Debug for DeconstructedPat<'p, 'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// Printing lists is a chore.
let mut first = true;
let mut start_or_continue = |s| {
if first {
first = false;
""
} else {
s
}
};
let mut start_or_comma = || start_or_continue(", ");
match &self.ctor {
Single | Variant(_) => match self.ty.kind() {
ty::Adt(def, _) if def.is_box() => {
// Without `box_patterns`, the only legal pattern of type `Box` is `_` (outside
// of `std`). So this branch is only reachable when the feature is enabled and
// the pattern is a box pattern.
let subpattern = self.iter_fields().next().unwrap();
write!(f, "box {subpattern:?}")
}
ty::Adt(..) | ty::Tuple(..) => {
let variant = match self.ty.kind() {
ty::Adt(adt, _) => Some(adt.variant(self.ctor.variant_index_for_adt(*adt))),
ty::Tuple(_) => None,
_ => unreachable!(),
};
if let Some(variant) = variant {
write!(f, "{}", variant.name)?;
}
// Without `cx`, we can't know which field corresponds to which, so we can't
// get the names of the fields. Instead we just display everything as a tuple
// struct, which should be good enough.
write!(f, "(")?;
for p in self.iter_fields() {
write!(f, "{}", start_or_comma())?;
write!(f, "{p:?}")?;
}
write!(f, ")")
}
// Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
// be careful to detect strings here. However a string literal pattern will never
// be reported as a non-exhaustiveness witness, so we can ignore this issue.
ty::Ref(_, _, mutbl) => {
let subpattern = self.iter_fields().next().unwrap();
write!(f, "&{}{:?}", mutbl.prefix_str(), subpattern)
}
_ => write!(f, "_"),
},
Slice(slice) => {
let mut subpatterns = self.fields.iter_patterns();
write!(f, "[")?;
match slice.kind {
FixedLen(_) => {
for p in subpatterns {
write!(f, "{}{:?}", start_or_comma(), p)?;
}
}
VarLen(prefix_len, _) => {
for p in subpatterns.by_ref().take(prefix_len) {
write!(f, "{}{:?}", start_or_comma(), p)?;
}
write!(f, "{}", start_or_comma())?;
write!(f, "..")?;
for p in subpatterns {
write!(f, "{}{:?}", start_or_comma(), p)?;
}
}
}
write!(f, "]")
}
Bool(b) => write!(f, "{b}"),
// Best-effort, will render signed ranges incorrectly
IntRange(range) => write!(f, "{range:?}"),
F32Range(lo, hi, end) => write!(f, "{lo}{end}{hi}"),
F64Range(lo, hi, end) => write!(f, "{lo}{end}{hi}"),
Str(value) => write!(f, "{value}"),
Opaque(..) => write!(f, "<constant pattern>"),
Or => {
for pat in self.iter_fields() {
write!(f, "{}{:?}", start_or_continue(" | "), pat)?;
}
Ok(())
}
Wildcard | Missing { .. } | NonExhaustive | Hidden => write!(f, "_ : {:?}", self.ty),
}
MatchCheckCtxt::debug_pat(f, self)
}
}
@ -633,11 +186,9 @@ impl<'tcx> WitnessPat<'tcx> {
/// For example, if `ctor` is a `Constructor::Variant` for `Option::Some`, we get the pattern
/// `Some(_)`.
pub(super) fn wild_from_ctor(pcx: &PatCtxt<'_, '_, 'tcx>, ctor: Constructor<'tcx>) -> Self {
// Reuse `Fields::wildcards` to get the types.
let fields = Fields::wildcards(pcx, &ctor)
.iter_patterns()
.map(|deco_pat| Self::wildcard(deco_pat.ty()))
.collect();
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();
Self::new(ctor, fields, pcx.ty)
}
@ -648,96 +199,6 @@ impl<'tcx> WitnessPat<'tcx> {
self.ty
}
/// Convert back to a `thir::Pat` for diagnostic purposes. This panics for patterns that don't
/// appear in diagnostics, like float ranges.
pub fn to_diagnostic_pat(&self, cx: &MatchCheckCtxt<'_, 'tcx>) -> Pat<'tcx> {
let is_wildcard = |pat: &Pat<'_>| matches!(pat.kind, PatKind::Wild);
let mut subpatterns = self.iter_fields().map(|p| Box::new(p.to_diagnostic_pat(cx)));
let kind = match &self.ctor {
Bool(b) => PatKind::Constant { value: mir::Const::from_bool(cx.tcx, *b) },
IntRange(range) => return range.to_diagnostic_pat(self.ty, cx.tcx),
Single | Variant(_) => match self.ty.kind() {
ty::Tuple(..) => PatKind::Leaf {
subpatterns: subpatterns
.enumerate()
.map(|(i, pattern)| FieldPat { field: FieldIdx::new(i), pattern })
.collect(),
},
ty::Adt(adt_def, _) if adt_def.is_box() => {
// Without `box_patterns`, the only legal pattern of type `Box` is `_` (outside
// of `std`). So this branch is only reachable when the feature is enabled and
// the pattern is a box pattern.
PatKind::Deref { subpattern: subpatterns.next().unwrap() }
}
ty::Adt(adt_def, args) => {
let variant_index = self.ctor.variant_index_for_adt(*adt_def);
let variant = &adt_def.variant(variant_index);
let subpatterns = Fields::list_variant_nonhidden_fields(cx, self.ty, variant)
.zip(subpatterns)
.map(|((field, _ty), pattern)| FieldPat { field, pattern })
.collect();
if adt_def.is_enum() {
PatKind::Variant { adt_def: *adt_def, args, variant_index, subpatterns }
} else {
PatKind::Leaf { subpatterns }
}
}
// Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
// be careful to reconstruct the correct constant pattern here. However a string
// literal pattern will never be reported as a non-exhaustiveness witness, so we
// ignore this issue.
ty::Ref(..) => PatKind::Deref { subpattern: subpatterns.next().unwrap() },
_ => bug!("unexpected ctor for type {:?} {:?}", self.ctor, self.ty),
},
Slice(slice) => {
match slice.kind {
FixedLen(_) => PatKind::Slice {
prefix: subpatterns.collect(),
slice: None,
suffix: Box::new([]),
},
VarLen(prefix, _) => {
let mut subpatterns = subpatterns.peekable();
let mut prefix: Vec<_> = subpatterns.by_ref().take(prefix).collect();
if slice.array_len.is_some() {
// Improves diagnostics a bit: if the type is a known-size array, instead
// of reporting `[x, _, .., _, y]`, we prefer to report `[x, .., y]`.
// This is incorrect if the size is not known, since `[_, ..]` captures
// arrays of lengths `>= 1` whereas `[..]` captures any length.
while !prefix.is_empty() && is_wildcard(prefix.last().unwrap()) {
prefix.pop();
}
while subpatterns.peek().is_some()
&& is_wildcard(subpatterns.peek().unwrap())
{
subpatterns.next();
}
}
let suffix: Box<[_]> = subpatterns.collect();
let wild = Pat::wildcard_from_ty(self.ty);
PatKind::Slice {
prefix: prefix.into_boxed_slice(),
slice: Some(Box::new(wild)),
suffix,
}
}
}
}
&Str(value) => PatKind::Constant { value },
Wildcard | NonExhaustive | Hidden => PatKind::Wild,
Missing { .. } => bug!(
"trying to convert a `Missing` constructor into a `Pat`; this is probably a bug,
`Missing` should have been processed in `apply_constructors`"
),
F32Range(..) | F64Range(..) | Opaque(..) | Or => {
bug!("can't convert to pattern: {:?}", self)
}
};
Pat { ty: self.ty, span: DUMMY_SP, kind }
}
pub fn iter_fields<'a>(&'a self) -> impl Iterator<Item = &'a WitnessPat<'tcx>> {
self.fields.iter()
}

75
compiler/rustc_pattern_analysis/src/usefulness.rs
View file

@ -551,66 +551,27 @@
//! I (Nadrieril) prefer to put new tests in `ui/pattern/usefulness` unless there's a specific
//! reason not to, for example if they crucially depend on a particular feature like `or_patterns`.
use self::ValidityConstraint::*;
use smallvec::{smallvec, SmallVec};
use std::fmt;
use rustc_data_structures::{captures::Captures, stack::ensure_sufficient_stack};
use rustc_hir::HirId;
use rustc_middle::ty::{self, Ty};
use rustc_session::lint;
use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
use rustc_span::{Span, DUMMY_SP};
use crate::constructor::{
Constructor, ConstructorSet, IntRange, MaybeInfiniteInt, SplitConstructorSet,
};
use crate::cx::MatchCheckCtxt;
use crate::errors::{
NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Overlap,
OverlappingRangeEndpoints, Uncovered,
};
use crate::pat::{DeconstructedPat, WitnessPat};
use rustc_arena::TypedArena;
use rustc_data_structures::{captures::Captures, stack::ensure_sufficient_stack};
use rustc_hir::def_id::DefId;
use rustc_hir::HirId;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_session::lint;
use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
use rustc_span::{Span, DUMMY_SP};
use smallvec::{smallvec, SmallVec};
use std::fmt;
pub struct MatchCheckCtxt<'p, 'tcx> {
pub tcx: TyCtxt<'tcx>,
/// The module in which the match occurs. This is necessary for
/// checking inhabited-ness of types because whether a type is (visibly)
/// inhabited can depend on whether it was defined in the current module or
/// not. E.g., `struct Foo { _private: ! }` cannot be seen to be empty
/// outside its module and should not be matchable with an empty match statement.
pub module: DefId,
pub param_env: ty::ParamEnv<'tcx>,
pub pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
/// Lint level at the match.
pub match_lint_level: HirId,
/// The span of the whole match, if applicable.
pub whole_match_span: Option<Span>,
/// Span of the scrutinee.
pub scrut_span: Span,
/// Only produce `NON_EXHAUSTIVE_OMITTED_PATTERNS` lint on refutable patterns.
pub refutable: bool,
/// Whether the data at the scrutinee is known to be valid. This is false if the scrutinee comes
/// from a union field, a pointer deref, or a reference deref (pending opsem decisions).
pub known_valid_scrutinee: bool,
}
impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
pub(super) fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
!ty.is_inhabited_from(self.tcx, self.module, self.param_env)
}
/// 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() {
ty::Adt(def, ..) => {
def.is_enum() && def.is_variant_list_non_exhaustive() && !def.did().is_local()
}
_ => false,
}
}
}
use self::ValidityConstraint::*;
#[derive(Copy, Clone)]
pub(super) struct PatCtxt<'a, 'p, 'tcx> {
@ -1244,7 +1205,9 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>(
// Analyze the constructors present in this column.
let ctors = matrix.heads().map(|p| p.ctor());
let split_set = ConstructorSet::for_ty(cx, ty).split(pcx, ctors);
let ctors_for_ty = &cx.ctors_for_ty(ty);
let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. }); // For diagnostics.
let split_set = ctors_for_ty.split(pcx, ctors);
let all_missing = split_set.present.is_empty();
// Build the set of constructors we will specialize with. It must cover the whole type.
@ -1259,7 +1222,7 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>(
}
// Decide what constructors to report.
let always_report_all = is_top_level && !IntRange::is_integral(pcx.ty);
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() =>
@ -1362,7 +1325,7 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
/// Do constructor splitting on the constructors of the column.
fn analyze_ctors(&self, pcx: &PatCtxt<'_, 'p, 'tcx>) -> SplitConstructorSet<'tcx> {
let column_ctors = self.patterns.iter().map(|p| p.ctor());
ConstructorSet::for_ty(pcx.cx, pcx.ty).split(pcx, column_ctors)
pcx.cx.ctors_for_ty(pcx.ty).split(pcx, column_ctors)
}
fn iter<'a>(&'a self) -> impl Iterator<Item = &'p DeconstructedPat<'p, 'tcx>> + Captures<'a> {
@ -1470,9 +1433,9 @@ fn lint_overlapping_range_endpoints<'p, 'tcx>(
let set = column.analyze_ctors(pcx);
if IntRange::is_integral(ty) {
if matches!(ty.kind(), ty::Char | ty::Int(_) | ty::Uint(_)) {
let emit_lint = |overlap: &IntRange, this_span: Span, overlapped_spans: &[Span]| {
let overlap_as_pat = overlap.to_diagnostic_pat(ty, cx.tcx);
let overlap_as_pat = cx.hoist_pat_range(overlap, ty);
let overlaps: Vec<_> = overlapped_spans
.iter()
.copied()