1 //! Validation of patterns/matches.
8 pub(crate) use self::check_match::check_match;
10 use crate::thir::util::UserAnnotatedTyHelpers;
12 use rustc_errors::struct_span_err;
14 use rustc_hir::def::{CtorOf, DefKind, Res};
15 use rustc_hir::pat_util::EnumerateAndAdjustIterator;
16 use rustc_hir::RangeEnd;
17 use rustc_index::vec::Idx;
18 use rustc_middle::mir::interpret::{get_slice_bytes, ConstValue};
19 use rustc_middle::mir::interpret::{ErrorHandled, LitToConstError, LitToConstInput};
20 use rustc_middle::mir::UserTypeProjection;
21 use rustc_middle::mir::{BorrowKind, Field, Mutability};
22 use rustc_middle::thir::{Ascription, BindingMode, FieldPat, Pat, PatKind, PatRange, PatTyProj};
23 use rustc_middle::ty::subst::{GenericArg, SubstsRef};
24 use rustc_middle::ty::{self, AdtDef, ConstKind, DefIdTree, Region, Ty, TyCtxt, UserType};
25 use rustc_span::{Span, Symbol};
27 use std::cmp::Ordering;
29 #[derive(Clone, Debug)]
30 crate enum PatternError {
31 AssocConstInPattern(Span),
32 ConstParamInPattern(Span),
33 StaticInPattern(Span),
37 crate struct PatCtxt<'a, 'tcx> {
38 crate tcx: TyCtxt<'tcx>,
39 crate param_env: ty::ParamEnv<'tcx>,
40 crate typeck_results: &'a ty::TypeckResults<'tcx>,
41 crate errors: Vec<PatternError>,
42 include_lint_checks: bool,
45 crate fn pat_from_hir<'a, 'tcx>(
47 param_env: ty::ParamEnv<'tcx>,
48 typeck_results: &'a ty::TypeckResults<'tcx>,
49 pat: &'tcx hir::Pat<'tcx>,
51 let mut pcx = PatCtxt::new(tcx, param_env, typeck_results);
52 let result = pcx.lower_pattern(pat);
53 if !pcx.errors.is_empty() {
54 let msg = format!("encountered errors lowering pattern: {:?}", pcx.errors);
55 tcx.sess.delay_span_bug(pat.span, &msg);
57 debug!("pat_from_hir({:?}) = {:?}", pat, result);
61 impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
64 param_env: ty::ParamEnv<'tcx>,
65 typeck_results: &'a ty::TypeckResults<'tcx>,
67 PatCtxt { tcx, param_env, typeck_results, errors: vec![], include_lint_checks: false }
70 crate fn include_lint_checks(&mut self) -> &mut Self {
71 self.include_lint_checks = true;
75 crate fn lower_pattern(&mut self, pat: &'tcx hir::Pat<'tcx>) -> Pat<'tcx> {
76 // When implicit dereferences have been inserted in this pattern, the unadjusted lowered
77 // pattern has the type that results *after* dereferencing. For example, in this code:
80 // match &&Some(0i32) {
81 // Some(n) => { ... },
86 // the type assigned to `Some(n)` in `unadjusted_pat` would be `Option<i32>` (this is
87 // determined in rustc_typeck::check::match). The adjustments would be
89 // `vec![&&Option<i32>, &Option<i32>]`.
91 // Applying the adjustments, we want to instead output `&&Some(n)` (as a THIR pattern). So
92 // we wrap the unadjusted pattern in `PatKind::Deref` repeatedly, consuming the
93 // adjustments in *reverse order* (last-in-first-out, so that the last `Deref` inserted
94 // gets the least-dereferenced type).
95 let unadjusted_pat = self.lower_pattern_unadjusted(pat);
96 self.typeck_results.pat_adjustments().get(pat.hir_id).unwrap_or(&vec![]).iter().rev().fold(
99 debug!("{:?}: wrapping pattern with type {:?}", pat, ref_ty);
103 kind: Box::new(PatKind::Deref { subpattern: pat }),
111 expr: &'tcx hir::Expr<'tcx>,
112 ) -> (PatKind<'tcx>, Option<Ascription<'tcx>>) {
113 match self.lower_lit(expr) {
114 PatKind::AscribeUserType { ascription, subpattern: Pat { kind: box kind, .. } } => {
115 (kind, Some(ascription))
117 kind => (kind, None),
121 fn lower_pattern_range(
129 assert_eq!(lo.ty(), ty);
130 assert_eq!(hi.ty(), ty);
131 let cmp = compare_const_vals(self.tcx, lo, hi, self.param_env, ty);
133 // `x..y` where `x < y`.
134 // Non-empty because the range includes at least `x`.
135 (RangeEnd::Excluded, Some(Ordering::Less)) => PatKind::Range(PatRange { lo, hi, end }),
136 // `x..y` where `x >= y`. The range is empty => error.
137 (RangeEnd::Excluded, _) => {
142 "lower range bound must be less than upper"
147 // `x..=y` where `x == y`.
148 (RangeEnd::Included, Some(Ordering::Equal)) => PatKind::Constant { value: lo },
149 // `x..=y` where `x < y`.
150 (RangeEnd::Included, Some(Ordering::Less)) => PatKind::Range(PatRange { lo, hi, end }),
151 // `x..=y` where `x > y` hence the range is empty => error.
152 (RangeEnd::Included, _) => {
153 let mut err = struct_span_err!(
157 "lower range bound must be less than or equal to upper"
159 err.span_label(span, "lower bound larger than upper bound");
160 if self.tcx.sess.teach(&err.get_code().unwrap()) {
162 "When matching against a range, the compiler \
163 verifies that the range is non-empty. Range \
164 patterns include both end-points, so this is \
165 equivalent to requiring the start of the range \
166 to be less than or equal to the end of the range.",
175 fn normalize_range_pattern_ends(
178 lo: Option<&PatKind<'tcx>>,
179 hi: Option<&PatKind<'tcx>>,
180 ) -> Option<(ty::Const<'tcx>, ty::Const<'tcx>)> {
182 (Some(PatKind::Constant { value: lo }), Some(PatKind::Constant { value: hi })) => {
185 (Some(PatKind::Constant { value: lo }), None) => {
186 Some((*lo, ty.numeric_max_val(self.tcx)?))
188 (None, Some(PatKind::Constant { value: hi })) => {
189 Some((ty.numeric_min_val(self.tcx)?, *hi))
195 fn lower_pattern_unadjusted(&mut self, pat: &'tcx hir::Pat<'tcx>) -> Pat<'tcx> {
196 let mut ty = self.typeck_results.node_type(pat.hir_id);
198 let kind = match pat.kind {
199 hir::PatKind::Wild => PatKind::Wild,
201 hir::PatKind::Lit(value) => self.lower_lit(value),
203 hir::PatKind::Range(ref lo_expr, ref hi_expr, end) => {
204 let (lo_expr, hi_expr) = (lo_expr.as_deref(), hi_expr.as_deref());
205 let lo_span = lo_expr.map_or(pat.span, |e| e.span);
206 let lo = lo_expr.map(|e| self.lower_range_expr(e));
207 let hi = hi_expr.map(|e| self.lower_range_expr(e));
209 let (lp, hp) = (lo.as_ref().map(|x| &x.0), hi.as_ref().map(|x| &x.0));
210 let mut kind = match self.normalize_range_pattern_ends(ty, lp, hp) {
211 Some((lc, hc)) => self.lower_pattern_range(ty, lc, hc, end, lo_span),
214 "found bad range pattern `{:?}` outside of error recovery",
217 self.tcx.sess.delay_span_bug(pat.span, msg);
222 // If we are handling a range with associated constants (e.g.
223 // `Foo::<'a>::A..=Foo::B`), we need to put the ascriptions for the associated
224 // constants somewhere. Have them on the range pattern.
225 for end in &[lo, hi] {
226 if let Some((_, Some(ascription))) = end {
227 let subpattern = Pat { span: pat.span, ty, kind: Box::new(kind) };
228 kind = PatKind::AscribeUserType { ascription: *ascription, subpattern };
235 hir::PatKind::Path(ref qpath) => {
236 return self.lower_path(qpath, pat.hir_id, pat.span);
239 hir::PatKind::Ref(ref subpattern, _) | hir::PatKind::Box(ref subpattern) => {
240 PatKind::Deref { subpattern: self.lower_pattern(subpattern) }
243 hir::PatKind::Slice(ref prefix, ref slice, ref suffix) => {
244 self.slice_or_array_pattern(pat.span, ty, prefix, slice, suffix)
247 hir::PatKind::Tuple(ref pats, ddpos) => {
248 let ty::Tuple(ref tys) = ty.kind() else {
249 span_bug!(pat.span, "unexpected type for tuple pattern: {:?}", ty);
251 let subpatterns = self.lower_tuple_subpats(pats, tys.len(), ddpos);
252 PatKind::Leaf { subpatterns }
255 hir::PatKind::Binding(_, id, ident, ref sub) => {
260 .expect("missing binding mode");
261 let (mutability, mode) = match bm {
262 ty::BindByValue(mutbl) => (mutbl, BindingMode::ByValue),
263 ty::BindByReference(hir::Mutability::Mut) => (
265 BindingMode::ByRef(BorrowKind::Mut { allow_two_phase_borrow: false }),
267 ty::BindByReference(hir::Mutability::Not) => {
268 (Mutability::Not, BindingMode::ByRef(BorrowKind::Shared))
272 // A ref x pattern is the same node used for x, and as such it has
273 // x's type, which is &T, where we want T (the type being matched).
275 if let ty::BindByReference(_) = bm {
276 if let ty::Ref(_, rty, _) = ty.kind() {
279 bug!("`ref {}` has wrong type {}", ident, ty);
289 subpattern: self.lower_opt_pattern(sub),
290 is_primary: id == pat.hir_id,
294 hir::PatKind::TupleStruct(ref qpath, ref pats, ddpos) => {
295 let res = self.typeck_results.qpath_res(qpath, pat.hir_id);
296 let ty::Adt(adt_def, _) = ty.kind() else {
297 span_bug!(pat.span, "tuple struct pattern not applied to an ADT {:?}", ty);
299 let variant_def = adt_def.variant_of_res(res);
300 let subpatterns = self.lower_tuple_subpats(pats, variant_def.fields.len(), ddpos);
301 self.lower_variant_or_leaf(res, pat.hir_id, pat.span, ty, subpatterns)
304 hir::PatKind::Struct(ref qpath, ref fields, _) => {
305 let res = self.typeck_results.qpath_res(qpath, pat.hir_id);
306 let subpatterns = fields
308 .map(|field| FieldPat {
309 field: Field::new(self.tcx.field_index(field.hir_id, self.typeck_results)),
310 pattern: self.lower_pattern(&field.pat),
314 self.lower_variant_or_leaf(res, pat.hir_id, pat.span, ty, subpatterns)
317 hir::PatKind::Or(ref pats) => PatKind::Or { pats: self.lower_patterns(pats) },
320 Pat { span: pat.span, ty, kind: Box::new(kind) }
323 fn lower_tuple_subpats(
325 pats: &'tcx [hir::Pat<'tcx>],
327 gap_pos: Option<usize>,
328 ) -> Vec<FieldPat<'tcx>> {
330 .enumerate_and_adjust(expected_len, gap_pos)
331 .map(|(i, subpattern)| FieldPat {
332 field: Field::new(i),
333 pattern: self.lower_pattern(subpattern),
338 fn lower_patterns(&mut self, pats: &'tcx [hir::Pat<'tcx>]) -> Vec<Pat<'tcx>> {
339 pats.iter().map(|p| self.lower_pattern(p)).collect()
342 fn lower_opt_pattern(&mut self, pat: &'tcx Option<&'tcx hir::Pat<'tcx>>) -> Option<Pat<'tcx>> {
343 pat.as_ref().map(|p| self.lower_pattern(p))
346 fn slice_or_array_pattern(
350 prefix: &'tcx [hir::Pat<'tcx>],
351 slice: &'tcx Option<&'tcx hir::Pat<'tcx>>,
352 suffix: &'tcx [hir::Pat<'tcx>],
354 let prefix = self.lower_patterns(prefix);
355 let slice = self.lower_opt_pattern(slice);
356 let suffix = self.lower_patterns(suffix);
358 // Matching a slice, `[T]`.
359 ty::Slice(..) => PatKind::Slice { prefix, slice, suffix },
360 // Fixed-length array, `[T; len]`.
361 ty::Array(_, len) => {
362 let len = len.eval_usize(self.tcx, self.param_env);
363 assert!(len >= prefix.len() as u64 + suffix.len() as u64);
364 PatKind::Array { prefix, slice, suffix }
366 _ => span_bug!(span, "bad slice pattern type {:?}", ty),
370 fn lower_variant_or_leaf(
376 subpatterns: Vec<FieldPat<'tcx>>,
378 let res = match res {
379 Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_id) => {
380 let variant_id = self.tcx.parent(variant_ctor_id);
381 Res::Def(DefKind::Variant, variant_id)
386 let mut kind = match res {
387 Res::Def(DefKind::Variant, variant_id) => {
388 let enum_id = self.tcx.parent(variant_id);
389 let adt_def = self.tcx.adt_def(enum_id);
390 if adt_def.is_enum() {
391 let substs = match ty.kind() {
392 ty::Adt(_, substs) | ty::FnDef(_, substs) => substs,
394 // Avoid ICE (#50585)
395 return PatKind::Wild;
397 _ => bug!("inappropriate type for def: {:?}", ty),
402 variant_index: adt_def.variant_index_with_id(variant_id),
406 PatKind::Leaf { subpatterns }
412 | DefKind::Ctor(CtorOf::Struct, ..)
419 | Res::SelfCtor(..) => PatKind::Leaf { subpatterns },
421 let pattern_error = match res {
422 Res::Def(DefKind::ConstParam, _) => PatternError::ConstParamInPattern(span),
423 Res::Def(DefKind::Static(_), _) => PatternError::StaticInPattern(span),
424 _ => PatternError::NonConstPath(span),
426 self.errors.push(pattern_error);
431 if let Some(user_ty) = self.user_substs_applied_to_ty_of_hir_id(hir_id) {
432 debug!("lower_variant_or_leaf: kind={:?} user_ty={:?} span={:?}", kind, user_ty, span);
433 kind = PatKind::AscribeUserType {
434 subpattern: Pat { span, ty, kind: Box::new(kind) },
435 ascription: Ascription {
436 user_ty: PatTyProj::from_user_type(user_ty),
438 variance: ty::Variance::Covariant,
446 /// Takes a HIR Path. If the path is a constant, evaluates it and feeds
447 /// it to `const_to_pat`. Any other path (like enum variants without fields)
448 /// is converted to the corresponding pattern via `lower_variant_or_leaf`.
449 fn lower_path(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) -> Pat<'tcx> {
450 let ty = self.typeck_results.node_type(id);
451 let res = self.typeck_results.qpath_res(qpath, id);
453 let pat_from_kind = |kind| Pat { span, ty, kind: Box::new(kind) };
455 let (def_id, is_associated_const) = match res {
456 Res::Def(DefKind::Const, def_id) => (def_id, false),
457 Res::Def(DefKind::AssocConst, def_id) => (def_id, true),
459 _ => return pat_from_kind(self.lower_variant_or_leaf(res, id, span, ty, vec![])),
462 // Use `Reveal::All` here because patterns are always monomorphic even if their function
464 let param_env_reveal_all = self.param_env.with_reveal_all_normalized(self.tcx);
465 let substs = self.typeck_results.node_substs(id);
466 let instance = match ty::Instance::resolve(self.tcx, param_env_reveal_all, def_id, substs) {
469 // It should be assoc consts if there's no error but we cannot resolve it.
470 debug_assert!(is_associated_const);
472 self.errors.push(PatternError::AssocConstInPattern(span));
474 return pat_from_kind(PatKind::Wild);
478 self.tcx.sess.span_err(span, "could not evaluate constant pattern");
479 return pat_from_kind(PatKind::Wild);
483 // `mir_const_qualif` must be called with the `DefId` of the item where the const is
484 // defined, not where it is declared. The difference is significant for associated
486 let mir_structural_match_violation = self.tcx.mir_const_qualif(instance.def_id()).custom_eq;
487 debug!("mir_structural_match_violation({:?}) -> {}", qpath, mir_structural_match_violation);
489 match self.tcx.const_eval_instance(param_env_reveal_all, instance, Some(span)) {
491 let const_ = ty::Const::from_value(self.tcx, value, ty);
492 let pattern = self.const_to_pat(const_, id, span, mir_structural_match_violation);
494 if !is_associated_const {
498 let user_provided_types = self.typeck_results().user_provided_types();
499 if let Some(u_ty) = user_provided_types.get(id) {
500 let user_ty = PatTyProj::from_user_type(*u_ty);
503 kind: Box::new(PatKind::AscribeUserType {
505 ascription: Ascription {
506 /// Note that use `Contravariant` here. See the
507 /// `variance` field documentation for details.
508 variance: ty::Variance::Contravariant,
519 Err(ErrorHandled::TooGeneric) => {
520 // While `Reported | Linted` cases will have diagnostics emitted already
521 // it is not true for TooGeneric case, so we need to give user more information.
522 self.tcx.sess.span_err(span, "constant pattern depends on a generic parameter");
523 pat_from_kind(PatKind::Wild)
526 self.tcx.sess.span_err(span, "could not evaluate constant pattern");
527 pat_from_kind(PatKind::Wild)
532 /// Converts inline const patterns.
533 fn lower_inline_const(
535 anon_const: &'tcx hir::AnonConst,
539 let anon_const_def_id = self.tcx.hir().local_def_id(anon_const.hir_id);
540 let value = ty::Const::from_inline_const(self.tcx, anon_const_def_id);
542 // Evaluate early like we do in `lower_path`.
543 let value = value.eval(self.tcx, self.param_env);
546 ConstKind::Param(_) => {
547 self.errors.push(PatternError::ConstParamInPattern(span));
548 return PatKind::Wild;
550 ConstKind::Unevaluated(_) => {
551 // If we land here it means the const can't be evaluated because it's `TooGeneric`.
552 self.tcx.sess.span_err(span, "constant pattern depends on a generic parameter");
553 return PatKind::Wild;
558 *self.const_to_pat(value, id, span, false).kind
561 /// Converts literals, paths and negation of literals to patterns.
562 /// The special case for negation exists to allow things like `-128_i8`
563 /// which would overflow if we tried to evaluate `128_i8` and then negate
565 fn lower_lit(&mut self, expr: &'tcx hir::Expr<'tcx>) -> PatKind<'tcx> {
566 let (lit, neg) = match expr.kind {
567 hir::ExprKind::Path(ref qpath) => {
568 return *self.lower_path(qpath, expr.hir_id, expr.span).kind;
570 hir::ExprKind::ConstBlock(ref anon_const) => {
571 return self.lower_inline_const(anon_const, expr.hir_id, expr.span);
573 hir::ExprKind::Lit(ref lit) => (lit, false),
574 hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => {
575 let hir::ExprKind::Lit(ref lit) = expr.kind else {
576 span_bug!(expr.span, "not a literal: {:?}", expr);
580 _ => span_bug!(expr.span, "not a literal: {:?}", expr),
584 LitToConstInput { lit: &lit.node, ty: self.typeck_results.expr_ty(expr), neg };
585 match self.tcx.at(expr.span).lit_to_const(lit_input) {
586 Ok(constant) => *self.const_to_pat(constant, expr.hir_id, lit.span, false).kind,
587 Err(LitToConstError::Reported) => PatKind::Wild,
588 Err(LitToConstError::TypeError) => bug!("lower_lit: had type error"),
593 impl<'tcx> UserAnnotatedTyHelpers<'tcx> for PatCtxt<'_, 'tcx> {
594 fn tcx(&self) -> TyCtxt<'tcx> {
598 fn typeck_results(&self) -> &ty::TypeckResults<'tcx> {
603 crate trait PatternFoldable<'tcx>: Sized {
604 fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
605 self.super_fold_with(folder)
608 fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self;
611 crate trait PatternFolder<'tcx>: Sized {
612 fn fold_pattern(&mut self, pattern: &Pat<'tcx>) -> Pat<'tcx> {
613 pattern.super_fold_with(self)
616 fn fold_pattern_kind(&mut self, kind: &PatKind<'tcx>) -> PatKind<'tcx> {
617 kind.super_fold_with(self)
621 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Box<T> {
622 fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
623 let content: T = (**self).fold_with(folder);
628 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Vec<T> {
629 fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
630 self.iter().map(|t| t.fold_with(folder)).collect()
634 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Option<T> {
635 fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
636 self.as_ref().map(|t| t.fold_with(folder))
640 macro_rules! CloneImpls {
641 (<$lt_tcx:tt> $($ty:ty),+) => {
643 impl<$lt_tcx> PatternFoldable<$lt_tcx> for $ty {
644 fn super_fold_with<F: PatternFolder<$lt_tcx>>(&self, _: &mut F) -> Self {
653 Span, Field, Mutability, Symbol, hir::HirId, usize, ty::Const<'tcx>,
654 Region<'tcx>, Ty<'tcx>, BindingMode, AdtDef<'tcx>,
655 SubstsRef<'tcx>, &'tcx GenericArg<'tcx>, UserType<'tcx>,
656 UserTypeProjection, PatTyProj<'tcx>
659 impl<'tcx> PatternFoldable<'tcx> for FieldPat<'tcx> {
660 fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
661 FieldPat { field: self.field.fold_with(folder), pattern: self.pattern.fold_with(folder) }
665 impl<'tcx> PatternFoldable<'tcx> for Pat<'tcx> {
666 fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
667 folder.fold_pattern(self)
670 fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
672 ty: self.ty.fold_with(folder),
673 span: self.span.fold_with(folder),
674 kind: self.kind.fold_with(folder),
679 impl<'tcx> PatternFoldable<'tcx> for PatKind<'tcx> {
680 fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
681 folder.fold_pattern_kind(self)
684 fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
686 PatKind::Wild => PatKind::Wild,
687 PatKind::AscribeUserType {
689 ascription: Ascription { variance, ref user_ty, user_ty_span },
690 } => PatKind::AscribeUserType {
691 subpattern: subpattern.fold_with(folder),
692 ascription: Ascription {
693 user_ty: user_ty.fold_with(folder),
698 PatKind::Binding { mutability, name, mode, var, ty, ref subpattern, is_primary } => {
700 mutability: mutability.fold_with(folder),
701 name: name.fold_with(folder),
702 mode: mode.fold_with(folder),
703 var: var.fold_with(folder),
704 ty: ty.fold_with(folder),
705 subpattern: subpattern.fold_with(folder),
709 PatKind::Variant { adt_def, substs, variant_index, ref subpatterns } => {
711 adt_def: adt_def.fold_with(folder),
712 substs: substs.fold_with(folder),
714 subpatterns: subpatterns.fold_with(folder),
717 PatKind::Leaf { ref subpatterns } => {
718 PatKind::Leaf { subpatterns: subpatterns.fold_with(folder) }
720 PatKind::Deref { ref subpattern } => {
721 PatKind::Deref { subpattern: subpattern.fold_with(folder) }
723 PatKind::Constant { value } => PatKind::Constant { value },
724 PatKind::Range(range) => PatKind::Range(range),
725 PatKind::Slice { ref prefix, ref slice, ref suffix } => PatKind::Slice {
726 prefix: prefix.fold_with(folder),
727 slice: slice.fold_with(folder),
728 suffix: suffix.fold_with(folder),
730 PatKind::Array { ref prefix, ref slice, ref suffix } => PatKind::Array {
731 prefix: prefix.fold_with(folder),
732 slice: slice.fold_with(folder),
733 suffix: suffix.fold_with(folder),
735 PatKind::Or { ref pats } => PatKind::Or { pats: pats.fold_with(folder) },
740 #[instrument(skip(tcx), level = "debug")]
741 crate fn compare_const_vals<'tcx>(
745 param_env: ty::ParamEnv<'tcx>,
747 ) -> Option<Ordering> {
748 let from_bool = |v: bool| v.then_some(Ordering::Equal);
750 let fallback = || from_bool(a == b);
752 // Use the fallback if any type differs
753 if a.ty() != b.ty() || a.ty() != ty {
757 // Early return for equal constants (so e.g. references to ZSTs can be compared, even if they
758 // are just integer addresses).
759 if a.val() == b.val() {
760 return from_bool(true);
763 let a_bits = a.try_eval_bits(tcx, param_env, ty);
764 let b_bits = b.try_eval_bits(tcx, param_env, ty);
766 if let (Some(a), Some(b)) = (a_bits, b_bits) {
767 use rustc_apfloat::Float;
768 return match *ty.kind() {
769 ty::Float(ty::FloatTy::F32) => {
770 let l = rustc_apfloat::ieee::Single::from_bits(a);
771 let r = rustc_apfloat::ieee::Single::from_bits(b);
774 ty::Float(ty::FloatTy::F64) => {
775 let l = rustc_apfloat::ieee::Double::from_bits(a);
776 let r = rustc_apfloat::ieee::Double::from_bits(b);
780 use rustc_middle::ty::layout::IntegerExt;
781 let size = rustc_target::abi::Integer::from_int_ty(&tcx, ity).size();
782 let a = size.sign_extend(a);
783 let b = size.sign_extend(b);
784 Some((a as i128).cmp(&(b as i128)))
786 _ => Some(a.cmp(&b)),
790 if let ty::Str = ty.kind() && let (
791 ty::ConstKind::Value(a_val @ ConstValue::Slice { .. }),
792 ty::ConstKind::Value(b_val @ ConstValue::Slice { .. }),
793 ) = (a.val(), b.val())
795 let a_bytes = get_slice_bytes(&tcx, a_val);
796 let b_bytes = get_slice_bytes(&tcx, b_val);
797 return from_bool(a_bytes == b_bytes);