1 //! Miscellaneous type-system utilities that are too small to deserve their own modules.
3 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
4 use crate::ty::layout::IntegerExt;
6 self, DefIdTree, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
9 use crate::ty::{GenericArgKind, SubstsRef};
10 use rustc_apfloat::Float as _;
11 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
12 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
13 use rustc_errors::ErrorGuaranteed;
15 use rustc_hir::def::{CtorOf, DefKind, Res};
16 use rustc_hir::def_id::DefId;
17 use rustc_index::bit_set::GrowableBitSet;
18 use rustc_macros::HashStable;
19 use rustc_span::{sym, DUMMY_SP};
20 use rustc_target::abi::{Integer, IntegerType, Size, TargetDataLayout};
21 use rustc_target::spec::abi::Abi;
22 use smallvec::SmallVec;
25 #[derive(Copy, Clone, Debug)]
26 pub struct Discr<'tcx> {
27 /// Bit representation of the discriminant (e.g., `-128i8` is `0xFF_u128`).
32 /// Used as an input to [`TyCtxt::uses_unique_generic_params`].
33 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
34 pub enum IgnoreRegions {
39 #[derive(Copy, Clone, Debug)]
40 pub enum NotUniqueParam<'tcx> {
41 DuplicateParam(ty::GenericArg<'tcx>),
42 NotParam(ty::GenericArg<'tcx>),
45 impl<'tcx> fmt::Display for Discr<'tcx> {
46 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
47 match *self.ty.kind() {
49 let size = ty::tls::with(|tcx| Integer::from_int_ty(&tcx, ity).size());
51 // sign extend the raw representation to be an i128
52 let x = size.sign_extend(x) as i128;
55 _ => write!(fmt, "{}", self.val),
60 fn int_size_and_signed<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> (Size, bool) {
61 let (int, signed) = match *ty.kind() {
62 ty::Int(ity) => (Integer::from_int_ty(&tcx, ity), true),
63 ty::Uint(uty) => (Integer::from_uint_ty(&tcx, uty), false),
64 _ => bug!("non integer discriminant"),
69 impl<'tcx> Discr<'tcx> {
70 /// Adds `1` to the value and wraps around if the maximum for the type is reached.
71 pub fn wrap_incr(self, tcx: TyCtxt<'tcx>) -> Self {
72 self.checked_add(tcx, 1).0
74 pub fn checked_add(self, tcx: TyCtxt<'tcx>, n: u128) -> (Self, bool) {
75 let (size, signed) = int_size_and_signed(tcx, self.ty);
76 let (val, oflo) = if signed {
77 let min = size.signed_int_min();
78 let max = size.signed_int_max();
79 let val = size.sign_extend(self.val) as i128;
80 assert!(n < (i128::MAX as u128));
82 let oflo = val > max - n;
83 let val = if oflo { min + (n - (max - val) - 1) } else { val + n };
84 // zero the upper bits
85 let val = val as u128;
86 let val = size.truncate(val);
89 let max = size.unsigned_int_max();
91 let oflo = val > max - n;
92 let val = if oflo { n - (max - val) - 1 } else { val + n };
95 (Self { val, ty: self.ty }, oflo)
99 pub trait IntTypeExt {
100 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
101 fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>>;
102 fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx>;
105 impl IntTypeExt for IntegerType {
106 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
108 IntegerType::Pointer(true) => tcx.types.isize,
109 IntegerType::Pointer(false) => tcx.types.usize,
110 IntegerType::Fixed(i, s) => i.to_ty(tcx, *s),
114 fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx> {
115 Discr { val: 0, ty: self.to_ty(tcx) }
118 fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>> {
119 if let Some(val) = val {
120 assert_eq!(self.to_ty(tcx), val.ty);
121 let (new, oflo) = val.checked_add(tcx, 1);
122 if oflo { None } else { Some(new) }
124 Some(self.initial_discriminant(tcx))
129 impl<'tcx> TyCtxt<'tcx> {
130 /// Creates a hash of the type `Ty` which will be the same no matter what crate
131 /// context it's calculated within. This is used by the `type_id` intrinsic.
132 pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
133 // We want the type_id be independent of the types free regions, so we
134 // erase them. The erase_regions() call will also anonymize bound
135 // regions, which is desirable too.
136 let ty = self.erase_regions(ty);
138 self.with_stable_hashing_context(|mut hcx| {
139 let mut hasher = StableHasher::new();
140 hcx.while_hashing_spans(false, |hcx| ty.hash_stable(hcx, &mut hasher));
145 pub fn res_generics_def_id(self, res: Res) -> Option<DefId> {
147 Res::Def(DefKind::Ctor(CtorOf::Variant, _), def_id) => {
148 Some(self.parent(self.parent(def_id)))
150 Res::Def(DefKind::Variant | DefKind::Ctor(CtorOf::Struct, _), def_id) => {
151 Some(self.parent(def_id))
153 // Other `DefKind`s don't have generics and would ICE when calling
163 | DefKind::TraitAlias
167 | DefKind::AssocConst
176 pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
177 if let ty::Adt(def, substs) = *ty.kind() {
178 for field in def.all_fields() {
179 let field_ty = field.ty(self, substs);
180 if let ty::Error(_) = field_ty.kind() {
188 /// Attempts to returns the deeply last field of nested structures, but
189 /// does not apply any normalization in its search. Returns the same type
190 /// if input `ty` is not a structure at all.
191 pub fn struct_tail_without_normalization(self, ty: Ty<'tcx>) -> Ty<'tcx> {
193 tcx.struct_tail_with_normalize(ty, |ty| ty, || {})
196 /// Returns the deeply last field of nested structures, or the same type if
197 /// not a structure at all. Corresponds to the only possible unsized field,
198 /// and its type can be used to determine unsizing strategy.
200 /// Should only be called if `ty` has no inference variables and does not
201 /// need its lifetimes preserved (e.g. as part of codegen); otherwise
202 /// normalization attempt may cause compiler bugs.
203 pub fn struct_tail_erasing_lifetimes(
206 param_env: ty::ParamEnv<'tcx>,
209 tcx.struct_tail_with_normalize(ty, |ty| tcx.normalize_erasing_regions(param_env, ty), || {})
212 /// Returns the deeply last field of nested structures, or the same type if
213 /// not a structure at all. Corresponds to the only possible unsized field,
214 /// and its type can be used to determine unsizing strategy.
216 /// This is parameterized over the normalization strategy (i.e. how to
217 /// handle `<T as Trait>::Assoc` and `impl Trait`); pass the identity
218 /// function to indicate no normalization should take place.
220 /// See also `struct_tail_erasing_lifetimes`, which is suitable for use
222 pub fn struct_tail_with_normalize(
225 mut normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
226 // This is currently used to allow us to walk a ValTree
227 // in lockstep with the type in order to get the ValTree branch that
228 // corresponds to an unsized field.
229 mut f: impl FnMut() -> (),
231 let recursion_limit = self.recursion_limit();
232 for iteration in 0.. {
233 if !recursion_limit.value_within_limit(iteration) {
234 return self.ty_error_with_message(
236 &format!("reached the recursion limit finding the struct tail for {}", ty),
240 ty::Adt(def, substs) => {
241 if !def.is_struct() {
244 match def.non_enum_variant().fields.last() {
247 ty = field.ty(self, substs);
253 ty::Tuple(tys) if let Some((&last_ty, _)) = tys.split_last() => {
258 ty::Tuple(_) => break,
260 ty::Projection(_) | ty::Opaque(..) => {
261 let normalized = normalize(ty);
262 if ty == normalized {
277 /// Same as applying `struct_tail` on `source` and `target`, but only
278 /// keeps going as long as the two types are instances of the same
279 /// structure definitions.
280 /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
281 /// whereas struct_tail produces `T`, and `Trait`, respectively.
283 /// Should only be called if the types have no inference variables and do
284 /// not need their lifetimes preserved (e.g., as part of codegen); otherwise,
285 /// normalization attempt may cause compiler bugs.
286 pub fn struct_lockstep_tails_erasing_lifetimes(
290 param_env: ty::ParamEnv<'tcx>,
291 ) -> (Ty<'tcx>, Ty<'tcx>) {
293 tcx.struct_lockstep_tails_with_normalize(source, target, |ty| {
294 tcx.normalize_erasing_regions(param_env, ty)
298 /// Same as applying `struct_tail` on `source` and `target`, but only
299 /// keeps going as long as the two types are instances of the same
300 /// structure definitions.
301 /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
302 /// whereas struct_tail produces `T`, and `Trait`, respectively.
304 /// See also `struct_lockstep_tails_erasing_lifetimes`, which is suitable for use
306 pub fn struct_lockstep_tails_with_normalize(
310 normalize: impl Fn(Ty<'tcx>) -> Ty<'tcx>,
311 ) -> (Ty<'tcx>, Ty<'tcx>) {
312 let (mut a, mut b) = (source, target);
314 match (&a.kind(), &b.kind()) {
315 (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
316 if a_def == b_def && a_def.is_struct() =>
318 if let Some(f) = a_def.non_enum_variant().fields.last() {
319 a = f.ty(self, a_substs);
320 b = f.ty(self, b_substs);
325 (&ty::Tuple(a_tys), &ty::Tuple(b_tys)) if a_tys.len() == b_tys.len() => {
326 if let Some(&a_last) = a_tys.last() {
328 b = *b_tys.last().unwrap();
333 (ty::Projection(_) | ty::Opaque(..), _)
334 | (_, ty::Projection(_) | ty::Opaque(..)) => {
335 // If either side is a projection, attempt to
336 // progress via normalization. (Should be safe to
337 // apply to both sides as normalization is
339 let a_norm = normalize(a);
340 let b_norm = normalize(b);
341 if a == a_norm && b == b_norm {
355 /// Calculate the destructor of a given type.
356 pub fn calculate_dtor(
359 validate: impl Fn(Self, DefId) -> Result<(), ErrorGuaranteed>,
360 ) -> Option<ty::Destructor> {
361 let drop_trait = self.lang_items().drop_trait()?;
362 self.ensure().coherent_trait(drop_trait);
364 let ty = self.type_of(adt_did);
365 let (did, constness) = self.find_map_relevant_impl(drop_trait, ty, |impl_did| {
366 if let Some(item_id) = self.associated_item_def_ids(impl_did).first() {
367 if validate(self, impl_did).is_ok() {
368 return Some((*item_id, self.constness(impl_did)));
374 Some(ty::Destructor { did, constness })
377 /// Returns the set of types that are required to be alive in
378 /// order to run the destructor of `def` (see RFCs 769 and
381 /// Note that this returns only the constraints for the
382 /// destructor of `def` itself. For the destructors of the
383 /// contents, you need `adt_dtorck_constraint`.
384 pub fn destructor_constraints(self, def: ty::AdtDef<'tcx>) -> Vec<ty::subst::GenericArg<'tcx>> {
385 let dtor = match def.destructor(self) {
387 debug!("destructor_constraints({:?}) - no dtor", def.did());
390 Some(dtor) => dtor.did,
393 let impl_def_id = self.parent(dtor);
394 let impl_generics = self.generics_of(impl_def_id);
396 // We have a destructor - all the parameters that are not
397 // pure_wrt_drop (i.e, don't have a #[may_dangle] attribute)
400 // We need to return the list of parameters from the ADTs
401 // generics/substs that correspond to impure parameters on the
402 // impl's generics. This is a bit ugly, but conceptually simple:
404 // Suppose our ADT looks like the following
406 // struct S<X, Y, Z>(X, Y, Z);
410 // impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
412 // We want to return the parameters (X, Y). For that, we match
413 // up the item-substs <X, Y, Z> with the substs on the impl ADT,
414 // <P1, P2, P0>, and then look up which of the impl substs refer to
415 // parameters marked as pure.
417 let impl_substs = match *self.type_of(impl_def_id).kind() {
418 ty::Adt(def_, substs) if def_ == def => substs,
422 let item_substs = match *self.type_of(def.did()).kind() {
423 ty::Adt(def_, substs) if def_ == def => substs,
427 let result = iter::zip(item_substs, impl_substs)
430 GenericArgKind::Lifetime(region) => match region.kind() {
431 ty::ReEarlyBound(ref ebr) => {
432 !impl_generics.region_param(ebr, self).pure_wrt_drop
434 // Error: not a region param
437 GenericArgKind::Type(ty) => match ty.kind() {
438 ty::Param(ref pt) => !impl_generics.type_param(pt, self).pure_wrt_drop,
439 // Error: not a type param
442 GenericArgKind::Const(ct) => match ct.kind() {
443 ty::ConstKind::Param(ref pc) => {
444 !impl_generics.const_param(pc, self).pure_wrt_drop
446 // Error: not a const param
451 .map(|(item_param, _)| item_param)
453 debug!("destructor_constraint({:?}) = {:?}", def.did(), result);
457 /// Checks whether each generic argument is simply a unique generic parameter.
458 pub fn uses_unique_generic_params(
460 substs: SubstsRef<'tcx>,
461 ignore_regions: IgnoreRegions,
462 ) -> Result<(), NotUniqueParam<'tcx>> {
463 let mut seen = GrowableBitSet::default();
466 GenericArgKind::Lifetime(lt) => {
467 if ignore_regions == IgnoreRegions::No {
468 let ty::ReEarlyBound(p) = lt.kind() else {
469 return Err(NotUniqueParam::NotParam(lt.into()))
471 if !seen.insert(p.index) {
472 return Err(NotUniqueParam::DuplicateParam(lt.into()));
476 GenericArgKind::Type(t) => match t.kind() {
478 if !seen.insert(p.index) {
479 return Err(NotUniqueParam::DuplicateParam(t.into()));
482 _ => return Err(NotUniqueParam::NotParam(t.into())),
484 GenericArgKind::Const(c) => match c.kind() {
485 ty::ConstKind::Param(p) => {
486 if !seen.insert(p.index) {
487 return Err(NotUniqueParam::DuplicateParam(c.into()));
490 _ => return Err(NotUniqueParam::NotParam(c.into())),
498 /// Returns `true` if `def_id` refers to a closure (e.g., `|x| x * 2`). Note
499 /// that closures have a `DefId`, but the closure *expression* also
500 /// has a `HirId` that is located within the context where the
501 /// closure appears (and, sadly, a corresponding `NodeId`, since
502 /// those are not yet phased out). The parent of the closure's
503 /// `DefId` will also be the context where it appears.
504 pub fn is_closure(self, def_id: DefId) -> bool {
505 matches!(self.def_kind(def_id), DefKind::Closure | DefKind::Generator)
508 /// Returns `true` if `def_id` refers to a definition that does not have its own
509 /// type-checking context, i.e. closure, generator or inline const.
510 pub fn is_typeck_child(self, def_id: DefId) -> bool {
512 self.def_kind(def_id),
513 DefKind::Closure | DefKind::Generator | DefKind::InlineConst
517 /// Returns `true` if `def_id` refers to a trait (i.e., `trait Foo { ... }`).
518 pub fn is_trait(self, def_id: DefId) -> bool {
519 self.def_kind(def_id) == DefKind::Trait
522 /// Returns `true` if `def_id` refers to a trait alias (i.e., `trait Foo = ...;`),
523 /// and `false` otherwise.
524 pub fn is_trait_alias(self, def_id: DefId) -> bool {
525 self.def_kind(def_id) == DefKind::TraitAlias
528 /// Returns `true` if this `DefId` refers to the implicit constructor for
529 /// a tuple struct like `struct Foo(u32)`, and `false` otherwise.
530 pub fn is_constructor(self, def_id: DefId) -> bool {
531 matches!(self.def_kind(def_id), DefKind::Ctor(..))
534 /// Given the `DefId`, returns the `DefId` of the innermost item that
535 /// has its own type-checking context or "inference environment".
537 /// For example, a closure has its own `DefId`, but it is type-checked
538 /// with the containing item. Similarly, an inline const block has its
539 /// own `DefId` but it is type-checked together with the containing item.
541 /// Therefore, when we fetch the
542 /// `typeck` the closure, for example, we really wind up
543 /// fetching the `typeck` the enclosing fn item.
544 pub fn typeck_root_def_id(self, def_id: DefId) -> DefId {
545 let mut def_id = def_id;
546 while self.is_typeck_child(def_id) {
547 def_id = self.parent(def_id);
552 /// Given the `DefId` and substs a closure, creates the type of
553 /// `self` argument that the closure expects. For example, for a
554 /// `Fn` closure, this would return a reference type `&T` where
555 /// `T = closure_ty`.
557 /// Returns `None` if this closure's kind has not yet been inferred.
558 /// This should only be possible during type checking.
560 /// Note that the return value is a late-bound region and hence
561 /// wrapped in a binder.
562 pub fn closure_env_ty(
564 closure_def_id: DefId,
565 closure_substs: SubstsRef<'tcx>,
566 env_region: ty::RegionKind<'tcx>,
567 ) -> Option<Ty<'tcx>> {
568 let closure_ty = self.mk_closure(closure_def_id, closure_substs);
569 let closure_kind_ty = closure_substs.as_closure().kind_ty();
570 let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
571 let env_ty = match closure_kind {
572 ty::ClosureKind::Fn => self.mk_imm_ref(self.mk_region(env_region), closure_ty),
573 ty::ClosureKind::FnMut => self.mk_mut_ref(self.mk_region(env_region), closure_ty),
574 ty::ClosureKind::FnOnce => closure_ty,
579 /// Returns `true` if the node pointed to by `def_id` is a `static` item.
581 pub fn is_static(self, def_id: DefId) -> bool {
582 matches!(self.def_kind(def_id), DefKind::Static(_))
586 pub fn static_mutability(self, def_id: DefId) -> Option<hir::Mutability> {
587 if let DefKind::Static(mt) = self.def_kind(def_id) { Some(mt) } else { None }
590 /// Returns `true` if this is a `static` item with the `#[thread_local]` attribute.
591 pub fn is_thread_local_static(self, def_id: DefId) -> bool {
592 self.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
595 /// Returns `true` if the node pointed to by `def_id` is a mutable `static` item.
597 pub fn is_mutable_static(self, def_id: DefId) -> bool {
598 self.static_mutability(def_id) == Some(hir::Mutability::Mut)
601 /// Get the type of the pointer to the static that we use in MIR.
602 pub fn static_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
603 // Make sure that any constants in the static's type are evaluated.
604 let static_ty = self.normalize_erasing_regions(ty::ParamEnv::empty(), self.type_of(def_id));
606 // Make sure that accesses to unsafe statics end up using raw pointers.
607 // For thread-locals, this needs to be kept in sync with `Rvalue::ty`.
608 if self.is_mutable_static(def_id) {
609 self.mk_mut_ptr(static_ty)
610 } else if self.is_foreign_item(def_id) {
611 self.mk_imm_ptr(static_ty)
613 self.mk_imm_ref(self.lifetimes.re_erased, static_ty)
617 /// Expands the given impl trait type, stopping if the type is recursive.
618 #[instrument(skip(self), level = "debug", ret)]
619 pub fn try_expand_impl_trait_type(
622 substs: SubstsRef<'tcx>,
623 ) -> Result<Ty<'tcx>, Ty<'tcx>> {
624 let mut visitor = OpaqueTypeExpander {
625 seen_opaque_tys: FxHashSet::default(),
626 expanded_cache: FxHashMap::default(),
627 primary_def_id: Some(def_id),
628 found_recursion: false,
629 found_any_recursion: false,
630 check_recursion: true,
634 let expanded_type = visitor.expand_opaque_ty(def_id, substs).unwrap();
635 if visitor.found_recursion { Err(expanded_type) } else { Ok(expanded_type) }
638 pub fn bound_type_of(self, def_id: DefId) -> ty::EarlyBinder<Ty<'tcx>> {
639 ty::EarlyBinder(self.type_of(def_id))
642 pub fn bound_trait_impl_trait_tys(
645 ) -> ty::EarlyBinder<Result<&'tcx FxHashMap<DefId, Ty<'tcx>>, ErrorGuaranteed>> {
646 ty::EarlyBinder(self.collect_trait_impl_trait_tys(def_id))
649 pub fn bound_fn_sig(self, def_id: DefId) -> ty::EarlyBinder<ty::PolyFnSig<'tcx>> {
650 ty::EarlyBinder(self.fn_sig(def_id))
653 pub fn bound_impl_trait_ref(
656 ) -> Option<ty::EarlyBinder<ty::TraitRef<'tcx>>> {
657 self.impl_trait_ref(def_id).map(|i| ty::EarlyBinder(i))
660 pub fn bound_explicit_item_bounds(
663 ) -> ty::EarlyBinder<&'tcx [(ty::Predicate<'tcx>, rustc_span::Span)]> {
664 ty::EarlyBinder(self.explicit_item_bounds(def_id))
667 pub fn bound_item_bounds(
670 ) -> ty::EarlyBinder<&'tcx ty::List<ty::Predicate<'tcx>>> {
671 ty::EarlyBinder(self.item_bounds(def_id))
674 pub fn bound_const_param_default(self, def_id: DefId) -> ty::EarlyBinder<ty::Const<'tcx>> {
675 ty::EarlyBinder(self.const_param_default(def_id))
678 pub fn bound_predicates_of(
681 ) -> ty::EarlyBinder<ty::generics::GenericPredicates<'tcx>> {
682 ty::EarlyBinder(self.predicates_of(def_id))
685 pub fn bound_explicit_predicates_of(
688 ) -> ty::EarlyBinder<ty::generics::GenericPredicates<'tcx>> {
689 ty::EarlyBinder(self.explicit_predicates_of(def_id))
692 pub fn bound_impl_subject(self, def_id: DefId) -> ty::EarlyBinder<ty::ImplSubject<'tcx>> {
693 ty::EarlyBinder(self.impl_subject(def_id))
697 struct OpaqueTypeExpander<'tcx> {
698 // Contains the DefIds of the opaque types that are currently being
699 // expanded. When we expand an opaque type we insert the DefId of
700 // that type, and when we finish expanding that type we remove the
702 seen_opaque_tys: FxHashSet<DefId>,
703 // Cache of all expansions we've seen so far. This is a critical
704 // optimization for some large types produced by async fn trees.
705 expanded_cache: FxHashMap<(DefId, SubstsRef<'tcx>), Ty<'tcx>>,
706 primary_def_id: Option<DefId>,
707 found_recursion: bool,
708 found_any_recursion: bool,
709 /// Whether or not to check for recursive opaque types.
710 /// This is `true` when we're explicitly checking for opaque type
711 /// recursion, and 'false' otherwise to avoid unnecessary work.
712 check_recursion: bool,
716 impl<'tcx> OpaqueTypeExpander<'tcx> {
717 fn expand_opaque_ty(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> Option<Ty<'tcx>> {
718 if self.found_any_recursion {
721 let substs = substs.fold_with(self);
722 if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
723 let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) {
724 Some(expanded_ty) => *expanded_ty,
726 let generic_ty = self.tcx.bound_type_of(def_id);
727 let concrete_ty = generic_ty.subst(self.tcx, substs);
728 let expanded_ty = self.fold_ty(concrete_ty);
729 self.expanded_cache.insert((def_id, substs), expanded_ty);
733 if self.check_recursion {
734 self.seen_opaque_tys.remove(&def_id);
738 // If another opaque type that we contain is recursive, then it
739 // will report the error, so we don't have to.
740 self.found_any_recursion = true;
741 self.found_recursion = def_id == *self.primary_def_id.as_ref().unwrap();
747 impl<'tcx> TypeFolder<'tcx> for OpaqueTypeExpander<'tcx> {
748 fn tcx(&self) -> TyCtxt<'tcx> {
752 fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
753 if let ty::Opaque(def_id, substs) = *t.kind() {
754 self.expand_opaque_ty(def_id, substs).unwrap_or(t)
755 } else if t.has_opaque_types() {
756 t.super_fold_with(self)
763 impl<'tcx> Ty<'tcx> {
764 /// Returns the maximum value for the given numeric type (including `char`s)
765 /// or returns `None` if the type is not numeric.
766 pub fn numeric_max_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
767 let val = match self.kind() {
768 ty::Int(_) | ty::Uint(_) => {
769 let (size, signed) = int_size_and_signed(tcx, self);
771 if signed { size.signed_int_max() as u128 } else { size.unsigned_int_max() };
774 ty::Char => Some(std::char::MAX as u128),
775 ty::Float(fty) => Some(match fty {
776 ty::FloatTy::F32 => rustc_apfloat::ieee::Single::INFINITY.to_bits(),
777 ty::FloatTy::F64 => rustc_apfloat::ieee::Double::INFINITY.to_bits(),
782 val.map(|v| ty::Const::from_bits(tcx, v, ty::ParamEnv::empty().and(self)))
785 /// Returns the minimum value for the given numeric type (including `char`s)
786 /// or returns `None` if the type is not numeric.
787 pub fn numeric_min_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
788 let val = match self.kind() {
789 ty::Int(_) | ty::Uint(_) => {
790 let (size, signed) = int_size_and_signed(tcx, self);
791 let val = if signed { size.truncate(size.signed_int_min() as u128) } else { 0 };
795 ty::Float(fty) => Some(match fty {
796 ty::FloatTy::F32 => (-::rustc_apfloat::ieee::Single::INFINITY).to_bits(),
797 ty::FloatTy::F64 => (-::rustc_apfloat::ieee::Double::INFINITY).to_bits(),
802 val.map(|v| ty::Const::from_bits(tcx, v, ty::ParamEnv::empty().and(self)))
805 /// Checks whether values of this type `T` are *moved* or *copied*
806 /// when referenced -- this amounts to a check for whether `T:
807 /// Copy`, but note that we **don't** consider lifetimes when
808 /// doing this check. This means that we may generate MIR which
809 /// does copies even when the type actually doesn't satisfy the
810 /// full requirements for the `Copy` trait (cc #29149) -- this
811 /// winds up being reported as an error during NLL borrow check.
812 pub fn is_copy_modulo_regions(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
813 self.is_trivially_pure_clone_copy() || tcx.is_copy_raw(param_env.and(self))
816 /// Checks whether values of this type `T` have a size known at
817 /// compile time (i.e., whether `T: Sized`). Lifetimes are ignored
818 /// for the purposes of this check, so it can be an
819 /// over-approximation in generic contexts, where one can have
820 /// strange rules like `<T as Foo<'static>>::Bar: Sized` that
821 /// actually carry lifetime requirements.
822 pub fn is_sized(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
823 self.is_trivially_sized(tcx) || tcx.is_sized_raw(param_env.and(self))
826 /// Checks whether values of this type `T` implement the `Freeze`
827 /// trait -- frozen types are those that do not contain an
828 /// `UnsafeCell` anywhere. This is a language concept used to
829 /// distinguish "true immutability", which is relevant to
830 /// optimization as well as the rules around static values. Note
831 /// that the `Freeze` trait is not exposed to end users and is
832 /// effectively an implementation detail.
833 pub fn is_freeze(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
834 self.is_trivially_freeze() || tcx.is_freeze_raw(param_env.and(self))
837 /// Fast path helper for testing if a type is `Freeze`.
839 /// Returning true means the type is known to be `Freeze`. Returning
840 /// `false` means nothing -- could be `Freeze`, might not be.
841 fn is_trivially_freeze(self) -> bool {
854 | ty::FnPtr(_) => true,
855 ty::Tuple(fields) => fields.iter().all(Self::is_trivially_freeze),
856 ty::Slice(elem_ty) | ty::Array(elem_ty, _) => elem_ty.is_trivially_freeze(),
863 | ty::GeneratorWitness(_)
868 | ty::Projection(_) => false,
872 /// Checks whether values of this type `T` implement the `Unpin` trait.
873 pub fn is_unpin(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
874 self.is_trivially_unpin() || tcx.is_unpin_raw(param_env.and(self))
877 /// Fast path helper for testing if a type is `Unpin`.
879 /// Returning true means the type is known to be `Unpin`. Returning
880 /// `false` means nothing -- could be `Unpin`, might not be.
881 fn is_trivially_unpin(self) -> bool {
894 | ty::FnPtr(_) => true,
895 ty::Tuple(fields) => fields.iter().all(Self::is_trivially_unpin),
896 ty::Slice(elem_ty) | ty::Array(elem_ty, _) => elem_ty.is_trivially_unpin(),
903 | ty::GeneratorWitness(_)
908 | ty::Projection(_) => false,
912 /// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely
913 /// non-copy and *might* have a destructor attached; if it returns
914 /// `false`, then `ty` definitely has no destructor (i.e., no drop glue).
916 /// (Note that this implies that if `ty` has a destructor attached,
917 /// then `needs_drop` will definitely return `true` for `ty`.)
919 /// Note that this method is used to check eligible types in unions.
921 pub fn needs_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
922 // Avoid querying in simple cases.
923 match needs_drop_components(self, &tcx.data_layout) {
924 Err(AlwaysRequiresDrop) => true,
926 let query_ty = match *components {
928 // If we've got a single component, call the query with that
929 // to increase the chance that we hit the query cache.
930 [component_ty] => component_ty,
934 // This doesn't depend on regions, so try to minimize distinct
936 // If normalization fails, we just use `query_ty`.
938 tcx.try_normalize_erasing_regions(param_env, query_ty).unwrap_or(query_ty);
940 tcx.needs_drop_raw(param_env.and(query_ty))
945 /// Checks if `ty` has a significant drop.
947 /// Note that this method can return false even if `ty` has a destructor
948 /// attached; even if that is the case then the adt has been marked with
949 /// the attribute `rustc_insignificant_dtor`.
951 /// Note that this method is used to check for change in drop order for
952 /// 2229 drop reorder migration analysis.
954 pub fn has_significant_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
955 // Avoid querying in simple cases.
956 match needs_drop_components(self, &tcx.data_layout) {
957 Err(AlwaysRequiresDrop) => true,
959 let query_ty = match *components {
961 // If we've got a single component, call the query with that
962 // to increase the chance that we hit the query cache.
963 [component_ty] => component_ty,
967 // FIXME(#86868): We should be canonicalizing, or else moving this to a method of inference
968 // context, or *something* like that, but for now just avoid passing inference
969 // variables to queries that can't cope with them. Instead, conservatively
970 // return "true" (may change drop order).
971 if query_ty.needs_infer() {
975 // This doesn't depend on regions, so try to minimize distinct
977 let erased = tcx.normalize_erasing_regions(param_env, query_ty);
978 tcx.has_significant_drop_raw(param_env.and(erased))
983 /// Returns `true` if equality for this type is both reflexive and structural.
985 /// Reflexive equality for a type is indicated by an `Eq` impl for that type.
987 /// Primitive types (`u32`, `str`) have structural equality by definition. For composite data
988 /// types, equality for the type as a whole is structural when it is the same as equality
989 /// between all components (fields, array elements, etc.) of that type. For ADTs, structural
990 /// equality is indicated by an implementation of `PartialStructuralEq` and `StructuralEq` for
993 /// This function is "shallow" because it may return `true` for a composite type whose fields
994 /// are not `StructuralEq`. For example, `[T; 4]` has structural equality regardless of `T`
995 /// because equality for arrays is determined by the equality of each array element. If you
996 /// want to know whether a given call to `PartialEq::eq` will proceed structurally all the way
997 /// down, you will need to use a type visitor.
999 pub fn is_structural_eq_shallow(self, tcx: TyCtxt<'tcx>) -> bool {
1001 // Look for an impl of both `PartialStructuralEq` and `StructuralEq`.
1002 ty::Adt(..) => tcx.has_structural_eq_impls(self),
1004 // Primitive types that satisfy `Eq`.
1005 ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Str | ty::Never => true,
1007 // Composite types that satisfy `Eq` when all of their fields do.
1009 // Because this function is "shallow", we return `true` for these composites regardless
1010 // of the type(s) contained within.
1011 ty::Ref(..) | ty::Array(..) | ty::Slice(_) | ty::Tuple(..) => true,
1013 // Raw pointers use bitwise comparison.
1014 ty::RawPtr(_) | ty::FnPtr(_) => true,
1016 // Floating point numbers are not `Eq`.
1017 ty::Float(_) => false,
1019 // Conservatively return `false` for all others...
1021 // Anonymous function types
1022 ty::FnDef(..) | ty::Closure(..) | ty::Dynamic(..) | ty::Generator(..) => false,
1024 // Generic or inferred types
1026 // FIXME(ecstaticmorse): Maybe we should `bug` here? This should probably only be
1027 // called for known, fully-monomorphized types.
1032 | ty::Placeholder(_)
1033 | ty::Infer(_) => false,
1035 ty::Foreign(_) | ty::GeneratorWitness(..) | ty::Error(_) => false,
1039 /// Peel off all reference types in this type until there are none left.
1041 /// This method is idempotent, i.e. `ty.peel_refs().peel_refs() == ty.peel_refs()`.
1046 /// - `&'a mut u8` -> `u8`
1047 /// - `&'a &'b u8` -> `u8`
1048 /// - `&'a *const &'b u8 -> *const &'b u8`
1049 pub fn peel_refs(self) -> Ty<'tcx> {
1051 while let ty::Ref(_, inner_ty, _) = ty.kind() {
1058 pub fn outer_exclusive_binder(self) -> ty::DebruijnIndex {
1059 self.0.outer_exclusive_binder
1063 pub enum ExplicitSelf<'tcx> {
1065 ByReference(ty::Region<'tcx>, hir::Mutability),
1066 ByRawPointer(hir::Mutability),
1071 impl<'tcx> ExplicitSelf<'tcx> {
1072 /// Categorizes an explicit self declaration like `self: SomeType`
1073 /// into either `self`, `&self`, `&mut self`, `Box<self>`, or
1075 /// This is mainly used to require the arbitrary_self_types feature
1076 /// in the case of `Other`, to improve error messages in the common cases,
1077 /// and to make `Other` non-object-safe.
1081 /// ```ignore (illustrative)
1082 /// impl<'a> Foo for &'a T {
1083 /// // Legal declarations:
1084 /// fn method1(self: &&'a T); // ExplicitSelf::ByReference
1085 /// fn method2(self: &'a T); // ExplicitSelf::ByValue
1086 /// fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox
1087 /// fn method4(self: Rc<&'a T>); // ExplicitSelf::Other
1089 /// // Invalid cases will be caught by `check_method_receiver`:
1090 /// fn method_err1(self: &'a mut T); // ExplicitSelf::Other
1091 /// fn method_err2(self: &'static T) // ExplicitSelf::ByValue
1092 /// fn method_err3(self: &&T) // ExplicitSelf::ByReference
1096 pub fn determine<P>(self_arg_ty: Ty<'tcx>, is_self_ty: P) -> ExplicitSelf<'tcx>
1098 P: Fn(Ty<'tcx>) -> bool,
1100 use self::ExplicitSelf::*;
1102 match *self_arg_ty.kind() {
1103 _ if is_self_ty(self_arg_ty) => ByValue,
1104 ty::Ref(region, ty, mutbl) if is_self_ty(ty) => ByReference(region, mutbl),
1105 ty::RawPtr(ty::TypeAndMut { ty, mutbl }) if is_self_ty(ty) => ByRawPointer(mutbl),
1106 ty::Adt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => ByBox,
1112 /// Returns a list of types such that the given type needs drop if and only if
1113 /// *any* of the returned types need drop. Returns `Err(AlwaysRequiresDrop)` if
1114 /// this type always needs drop.
1115 pub fn needs_drop_components<'tcx>(
1117 target_layout: &TargetDataLayout,
1118 ) -> Result<SmallVec<[Ty<'tcx>; 2]>, AlwaysRequiresDrop> {
1120 ty::Infer(ty::FreshIntTy(_))
1121 | ty::Infer(ty::FreshFloatTy(_))
1130 | ty::GeneratorWitness(..)
1133 | ty::Str => Ok(SmallVec::new()),
1135 // Foreign types can never have destructors.
1136 ty::Foreign(..) => Ok(SmallVec::new()),
1138 ty::Dynamic(..) | ty::Error(_) => Err(AlwaysRequiresDrop),
1140 ty::Slice(ty) => needs_drop_components(*ty, target_layout),
1141 ty::Array(elem_ty, size) => {
1142 match needs_drop_components(*elem_ty, target_layout) {
1143 Ok(v) if v.is_empty() => Ok(v),
1144 res => match size.kind().try_to_bits(target_layout.pointer_size) {
1145 // Arrays of size zero don't need drop, even if their element
1147 Some(0) => Ok(SmallVec::new()),
1149 // We don't know which of the cases above we are in, so
1150 // return the whole type and let the caller decide what to
1152 None => Ok(smallvec![ty]),
1156 // If any field needs drop, then the whole tuple does.
1157 ty::Tuple(fields) => fields.iter().try_fold(SmallVec::new(), move |mut acc, elem| {
1158 acc.extend(needs_drop_components(elem, target_layout)?);
1162 // These require checking for `Copy` bounds or `Adt` destructors.
1164 | ty::Projection(..)
1167 | ty::Placeholder(..)
1171 | ty::Generator(..) => Ok(smallvec![ty]),
1175 pub fn is_trivially_const_drop<'tcx>(ty: Ty<'tcx>) -> bool {
1182 | ty::Infer(ty::IntVar(_))
1183 | ty::Infer(ty::FloatVar(_))
1190 | ty::Foreign(_) => true,
1197 | ty::Placeholder(_)
1199 | ty::Infer(_) => false,
1201 // Not trivial because they have components, and instead of looking inside,
1202 // we'll just perform trait selection.
1203 ty::Closure(..) | ty::Generator(..) | ty::GeneratorWitness(_) | ty::Adt(..) => false,
1205 ty::Array(ty, _) | ty::Slice(ty) => is_trivially_const_drop(ty),
1207 ty::Tuple(tys) => tys.iter().all(|ty| is_trivially_const_drop(ty)),
1211 /// Does the equivalent of
1212 /// ```ignore (ilustrative)
1213 /// let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
1214 /// folder.tcx().intern_*(&v)
1216 pub fn fold_list<'tcx, F, T>(
1217 list: &'tcx ty::List<T>,
1219 intern: impl FnOnce(TyCtxt<'tcx>, &[T]) -> &'tcx ty::List<T>,
1220 ) -> Result<&'tcx ty::List<T>, F::Error>
1222 F: FallibleTypeFolder<'tcx>,
1223 T: TypeFoldable<'tcx> + PartialEq + Copy,
1225 let mut iter = list.iter();
1226 // Look for the first element that changed
1227 match iter.by_ref().enumerate().find_map(|(i, t)| match t.try_fold_with(folder) {
1228 Ok(new_t) if new_t == t => None,
1229 new_t => Some((i, new_t)),
1231 Some((i, Ok(new_t))) => {
1232 // An element changed, prepare to intern the resulting list
1233 let mut new_list = SmallVec::<[_; 8]>::with_capacity(list.len());
1234 new_list.extend_from_slice(&list[..i]);
1235 new_list.push(new_t);
1237 new_list.push(t.try_fold_with(folder)?)
1239 Ok(intern(folder.tcx(), &new_list))
1241 Some((_, Err(err))) => {
1248 #[derive(Copy, Clone, Debug, HashStable, TyEncodable, TyDecodable)]
1249 pub struct AlwaysRequiresDrop;
1251 /// Reveals all opaque types in the given value, replacing them
1252 /// with their underlying types.
1253 pub fn reveal_opaque_types_in_bounds<'tcx>(
1255 val: &'tcx ty::List<ty::Predicate<'tcx>>,
1256 ) -> &'tcx ty::List<ty::Predicate<'tcx>> {
1257 let mut visitor = OpaqueTypeExpander {
1258 seen_opaque_tys: FxHashSet::default(),
1259 expanded_cache: FxHashMap::default(),
1260 primary_def_id: None,
1261 found_recursion: false,
1262 found_any_recursion: false,
1263 check_recursion: false,
1266 val.fold_with(&mut visitor)
1269 /// Determines whether an item is annotated with `doc(hidden)`.
1270 pub fn is_doc_hidden(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
1271 tcx.get_attrs(def_id, sym::doc)
1272 .filter_map(|attr| attr.meta_item_list())
1273 .any(|items| items.iter().any(|item| item.has_name(sym::hidden)))
1276 /// Determines whether an item is annotated with `doc(notable_trait)`.
1277 pub fn is_doc_notable_trait(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
1278 tcx.get_attrs(def_id, sym::doc)
1279 .filter_map(|attr| attr.meta_item_list())
1280 .any(|items| items.iter().any(|item| item.has_name(sym::notable_trait)))
1283 /// Determines whether an item is an intrinsic by Abi.
1284 pub fn is_intrinsic(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
1285 matches!(tcx.fn_sig(def_id).abi(), Abi::RustIntrinsic | Abi::PlatformIntrinsic)
1288 pub fn provide(providers: &mut ty::query::Providers) {
1289 *providers = ty::query::Providers {
1290 reveal_opaque_types_in_bounds,
1292 is_doc_notable_trait,