1 //! Miscellaneous type-system utilities that are too small to deserve their own modules.
3 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
5 use crate::ty::layout::IntegerExt;
7 self, DefIdTree, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
10 use crate::ty::{GenericArgKind, SubstsRef};
11 use rustc_apfloat::Float as _;
12 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
13 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
14 use rustc_errors::ErrorGuaranteed;
16 use rustc_hir::def::{CtorOf, DefKind, Res};
17 use rustc_hir::def_id::DefId;
18 use rustc_index::bit_set::GrowableBitSet;
19 use rustc_index::vec::{Idx, IndexVec};
20 use rustc_macros::HashStable;
21 use rustc_span::{sym, DUMMY_SP};
22 use rustc_target::abi::{Integer, IntegerType, Size, TargetDataLayout};
23 use rustc_target::spec::abi::Abi;
24 use smallvec::SmallVec;
27 #[derive(Copy, Clone, Debug)]
28 pub struct Discr<'tcx> {
29 /// Bit representation of the discriminant (e.g., `-128i8` is `0xFF_u128`).
34 /// Used as an input to [`TyCtxt::uses_unique_generic_params`].
35 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
36 pub enum IgnoreRegions {
41 #[derive(Copy, Clone, Debug)]
42 pub enum NotUniqueParam<'tcx> {
43 DuplicateParam(ty::GenericArg<'tcx>),
44 NotParam(ty::GenericArg<'tcx>),
47 impl<'tcx> fmt::Display for Discr<'tcx> {
48 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
49 match *self.ty.kind() {
51 let size = ty::tls::with(|tcx| Integer::from_int_ty(&tcx, ity).size());
53 // sign extend the raw representation to be an i128
54 let x = size.sign_extend(x) as i128;
57 _ => write!(fmt, "{}", self.val),
62 fn int_size_and_signed<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> (Size, bool) {
63 let (int, signed) = match *ty.kind() {
64 ty::Int(ity) => (Integer::from_int_ty(&tcx, ity), true),
65 ty::Uint(uty) => (Integer::from_uint_ty(&tcx, uty), false),
66 _ => bug!("non integer discriminant"),
71 impl<'tcx> Discr<'tcx> {
72 /// Adds `1` to the value and wraps around if the maximum for the type is reached.
73 pub fn wrap_incr(self, tcx: TyCtxt<'tcx>) -> Self {
74 self.checked_add(tcx, 1).0
76 pub fn checked_add(self, tcx: TyCtxt<'tcx>, n: u128) -> (Self, bool) {
77 let (size, signed) = int_size_and_signed(tcx, self.ty);
78 let (val, oflo) = if signed {
79 let min = size.signed_int_min();
80 let max = size.signed_int_max();
81 let val = size.sign_extend(self.val) as i128;
82 assert!(n < (i128::MAX as u128));
84 let oflo = val > max - n;
85 let val = if oflo { min + (n - (max - val) - 1) } else { val + n };
86 // zero the upper bits
87 let val = val as u128;
88 let val = size.truncate(val);
91 let max = size.unsigned_int_max();
93 let oflo = val > max - n;
94 let val = if oflo { n - (max - val) - 1 } else { val + n };
97 (Self { val, ty: self.ty }, oflo)
101 pub trait IntTypeExt {
102 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
103 fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>>;
104 fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx>;
107 impl IntTypeExt for IntegerType {
108 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
110 IntegerType::Pointer(true) => tcx.types.isize,
111 IntegerType::Pointer(false) => tcx.types.usize,
112 IntegerType::Fixed(i, s) => i.to_ty(tcx, *s),
116 fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx> {
117 Discr { val: 0, ty: self.to_ty(tcx) }
120 fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>> {
121 if let Some(val) = val {
122 assert_eq!(self.to_ty(tcx), val.ty);
123 let (new, oflo) = val.checked_add(tcx, 1);
124 if oflo { None } else { Some(new) }
126 Some(self.initial_discriminant(tcx))
131 impl<'tcx> TyCtxt<'tcx> {
132 /// Creates a hash of the type `Ty` which will be the same no matter what crate
133 /// context it's calculated within. This is used by the `type_id` intrinsic.
134 pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
135 // We want the type_id be independent of the types free regions, so we
136 // erase them. The erase_regions() call will also anonymize bound
137 // regions, which is desirable too.
138 let ty = self.erase_regions(ty);
140 self.with_stable_hashing_context(|mut hcx| {
141 let mut hasher = StableHasher::new();
142 hcx.while_hashing_spans(false, |hcx| ty.hash_stable(hcx, &mut hasher));
147 pub fn res_generics_def_id(self, res: Res) -> Option<DefId> {
149 Res::Def(DefKind::Ctor(CtorOf::Variant, _), def_id) => {
150 Some(self.parent(self.parent(def_id)))
152 Res::Def(DefKind::Variant | DefKind::Ctor(CtorOf::Struct, _), def_id) => {
153 Some(self.parent(def_id))
155 // Other `DefKind`s don't have generics and would ICE when calling
165 | DefKind::TraitAlias
169 | DefKind::AssocConst
178 pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
179 if let ty::Adt(def, substs) = *ty.kind() {
180 for field in def.all_fields() {
181 let field_ty = field.ty(self, substs);
182 if let ty::Error(_) = field_ty.kind() {
190 /// Attempts to returns the deeply last field of nested structures, but
191 /// does not apply any normalization in its search. Returns the same type
192 /// if input `ty` is not a structure at all.
193 pub fn struct_tail_without_normalization(self, ty: Ty<'tcx>) -> Ty<'tcx> {
195 tcx.struct_tail_with_normalize(ty, |ty| ty, || {})
198 /// Returns the deeply last field of nested structures, or the same type if
199 /// not a structure at all. Corresponds to the only possible unsized field,
200 /// and its type can be used to determine unsizing strategy.
202 /// Should only be called if `ty` has no inference variables and does not
203 /// need its lifetimes preserved (e.g. as part of codegen); otherwise
204 /// normalization attempt may cause compiler bugs.
205 pub fn struct_tail_erasing_lifetimes(
208 param_env: ty::ParamEnv<'tcx>,
211 tcx.struct_tail_with_normalize(ty, |ty| tcx.normalize_erasing_regions(param_env, ty), || {})
214 /// Returns the deeply last field of nested structures, or the same type if
215 /// not a structure at all. Corresponds to the only possible unsized field,
216 /// and its type can be used to determine unsizing strategy.
218 /// This is parameterized over the normalization strategy (i.e. how to
219 /// handle `<T as Trait>::Assoc` and `impl Trait`); pass the identity
220 /// function to indicate no normalization should take place.
222 /// See also `struct_tail_erasing_lifetimes`, which is suitable for use
224 pub fn struct_tail_with_normalize(
227 mut normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
228 // This is currently used to allow us to walk a ValTree
229 // in lockstep with the type in order to get the ValTree branch that
230 // corresponds to an unsized field.
231 mut f: impl FnMut() -> (),
233 let recursion_limit = self.recursion_limit();
234 for iteration in 0.. {
235 if !recursion_limit.value_within_limit(iteration) {
236 return self.ty_error_with_message(
238 &format!("reached the recursion limit finding the struct tail for {}", ty),
242 ty::Adt(def, substs) => {
243 if !def.is_struct() {
246 match def.non_enum_variant().fields.last() {
249 ty = field.ty(self, substs);
255 ty::Tuple(tys) if let Some((&last_ty, _)) = tys.split_last() => {
260 ty::Tuple(_) => break,
263 let normalized = normalize(ty);
264 if ty == normalized {
279 /// Same as applying `struct_tail` on `source` and `target`, but only
280 /// keeps going as long as the two types are instances of the same
281 /// structure definitions.
282 /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
283 /// whereas struct_tail produces `T`, and `Trait`, respectively.
285 /// Should only be called if the types have no inference variables and do
286 /// not need their lifetimes preserved (e.g., as part of codegen); otherwise,
287 /// normalization attempt may cause compiler bugs.
288 pub fn struct_lockstep_tails_erasing_lifetimes(
292 param_env: ty::ParamEnv<'tcx>,
293 ) -> (Ty<'tcx>, Ty<'tcx>) {
295 tcx.struct_lockstep_tails_with_normalize(source, target, |ty| {
296 tcx.normalize_erasing_regions(param_env, ty)
300 /// Same as applying `struct_tail` on `source` and `target`, but only
301 /// keeps going as long as the two types are instances of the same
302 /// structure definitions.
303 /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
304 /// whereas struct_tail produces `T`, and `Trait`, respectively.
306 /// See also `struct_lockstep_tails_erasing_lifetimes`, which is suitable for use
308 pub fn struct_lockstep_tails_with_normalize(
312 normalize: impl Fn(Ty<'tcx>) -> Ty<'tcx>,
313 ) -> (Ty<'tcx>, Ty<'tcx>) {
314 let (mut a, mut b) = (source, target);
316 match (&a.kind(), &b.kind()) {
317 (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
318 if a_def == b_def && a_def.is_struct() =>
320 if let Some(f) = a_def.non_enum_variant().fields.last() {
321 a = f.ty(self, a_substs);
322 b = f.ty(self, b_substs);
327 (&ty::Tuple(a_tys), &ty::Tuple(b_tys)) if a_tys.len() == b_tys.len() => {
328 if let Some(&a_last) = a_tys.last() {
330 b = *b_tys.last().unwrap();
335 (ty::Alias(..), _) | (_, ty::Alias(..)) => {
336 // If either side is a projection, attempt to
337 // progress via normalization. (Should be safe to
338 // apply to both sides as normalization is
340 let a_norm = normalize(a);
341 let b_norm = normalize(b);
342 if a == a_norm && b == b_norm {
356 /// Calculate the destructor of a given type.
357 pub fn calculate_dtor(
360 validate: impl Fn(Self, DefId) -> Result<(), ErrorGuaranteed>,
361 ) -> Option<ty::Destructor> {
362 let drop_trait = self.lang_items().drop_trait()?;
363 self.ensure().coherent_trait(drop_trait);
365 let ty = self.type_of(adt_did);
366 let (did, constness) = self.find_map_relevant_impl(drop_trait, ty, |impl_did| {
367 if let Some(item_id) = self.associated_item_def_ids(impl_did).first() {
368 if validate(self, impl_did).is_ok() {
369 return Some((*item_id, self.constness(impl_did)));
375 Some(ty::Destructor { did, constness })
378 /// Returns the set of types that are required to be alive in
379 /// order to run the destructor of `def` (see RFCs 769 and
382 /// Note that this returns only the constraints for the
383 /// destructor of `def` itself. For the destructors of the
384 /// contents, you need `adt_dtorck_constraint`.
385 pub fn destructor_constraints(self, def: ty::AdtDef<'tcx>) -> Vec<ty::subst::GenericArg<'tcx>> {
386 let dtor = match def.destructor(self) {
388 debug!("destructor_constraints({:?}) - no dtor", def.did());
391 Some(dtor) => dtor.did,
394 let impl_def_id = self.parent(dtor);
395 let impl_generics = self.generics_of(impl_def_id);
397 // We have a destructor - all the parameters that are not
398 // pure_wrt_drop (i.e, don't have a #[may_dangle] attribute)
401 // We need to return the list of parameters from the ADTs
402 // generics/substs that correspond to impure parameters on the
403 // impl's generics. This is a bit ugly, but conceptually simple:
405 // Suppose our ADT looks like the following
407 // struct S<X, Y, Z>(X, Y, Z);
411 // impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
413 // We want to return the parameters (X, Y). For that, we match
414 // up the item-substs <X, Y, Z> with the substs on the impl ADT,
415 // <P1, P2, P0>, and then look up which of the impl substs refer to
416 // parameters marked as pure.
418 let impl_substs = match *self.type_of(impl_def_id).kind() {
419 ty::Adt(def_, substs) if def_ == def => substs,
423 let item_substs = match *self.type_of(def.did()).kind() {
424 ty::Adt(def_, substs) if def_ == def => substs,
428 let result = iter::zip(item_substs, impl_substs)
431 GenericArgKind::Lifetime(region) => match region.kind() {
432 ty::ReEarlyBound(ref ebr) => {
433 !impl_generics.region_param(ebr, self).pure_wrt_drop
435 // Error: not a region param
438 GenericArgKind::Type(ty) => match ty.kind() {
439 ty::Param(ref pt) => !impl_generics.type_param(pt, self).pure_wrt_drop,
440 // Error: not a type param
443 GenericArgKind::Const(ct) => match ct.kind() {
444 ty::ConstKind::Param(ref pc) => {
445 !impl_generics.const_param(pc, self).pure_wrt_drop
447 // Error: not a const param
452 .map(|(item_param, _)| item_param)
454 debug!("destructor_constraint({:?}) = {:?}", def.did(), result);
458 /// Checks whether each generic argument is simply a unique generic parameter.
459 pub fn uses_unique_generic_params(
461 substs: SubstsRef<'tcx>,
462 ignore_regions: IgnoreRegions,
463 ) -> Result<(), NotUniqueParam<'tcx>> {
464 let mut seen = GrowableBitSet::default();
467 GenericArgKind::Lifetime(lt) => {
468 if ignore_regions == IgnoreRegions::No {
469 let ty::ReEarlyBound(p) = lt.kind() else {
470 return Err(NotUniqueParam::NotParam(lt.into()))
472 if !seen.insert(p.index) {
473 return Err(NotUniqueParam::DuplicateParam(lt.into()));
477 GenericArgKind::Type(t) => match t.kind() {
479 if !seen.insert(p.index) {
480 return Err(NotUniqueParam::DuplicateParam(t.into()));
483 _ => return Err(NotUniqueParam::NotParam(t.into())),
485 GenericArgKind::Const(c) => match c.kind() {
486 ty::ConstKind::Param(p) => {
487 if !seen.insert(p.index) {
488 return Err(NotUniqueParam::DuplicateParam(c.into()));
491 _ => return Err(NotUniqueParam::NotParam(c.into())),
499 /// Returns `true` if `def_id` refers to a closure (e.g., `|x| x * 2`). Note
500 /// that closures have a `DefId`, but the closure *expression* also
501 /// has a `HirId` that is located within the context where the
502 /// closure appears (and, sadly, a corresponding `NodeId`, since
503 /// those are not yet phased out). The parent of the closure's
504 /// `DefId` will also be the context where it appears.
505 pub fn is_closure(self, def_id: DefId) -> bool {
506 matches!(self.def_kind(def_id), DefKind::Closure | DefKind::Generator)
509 /// Returns `true` if `def_id` refers to a definition that does not have its own
510 /// type-checking context, i.e. closure, generator or inline const.
511 pub fn is_typeck_child(self, def_id: DefId) -> bool {
513 self.def_kind(def_id),
514 DefKind::Closure | DefKind::Generator | DefKind::InlineConst
518 /// Returns `true` if `def_id` refers to a trait (i.e., `trait Foo { ... }`).
519 pub fn is_trait(self, def_id: DefId) -> bool {
520 self.def_kind(def_id) == DefKind::Trait
523 /// Returns `true` if `def_id` refers to a trait alias (i.e., `trait Foo = ...;`),
524 /// and `false` otherwise.
525 pub fn is_trait_alias(self, def_id: DefId) -> bool {
526 self.def_kind(def_id) == DefKind::TraitAlias
529 /// Returns `true` if this `DefId` refers to the implicit constructor for
530 /// a tuple struct like `struct Foo(u32)`, and `false` otherwise.
531 pub fn is_constructor(self, def_id: DefId) -> bool {
532 matches!(self.def_kind(def_id), DefKind::Ctor(..))
535 /// Given the `DefId`, returns the `DefId` of the innermost item that
536 /// has its own type-checking context or "inference environment".
538 /// For example, a closure has its own `DefId`, but it is type-checked
539 /// with the containing item. Similarly, an inline const block has its
540 /// own `DefId` but it is type-checked together with the containing item.
542 /// Therefore, when we fetch the
543 /// `typeck` the closure, for example, we really wind up
544 /// fetching the `typeck` the enclosing fn item.
545 pub fn typeck_root_def_id(self, def_id: DefId) -> DefId {
546 let mut def_id = def_id;
547 while self.is_typeck_child(def_id) {
548 def_id = self.parent(def_id);
553 /// Given the `DefId` and substs a closure, creates the type of
554 /// `self` argument that the closure expects. For example, for a
555 /// `Fn` closure, this would return a reference type `&T` where
556 /// `T = closure_ty`.
558 /// Returns `None` if this closure's kind has not yet been inferred.
559 /// This should only be possible during type checking.
561 /// Note that the return value is a late-bound region and hence
562 /// wrapped in a binder.
563 pub fn closure_env_ty(
565 closure_def_id: DefId,
566 closure_substs: SubstsRef<'tcx>,
567 env_region: ty::RegionKind<'tcx>,
568 ) -> Option<Ty<'tcx>> {
569 let closure_ty = self.mk_closure(closure_def_id, closure_substs);
570 let closure_kind_ty = closure_substs.as_closure().kind_ty();
571 let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
572 let env_ty = match closure_kind {
573 ty::ClosureKind::Fn => self.mk_imm_ref(self.mk_region(env_region), closure_ty),
574 ty::ClosureKind::FnMut => self.mk_mut_ref(self.mk_region(env_region), closure_ty),
575 ty::ClosureKind::FnOnce => closure_ty,
580 /// Returns `true` if the node pointed to by `def_id` is a `static` item.
582 pub fn is_static(self, def_id: DefId) -> bool {
583 matches!(self.def_kind(def_id), DefKind::Static(_))
587 pub fn static_mutability(self, def_id: DefId) -> Option<hir::Mutability> {
588 if let DefKind::Static(mt) = self.def_kind(def_id) { Some(mt) } else { None }
591 /// Returns `true` if this is a `static` item with the `#[thread_local]` attribute.
592 pub fn is_thread_local_static(self, def_id: DefId) -> bool {
593 self.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
596 /// Returns `true` if the node pointed to by `def_id` is a mutable `static` item.
598 pub fn is_mutable_static(self, def_id: DefId) -> bool {
599 self.static_mutability(def_id) == Some(hir::Mutability::Mut)
602 /// Get the type of the pointer to the static that we use in MIR.
603 pub fn static_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
604 // Make sure that any constants in the static's type are evaluated.
605 let static_ty = self.normalize_erasing_regions(ty::ParamEnv::empty(), self.type_of(def_id));
607 // Make sure that accesses to unsafe statics end up using raw pointers.
608 // For thread-locals, this needs to be kept in sync with `Rvalue::ty`.
609 if self.is_mutable_static(def_id) {
610 self.mk_mut_ptr(static_ty)
611 } else if self.is_foreign_item(def_id) {
612 self.mk_imm_ptr(static_ty)
614 self.mk_imm_ref(self.lifetimes.re_erased, static_ty)
618 /// Return the set of types that should be taken into accound when checking
619 /// trait bounds on a generator's internal state.
620 pub fn generator_hidden_types(
623 ) -> impl Iterator<Item = ty::EarlyBinder<Ty<'tcx>>> {
624 let generator_layout = &self.mir_generator_witnesses(def_id);
628 .filter(|decl| !decl.ignore_for_traits)
629 .map(|decl| ty::EarlyBinder(decl.ty))
632 /// Normalizes all opaque types in the given value, replacing them
633 /// with their underlying types.
634 pub fn expand_opaque_types(self, val: Ty<'tcx>) -> Ty<'tcx> {
635 let mut visitor = OpaqueTypeExpander {
636 seen_opaque_tys: FxHashSet::default(),
637 expanded_cache: FxHashMap::default(),
638 primary_def_id: None,
639 found_recursion: false,
640 found_any_recursion: false,
641 check_recursion: false,
642 expand_generators: false,
645 val.fold_with(&mut visitor)
648 /// Expands the given impl trait type, stopping if the type is recursive.
649 #[instrument(skip(self), level = "debug", ret)]
650 pub fn try_expand_impl_trait_type(
653 substs: SubstsRef<'tcx>,
654 ) -> Result<Ty<'tcx>, Ty<'tcx>> {
655 let mut visitor = OpaqueTypeExpander {
656 seen_opaque_tys: FxHashSet::default(),
657 expanded_cache: FxHashMap::default(),
658 primary_def_id: Some(def_id),
659 found_recursion: false,
660 found_any_recursion: false,
661 check_recursion: true,
662 expand_generators: true,
666 let expanded_type = visitor.expand_opaque_ty(def_id, substs).unwrap();
667 if visitor.found_recursion { Err(expanded_type) } else { Ok(expanded_type) }
670 pub fn bound_return_position_impl_trait_in_trait_tys(
673 ) -> ty::EarlyBinder<Result<&'tcx FxHashMap<DefId, Ty<'tcx>>, ErrorGuaranteed>> {
674 ty::EarlyBinder(self.collect_return_position_impl_trait_in_trait_tys(def_id))
677 pub fn bound_explicit_item_bounds(
680 ) -> ty::EarlyBinder<&'tcx [(ty::Predicate<'tcx>, rustc_span::Span)]> {
681 ty::EarlyBinder(self.explicit_item_bounds(def_id))
684 pub fn bound_impl_subject(self, def_id: DefId) -> ty::EarlyBinder<ty::ImplSubject<'tcx>> {
685 ty::EarlyBinder(self.impl_subject(def_id))
688 /// Returns names of captured upvars for closures and generators.
690 /// Here are some examples:
691 /// - `name__field1__field2` when the upvar is captured by value.
692 /// - `_ref__name__field` when the upvar is captured by reference.
694 /// For generators this only contains upvars that are shared by all states.
695 pub fn closure_saved_names_of_captured_variables(
698 ) -> SmallVec<[String; 16]> {
699 let body = self.optimized_mir(def_id);
704 let is_ref = match var.value {
705 mir::VarDebugInfoContents::Place(place)
706 if place.local == mir::Local::new(1) =>
708 // The projection is either `[.., Field, Deref]` or `[.., Field]`. It
709 // implies whether the variable is captured by value or by reference.
710 matches!(place.projection.last().unwrap(), mir::ProjectionElem::Deref)
714 let prefix = if is_ref { "_ref__" } else { "" };
715 Some(prefix.to_owned() + var.name.as_str())
720 // FIXME(eddyb) maybe precompute this? Right now it's computed once
721 // per generator monomorphization, but it doesn't depend on substs.
722 pub fn generator_layout_and_saved_local_names(
726 &'tcx ty::GeneratorLayout<'tcx>,
727 IndexVec<mir::GeneratorSavedLocal, Option<rustc_span::Symbol>>,
730 let body = tcx.optimized_mir(def_id);
731 let generator_layout = body.generator_layout().unwrap();
732 let mut generator_saved_local_names =
733 IndexVec::from_elem(None, &generator_layout.field_tys);
735 let state_arg = mir::Local::new(1);
736 for var in &body.var_debug_info {
737 let mir::VarDebugInfoContents::Place(place) = &var.value else { continue };
738 if place.local != state_arg {
741 match place.projection[..] {
743 // Deref of the `Pin<&mut Self>` state argument.
744 mir::ProjectionElem::Field(..),
745 mir::ProjectionElem::Deref,
746 // Field of a variant of the state.
747 mir::ProjectionElem::Downcast(_, variant),
748 mir::ProjectionElem::Field(field, _),
750 let name = &mut generator_saved_local_names
751 [generator_layout.variant_fields[variant][field]];
753 name.replace(var.name);
759 (generator_layout, generator_saved_local_names)
763 struct OpaqueTypeExpander<'tcx> {
764 // Contains the DefIds of the opaque types that are currently being
765 // expanded. When we expand an opaque type we insert the DefId of
766 // that type, and when we finish expanding that type we remove the
768 seen_opaque_tys: FxHashSet<DefId>,
769 // Cache of all expansions we've seen so far. This is a critical
770 // optimization for some large types produced by async fn trees.
771 expanded_cache: FxHashMap<(DefId, SubstsRef<'tcx>), Ty<'tcx>>,
772 primary_def_id: Option<DefId>,
773 found_recursion: bool,
774 found_any_recursion: bool,
775 expand_generators: bool,
776 /// Whether or not to check for recursive opaque types.
777 /// This is `true` when we're explicitly checking for opaque type
778 /// recursion, and 'false' otherwise to avoid unnecessary work.
779 check_recursion: bool,
783 impl<'tcx> OpaqueTypeExpander<'tcx> {
784 fn expand_opaque_ty(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> Option<Ty<'tcx>> {
785 if self.found_any_recursion {
788 let substs = substs.fold_with(self);
789 if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
790 let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) {
791 Some(expanded_ty) => *expanded_ty,
793 let generic_ty = self.tcx.bound_type_of(def_id);
794 let concrete_ty = generic_ty.subst(self.tcx, substs);
795 let expanded_ty = self.fold_ty(concrete_ty);
796 self.expanded_cache.insert((def_id, substs), expanded_ty);
800 if self.check_recursion {
801 self.seen_opaque_tys.remove(&def_id);
805 // If another opaque type that we contain is recursive, then it
806 // will report the error, so we don't have to.
807 self.found_any_recursion = true;
808 self.found_recursion = def_id == *self.primary_def_id.as_ref().unwrap();
813 fn expand_generator(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> Option<Ty<'tcx>> {
814 if self.found_any_recursion {
817 let substs = substs.fold_with(self);
818 if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
819 let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) {
820 Some(expanded_ty) => *expanded_ty,
822 for bty in self.tcx.generator_hidden_types(def_id) {
823 let hidden_ty = bty.subst(self.tcx, substs);
824 self.fold_ty(hidden_ty);
826 let expanded_ty = self.tcx.mk_generator_witness_mir(def_id, substs);
827 self.expanded_cache.insert((def_id, substs), expanded_ty);
831 if self.check_recursion {
832 self.seen_opaque_tys.remove(&def_id);
836 // If another opaque type that we contain is recursive, then it
837 // will report the error, so we don't have to.
838 self.found_any_recursion = true;
839 self.found_recursion = def_id == *self.primary_def_id.as_ref().unwrap();
845 impl<'tcx> TypeFolder<'tcx> for OpaqueTypeExpander<'tcx> {
846 fn tcx(&self) -> TyCtxt<'tcx> {
850 fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
851 let mut t = if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) = *t.kind() {
852 self.expand_opaque_ty(def_id, substs).unwrap_or(t)
853 } else if t.has_opaque_types() || t.has_generators() {
854 t.super_fold_with(self)
858 if self.expand_generators {
859 if let ty::GeneratorWitnessMIR(def_id, substs) = *t.kind() {
860 t = self.expand_generator(def_id, substs).unwrap_or(t);
867 impl<'tcx> Ty<'tcx> {
868 /// Returns the maximum value for the given numeric type (including `char`s)
869 /// or returns `None` if the type is not numeric.
870 pub fn numeric_max_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
871 let val = match self.kind() {
872 ty::Int(_) | ty::Uint(_) => {
873 let (size, signed) = int_size_and_signed(tcx, self);
875 if signed { size.signed_int_max() as u128 } else { size.unsigned_int_max() };
878 ty::Char => Some(std::char::MAX as u128),
879 ty::Float(fty) => Some(match fty {
880 ty::FloatTy::F32 => rustc_apfloat::ieee::Single::INFINITY.to_bits(),
881 ty::FloatTy::F64 => rustc_apfloat::ieee::Double::INFINITY.to_bits(),
886 val.map(|v| ty::Const::from_bits(tcx, v, ty::ParamEnv::empty().and(self)))
889 /// Returns the minimum value for the given numeric type (including `char`s)
890 /// or returns `None` if the type is not numeric.
891 pub fn numeric_min_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
892 let val = match self.kind() {
893 ty::Int(_) | ty::Uint(_) => {
894 let (size, signed) = int_size_and_signed(tcx, self);
895 let val = if signed { size.truncate(size.signed_int_min() as u128) } else { 0 };
899 ty::Float(fty) => Some(match fty {
900 ty::FloatTy::F32 => (-::rustc_apfloat::ieee::Single::INFINITY).to_bits(),
901 ty::FloatTy::F64 => (-::rustc_apfloat::ieee::Double::INFINITY).to_bits(),
906 val.map(|v| ty::Const::from_bits(tcx, v, ty::ParamEnv::empty().and(self)))
909 /// Checks whether values of this type `T` are *moved* or *copied*
910 /// when referenced -- this amounts to a check for whether `T:
911 /// Copy`, but note that we **don't** consider lifetimes when
912 /// doing this check. This means that we may generate MIR which
913 /// does copies even when the type actually doesn't satisfy the
914 /// full requirements for the `Copy` trait (cc #29149) -- this
915 /// winds up being reported as an error during NLL borrow check.
916 pub fn is_copy_modulo_regions(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
917 self.is_trivially_pure_clone_copy() || tcx.is_copy_raw(param_env.and(self))
920 /// Checks whether values of this type `T` have a size known at
921 /// compile time (i.e., whether `T: Sized`). Lifetimes are ignored
922 /// for the purposes of this check, so it can be an
923 /// over-approximation in generic contexts, where one can have
924 /// strange rules like `<T as Foo<'static>>::Bar: Sized` that
925 /// actually carry lifetime requirements.
926 pub fn is_sized(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
927 self.is_trivially_sized(tcx) || tcx.is_sized_raw(param_env.and(self))
930 /// Checks whether values of this type `T` implement the `Freeze`
931 /// trait -- frozen types are those that do not contain an
932 /// `UnsafeCell` anywhere. This is a language concept used to
933 /// distinguish "true immutability", which is relevant to
934 /// optimization as well as the rules around static values. Note
935 /// that the `Freeze` trait is not exposed to end users and is
936 /// effectively an implementation detail.
937 pub fn is_freeze(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
938 self.is_trivially_freeze() || tcx.is_freeze_raw(param_env.and(self))
941 /// Fast path helper for testing if a type is `Freeze`.
943 /// Returning true means the type is known to be `Freeze`. Returning
944 /// `false` means nothing -- could be `Freeze`, might not be.
945 fn is_trivially_freeze(self) -> bool {
958 | ty::FnPtr(_) => true,
959 ty::Tuple(fields) => fields.iter().all(Self::is_trivially_freeze),
960 ty::Slice(elem_ty) | ty::Array(elem_ty, _) => elem_ty.is_trivially_freeze(),
967 | ty::GeneratorWitness(_)
968 | ty::GeneratorWitnessMIR(..)
972 | ty::Placeholder(_) => false,
976 /// Checks whether values of this type `T` implement the `Unpin` trait.
977 pub fn is_unpin(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
978 self.is_trivially_unpin() || tcx.is_unpin_raw(param_env.and(self))
981 /// Fast path helper for testing if a type is `Unpin`.
983 /// Returning true means the type is known to be `Unpin`. Returning
984 /// `false` means nothing -- could be `Unpin`, might not be.
985 fn is_trivially_unpin(self) -> bool {
998 | ty::FnPtr(_) => true,
999 ty::Tuple(fields) => fields.iter().all(Self::is_trivially_unpin),
1000 ty::Slice(elem_ty) | ty::Array(elem_ty, _) => elem_ty.is_trivially_unpin(),
1007 | ty::GeneratorWitness(_)
1008 | ty::GeneratorWitnessMIR(..)
1012 | ty::Placeholder(_) => false,
1016 /// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely
1017 /// non-copy and *might* have a destructor attached; if it returns
1018 /// `false`, then `ty` definitely has no destructor (i.e., no drop glue).
1020 /// (Note that this implies that if `ty` has a destructor attached,
1021 /// then `needs_drop` will definitely return `true` for `ty`.)
1023 /// Note that this method is used to check eligible types in unions.
1025 pub fn needs_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
1026 // Avoid querying in simple cases.
1027 match needs_drop_components(self, &tcx.data_layout) {
1028 Err(AlwaysRequiresDrop) => true,
1030 let query_ty = match *components {
1032 // If we've got a single component, call the query with that
1033 // to increase the chance that we hit the query cache.
1034 [component_ty] => component_ty,
1038 // This doesn't depend on regions, so try to minimize distinct
1040 // If normalization fails, we just use `query_ty`.
1042 tcx.try_normalize_erasing_regions(param_env, query_ty).unwrap_or(query_ty);
1044 tcx.needs_drop_raw(param_env.and(query_ty))
1049 /// Checks if `ty` has a significant drop.
1051 /// Note that this method can return false even if `ty` has a destructor
1052 /// attached; even if that is the case then the adt has been marked with
1053 /// the attribute `rustc_insignificant_dtor`.
1055 /// Note that this method is used to check for change in drop order for
1056 /// 2229 drop reorder migration analysis.
1058 pub fn has_significant_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
1059 // Avoid querying in simple cases.
1060 match needs_drop_components(self, &tcx.data_layout) {
1061 Err(AlwaysRequiresDrop) => true,
1063 let query_ty = match *components {
1065 // If we've got a single component, call the query with that
1066 // to increase the chance that we hit the query cache.
1067 [component_ty] => component_ty,
1071 // FIXME(#86868): We should be canonicalizing, or else moving this to a method of inference
1072 // context, or *something* like that, but for now just avoid passing inference
1073 // variables to queries that can't cope with them. Instead, conservatively
1074 // return "true" (may change drop order).
1075 if query_ty.needs_infer() {
1079 // This doesn't depend on regions, so try to minimize distinct
1081 let erased = tcx.normalize_erasing_regions(param_env, query_ty);
1082 tcx.has_significant_drop_raw(param_env.and(erased))
1087 /// Returns `true` if equality for this type is both reflexive and structural.
1089 /// Reflexive equality for a type is indicated by an `Eq` impl for that type.
1091 /// Primitive types (`u32`, `str`) have structural equality by definition. For composite data
1092 /// types, equality for the type as a whole is structural when it is the same as equality
1093 /// between all components (fields, array elements, etc.) of that type. For ADTs, structural
1094 /// equality is indicated by an implementation of `PartialStructuralEq` and `StructuralEq` for
1097 /// This function is "shallow" because it may return `true` for a composite type whose fields
1098 /// are not `StructuralEq`. For example, `[T; 4]` has structural equality regardless of `T`
1099 /// because equality for arrays is determined by the equality of each array element. If you
1100 /// want to know whether a given call to `PartialEq::eq` will proceed structurally all the way
1101 /// down, you will need to use a type visitor.
1103 pub fn is_structural_eq_shallow(self, tcx: TyCtxt<'tcx>) -> bool {
1105 // Look for an impl of both `PartialStructuralEq` and `StructuralEq`.
1106 ty::Adt(..) => tcx.has_structural_eq_impls(self),
1108 // Primitive types that satisfy `Eq`.
1109 ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Str | ty::Never => true,
1111 // Composite types that satisfy `Eq` when all of their fields do.
1113 // Because this function is "shallow", we return `true` for these composites regardless
1114 // of the type(s) contained within.
1115 ty::Ref(..) | ty::Array(..) | ty::Slice(_) | ty::Tuple(..) => true,
1117 // Raw pointers use bitwise comparison.
1118 ty::RawPtr(_) | ty::FnPtr(_) => true,
1120 // Floating point numbers are not `Eq`.
1121 ty::Float(_) => false,
1123 // Conservatively return `false` for all others...
1125 // Anonymous function types
1126 ty::FnDef(..) | ty::Closure(..) | ty::Dynamic(..) | ty::Generator(..) => false,
1128 // Generic or inferred types
1130 // FIXME(ecstaticmorse): Maybe we should `bug` here? This should probably only be
1131 // called for known, fully-monomorphized types.
1132 ty::Alias(..) | ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) => {
1137 | ty::GeneratorWitness(..)
1138 | ty::GeneratorWitnessMIR(..)
1139 | ty::Error(_) => false,
1143 /// Peel off all reference types in this type until there are none left.
1145 /// This method is idempotent, i.e. `ty.peel_refs().peel_refs() == ty.peel_refs()`.
1150 /// - `&'a mut u8` -> `u8`
1151 /// - `&'a &'b u8` -> `u8`
1152 /// - `&'a *const &'b u8 -> *const &'b u8`
1153 pub fn peel_refs(self) -> Ty<'tcx> {
1155 while let ty::Ref(_, inner_ty, _) = ty.kind() {
1162 pub fn outer_exclusive_binder(self) -> ty::DebruijnIndex {
1163 self.0.outer_exclusive_binder
1167 pub enum ExplicitSelf<'tcx> {
1169 ByReference(ty::Region<'tcx>, hir::Mutability),
1170 ByRawPointer(hir::Mutability),
1175 impl<'tcx> ExplicitSelf<'tcx> {
1176 /// Categorizes an explicit self declaration like `self: SomeType`
1177 /// into either `self`, `&self`, `&mut self`, `Box<self>`, or
1179 /// This is mainly used to require the arbitrary_self_types feature
1180 /// in the case of `Other`, to improve error messages in the common cases,
1181 /// and to make `Other` non-object-safe.
1185 /// ```ignore (illustrative)
1186 /// impl<'a> Foo for &'a T {
1187 /// // Legal declarations:
1188 /// fn method1(self: &&'a T); // ExplicitSelf::ByReference
1189 /// fn method2(self: &'a T); // ExplicitSelf::ByValue
1190 /// fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox
1191 /// fn method4(self: Rc<&'a T>); // ExplicitSelf::Other
1193 /// // Invalid cases will be caught by `check_method_receiver`:
1194 /// fn method_err1(self: &'a mut T); // ExplicitSelf::Other
1195 /// fn method_err2(self: &'static T) // ExplicitSelf::ByValue
1196 /// fn method_err3(self: &&T) // ExplicitSelf::ByReference
1200 pub fn determine<P>(self_arg_ty: Ty<'tcx>, is_self_ty: P) -> ExplicitSelf<'tcx>
1202 P: Fn(Ty<'tcx>) -> bool,
1204 use self::ExplicitSelf::*;
1206 match *self_arg_ty.kind() {
1207 _ if is_self_ty(self_arg_ty) => ByValue,
1208 ty::Ref(region, ty, mutbl) if is_self_ty(ty) => ByReference(region, mutbl),
1209 ty::RawPtr(ty::TypeAndMut { ty, mutbl }) if is_self_ty(ty) => ByRawPointer(mutbl),
1210 ty::Adt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => ByBox,
1216 /// Returns a list of types such that the given type needs drop if and only if
1217 /// *any* of the returned types need drop. Returns `Err(AlwaysRequiresDrop)` if
1218 /// this type always needs drop.
1219 pub fn needs_drop_components<'tcx>(
1221 target_layout: &TargetDataLayout,
1222 ) -> Result<SmallVec<[Ty<'tcx>; 2]>, AlwaysRequiresDrop> {
1224 ty::Infer(ty::FreshIntTy(_))
1225 | ty::Infer(ty::FreshFloatTy(_))
1234 | ty::GeneratorWitness(..)
1235 | ty::GeneratorWitnessMIR(..)
1238 | ty::Str => Ok(SmallVec::new()),
1240 // Foreign types can never have destructors.
1241 ty::Foreign(..) => Ok(SmallVec::new()),
1243 ty::Dynamic(..) | ty::Error(_) => Err(AlwaysRequiresDrop),
1245 ty::Slice(ty) => needs_drop_components(*ty, target_layout),
1246 ty::Array(elem_ty, size) => {
1247 match needs_drop_components(*elem_ty, target_layout) {
1248 Ok(v) if v.is_empty() => Ok(v),
1249 res => match size.kind().try_to_bits(target_layout.pointer_size) {
1250 // Arrays of size zero don't need drop, even if their element
1252 Some(0) => Ok(SmallVec::new()),
1254 // We don't know which of the cases above we are in, so
1255 // return the whole type and let the caller decide what to
1257 None => Ok(smallvec![ty]),
1261 // If any field needs drop, then the whole tuple does.
1262 ty::Tuple(fields) => fields.iter().try_fold(SmallVec::new(), move |mut acc, elem| {
1263 acc.extend(needs_drop_components(elem, target_layout)?);
1267 // These require checking for `Copy` bounds or `Adt` destructors.
1272 | ty::Placeholder(..)
1275 | ty::Generator(..) => Ok(smallvec![ty]),
1279 pub fn is_trivially_const_drop(ty: Ty<'_>) -> bool {
1286 | ty::Infer(ty::IntVar(_))
1287 | ty::Infer(ty::FloatVar(_))
1294 | ty::Foreign(_) => true,
1301 | ty::Placeholder(_)
1302 | ty::Infer(_) => false,
1304 // Not trivial because they have components, and instead of looking inside,
1305 // we'll just perform trait selection.
1308 | ty::GeneratorWitness(_)
1309 | ty::GeneratorWitnessMIR(..)
1310 | ty::Adt(..) => false,
1312 ty::Array(ty, _) | ty::Slice(ty) => is_trivially_const_drop(ty),
1314 ty::Tuple(tys) => tys.iter().all(|ty| is_trivially_const_drop(ty)),
1318 /// Does the equivalent of
1319 /// ```ignore (ilustrative)
1320 /// let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
1321 /// folder.tcx().intern_*(&v)
1323 pub fn fold_list<'tcx, F, T>(
1324 list: &'tcx ty::List<T>,
1326 intern: impl FnOnce(TyCtxt<'tcx>, &[T]) -> &'tcx ty::List<T>,
1327 ) -> Result<&'tcx ty::List<T>, F::Error>
1329 F: FallibleTypeFolder<'tcx>,
1330 T: TypeFoldable<'tcx> + PartialEq + Copy,
1332 let mut iter = list.iter();
1333 // Look for the first element that changed
1334 match iter.by_ref().enumerate().find_map(|(i, t)| match t.try_fold_with(folder) {
1335 Ok(new_t) if new_t == t => None,
1336 new_t => Some((i, new_t)),
1338 Some((i, Ok(new_t))) => {
1339 // An element changed, prepare to intern the resulting list
1340 let mut new_list = SmallVec::<[_; 8]>::with_capacity(list.len());
1341 new_list.extend_from_slice(&list[..i]);
1342 new_list.push(new_t);
1344 new_list.push(t.try_fold_with(folder)?)
1346 Ok(intern(folder.tcx(), &new_list))
1348 Some((_, Err(err))) => {
1355 #[derive(Copy, Clone, Debug, HashStable, TyEncodable, TyDecodable)]
1356 pub struct AlwaysRequiresDrop;
1358 /// Reveals all opaque types in the given value, replacing them
1359 /// with their underlying types.
1360 pub fn reveal_opaque_types_in_bounds<'tcx>(
1362 val: &'tcx ty::List<ty::Predicate<'tcx>>,
1363 ) -> &'tcx ty::List<ty::Predicate<'tcx>> {
1364 let mut visitor = OpaqueTypeExpander {
1365 seen_opaque_tys: FxHashSet::default(),
1366 expanded_cache: FxHashMap::default(),
1367 primary_def_id: None,
1368 found_recursion: false,
1369 found_any_recursion: false,
1370 check_recursion: false,
1371 expand_generators: false,
1374 val.fold_with(&mut visitor)
1377 /// Determines whether an item is annotated with `doc(hidden)`.
1378 fn is_doc_hidden(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
1379 assert!(def_id.is_local());
1380 tcx.get_attrs(def_id, sym::doc)
1381 .filter_map(|attr| attr.meta_item_list())
1382 .any(|items| items.iter().any(|item| item.has_name(sym::hidden)))
1385 /// Determines whether an item is annotated with `doc(notable_trait)`.
1386 pub fn is_doc_notable_trait(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
1387 tcx.get_attrs(def_id, sym::doc)
1388 .filter_map(|attr| attr.meta_item_list())
1389 .any(|items| items.iter().any(|item| item.has_name(sym::notable_trait)))
1392 /// Determines whether an item is an intrinsic by Abi.
1393 pub fn is_intrinsic(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
1394 matches!(tcx.fn_sig(def_id).skip_binder().abi(), Abi::RustIntrinsic | Abi::PlatformIntrinsic)
1397 pub fn provide(providers: &mut ty::query::Providers) {
1398 *providers = ty::query::Providers {
1399 reveal_opaque_types_in_bounds,
1401 is_doc_notable_trait,