1 //! Miscellaneous type-system utilities that are too small to deserve their own modules.
3 use crate::hir::def::Def;
4 use crate::hir::def_id::DefId;
5 use crate::hir::map::DefPathData;
6 use crate::hir::{self, Node};
7 use crate::ich::NodeIdHashingMode;
8 use crate::traits::{self, ObligationCause};
9 use crate::ty::{self, Ty, TyCtxt, GenericParamDefKind, TypeFoldable};
10 use crate::ty::subst::{Subst, Substs, UnpackedKind};
11 use crate::ty::query::TyCtxtAt;
12 use crate::ty::TyKind::*;
13 use crate::ty::layout::{Integer, IntegerExt};
14 use crate::util::common::ErrorReported;
15 use crate::middle::lang_items;
17 use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
18 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
21 use syntax::attr::{self, SignedInt, UnsignedInt};
22 use syntax_pos::{Span, DUMMY_SP};
24 #[derive(Copy, Clone, Debug)]
25 pub struct Discr<'tcx> {
26 /// Bit representation of the discriminant (e.g., `-128i8` is `0xFF_u128`).
31 impl<'tcx> fmt::Display for Discr<'tcx> {
32 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
35 let bits = ty::tls::with(|tcx| {
36 Integer::from_attr(&tcx, SignedInt(ity)).size().bits()
38 let x = self.val as i128;
39 // sign extend the raw representation to be an i128
40 let x = (x << (128 - bits)) >> (128 - bits);
43 _ => write!(fmt, "{}", self.val),
48 impl<'tcx> Discr<'tcx> {
49 /// Adds `1` to the value and wraps around if the maximum for the type is reached.
50 pub fn wrap_incr<'a, 'gcx>(self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Self {
51 self.checked_add(tcx, 1).0
53 pub fn checked_add<'a, 'gcx>(self, tcx: TyCtxt<'a, 'gcx, 'tcx>, n: u128) -> (Self, bool) {
54 let (int, signed) = match self.ty.sty {
55 Int(ity) => (Integer::from_attr(&tcx, SignedInt(ity)), true),
56 Uint(uty) => (Integer::from_attr(&tcx, UnsignedInt(uty)), false),
57 _ => bug!("non integer discriminant"),
60 let bit_size = int.size().bits();
61 let shift = 128 - bit_size;
67 let min = sext(1_u128 << (bit_size - 1));
68 let max = i128::max_value() >> shift;
69 let val = sext(self.val);
70 assert!(n < (i128::max_value() as u128));
72 let oflo = val > max - n;
74 min + (n - (max - val) - 1)
78 // zero the upper bits
79 let val = val as u128;
80 let val = (val << shift) >> shift;
86 let max = u128::max_value() >> shift;
88 let oflo = val > max - n;
102 pub trait IntTypeExt {
103 fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx>;
104 fn disr_incr<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, val: Option<Discr<'tcx>>)
105 -> Option<Discr<'tcx>>;
106 fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Discr<'tcx>;
109 impl IntTypeExt for attr::IntType {
110 fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
112 SignedInt(ast::IntTy::I8) => tcx.types.i8,
113 SignedInt(ast::IntTy::I16) => tcx.types.i16,
114 SignedInt(ast::IntTy::I32) => tcx.types.i32,
115 SignedInt(ast::IntTy::I64) => tcx.types.i64,
116 SignedInt(ast::IntTy::I128) => tcx.types.i128,
117 SignedInt(ast::IntTy::Isize) => tcx.types.isize,
118 UnsignedInt(ast::UintTy::U8) => tcx.types.u8,
119 UnsignedInt(ast::UintTy::U16) => tcx.types.u16,
120 UnsignedInt(ast::UintTy::U32) => tcx.types.u32,
121 UnsignedInt(ast::UintTy::U64) => tcx.types.u64,
122 UnsignedInt(ast::UintTy::U128) => tcx.types.u128,
123 UnsignedInt(ast::UintTy::Usize) => tcx.types.usize,
127 fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Discr<'tcx> {
134 fn disr_incr<'a, 'tcx>(
136 tcx: TyCtxt<'a, 'tcx, 'tcx>,
137 val: Option<Discr<'tcx>>,
138 ) -> Option<Discr<'tcx>> {
139 if let Some(val) = val {
140 assert_eq!(self.to_ty(tcx), val.ty);
141 let (new, oflo) = val.checked_add(tcx, 1);
148 Some(self.initial_discriminant(tcx))
155 pub enum CopyImplementationError<'tcx> {
156 InfrigingFields(Vec<&'tcx ty::FieldDef>),
161 /// Describes whether a type is representable. For types that are not
162 /// representable, 'SelfRecursive' and 'ContainsRecursive' are used to
163 /// distinguish between types that are recursive with themselves and types that
164 /// contain a different recursive type. These cases can therefore be treated
165 /// differently when reporting errors.
167 /// The ordering of the cases is significant. They are sorted so that cmp::max
168 /// will keep the "more erroneous" of two values.
169 #[derive(Clone, PartialOrd, Ord, Eq, PartialEq, Debug)]
170 pub enum Representability {
173 SelfRecursive(Vec<Span>),
176 impl<'tcx> ty::ParamEnv<'tcx> {
177 pub fn can_type_implement_copy<'a>(self,
178 tcx: TyCtxt<'a, 'tcx, 'tcx>,
180 -> Result<(), CopyImplementationError<'tcx>> {
181 // FIXME: (@jroesch) float this code up
182 tcx.infer_ctxt().enter(|infcx| {
183 let (adt, substs) = match self_type.sty {
184 // These types used to have a builtin impl.
185 // Now libcore provides that impl.
186 ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Float(_) |
187 ty::Char | ty::RawPtr(..) | ty::Never |
188 ty::Ref(_, _, hir::MutImmutable) => return Ok(()),
190 ty::Adt(adt, substs) => (adt, substs),
192 _ => return Err(CopyImplementationError::NotAnAdt),
195 let mut infringing = Vec::new();
196 for variant in &adt.variants {
197 for field in &variant.fields {
198 let ty = field.ty(tcx, substs);
199 if ty.references_error() {
202 let span = tcx.def_span(field.did);
203 let cause = ObligationCause { span, ..ObligationCause::dummy() };
204 let ctx = traits::FulfillmentContext::new();
205 match traits::fully_normalize(&infcx, ctx, cause, self, &ty) {
206 Ok(ty) => if !infcx.type_is_copy_modulo_regions(self, ty, span) {
207 infringing.push(field);
210 infcx.report_fulfillment_errors(&errors, None, false);
215 if !infringing.is_empty() {
216 return Err(CopyImplementationError::InfrigingFields(infringing));
218 if adt.has_dtor(tcx) {
219 return Err(CopyImplementationError::HasDestructor);
227 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
228 /// Creates a hash of the type `Ty` which will be the same no matter what crate
229 /// context it's calculated within. This is used by the `type_id` intrinsic.
230 pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
231 let mut hasher = StableHasher::new();
232 let mut hcx = self.create_stable_hashing_context();
234 // We want the type_id be independent of the types free regions, so we
235 // erase them. The erase_regions() call will also anonymize bound
236 // regions, which is desirable too.
237 let ty = self.erase_regions(&ty);
239 hcx.while_hashing_spans(false, |hcx| {
240 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
241 ty.hash_stable(hcx, &mut hasher);
248 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
249 pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
250 if let ty::Adt(def, substs) = ty.sty {
251 for field in def.all_fields() {
252 let field_ty = field.ty(self, substs);
253 if let Error = field_ty.sty {
261 /// Returns the deeply last field of nested structures, or the same type,
262 /// if not a structure at all. Corresponds to the only possible unsized
263 /// field, and its type can be used to determine unsizing strategy.
264 pub fn struct_tail(self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
267 ty::Adt(def, substs) => {
268 if !def.is_struct() {
271 match def.non_enum_variant().fields.last() {
272 Some(f) => ty = f.ty(self, substs),
278 if let Some((&last_ty, _)) = tys.split_last() {
293 /// Same as applying struct_tail on `source` and `target`, but only
294 /// keeps going as long as the two types are instances of the same
295 /// structure definitions.
296 /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
297 /// whereas struct_tail produces `T`, and `Trait`, respectively.
298 pub fn struct_lockstep_tails(self,
301 -> (Ty<'tcx>, Ty<'tcx>) {
302 let (mut a, mut b) = (source, target);
304 match (&a.sty, &b.sty) {
305 (&Adt(a_def, a_substs), &Adt(b_def, b_substs))
306 if a_def == b_def && a_def.is_struct() => {
307 if let Some(f) = a_def.non_enum_variant().fields.last() {
308 a = f.ty(self, a_substs);
309 b = f.ty(self, b_substs);
314 (&Tuple(a_tys), &Tuple(b_tys))
315 if a_tys.len() == b_tys.len() => {
316 if let Some(a_last) = a_tys.last() {
318 b = b_tys.last().unwrap();
329 /// Given a set of predicates that apply to an object type, returns
330 /// the region bounds that the (erased) `Self` type must
331 /// outlive. Precisely *because* the `Self` type is erased, the
332 /// parameter `erased_self_ty` must be supplied to indicate what type
333 /// has been used to represent `Self` in the predicates
334 /// themselves. This should really be a unique type; `FreshTy(0)` is a
337 /// N.B., in some cases, particularly around higher-ranked bounds,
338 /// this function returns a kind of conservative approximation.
339 /// That is, all regions returned by this function are definitely
340 /// required, but there may be other region bounds that are not
341 /// returned, as well as requirements like `for<'a> T: 'a`.
343 /// Requires that trait definitions have been processed so that we can
344 /// elaborate predicates and walk supertraits.
346 // FIXME: callers may only have a `&[Predicate]`, not a `Vec`, so that's
347 // what this code should accept.
348 pub fn required_region_bounds(self,
349 erased_self_ty: Ty<'tcx>,
350 predicates: Vec<ty::Predicate<'tcx>>)
351 -> Vec<ty::Region<'tcx>> {
352 debug!("required_region_bounds(erased_self_ty={:?}, predicates={:?})",
356 assert!(!erased_self_ty.has_escaping_bound_vars());
358 traits::elaborate_predicates(self, predicates)
359 .filter_map(|predicate| {
361 ty::Predicate::Projection(..) |
362 ty::Predicate::Trait(..) |
363 ty::Predicate::Subtype(..) |
364 ty::Predicate::WellFormed(..) |
365 ty::Predicate::ObjectSafe(..) |
366 ty::Predicate::ClosureKind(..) |
367 ty::Predicate::RegionOutlives(..) |
368 ty::Predicate::ConstEvaluatable(..) => {
371 ty::Predicate::TypeOutlives(predicate) => {
372 // Search for a bound of the form `erased_self_ty
373 // : 'a`, but be wary of something like `for<'a>
374 // erased_self_ty : 'a` (we interpret a
375 // higher-ranked bound like that as 'static,
376 // though at present the code in `fulfill.rs`
377 // considers such bounds to be unsatisfiable, so
378 // it's kind of a moot point since you could never
379 // construct such an object, but this seems
380 // correct even if that code changes).
381 let ty::OutlivesPredicate(ref t, ref r) = predicate.skip_binder();
382 if t == &erased_self_ty && !r.has_escaping_bound_vars() {
393 /// Calculate the destructor of a given type.
394 pub fn calculate_dtor(
397 validate: &mut dyn FnMut(Self, DefId) -> Result<(), ErrorReported>
398 ) -> Option<ty::Destructor> {
399 let drop_trait = if let Some(def_id) = self.lang_items().drop_trait() {
405 self.ensure().coherent_trait(drop_trait);
407 let mut dtor_did = None;
408 let ty = self.type_of(adt_did);
409 self.for_each_relevant_impl(drop_trait, ty, |impl_did| {
410 if let Some(item) = self.associated_items(impl_did).next() {
411 if validate(self, impl_did).is_ok() {
412 dtor_did = Some(item.def_id);
417 Some(ty::Destructor { did: dtor_did? })
420 /// Returns the set of types that are required to be alive in
421 /// order to run the destructor of `def` (see RFCs 769 and
424 /// Note that this returns only the constraints for the
425 /// destructor of `def` itself. For the destructors of the
426 /// contents, you need `adt_dtorck_constraint`.
427 pub fn destructor_constraints(self, def: &'tcx ty::AdtDef)
428 -> Vec<ty::subst::Kind<'tcx>>
430 let dtor = match def.destructor(self) {
432 debug!("destructor_constraints({:?}) - no dtor", def.did);
435 Some(dtor) => dtor.did
438 // RFC 1238: if the destructor method is tagged with the
439 // attribute `unsafe_destructor_blind_to_params`, then the
440 // compiler is being instructed to *assume* that the
441 // destructor will not access borrowed data,
442 // even if such data is otherwise reachable.
444 // Such access can be in plain sight (e.g., dereferencing
445 // `*foo.0` of `Foo<'a>(&'a u32)`) or indirectly hidden
446 // (e.g., calling `foo.0.clone()` of `Foo<T:Clone>`).
447 if self.has_attr(dtor, "unsafe_destructor_blind_to_params") {
448 debug!("destructor_constraint({:?}) - blind", def.did);
452 let impl_def_id = self.associated_item(dtor).container.id();
453 let impl_generics = self.generics_of(impl_def_id);
455 // We have a destructor - all the parameters that are not
456 // pure_wrt_drop (i.e, don't have a #[may_dangle] attribute)
459 // We need to return the list of parameters from the ADTs
460 // generics/substs that correspond to impure parameters on the
461 // impl's generics. This is a bit ugly, but conceptually simple:
463 // Suppose our ADT looks like the following
465 // struct S<X, Y, Z>(X, Y, Z);
469 // impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
471 // We want to return the parameters (X, Y). For that, we match
472 // up the item-substs <X, Y, Z> with the substs on the impl ADT,
473 // <P1, P2, P0>, and then look up which of the impl substs refer to
474 // parameters marked as pure.
476 let impl_substs = match self.type_of(impl_def_id).sty {
477 ty::Adt(def_, substs) if def_ == def => substs,
481 let item_substs = match self.type_of(def.did).sty {
482 ty::Adt(def_, substs) if def_ == def => substs,
486 let result = item_substs.iter().zip(impl_substs.iter())
489 UnpackedKind::Lifetime(&ty::RegionKind::ReEarlyBound(ref ebr)) => {
490 !impl_generics.region_param(ebr, self).pure_wrt_drop
492 UnpackedKind::Type(&ty::TyS {
493 sty: ty::Param(ref pt), ..
495 !impl_generics.type_param(pt, self).pure_wrt_drop
497 UnpackedKind::Lifetime(_) | UnpackedKind::Type(_) => {
498 // not a type or region param - this should be reported
504 .map(|(&item_param, _)| item_param)
506 debug!("destructor_constraint({:?}) = {:?}", def.did, result);
510 /// Returns `true` if `def_id` refers to a closure (e.g., `|x| x * 2`). Note
511 /// that closures have a `DefId`, but the closure *expression* also
512 /// has a `HirId` that is located within the context where the
513 /// closure appears (and, sadly, a corresponding `NodeId`, since
514 /// those are not yet phased out). The parent of the closure's
515 /// `DefId` will also be the context where it appears.
516 pub fn is_closure(self, def_id: DefId) -> bool {
517 self.def_key(def_id).disambiguated_data.data == DefPathData::ClosureExpr
520 /// Returns `true` if `def_id` refers to a trait (i.e., `trait Foo { ... }`).
521 pub fn is_trait(self, def_id: DefId) -> bool {
522 if let DefPathData::Trait(_) = self.def_key(def_id).disambiguated_data.data {
529 /// Returns `true` if `def_id` refers to a trait alias (i.e., `trait Foo = ...;`),
530 /// and `false` otherwise.
531 pub fn is_trait_alias(self, def_id: DefId) -> bool {
532 if let DefPathData::TraitAlias(_) = self.def_key(def_id).disambiguated_data.data {
539 /// Returns `true` if this `DefId` refers to the implicit constructor for
540 /// a tuple struct like `struct Foo(u32)`, and `false` otherwise.
541 pub fn is_struct_constructor(self, def_id: DefId) -> bool {
542 self.def_key(def_id).disambiguated_data.data == DefPathData::StructCtor
545 /// Given the `DefId` of a fn or closure, returns the `DefId` of
546 /// the innermost fn item that the closure is contained within.
547 /// This is a significant `DefId` because, when we do
548 /// type-checking, we type-check this fn item and all of its
549 /// (transitive) closures together. Therefore, when we fetch the
550 /// `typeck_tables_of` the closure, for example, we really wind up
551 /// fetching the `typeck_tables_of` the enclosing fn item.
552 pub fn closure_base_def_id(self, def_id: DefId) -> DefId {
553 let mut def_id = def_id;
554 while self.is_closure(def_id) {
555 def_id = self.parent_def_id(def_id).unwrap_or_else(|| {
556 bug!("closure {:?} has no parent", def_id);
562 /// Given the `DefId` and substs a closure, creates the type of
563 /// `self` argument that the closure expects. For example, for a
564 /// `Fn` closure, this would return a reference type `&T` where
565 /// `T = closure_ty`.
567 /// Returns `None` if this closure's kind has not yet been inferred.
568 /// This should only be possible during type checking.
570 /// Note that the return value is a late-bound region and hence
571 /// wrapped in a binder.
572 pub fn closure_env_ty(self,
573 closure_def_id: DefId,
574 closure_substs: ty::ClosureSubsts<'tcx>)
575 -> Option<ty::Binder<Ty<'tcx>>>
577 let closure_ty = self.mk_closure(closure_def_id, closure_substs);
578 let env_region = ty::ReLateBound(ty::INNERMOST, ty::BrEnv);
579 let closure_kind_ty = closure_substs.closure_kind_ty(closure_def_id, self);
580 let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
581 let env_ty = match closure_kind {
582 ty::ClosureKind::Fn => self.mk_imm_ref(self.mk_region(env_region), closure_ty),
583 ty::ClosureKind::FnMut => self.mk_mut_ref(self.mk_region(env_region), closure_ty),
584 ty::ClosureKind::FnOnce => closure_ty,
586 Some(ty::Binder::bind(env_ty))
589 /// Given the `DefId` of some item that has no type parameters, make
590 /// a suitable "empty substs" for it.
591 pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> &'tcx Substs<'tcx> {
592 Substs::for_item(self, item_def_id, |param, _| {
594 GenericParamDefKind::Lifetime => self.types.re_erased.into(),
595 GenericParamDefKind::Type {..} => {
596 bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
602 /// Returns `true` if the node pointed to by `def_id` is a static item, and its mutability.
603 pub fn is_static(&self, def_id: DefId) -> Option<hir::Mutability> {
604 if let Some(node) = self.hir().get_if_local(def_id) {
606 Node::Item(&hir::Item {
607 node: hir::ItemKind::Static(_, mutbl, _), ..
609 Node::ForeignItem(&hir::ForeignItem {
610 node: hir::ForeignItemKind::Static(_, is_mutbl), ..
613 hir::Mutability::MutMutable
615 hir::Mutability::MutImmutable
620 match self.describe_def(def_id) {
621 Some(Def::Static(_, is_mutbl)) =>
623 hir::Mutability::MutMutable
625 hir::Mutability::MutImmutable
632 /// Expands the given impl trait type, stopping if the type is recursive.
633 pub fn try_expand_impl_trait_type(
636 substs: &'tcx Substs<'tcx>,
637 ) -> Result<Ty<'tcx>, Ty<'tcx>> {
638 use crate::ty::fold::TypeFolder;
640 struct OpaqueTypeExpander<'a, 'gcx, 'tcx> {
641 // Contains the DefIds of the opaque types that are currently being
642 // expanded. When we expand an opaque type we insert the DefId of
643 // that type, and when we finish expanding that type we remove the
645 seen_opaque_tys: FxHashSet<DefId>,
646 primary_def_id: DefId,
647 found_recursion: bool,
648 tcx: TyCtxt<'a, 'gcx, 'tcx>,
651 impl<'a, 'gcx, 'tcx> OpaqueTypeExpander<'a, 'gcx, 'tcx> {
655 substs: &'tcx Substs<'tcx>,
656 ) -> Option<Ty<'tcx>> {
657 if self.found_recursion {
659 } else if self.seen_opaque_tys.insert(def_id) {
660 let generic_ty = self.tcx.type_of(def_id);
661 let concrete_ty = generic_ty.subst(self.tcx, substs);
662 let expanded_ty = self.fold_ty(concrete_ty);
663 self.seen_opaque_tys.remove(&def_id);
666 // If another opaque type that we contain is recursive, then it
667 // will report the error, so we don't have to.
668 self.found_recursion = def_id == self.primary_def_id;
674 impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for OpaqueTypeExpander<'a, 'gcx, 'tcx> {
675 fn tcx(&self) -> TyCtxt<'_, 'gcx, 'tcx> {
679 fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
680 if let ty::Opaque(def_id, substs) = t.sty {
681 self.expand_opaque_ty(def_id, substs).unwrap_or(t)
683 t.super_fold_with(self)
688 let mut visitor = OpaqueTypeExpander {
689 seen_opaque_tys: FxHashSet::default(),
690 primary_def_id: def_id,
691 found_recursion: false,
694 let expanded_type = visitor.expand_opaque_ty(def_id, substs).unwrap();
695 if visitor.found_recursion {
703 impl<'a, 'tcx> ty::TyS<'tcx> {
704 /// Checks whether values of this type `T` are *moved* or *copied*
705 /// when referenced -- this amounts to a check for whether `T:
706 /// Copy`, but note that we **don't** consider lifetimes when
707 /// doing this check. This means that we may generate MIR which
708 /// does copies even when the type actually doesn't satisfy the
709 /// full requirements for the `Copy` trait (cc #29149) -- this
710 /// winds up being reported as an error during NLL borrow check.
711 pub fn is_copy_modulo_regions(&'tcx self,
712 tcx: TyCtxt<'a, 'tcx, 'tcx>,
713 param_env: ty::ParamEnv<'tcx>,
716 tcx.at(span).is_copy_raw(param_env.and(self))
719 /// Checks whether values of this type `T` have a size known at
720 /// compile time (i.e., whether `T: Sized`). Lifetimes are ignored
721 /// for the purposes of this check, so it can be an
722 /// over-approximation in generic contexts, where one can have
723 /// strange rules like `<T as Foo<'static>>::Bar: Sized` that
724 /// actually carry lifetime requirements.
725 pub fn is_sized(&'tcx self,
726 tcx_at: TyCtxtAt<'a, 'tcx, 'tcx>,
727 param_env: ty::ParamEnv<'tcx>)-> bool
729 tcx_at.is_sized_raw(param_env.and(self))
732 /// Checks whether values of this type `T` implement the `Freeze`
733 /// trait -- frozen types are those that do not contain a
734 /// `UnsafeCell` anywhere. This is a language concept used to
735 /// distinguish "true immutability", which is relevant to
736 /// optimization as well as the rules around static values. Note
737 /// that the `Freeze` trait is not exposed to end users and is
738 /// effectively an implementation detail.
739 pub fn is_freeze(&'tcx self,
740 tcx: TyCtxt<'a, 'tcx, 'tcx>,
741 param_env: ty::ParamEnv<'tcx>,
744 tcx.at(span).is_freeze_raw(param_env.and(self))
747 /// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely
748 /// non-copy and *might* have a destructor attached; if it returns
749 /// `false`, then `ty` definitely has no destructor (i.e., no drop glue).
751 /// (Note that this implies that if `ty` has a destructor attached,
752 /// then `needs_drop` will definitely return `true` for `ty`.)
754 pub fn needs_drop(&'tcx self,
755 tcx: TyCtxt<'a, 'tcx, 'tcx>,
756 param_env: ty::ParamEnv<'tcx>)
758 tcx.needs_drop_raw(param_env.and(self))
761 pub fn same_type(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
762 match (&a.sty, &b.sty) {
763 (&Adt(did_a, substs_a), &Adt(did_b, substs_b)) => {
768 substs_a.types().zip(substs_b.types()).all(|(a, b)| Self::same_type(a, b))
774 /// Check whether a type is representable. This means it cannot contain unboxed
775 /// structural recursion. This check is needed for structs and enums.
776 pub fn is_representable(&'tcx self,
777 tcx: TyCtxt<'a, 'tcx, 'tcx>,
781 // Iterate until something non-representable is found
782 fn fold_repr<It: Iterator<Item=Representability>>(iter: It) -> Representability {
783 iter.fold(Representability::Representable, |r1, r2| {
785 (Representability::SelfRecursive(v1),
786 Representability::SelfRecursive(v2)) => {
787 Representability::SelfRecursive(v1.into_iter().chain(v2).collect())
789 (r1, r2) => cmp::max(r1, r2)
794 fn are_inner_types_recursive<'a, 'tcx>(
795 tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span,
796 seen: &mut Vec<Ty<'tcx>>,
797 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
803 // Find non representable
804 fold_repr(ts.iter().map(|ty| {
805 is_type_structurally_recursive(tcx, sp, seen, representable_cache, ty)
808 // Fixed-length vectors.
809 // FIXME(#11924) Behavior undecided for zero-length vectors.
811 is_type_structurally_recursive(tcx, sp, seen, representable_cache, ty)
813 Adt(def, substs) => {
814 // Find non representable fields with their spans
815 fold_repr(def.all_fields().map(|field| {
816 let ty = field.ty(tcx, substs);
817 let span = tcx.hir().span_if_local(field.did).unwrap_or(sp);
818 match is_type_structurally_recursive(tcx, span, seen,
819 representable_cache, ty)
821 Representability::SelfRecursive(_) => {
822 Representability::SelfRecursive(vec![span])
829 // this check is run on type definitions, so we don't expect
830 // to see closure types
831 bug!("requires check invoked on inapplicable type: {:?}", ty)
833 _ => Representability::Representable,
837 fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: &'tcx ty::AdtDef) -> bool {
846 // Does the type `ty` directly (without indirection through a pointer)
847 // contain any types on stack `seen`?
848 fn is_type_structurally_recursive<'a, 'tcx>(
849 tcx: TyCtxt<'a, 'tcx, 'tcx>,
851 seen: &mut Vec<Ty<'tcx>>,
852 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
853 ty: Ty<'tcx>) -> Representability
855 debug!("is_type_structurally_recursive: {:?} {:?}", ty, sp);
856 if let Some(representability) = representable_cache.get(ty) {
857 debug!("is_type_structurally_recursive: {:?} {:?} - (cached) {:?}",
858 ty, sp, representability);
859 return representability.clone();
862 let representability = is_type_structurally_recursive_inner(
863 tcx, sp, seen, representable_cache, ty);
865 representable_cache.insert(ty, representability.clone());
869 fn is_type_structurally_recursive_inner<'a, 'tcx>(
870 tcx: TyCtxt<'a, 'tcx, 'tcx>,
872 seen: &mut Vec<Ty<'tcx>>,
873 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
874 ty: Ty<'tcx>) -> Representability
879 // Iterate through stack of previously seen types.
880 let mut iter = seen.iter();
882 // The first item in `seen` is the type we are actually curious about.
883 // We want to return SelfRecursive if this type contains itself.
884 // It is important that we DON'T take generic parameters into account
885 // for this check, so that Bar<T> in this example counts as SelfRecursive:
888 // struct Bar<T> { x: Bar<Foo> }
890 if let Some(&seen_type) = iter.next() {
891 if same_struct_or_enum(seen_type, def) {
892 debug!("SelfRecursive: {:?} contains {:?}",
895 return Representability::SelfRecursive(vec![sp]);
899 // We also need to know whether the first item contains other types
900 // that are structurally recursive. If we don't catch this case, we
901 // will recurse infinitely for some inputs.
903 // It is important that we DO take generic parameters into account
904 // here, so that code like this is considered SelfRecursive, not
905 // ContainsRecursive:
907 // struct Foo { Option<Option<Foo>> }
909 for &seen_type in iter {
910 if ty::TyS::same_type(ty, seen_type) {
911 debug!("ContainsRecursive: {:?} contains {:?}",
914 return Representability::ContainsRecursive;
919 // For structs and enums, track all previously seen types by pushing them
920 // onto the 'seen' stack.
922 let out = are_inner_types_recursive(tcx, sp, seen, representable_cache, ty);
927 // No need to push in other cases.
928 are_inner_types_recursive(tcx, sp, seen, representable_cache, ty)
933 debug!("is_type_representable: {:?}", self);
935 // To avoid a stack overflow when checking an enum variant or struct that
936 // contains a different, structurally recursive type, maintain a stack
937 // of seen types and check recursion for each of them (issues #3008, #3779).
938 let mut seen: Vec<Ty<'_>> = Vec::new();
939 let mut representable_cache = FxHashMap::default();
940 let r = is_type_structurally_recursive(
941 tcx, sp, &mut seen, &mut representable_cache, self);
942 debug!("is_type_representable: {:?} is {:?}", self, r);
947 fn is_copy_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
948 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
951 let (param_env, ty) = query.into_parts();
952 let trait_def_id = tcx.require_lang_item(lang_items::CopyTraitLangItem);
954 .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
963 fn is_sized_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
964 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
967 let (param_env, ty) = query.into_parts();
968 let trait_def_id = tcx.require_lang_item(lang_items::SizedTraitLangItem);
970 .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
979 fn is_freeze_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
980 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
983 let (param_env, ty) = query.into_parts();
984 let trait_def_id = tcx.require_lang_item(lang_items::FreezeTraitLangItem);
986 .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
995 fn needs_drop_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
996 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
999 let (param_env, ty) = query.into_parts();
1001 let needs_drop = |ty: Ty<'tcx>| -> bool {
1002 tcx.try_needs_drop_raw(DUMMY_SP, param_env.and(ty)).unwrap_or_else(|mut bug| {
1003 // Cycles should be reported as an error by `check_representable`.
1005 // Consider the type as not needing drop in the meanwhile to
1006 // avoid further errors.
1008 // In case we forgot to emit a bug elsewhere, delay our
1009 // diagnostic to get emitted as a compiler bug.
1015 assert!(!ty.needs_infer());
1018 // Fast-path for primitive types
1019 ty::Infer(ty::FreshIntTy(_)) | ty::Infer(ty::FreshFloatTy(_)) |
1020 ty::Bool | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Never |
1021 ty::FnDef(..) | ty::FnPtr(_) | ty::Char | ty::GeneratorWitness(..) |
1022 ty::RawPtr(_) | ty::Ref(..) | ty::Str => false,
1024 // Foreign types can never have destructors
1025 ty::Foreign(..) => false,
1027 // `ManuallyDrop` doesn't have a destructor regardless of field types.
1028 ty::Adt(def, _) if Some(def.did) == tcx.lang_items().manually_drop() => false,
1030 // Issue #22536: We first query `is_copy_modulo_regions`. It sees a
1031 // normalized version of the type, and therefore will definitely
1032 // know whether the type implements Copy (and thus needs no
1033 // cleanup/drop/zeroing) ...
1034 _ if ty.is_copy_modulo_regions(tcx, param_env, DUMMY_SP) => false,
1036 // ... (issue #22536 continued) but as an optimization, still use
1037 // prior logic of asking for the structural "may drop".
1039 // FIXME(#22815): Note that this is a conservative heuristic;
1040 // it may report that the type "may drop" when actual type does
1041 // not actually have a destructor associated with it. But since
1042 // the type absolutely did not have the `Copy` bound attached
1043 // (see above), it is sound to treat it as having a destructor.
1045 // User destructors are the only way to have concrete drop types.
1046 ty::Adt(def, _) if def.has_dtor(tcx) => true,
1048 // Can refer to a type which may drop.
1049 // FIXME(eddyb) check this against a ParamEnv.
1050 ty::Dynamic(..) | ty::Projection(..) | ty::Param(_) | ty::Bound(..) |
1051 ty::Placeholder(..) | ty::Opaque(..) | ty::Infer(_) | ty::Error => true,
1053 ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
1055 // Structural recursion.
1056 ty::Array(ty, _) | ty::Slice(ty) => needs_drop(ty),
1058 ty::Closure(def_id, ref substs) => substs.upvar_tys(def_id, tcx).any(needs_drop),
1060 // Pessimistically assume that all generators will require destructors
1061 // as we don't know if a destructor is a noop or not until after the MIR
1062 // state transformation pass
1063 ty::Generator(..) => true,
1065 ty::Tuple(ref tys) => tys.iter().cloned().any(needs_drop),
1067 // unions don't have destructors because of the child types,
1068 // only if they manually implement `Drop` (handled above).
1069 ty::Adt(def, _) if def.is_union() => false,
1071 ty::Adt(def, substs) =>
1072 def.variants.iter().any(
1073 |variant| variant.fields.iter().any(
1074 |field| needs_drop(field.ty(tcx, substs)))),
1078 pub enum ExplicitSelf<'tcx> {
1080 ByReference(ty::Region<'tcx>, hir::Mutability),
1081 ByRawPointer(hir::Mutability),
1086 impl<'tcx> ExplicitSelf<'tcx> {
1087 /// Categorizes an explicit self declaration like `self: SomeType`
1088 /// into either `self`, `&self`, `&mut self`, `Box<self>`, or
1090 /// This is mainly used to require the arbitrary_self_types feature
1091 /// in the case of `Other`, to improve error messages in the common cases,
1092 /// and to make `Other` non-object-safe.
1097 /// impl<'a> Foo for &'a T {
1098 /// // Legal declarations:
1099 /// fn method1(self: &&'a T); // ExplicitSelf::ByReference
1100 /// fn method2(self: &'a T); // ExplicitSelf::ByValue
1101 /// fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox
1102 /// fn method4(self: Rc<&'a T>); // ExplicitSelf::Other
1104 /// // Invalid cases will be caught by `check_method_receiver`:
1105 /// fn method_err1(self: &'a mut T); // ExplicitSelf::Other
1106 /// fn method_err2(self: &'static T) // ExplicitSelf::ByValue
1107 /// fn method_err3(self: &&T) // ExplicitSelf::ByReference
1111 pub fn determine<P>(
1112 self_arg_ty: Ty<'tcx>,
1114 ) -> ExplicitSelf<'tcx>
1116 P: Fn(Ty<'tcx>) -> bool
1118 use self::ExplicitSelf::*;
1120 match self_arg_ty.sty {
1121 _ if is_self_ty(self_arg_ty) => ByValue,
1122 ty::Ref(region, ty, mutbl) if is_self_ty(ty) => {
1123 ByReference(region, mutbl)
1125 ty::RawPtr(ty::TypeAndMut { ty, mutbl }) if is_self_ty(ty) => {
1128 ty::Adt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => {
1136 pub fn provide(providers: &mut ty::query::Providers<'_>) {
1137 *providers = ty::query::Providers {