1 //! Miscellaneous type-system utilities that are too small to deserve their own modules.
4 use crate::hir::def::DefKind;
5 use crate::hir::def_id::DefId;
6 use crate::hir::map::DefPathData;
7 use crate::mir::interpret::{sign_extend, truncate};
8 use crate::ich::NodeIdHashingMode;
9 use crate::traits::{self, ObligationCause};
10 use crate::ty::{self, DefIdTree, Ty, TyCtxt, GenericParamDefKind, TypeFoldable};
11 use crate::ty::subst::{Subst, InternalSubsts, SubstsRef, UnpackedKind};
12 use crate::ty::query::TyCtxtAt;
13 use crate::ty::TyKind::*;
14 use crate::ty::layout::{Integer, IntegerExt};
15 use crate::mir::interpret::ConstValue;
16 use crate::util::common::ErrorReported;
17 use crate::middle::lang_items;
19 use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
20 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
21 use rustc_macros::HashStable;
24 use syntax::attr::{self, SignedInt, UnsignedInt};
25 use syntax_pos::{Span, DUMMY_SP};
27 #[derive(Copy, Clone, Debug)]
28 pub struct Discr<'tcx> {
29 /// Bit representation of the discriminant (e.g., `-128i8` is `0xFF_u128`).
34 impl<'tcx> fmt::Display for Discr<'tcx> {
35 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
38 let size = ty::tls::with(|tcx| {
39 Integer::from_attr(&tcx, SignedInt(ity)).size()
42 // sign extend the raw representation to be an i128
43 let x = sign_extend(x, size) as i128;
46 _ => write!(fmt, "{}", self.val),
51 impl<'tcx> Discr<'tcx> {
52 /// Adds `1` to the value and wraps around if the maximum for the type is reached.
53 pub fn wrap_incr(self, tcx: TyCtxt<'tcx>) -> Self {
54 self.checked_add(tcx, 1).0
56 pub fn checked_add(self, tcx: TyCtxt<'tcx>, n: u128) -> (Self, bool) {
57 let (int, signed) = match self.ty.sty {
58 Int(ity) => (Integer::from_attr(&tcx, SignedInt(ity)), true),
59 Uint(uty) => (Integer::from_attr(&tcx, UnsignedInt(uty)), false),
60 _ => bug!("non integer discriminant"),
63 let size = int.size();
64 let bit_size = int.size().bits();
65 let shift = 128 - bit_size;
68 sign_extend(u, size) as i128
70 let min = sext(1_u128 << (bit_size - 1));
71 let max = i128::max_value() >> shift;
72 let val = sext(self.val);
73 assert!(n < (i128::max_value() as u128));
75 let oflo = val > max - n;
77 min + (n - (max - val) - 1)
81 // zero the upper bits
82 let val = val as u128;
83 let val = truncate(val, size);
89 let max = u128::max_value() >> shift;
91 let oflo = val > max - n;
105 pub trait IntTypeExt {
106 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
107 fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>>;
108 fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx>;
111 impl IntTypeExt for attr::IntType {
112 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
114 SignedInt(ast::IntTy::I8) => tcx.types.i8,
115 SignedInt(ast::IntTy::I16) => tcx.types.i16,
116 SignedInt(ast::IntTy::I32) => tcx.types.i32,
117 SignedInt(ast::IntTy::I64) => tcx.types.i64,
118 SignedInt(ast::IntTy::I128) => tcx.types.i128,
119 SignedInt(ast::IntTy::Isize) => tcx.types.isize,
120 UnsignedInt(ast::UintTy::U8) => tcx.types.u8,
121 UnsignedInt(ast::UintTy::U16) => tcx.types.u16,
122 UnsignedInt(ast::UintTy::U32) => tcx.types.u32,
123 UnsignedInt(ast::UintTy::U64) => tcx.types.u64,
124 UnsignedInt(ast::UintTy::U128) => tcx.types.u128,
125 UnsignedInt(ast::UintTy::Usize) => tcx.types.usize,
129 fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx> {
136 fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>> {
137 if let Some(val) = val {
138 assert_eq!(self.to_ty(tcx), val.ty);
139 let (new, oflo) = val.checked_add(tcx, 1);
146 Some(self.initial_discriminant(tcx))
153 pub enum CopyImplementationError<'tcx> {
154 InfrigingFields(Vec<&'tcx ty::FieldDef>),
159 /// Describes whether a type is representable. For types that are not
160 /// representable, 'SelfRecursive' and 'ContainsRecursive' are used to
161 /// distinguish between types that are recursive with themselves and types that
162 /// contain a different recursive type. These cases can therefore be treated
163 /// differently when reporting errors.
165 /// The ordering of the cases is significant. They are sorted so that cmp::max
166 /// will keep the "more erroneous" of two values.
167 #[derive(Clone, PartialOrd, Ord, Eq, PartialEq, Debug)]
168 pub enum Representability {
171 SelfRecursive(Vec<Span>),
174 impl<'tcx> ty::ParamEnv<'tcx> {
175 pub fn can_type_implement_copy(
179 ) -> Result<(), CopyImplementationError<'tcx>> {
180 // FIXME: (@jroesch) float this code up
181 tcx.infer_ctxt().enter(|infcx| {
182 let (adt, substs) = match self_type.sty {
183 // These types used to have a builtin impl.
184 // Now libcore provides that impl.
185 ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Float(_) |
186 ty::Char | ty::RawPtr(..) | ty::Never |
187 ty::Ref(_, _, hir::MutImmutable) => return Ok(()),
189 ty::Adt(adt, substs) => (adt, substs),
191 _ => return Err(CopyImplementationError::NotAnAdt),
194 let mut infringing = Vec::new();
195 for variant in &adt.variants {
196 for field in &variant.fields {
197 let ty = field.ty(tcx, substs);
198 if ty.references_error() {
201 let span = tcx.def_span(field.did);
202 let cause = ObligationCause { span, ..ObligationCause::dummy() };
203 let ctx = traits::FulfillmentContext::new();
204 match traits::fully_normalize(&infcx, ctx, cause, self, &ty) {
205 Ok(ty) => if !infcx.type_is_copy_modulo_regions(self, ty, span) {
206 infringing.push(field);
209 infcx.report_fulfillment_errors(&errors, None, false);
214 if !infringing.is_empty() {
215 return Err(CopyImplementationError::InfrigingFields(infringing));
217 if adt.has_dtor(tcx) {
218 return Err(CopyImplementationError::HasDestructor);
226 impl<'tcx> TyCtxt<'tcx> {
227 /// Creates a hash of the type `Ty` which will be the same no matter what crate
228 /// context it's calculated within. This is used by the `type_id` intrinsic.
229 pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
230 let mut hasher = StableHasher::new();
231 let mut hcx = self.create_stable_hashing_context();
233 // We want the type_id be independent of the types free regions, so we
234 // erase them. The erase_regions() call will also anonymize bound
235 // regions, which is desirable too.
236 let ty = self.erase_regions(&ty);
238 hcx.while_hashing_spans(false, |hcx| {
239 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
240 ty.hash_stable(hcx, &mut hasher);
247 impl<'tcx> TyCtxt<'tcx> {
248 pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
249 if let ty::Adt(def, substs) = ty.sty {
250 for field in def.all_fields() {
251 let field_ty = field.ty(self, substs);
252 if let Error = field_ty.sty {
260 /// Attempts to returns the deeply last field of nested structures, but
261 /// does not apply any normalization in its search. Returns the same type
262 /// if input `ty` is not a structure at all.
263 pub fn struct_tail_without_normalization(self, ty: Ty<'tcx>) -> Ty<'tcx>
266 tcx.struct_tail_with_normalize(ty, |ty| ty)
269 /// Returns the deeply last field of nested structures, or the same type if
270 /// not a structure at all. Corresponds to the only possible unsized field,
271 /// and its type can be used to determine unsizing strategy.
273 /// Should only be called if `ty` has no inference variables and does not
274 /// need its lifetimes preserved (e.g. as part of codegen); otherwise
275 /// normalization attempt may cause compiler bugs.
276 pub fn struct_tail_erasing_lifetimes(self,
278 param_env: ty::ParamEnv<'tcx>)
282 tcx.struct_tail_with_normalize(ty, |ty| tcx.normalize_erasing_regions(param_env, ty))
285 /// Returns the deeply last field of nested structures, or the same type if
286 /// not a structure at all. Corresponds to the only possible unsized field,
287 /// and its type can be used to determine unsizing strategy.
289 /// This is parameterized over the normalization strategy (i.e. how to
290 /// handle `<T as Trait>::Assoc` and `impl Trait`); pass the identity
291 /// function to indicate no normalization should take place.
293 /// See also `struct_tail_erasing_lifetimes`, which is suitable for use
295 pub fn struct_tail_with_normalize(self,
297 normalize: impl Fn(Ty<'tcx>) -> Ty<'tcx>)
302 ty::Adt(def, substs) => {
303 if !def.is_struct() {
306 match def.non_enum_variant().fields.last() {
307 Some(f) => ty = f.ty(self, substs),
313 if let Some((&last_ty, _)) = tys.split_last() {
314 ty = last_ty.expect_ty();
320 ty::Projection(_) | ty::Opaque(..) => {
321 let normalized = normalize(ty);
322 if ty == normalized {
337 /// Same as applying struct_tail on `source` and `target`, but only
338 /// keeps going as long as the two types are instances of the same
339 /// structure definitions.
340 /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
341 /// whereas struct_tail produces `T`, and `Trait`, respectively.
343 /// Should only be called if the types have no inference variables and do
344 /// not need their lifetimes preserved (e.g. as part of codegen); otherwise
345 /// normalization attempt may cause compiler bugs.
346 pub fn struct_lockstep_tails_erasing_lifetimes(self,
349 param_env: ty::ParamEnv<'tcx>)
350 -> (Ty<'tcx>, Ty<'tcx>)
353 tcx.struct_lockstep_tails_with_normalize(
354 source, target, |ty| tcx.normalize_erasing_regions(param_env, ty))
357 /// Same as applying struct_tail on `source` and `target`, but only
358 /// keeps going as long as the two types are instances of the same
359 /// structure definitions.
360 /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
361 /// whereas struct_tail produces `T`, and `Trait`, respectively.
363 /// See also `struct_lockstep_tails_erasing_lifetimes`, which is suitable for use
365 pub fn struct_lockstep_tails_with_normalize(self,
368 normalize: impl Fn(Ty<'tcx>) -> Ty<'tcx>)
369 -> (Ty<'tcx>, Ty<'tcx>)
371 let (mut a, mut b) = (source, target);
373 match (&a.sty, &b.sty) {
374 (&Adt(a_def, a_substs), &Adt(b_def, b_substs))
375 if a_def == b_def && a_def.is_struct() => {
376 if let Some(f) = a_def.non_enum_variant().fields.last() {
377 a = f.ty(self, a_substs);
378 b = f.ty(self, b_substs);
383 (&Tuple(a_tys), &Tuple(b_tys))
384 if a_tys.len() == b_tys.len() => {
385 if let Some(a_last) = a_tys.last() {
386 a = a_last.expect_ty();
387 b = b_tys.last().unwrap().expect_ty();
392 (ty::Projection(_), _) | (ty::Opaque(..), _) |
393 (_, ty::Projection(_)) | (_, ty::Opaque(..)) => {
394 // If either side is a projection, attempt to
395 // progress via normalization. (Should be safe to
396 // apply to both sides as normalization is
398 let a_norm = normalize(a);
399 let b_norm = normalize(b);
400 if a == a_norm && b == b_norm {
414 /// Given a set of predicates that apply to an object type, returns
415 /// the region bounds that the (erased) `Self` type must
416 /// outlive. Precisely *because* the `Self` type is erased, the
417 /// parameter `erased_self_ty` must be supplied to indicate what type
418 /// has been used to represent `Self` in the predicates
419 /// themselves. This should really be a unique type; `FreshTy(0)` is a
422 /// N.B., in some cases, particularly around higher-ranked bounds,
423 /// this function returns a kind of conservative approximation.
424 /// That is, all regions returned by this function are definitely
425 /// required, but there may be other region bounds that are not
426 /// returned, as well as requirements like `for<'a> T: 'a`.
428 /// Requires that trait definitions have been processed so that we can
429 /// elaborate predicates and walk supertraits.
431 // FIXME: callers may only have a `&[Predicate]`, not a `Vec`, so that's
432 // what this code should accept.
433 pub fn required_region_bounds(self,
434 erased_self_ty: Ty<'tcx>,
435 predicates: Vec<ty::Predicate<'tcx>>)
436 -> Vec<ty::Region<'tcx>> {
437 debug!("required_region_bounds(erased_self_ty={:?}, predicates={:?})",
441 assert!(!erased_self_ty.has_escaping_bound_vars());
443 traits::elaborate_predicates(self, predicates)
444 .filter_map(|predicate| {
446 ty::Predicate::Projection(..) |
447 ty::Predicate::Trait(..) |
448 ty::Predicate::Subtype(..) |
449 ty::Predicate::WellFormed(..) |
450 ty::Predicate::ObjectSafe(..) |
451 ty::Predicate::ClosureKind(..) |
452 ty::Predicate::RegionOutlives(..) |
453 ty::Predicate::ConstEvaluatable(..) => {
456 ty::Predicate::TypeOutlives(predicate) => {
457 // Search for a bound of the form `erased_self_ty
458 // : 'a`, but be wary of something like `for<'a>
459 // erased_self_ty : 'a` (we interpret a
460 // higher-ranked bound like that as 'static,
461 // though at present the code in `fulfill.rs`
462 // considers such bounds to be unsatisfiable, so
463 // it's kind of a moot point since you could never
464 // construct such an object, but this seems
465 // correct even if that code changes).
466 let ty::OutlivesPredicate(ref t, ref r) = predicate.skip_binder();
467 if t == &erased_self_ty && !r.has_escaping_bound_vars() {
478 /// Calculate the destructor of a given type.
479 pub fn calculate_dtor(
482 validate: &mut dyn FnMut(Self, DefId) -> Result<(), ErrorReported>
483 ) -> Option<ty::Destructor> {
484 let drop_trait = if let Some(def_id) = self.lang_items().drop_trait() {
490 self.ensure().coherent_trait(drop_trait);
492 let mut dtor_did = None;
493 let ty = self.type_of(adt_did);
494 self.for_each_relevant_impl(drop_trait, ty, |impl_did| {
495 if let Some(item) = self.associated_items(impl_did).next() {
496 if validate(self, impl_did).is_ok() {
497 dtor_did = Some(item.def_id);
502 Some(ty::Destructor { did: dtor_did? })
505 /// Returns the set of types that are required to be alive in
506 /// order to run the destructor of `def` (see RFCs 769 and
509 /// Note that this returns only the constraints for the
510 /// destructor of `def` itself. For the destructors of the
511 /// contents, you need `adt_dtorck_constraint`.
512 pub fn destructor_constraints(self, def: &'tcx ty::AdtDef)
513 -> Vec<ty::subst::Kind<'tcx>>
515 let dtor = match def.destructor(self) {
517 debug!("destructor_constraints({:?}) - no dtor", def.did);
520 Some(dtor) => dtor.did
523 let impl_def_id = self.associated_item(dtor).container.id();
524 let impl_generics = self.generics_of(impl_def_id);
526 // We have a destructor - all the parameters that are not
527 // pure_wrt_drop (i.e, don't have a #[may_dangle] attribute)
530 // We need to return the list of parameters from the ADTs
531 // generics/substs that correspond to impure parameters on the
532 // impl's generics. This is a bit ugly, but conceptually simple:
534 // Suppose our ADT looks like the following
536 // struct S<X, Y, Z>(X, Y, Z);
540 // impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
542 // We want to return the parameters (X, Y). For that, we match
543 // up the item-substs <X, Y, Z> with the substs on the impl ADT,
544 // <P1, P2, P0>, and then look up which of the impl substs refer to
545 // parameters marked as pure.
547 let impl_substs = match self.type_of(impl_def_id).sty {
548 ty::Adt(def_, substs) if def_ == def => substs,
552 let item_substs = match self.type_of(def.did).sty {
553 ty::Adt(def_, substs) if def_ == def => substs,
557 let result = item_substs.iter().zip(impl_substs.iter())
560 UnpackedKind::Lifetime(&ty::RegionKind::ReEarlyBound(ref ebr)) => {
561 !impl_generics.region_param(ebr, self).pure_wrt_drop
563 UnpackedKind::Type(&ty::TyS {
564 sty: ty::Param(ref pt), ..
566 !impl_generics.type_param(pt, self).pure_wrt_drop
568 UnpackedKind::Const(&ty::Const {
569 val: ConstValue::Param(ref pc),
572 !impl_generics.const_param(pc, self).pure_wrt_drop
574 UnpackedKind::Lifetime(_) |
575 UnpackedKind::Type(_) |
576 UnpackedKind::Const(_) => {
577 // Not a type, const or region param: this should be reported
583 .map(|(&item_param, _)| item_param)
585 debug!("destructor_constraint({:?}) = {:?}", def.did, result);
589 /// Returns `true` if `def_id` refers to a closure (e.g., `|x| x * 2`). Note
590 /// that closures have a `DefId`, but the closure *expression* also
591 /// has a `HirId` that is located within the context where the
592 /// closure appears (and, sadly, a corresponding `NodeId`, since
593 /// those are not yet phased out). The parent of the closure's
594 /// `DefId` will also be the context where it appears.
595 pub fn is_closure(self, def_id: DefId) -> bool {
596 self.def_key(def_id).disambiguated_data.data == DefPathData::ClosureExpr
599 /// Returns `true` if `def_id` refers to a trait (i.e., `trait Foo { ... }`).
600 pub fn is_trait(self, def_id: DefId) -> bool {
601 self.def_kind(def_id) == Some(DefKind::Trait)
604 /// Returns `true` if `def_id` refers to a trait alias (i.e., `trait Foo = ...;`),
605 /// and `false` otherwise.
606 pub fn is_trait_alias(self, def_id: DefId) -> bool {
607 self.def_kind(def_id) == Some(DefKind::TraitAlias)
610 /// Returns `true` if this `DefId` refers to the implicit constructor for
611 /// a tuple struct like `struct Foo(u32)`, and `false` otherwise.
612 pub fn is_constructor(self, def_id: DefId) -> bool {
613 self.def_key(def_id).disambiguated_data.data == DefPathData::Ctor
616 /// Given the def-ID of a fn or closure, returns the def-ID of
617 /// the innermost fn item that the closure is contained within.
618 /// This is a significant `DefId` because, when we do
619 /// type-checking, we type-check this fn item and all of its
620 /// (transitive) closures together. Therefore, when we fetch the
621 /// `typeck_tables_of` the closure, for example, we really wind up
622 /// fetching the `typeck_tables_of` the enclosing fn item.
623 pub fn closure_base_def_id(self, def_id: DefId) -> DefId {
624 let mut def_id = def_id;
625 while self.is_closure(def_id) {
626 def_id = self.parent(def_id).unwrap_or_else(|| {
627 bug!("closure {:?} has no parent", def_id);
633 /// Given the `DefId` and substs a closure, creates the type of
634 /// `self` argument that the closure expects. For example, for a
635 /// `Fn` closure, this would return a reference type `&T` where
636 /// `T = closure_ty`.
638 /// Returns `None` if this closure's kind has not yet been inferred.
639 /// This should only be possible during type checking.
641 /// Note that the return value is a late-bound region and hence
642 /// wrapped in a binder.
643 pub fn closure_env_ty(self,
644 closure_def_id: DefId,
645 closure_substs: ty::ClosureSubsts<'tcx>)
646 -> Option<ty::Binder<Ty<'tcx>>>
648 let closure_ty = self.mk_closure(closure_def_id, closure_substs);
649 let env_region = ty::ReLateBound(ty::INNERMOST, ty::BrEnv);
650 let closure_kind_ty = closure_substs.closure_kind_ty(closure_def_id, self);
651 let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
652 let env_ty = match closure_kind {
653 ty::ClosureKind::Fn => self.mk_imm_ref(self.mk_region(env_region), closure_ty),
654 ty::ClosureKind::FnMut => self.mk_mut_ref(self.mk_region(env_region), closure_ty),
655 ty::ClosureKind::FnOnce => closure_ty,
657 Some(ty::Binder::bind(env_ty))
660 /// Given the `DefId` of some item that has no type or const parameters, make
661 /// a suitable "empty substs" for it.
662 pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> SubstsRef<'tcx> {
663 InternalSubsts::for_item(self, item_def_id, |param, _| {
665 GenericParamDefKind::Lifetime => self.lifetimes.re_erased.into(),
666 GenericParamDefKind::Type { .. } => {
667 bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
669 GenericParamDefKind::Const { .. } => {
670 bug!("empty_substs_for_def_id: {:?} has const parameters", item_def_id)
676 /// Returns `true` if the node pointed to by `def_id` is a `static` item.
677 pub fn is_static(&self, def_id: DefId) -> bool {
678 self.static_mutability(def_id).is_some()
681 /// Returns `true` if the node pointed to by `def_id` is a mutable `static` item.
682 pub fn is_mutable_static(&self, def_id: DefId) -> bool {
683 self.static_mutability(def_id) == Some(hir::MutMutable)
686 /// Expands the given impl trait type, stopping if the type is recursive.
687 pub fn try_expand_impl_trait_type(
690 substs: SubstsRef<'tcx>,
691 ) -> Result<Ty<'tcx>, Ty<'tcx>> {
692 use crate::ty::fold::TypeFolder;
694 struct OpaqueTypeExpander<'tcx> {
695 // Contains the DefIds of the opaque types that are currently being
696 // expanded. When we expand an opaque type we insert the DefId of
697 // that type, and when we finish expanding that type we remove the
699 seen_opaque_tys: FxHashSet<DefId>,
700 primary_def_id: DefId,
701 found_recursion: bool,
705 impl<'tcx> OpaqueTypeExpander<'tcx> {
709 substs: SubstsRef<'tcx>,
710 ) -> Option<Ty<'tcx>> {
711 if self.found_recursion {
714 let substs = substs.fold_with(self);
715 if self.seen_opaque_tys.insert(def_id) {
716 let generic_ty = self.tcx.type_of(def_id);
717 let concrete_ty = generic_ty.subst(self.tcx, substs);
718 let expanded_ty = self.fold_ty(concrete_ty);
719 self.seen_opaque_tys.remove(&def_id);
722 // If another opaque type that we contain is recursive, then it
723 // will report the error, so we don't have to.
724 self.found_recursion = def_id == self.primary_def_id;
730 impl<'tcx> TypeFolder<'tcx> for OpaqueTypeExpander<'tcx> {
731 fn tcx(&self) -> TyCtxt<'tcx> {
735 fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
736 if let ty::Opaque(def_id, substs) = t.sty {
737 self.expand_opaque_ty(def_id, substs).unwrap_or(t)
739 t.super_fold_with(self)
744 let mut visitor = OpaqueTypeExpander {
745 seen_opaque_tys: FxHashSet::default(),
746 primary_def_id: def_id,
747 found_recursion: false,
750 let expanded_type = visitor.expand_opaque_ty(def_id, substs).unwrap();
751 if visitor.found_recursion {
759 impl<'tcx> ty::TyS<'tcx> {
760 /// Checks whether values of this type `T` are *moved* or *copied*
761 /// when referenced -- this amounts to a check for whether `T:
762 /// Copy`, but note that we **don't** consider lifetimes when
763 /// doing this check. This means that we may generate MIR which
764 /// does copies even when the type actually doesn't satisfy the
765 /// full requirements for the `Copy` trait (cc #29149) -- this
766 /// winds up being reported as an error during NLL borrow check.
767 pub fn is_copy_modulo_regions(
770 param_env: ty::ParamEnv<'tcx>,
773 tcx.at(span).is_copy_raw(param_env.and(self))
776 /// Checks whether values of this type `T` have a size known at
777 /// compile time (i.e., whether `T: Sized`). Lifetimes are ignored
778 /// for the purposes of this check, so it can be an
779 /// over-approximation in generic contexts, where one can have
780 /// strange rules like `<T as Foo<'static>>::Bar: Sized` that
781 /// actually carry lifetime requirements.
782 pub fn is_sized(&'tcx self, tcx_at: TyCtxtAt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
783 tcx_at.is_sized_raw(param_env.and(self))
786 /// Checks whether values of this type `T` implement the `Freeze`
787 /// trait -- frozen types are those that do not contain a
788 /// `UnsafeCell` anywhere. This is a language concept used to
789 /// distinguish "true immutability", which is relevant to
790 /// optimization as well as the rules around static values. Note
791 /// that the `Freeze` trait is not exposed to end users and is
792 /// effectively an implementation detail.
796 param_env: ty::ParamEnv<'tcx>,
799 tcx.at(span).is_freeze_raw(param_env.and(self))
802 /// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely
803 /// non-copy and *might* have a destructor attached; if it returns
804 /// `false`, then `ty` definitely has no destructor (i.e., no drop glue).
806 /// (Note that this implies that if `ty` has a destructor attached,
807 /// then `needs_drop` will definitely return `true` for `ty`.)
809 pub fn needs_drop(&'tcx self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
810 tcx.needs_drop_raw(param_env.and(self)).0
813 pub fn same_type(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
814 match (&a.sty, &b.sty) {
815 (&Adt(did_a, substs_a), &Adt(did_b, substs_b)) => {
820 substs_a.types().zip(substs_b.types()).all(|(a, b)| Self::same_type(a, b))
826 /// Check whether a type is representable. This means it cannot contain unboxed
827 /// structural recursion. This check is needed for structs and enums.
828 pub fn is_representable(&'tcx self, tcx: TyCtxt<'tcx>, sp: Span) -> Representability {
829 // Iterate until something non-representable is found
830 fn fold_repr<It: Iterator<Item=Representability>>(iter: It) -> Representability {
831 iter.fold(Representability::Representable, |r1, r2| {
833 (Representability::SelfRecursive(v1),
834 Representability::SelfRecursive(v2)) => {
835 Representability::SelfRecursive(v1.into_iter().chain(v2).collect())
837 (r1, r2) => cmp::max(r1, r2)
842 fn are_inner_types_recursive<'tcx>(
845 seen: &mut Vec<Ty<'tcx>>,
846 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
848 ) -> Representability {
851 // Find non representable
852 fold_repr(ty.tuple_fields().map(|ty| {
853 is_type_structurally_recursive(
862 // Fixed-length vectors.
863 // FIXME(#11924) Behavior undecided for zero-length vectors.
865 is_type_structurally_recursive(tcx, sp, seen, representable_cache, ty)
867 Adt(def, substs) => {
868 // Find non representable fields with their spans
869 fold_repr(def.all_fields().map(|field| {
870 let ty = field.ty(tcx, substs);
871 let span = tcx.hir().span_if_local(field.did).unwrap_or(sp);
872 match is_type_structurally_recursive(tcx, span, seen,
873 representable_cache, ty)
875 Representability::SelfRecursive(_) => {
876 Representability::SelfRecursive(vec![span])
883 // this check is run on type definitions, so we don't expect
884 // to see closure types
885 bug!("requires check invoked on inapplicable type: {:?}", ty)
887 _ => Representability::Representable,
891 fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: &'tcx ty::AdtDef) -> bool {
900 // Does the type `ty` directly (without indirection through a pointer)
901 // contain any types on stack `seen`?
902 fn is_type_structurally_recursive<'tcx>(
905 seen: &mut Vec<Ty<'tcx>>,
906 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
908 ) -> Representability {
909 debug!("is_type_structurally_recursive: {:?} {:?}", ty, sp);
910 if let Some(representability) = representable_cache.get(ty) {
911 debug!("is_type_structurally_recursive: {:?} {:?} - (cached) {:?}",
912 ty, sp, representability);
913 return representability.clone();
916 let representability = is_type_structurally_recursive_inner(
917 tcx, sp, seen, representable_cache, ty);
919 representable_cache.insert(ty, representability.clone());
923 fn is_type_structurally_recursive_inner<'tcx>(
926 seen: &mut Vec<Ty<'tcx>>,
927 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
929 ) -> Representability {
933 // Iterate through stack of previously seen types.
934 let mut iter = seen.iter();
936 // The first item in `seen` is the type we are actually curious about.
937 // We want to return SelfRecursive if this type contains itself.
938 // It is important that we DON'T take generic parameters into account
939 // for this check, so that Bar<T> in this example counts as SelfRecursive:
942 // struct Bar<T> { x: Bar<Foo> }
944 if let Some(&seen_type) = iter.next() {
945 if same_struct_or_enum(seen_type, def) {
946 debug!("SelfRecursive: {:?} contains {:?}",
949 return Representability::SelfRecursive(vec![sp]);
953 // We also need to know whether the first item contains other types
954 // that are structurally recursive. If we don't catch this case, we
955 // will recurse infinitely for some inputs.
957 // It is important that we DO take generic parameters into account
958 // here, so that code like this is considered SelfRecursive, not
959 // ContainsRecursive:
961 // struct Foo { Option<Option<Foo>> }
963 for &seen_type in iter {
964 if ty::TyS::same_type(ty, seen_type) {
965 debug!("ContainsRecursive: {:?} contains {:?}",
968 return Representability::ContainsRecursive;
973 // For structs and enums, track all previously seen types by pushing them
974 // onto the 'seen' stack.
976 let out = are_inner_types_recursive(tcx, sp, seen, representable_cache, ty);
981 // No need to push in other cases.
982 are_inner_types_recursive(tcx, sp, seen, representable_cache, ty)
987 debug!("is_type_representable: {:?}", self);
989 // To avoid a stack overflow when checking an enum variant or struct that
990 // contains a different, structurally recursive type, maintain a stack
991 // of seen types and check recursion for each of them (issues #3008, #3779).
992 let mut seen: Vec<Ty<'_>> = Vec::new();
993 let mut representable_cache = FxHashMap::default();
994 let r = is_type_structurally_recursive(
995 tcx, sp, &mut seen, &mut representable_cache, self);
996 debug!("is_type_representable: {:?} is {:?}", self, r);
1001 fn is_copy_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
1002 let (param_env, ty) = query.into_parts();
1003 let trait_def_id = tcx.require_lang_item(lang_items::CopyTraitLangItem, None);
1005 .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
1014 fn is_sized_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
1015 let (param_env, ty) = query.into_parts();
1016 let trait_def_id = tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
1018 .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
1027 fn is_freeze_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
1028 let (param_env, ty) = query.into_parts();
1029 let trait_def_id = tcx.require_lang_item(lang_items::FreezeTraitLangItem, None);
1031 .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
1040 #[derive(Clone, HashStable)]
1041 pub struct NeedsDrop(pub bool);
1043 fn needs_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> NeedsDrop {
1044 let (param_env, ty) = query.into_parts();
1046 let needs_drop = |ty: Ty<'tcx>| -> bool {
1047 tcx.needs_drop_raw(param_env.and(ty)).0
1050 assert!(!ty.needs_infer());
1052 NeedsDrop(match ty.sty {
1053 // Fast-path for primitive types
1054 ty::Infer(ty::FreshIntTy(_)) | ty::Infer(ty::FreshFloatTy(_)) |
1055 ty::Bool | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Never |
1056 ty::FnDef(..) | ty::FnPtr(_) | ty::Char | ty::GeneratorWitness(..) |
1057 ty::RawPtr(_) | ty::Ref(..) | ty::Str => false,
1059 // Foreign types can never have destructors
1060 ty::Foreign(..) => false,
1062 // `ManuallyDrop` doesn't have a destructor regardless of field types.
1063 ty::Adt(def, _) if Some(def.did) == tcx.lang_items().manually_drop() => false,
1065 // Issue #22536: We first query `is_copy_modulo_regions`. It sees a
1066 // normalized version of the type, and therefore will definitely
1067 // know whether the type implements Copy (and thus needs no
1068 // cleanup/drop/zeroing) ...
1069 _ if ty.is_copy_modulo_regions(tcx, param_env, DUMMY_SP) => false,
1071 // ... (issue #22536 continued) but as an optimization, still use
1072 // prior logic of asking for the structural "may drop".
1074 // FIXME(#22815): Note that this is a conservative heuristic;
1075 // it may report that the type "may drop" when actual type does
1076 // not actually have a destructor associated with it. But since
1077 // the type absolutely did not have the `Copy` bound attached
1078 // (see above), it is sound to treat it as having a destructor.
1080 // User destructors are the only way to have concrete drop types.
1081 ty::Adt(def, _) if def.has_dtor(tcx) => true,
1083 // Can refer to a type which may drop.
1084 // FIXME(eddyb) check this against a ParamEnv.
1085 ty::Dynamic(..) | ty::Projection(..) | ty::Param(_) | ty::Bound(..) |
1086 ty::Placeholder(..) | ty::Opaque(..) | ty::Infer(_) | ty::Error => true,
1088 ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
1090 // Structural recursion.
1091 ty::Array(ty, _) | ty::Slice(ty) => needs_drop(ty),
1093 ty::Closure(def_id, ref substs) => substs.upvar_tys(def_id, tcx).any(needs_drop),
1095 // Pessimistically assume that all generators will require destructors
1096 // as we don't know if a destructor is a noop or not until after the MIR
1097 // state transformation pass
1098 ty::Generator(..) => true,
1100 ty::Tuple(..) => ty.tuple_fields().any(needs_drop),
1102 // unions don't have destructors because of the child types,
1103 // only if they manually implement `Drop` (handled above).
1104 ty::Adt(def, _) if def.is_union() => false,
1106 ty::Adt(def, substs) =>
1107 def.variants.iter().any(
1108 |variant| variant.fields.iter().any(
1109 |field| needs_drop(field.ty(tcx, substs)))),
1113 pub enum ExplicitSelf<'tcx> {
1115 ByReference(ty::Region<'tcx>, hir::Mutability),
1116 ByRawPointer(hir::Mutability),
1121 impl<'tcx> ExplicitSelf<'tcx> {
1122 /// Categorizes an explicit self declaration like `self: SomeType`
1123 /// into either `self`, `&self`, `&mut self`, `Box<self>`, or
1125 /// This is mainly used to require the arbitrary_self_types feature
1126 /// in the case of `Other`, to improve error messages in the common cases,
1127 /// and to make `Other` non-object-safe.
1132 /// impl<'a> Foo for &'a T {
1133 /// // Legal declarations:
1134 /// fn method1(self: &&'a T); // ExplicitSelf::ByReference
1135 /// fn method2(self: &'a T); // ExplicitSelf::ByValue
1136 /// fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox
1137 /// fn method4(self: Rc<&'a T>); // ExplicitSelf::Other
1139 /// // Invalid cases will be caught by `check_method_receiver`:
1140 /// fn method_err1(self: &'a mut T); // ExplicitSelf::Other
1141 /// fn method_err2(self: &'static T) // ExplicitSelf::ByValue
1142 /// fn method_err3(self: &&T) // ExplicitSelf::ByReference
1146 pub fn determine<P>(
1147 self_arg_ty: Ty<'tcx>,
1149 ) -> ExplicitSelf<'tcx>
1151 P: Fn(Ty<'tcx>) -> bool
1153 use self::ExplicitSelf::*;
1155 match self_arg_ty.sty {
1156 _ if is_self_ty(self_arg_ty) => ByValue,
1157 ty::Ref(region, ty, mutbl) if is_self_ty(ty) => {
1158 ByReference(region, mutbl)
1160 ty::RawPtr(ty::TypeAndMut { ty, mutbl }) if is_self_ty(ty) => {
1163 ty::Adt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => {
1171 pub fn provide(providers: &mut ty::query::Providers<'_>) {
1172 *providers = ty::query::Providers {