1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! misc. type-system utilities too small to deserve their own file
13 use hir::def_id::{DefId, LOCAL_CRATE};
14 use hir::map::DefPathData;
16 use ich::{StableHashingContext, NodeIdHashingMode};
17 use traits::{self, Reveal};
18 use ty::{self, Ty, TyCtxt, TypeFoldable};
19 use ty::fold::TypeVisitor;
20 use ty::layout::{Layout, LayoutError};
21 use ty::subst::{Subst, Kind};
22 use ty::TypeVariants::*;
23 use util::common::ErrorReported;
24 use middle::lang_items;
26 use rustc_const_math::{ConstInt, ConstIsize, ConstUsize};
27 use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
32 use syntax::ast::{self, Name};
33 use syntax::attr::{self, SignedInt, UnsignedInt};
34 use syntax_pos::{Span, DUMMY_SP};
38 pub trait IntTypeExt {
39 fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx>;
40 fn disr_incr<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, val: Option<Disr>)
42 fn assert_ty_matches(&self, val: Disr);
43 fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Disr;
47 macro_rules! typed_literal {
48 ($tcx:expr, $ty:expr, $lit:expr) => {
50 SignedInt(ast::IntTy::I8) => ConstInt::I8($lit),
51 SignedInt(ast::IntTy::I16) => ConstInt::I16($lit),
52 SignedInt(ast::IntTy::I32) => ConstInt::I32($lit),
53 SignedInt(ast::IntTy::I64) => ConstInt::I64($lit),
54 SignedInt(ast::IntTy::I128) => ConstInt::I128($lit),
55 SignedInt(ast::IntTy::Is) => match $tcx.sess.target.int_type {
56 ast::IntTy::I16 => ConstInt::Isize(ConstIsize::Is16($lit)),
57 ast::IntTy::I32 => ConstInt::Isize(ConstIsize::Is32($lit)),
58 ast::IntTy::I64 => ConstInt::Isize(ConstIsize::Is64($lit)),
61 UnsignedInt(ast::UintTy::U8) => ConstInt::U8($lit),
62 UnsignedInt(ast::UintTy::U16) => ConstInt::U16($lit),
63 UnsignedInt(ast::UintTy::U32) => ConstInt::U32($lit),
64 UnsignedInt(ast::UintTy::U64) => ConstInt::U64($lit),
65 UnsignedInt(ast::UintTy::U128) => ConstInt::U128($lit),
66 UnsignedInt(ast::UintTy::Us) => match $tcx.sess.target.uint_type {
67 ast::UintTy::U16 => ConstInt::Usize(ConstUsize::Us16($lit)),
68 ast::UintTy::U32 => ConstInt::Usize(ConstUsize::Us32($lit)),
69 ast::UintTy::U64 => ConstInt::Usize(ConstUsize::Us64($lit)),
76 impl IntTypeExt for attr::IntType {
77 fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
79 SignedInt(ast::IntTy::I8) => tcx.types.i8,
80 SignedInt(ast::IntTy::I16) => tcx.types.i16,
81 SignedInt(ast::IntTy::I32) => tcx.types.i32,
82 SignedInt(ast::IntTy::I64) => tcx.types.i64,
83 SignedInt(ast::IntTy::I128) => tcx.types.i128,
84 SignedInt(ast::IntTy::Is) => tcx.types.isize,
85 UnsignedInt(ast::UintTy::U8) => tcx.types.u8,
86 UnsignedInt(ast::UintTy::U16) => tcx.types.u16,
87 UnsignedInt(ast::UintTy::U32) => tcx.types.u32,
88 UnsignedInt(ast::UintTy::U64) => tcx.types.u64,
89 UnsignedInt(ast::UintTy::U128) => tcx.types.u128,
90 UnsignedInt(ast::UintTy::Us) => tcx.types.usize,
94 fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Disr {
95 typed_literal!(tcx, *self, 0)
98 fn assert_ty_matches(&self, val: Disr) {
100 (SignedInt(ast::IntTy::I8), ConstInt::I8(_)) => {},
101 (SignedInt(ast::IntTy::I16), ConstInt::I16(_)) => {},
102 (SignedInt(ast::IntTy::I32), ConstInt::I32(_)) => {},
103 (SignedInt(ast::IntTy::I64), ConstInt::I64(_)) => {},
104 (SignedInt(ast::IntTy::I128), ConstInt::I128(_)) => {},
105 (SignedInt(ast::IntTy::Is), ConstInt::Isize(_)) => {},
106 (UnsignedInt(ast::UintTy::U8), ConstInt::U8(_)) => {},
107 (UnsignedInt(ast::UintTy::U16), ConstInt::U16(_)) => {},
108 (UnsignedInt(ast::UintTy::U32), ConstInt::U32(_)) => {},
109 (UnsignedInt(ast::UintTy::U64), ConstInt::U64(_)) => {},
110 (UnsignedInt(ast::UintTy::U128), ConstInt::U128(_)) => {},
111 (UnsignedInt(ast::UintTy::Us), ConstInt::Usize(_)) => {},
112 _ => bug!("disr type mismatch: {:?} vs {:?}", self, val),
116 fn disr_incr<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, val: Option<Disr>)
118 if let Some(val) = val {
119 self.assert_ty_matches(val);
120 (val + typed_literal!(tcx, *self, 1)).ok()
122 Some(self.initial_discriminant(tcx))
128 #[derive(Copy, Clone)]
129 pub enum CopyImplementationError<'tcx> {
130 InfrigingField(&'tcx ty::FieldDef),
135 /// Describes whether a type is representable. For types that are not
136 /// representable, 'SelfRecursive' and 'ContainsRecursive' are used to
137 /// distinguish between types that are recursive with themselves and types that
138 /// contain a different recursive type. These cases can therefore be treated
139 /// differently when reporting errors.
141 /// The ordering of the cases is significant. They are sorted so that cmp::max
142 /// will keep the "more erroneous" of two values.
143 #[derive(Clone, PartialOrd, Ord, Eq, PartialEq, Debug)]
144 pub enum Representability {
147 SelfRecursive(Vec<Span>),
150 impl<'tcx> ty::ParamEnv<'tcx> {
151 /// Construct a trait environment suitable for contexts where
152 /// there are no where clauses in scope.
153 pub fn empty() -> Self {
154 Self::new(ty::Slice::empty())
157 /// Construct a trait environment with the given set of predicates.
158 pub fn new(caller_bounds: &'tcx ty::Slice<ty::Predicate<'tcx>>) -> Self {
159 ty::ParamEnv { caller_bounds }
162 pub fn can_type_implement_copy<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
163 self_type: Ty<'tcx>, span: Span)
164 -> Result<(), CopyImplementationError> {
165 // FIXME: (@jroesch) float this code up
166 tcx.infer_ctxt(self.clone(), Reveal::UserFacing).enter(|infcx| {
167 let (adt, substs) = match self_type.sty {
168 ty::TyAdt(adt, substs) => (adt, substs),
169 _ => return Err(CopyImplementationError::NotAnAdt),
172 let field_implements_copy = |field: &ty::FieldDef| {
173 let cause = traits::ObligationCause::dummy();
174 match traits::fully_normalize(&infcx, cause, &field.ty(tcx, substs)) {
175 Ok(ty) => !infcx.type_moves_by_default(ty, span),
180 for variant in &adt.variants {
181 for field in &variant.fields {
182 if !field_implements_copy(field) {
183 return Err(CopyImplementationError::InfrigingField(field));
188 if adt.has_dtor(tcx) {
189 return Err(CopyImplementationError::HasDestructor);
197 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
198 /// Creates a hash of the type `Ty` which will be the same no matter what crate
199 /// context it's calculated within. This is used by the `type_id` intrinsic.
200 pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
201 let mut hasher = StableHasher::new();
202 let mut hcx = StableHashingContext::new(self);
204 hcx.while_hashing_spans(false, |hcx| {
205 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
206 ty.hash_stable(hcx, &mut hasher);
213 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
214 pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
216 ty::TyAdt(def, substs) => {
217 for field in def.all_fields() {
218 let field_ty = field.ty(self, substs);
219 if let TyError = field_ty.sty {
229 /// Returns the type of element at index `i` in tuple or tuple-like type `t`.
230 /// For an enum `t`, `variant` is None only if `t` is a univariant enum.
231 pub fn positional_element_ty(self,
234 variant: Option<DefId>) -> Option<Ty<'tcx>> {
235 match (&ty.sty, variant) {
236 (&TyAdt(adt, substs), Some(vid)) => {
237 adt.variant_with_id(vid).fields.get(i).map(|f| f.ty(self, substs))
239 (&TyAdt(adt, substs), None) => {
240 // Don't use `struct_variant`, this may be a univariant enum.
241 adt.variants[0].fields.get(i).map(|f| f.ty(self, substs))
243 (&TyTuple(ref v, _), None) => v.get(i).cloned(),
248 /// Returns the type of element at field `n` in struct or struct-like type `t`.
249 /// For an enum `t`, `variant` must be some def id.
250 pub fn named_element_ty(self,
253 variant: Option<DefId>) -> Option<Ty<'tcx>> {
254 match (&ty.sty, variant) {
255 (&TyAdt(adt, substs), Some(vid)) => {
256 adt.variant_with_id(vid).find_field_named(n).map(|f| f.ty(self, substs))
258 (&TyAdt(adt, substs), None) => {
259 adt.struct_variant().find_field_named(n).map(|f| f.ty(self, substs))
265 /// Returns the deeply last field of nested structures, or the same type,
266 /// if not a structure at all. Corresponds to the only possible unsized
267 /// field, and its type can be used to determine unsizing strategy.
268 pub fn struct_tail(self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
271 ty::TyAdt(def, substs) => {
272 if !def.is_struct() {
275 match def.struct_variant().fields.last() {
276 Some(f) => ty = f.ty(self, substs),
281 ty::TyTuple(tys, _) => {
282 if let Some((&last_ty, _)) = tys.split_last() {
297 /// Same as applying struct_tail on `source` and `target`, but only
298 /// keeps going as long as the two types are instances of the same
299 /// structure definitions.
300 /// For `(Foo<Foo<T>>, Foo<Trait>)`, the result will be `(Foo<T>, Trait)`,
301 /// whereas struct_tail produces `T`, and `Trait`, respectively.
302 pub fn struct_lockstep_tails(self,
305 -> (Ty<'tcx>, Ty<'tcx>) {
306 let (mut a, mut b) = (source, target);
307 while let (&TyAdt(a_def, a_substs), &TyAdt(b_def, b_substs)) = (&a.sty, &b.sty) {
308 if a_def != b_def || !a_def.is_struct() {
311 match a_def.struct_variant().fields.last() {
313 a = f.ty(self, a_substs);
314 b = f.ty(self, b_substs);
322 /// Given a set of predicates that apply to an object type, returns
323 /// the region bounds that the (erased) `Self` type must
324 /// outlive. Precisely *because* the `Self` type is erased, the
325 /// parameter `erased_self_ty` must be supplied to indicate what type
326 /// has been used to represent `Self` in the predicates
327 /// themselves. This should really be a unique type; `FreshTy(0)` is a
330 /// NB: in some cases, particularly around higher-ranked bounds,
331 /// this function returns a kind of conservative approximation.
332 /// That is, all regions returned by this function are definitely
333 /// required, but there may be other region bounds that are not
334 /// returned, as well as requirements like `for<'a> T: 'a`.
336 /// Requires that trait definitions have been processed so that we can
337 /// elaborate predicates and walk supertraits.
339 /// FIXME callers may only have a &[Predicate], not a Vec, so that's
340 /// what this code should accept.
341 pub fn required_region_bounds(self,
342 erased_self_ty: Ty<'tcx>,
343 predicates: Vec<ty::Predicate<'tcx>>)
344 -> Vec<ty::Region<'tcx>> {
345 debug!("required_region_bounds(erased_self_ty={:?}, predicates={:?})",
349 assert!(!erased_self_ty.has_escaping_regions());
351 traits::elaborate_predicates(self, predicates)
352 .filter_map(|predicate| {
354 ty::Predicate::Projection(..) |
355 ty::Predicate::Trait(..) |
356 ty::Predicate::Equate(..) |
357 ty::Predicate::Subtype(..) |
358 ty::Predicate::WellFormed(..) |
359 ty::Predicate::ObjectSafe(..) |
360 ty::Predicate::ClosureKind(..) |
361 ty::Predicate::RegionOutlives(..) => {
364 ty::Predicate::TypeOutlives(ty::Binder(ty::OutlivesPredicate(t, r))) => {
365 // Search for a bound of the form `erased_self_ty
366 // : 'a`, but be wary of something like `for<'a>
367 // erased_self_ty : 'a` (we interpret a
368 // higher-ranked bound like that as 'static,
369 // though at present the code in `fulfill.rs`
370 // considers such bounds to be unsatisfiable, so
371 // it's kind of a moot point since you could never
372 // construct such an object, but this seems
373 // correct even if that code changes).
374 if t == erased_self_ty && !r.has_escaping_regions() {
385 /// Calculate the destructor of a given type.
386 pub fn calculate_dtor(
389 validate: &mut FnMut(Self, DefId) -> Result<(), ErrorReported>
390 ) -> Option<ty::Destructor> {
391 let drop_trait = if let Some(def_id) = self.lang_items.drop_trait() {
397 self.coherent_trait((LOCAL_CRATE, drop_trait));
399 let mut dtor_did = None;
400 let ty = self.type_of(adt_did);
401 self.trait_def(drop_trait).for_each_relevant_impl(self, ty, |impl_did| {
402 if let Some(item) = self.associated_items(impl_did).next() {
403 if let Ok(()) = validate(self, impl_did) {
404 dtor_did = Some(item.def_id);
409 let dtor_did = match dtor_did {
414 Some(ty::Destructor { did: dtor_did })
417 /// Return the set of types that are required to be alive in
418 /// order to run the destructor of `def` (see RFCs 769 and
421 /// Note that this returns only the constraints for the
422 /// destructor of `def` itself. For the destructors of the
423 /// contents, you need `adt_dtorck_constraint`.
424 pub fn destructor_constraints(self, def: &'tcx ty::AdtDef)
425 -> Vec<ty::subst::Kind<'tcx>>
427 let dtor = match def.destructor(self) {
429 debug!("destructor_constraints({:?}) - no dtor", def.did);
432 Some(dtor) => dtor.did
435 // RFC 1238: if the destructor method is tagged with the
436 // attribute `unsafe_destructor_blind_to_params`, then the
437 // compiler is being instructed to *assume* that the
438 // destructor will not access borrowed data,
439 // even if such data is otherwise reachable.
441 // Such access can be in plain sight (e.g. dereferencing
442 // `*foo.0` of `Foo<'a>(&'a u32)`) or indirectly hidden
443 // (e.g. calling `foo.0.clone()` of `Foo<T:Clone>`).
444 if self.has_attr(dtor, "unsafe_destructor_blind_to_params") {
445 debug!("destructor_constraint({:?}) - blind", def.did);
449 let impl_def_id = self.associated_item(dtor).container.id();
450 let impl_generics = self.generics_of(impl_def_id);
452 // We have a destructor - all the parameters that are not
453 // pure_wrt_drop (i.e, don't have a #[may_dangle] attribute)
456 // We need to return the list of parameters from the ADTs
457 // generics/substs that correspond to impure parameters on the
458 // impl's generics. This is a bit ugly, but conceptually simple:
460 // Suppose our ADT looks like the following
462 // struct S<X, Y, Z>(X, Y, Z);
466 // impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
468 // We want to return the parameters (X, Y). For that, we match
469 // up the item-substs <X, Y, Z> with the substs on the impl ADT,
470 // <P1, P2, P0>, and then look up which of the impl substs refer to
471 // parameters marked as pure.
473 let impl_substs = match self.type_of(impl_def_id).sty {
474 ty::TyAdt(def_, substs) if def_ == def => substs,
478 let item_substs = match self.type_of(def.did).sty {
479 ty::TyAdt(def_, substs) if def_ == def => substs,
483 let result = item_substs.iter().zip(impl_substs.iter())
485 if let Some(&ty::RegionKind::ReEarlyBound(ref ebr)) = k.as_region() {
486 !impl_generics.region_param(ebr).pure_wrt_drop
487 } else if let Some(&ty::TyS {
488 sty: ty::TypeVariants::TyParam(ref pt), ..
490 !impl_generics.type_param(pt).pure_wrt_drop
492 // not a type or region param - this should be reported
496 }).map(|(&item_param, _)| item_param).collect();
497 debug!("destructor_constraint({:?}) = {:?}", def.did, result);
501 /// Return a set of constraints that needs to be satisfied in
502 /// order for `ty` to be valid for destruction.
503 pub fn dtorck_constraint_for_ty(self,
508 -> Result<ty::DtorckConstraint<'tcx>, ErrorReported>
510 debug!("dtorck_constraint_for_ty({:?}, {:?}, {:?}, {:?})",
511 span, for_ty, depth, ty);
513 if depth >= self.sess.recursion_limit.get() {
514 let mut err = struct_span_err!(
515 self.sess, span, E0320,
516 "overflow while adding drop-check rules for {}", for_ty);
517 err.note(&format!("overflowed on {}", ty));
519 return Err(ErrorReported);
522 let result = match ty.sty {
523 ty::TyBool | ty::TyChar | ty::TyInt(_) | ty::TyUint(_) |
524 ty::TyFloat(_) | ty::TyStr | ty::TyNever |
525 ty::TyRawPtr(..) | ty::TyRef(..) | ty::TyFnDef(..) | ty::TyFnPtr(_) => {
526 // these types never have a destructor
527 Ok(ty::DtorckConstraint::empty())
530 ty::TyArray(ety, _) | ty::TySlice(ety) => {
531 // single-element containers, behave like their element
532 self.dtorck_constraint_for_ty(span, for_ty, depth+1, ety)
535 ty::TyTuple(tys, _) => {
536 tys.iter().map(|ty| {
537 self.dtorck_constraint_for_ty(span, for_ty, depth+1, ty)
541 ty::TyClosure(def_id, substs) => {
542 substs.upvar_tys(def_id, self).map(|ty| {
543 self.dtorck_constraint_for_ty(span, for_ty, depth+1, ty)
547 ty::TyAdt(def, substs) => {
548 let ty::DtorckConstraint {
549 dtorck_types, outlives
550 } = self.at(span).adt_dtorck_constraint(def.did);
551 Ok(ty::DtorckConstraint {
552 // FIXME: we can try to recursively `dtorck_constraint_on_ty`
553 // there, but that needs some way to handle cycles.
554 dtorck_types: dtorck_types.subst(self, substs),
555 outlives: outlives.subst(self, substs)
559 // Objects must be alive in order for their destructor
561 ty::TyDynamic(..) => Ok(ty::DtorckConstraint {
562 outlives: vec![Kind::from(ty)],
563 dtorck_types: vec![],
566 // Types that can't be resolved. Pass them forward.
567 ty::TyProjection(..) | ty::TyAnon(..) | ty::TyParam(..) => {
568 Ok(ty::DtorckConstraint {
570 dtorck_types: vec![ty],
574 ty::TyInfer(..) | ty::TyError => {
575 self.sess.delay_span_bug(span, "unresolved type in dtorck");
580 debug!("dtorck_constraint_for_ty({:?}) = {:?}", ty, result);
584 pub fn closure_base_def_id(self, def_id: DefId) -> DefId {
585 let mut def_id = def_id;
586 while self.def_key(def_id).disambiguated_data.data == DefPathData::ClosureExpr {
587 def_id = self.parent_def_id(def_id).unwrap_or_else(|| {
588 bug!("closure {:?} has no parent", def_id);
594 /// Given the def-id of some item that has no type parameters, make
595 /// a suitable "empty substs" for it.
596 pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> &'tcx ty::Substs<'tcx> {
597 ty::Substs::for_item(self, item_def_id,
598 |_, _| self.types.re_erased,
600 bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
604 pub fn const_usize(&self, val: u16) -> ConstInt {
605 match self.sess.target.uint_type {
606 ast::UintTy::U16 => ConstInt::Usize(ConstUsize::Us16(val as u16)),
607 ast::UintTy::U32 => ConstInt::Usize(ConstUsize::Us32(val as u32)),
608 ast::UintTy::U64 => ConstInt::Usize(ConstUsize::Us64(val as u64)),
614 pub struct TypeIdHasher<'a, 'gcx: 'a+'tcx, 'tcx: 'a, W> {
615 tcx: TyCtxt<'a, 'gcx, 'tcx>,
616 state: StableHasher<W>,
619 impl<'a, 'gcx, 'tcx, W> TypeIdHasher<'a, 'gcx, 'tcx, W>
620 where W: StableHasherResult
622 pub fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Self {
623 TypeIdHasher { tcx: tcx, state: StableHasher::new() }
626 pub fn finish(self) -> W {
630 pub fn hash<T: Hash>(&mut self, x: T) {
631 x.hash(&mut self.state);
634 fn hash_discriminant_u8<T>(&mut self, x: &T) {
636 intrinsics::discriminant_value(x)
639 assert_eq!(v, b as u64);
643 fn def_id(&mut self, did: DefId) {
644 // Hash the DefPath corresponding to the DefId, which is independent
645 // of compiler internal state. We already have a stable hash value of
646 // all DefPaths available via tcx.def_path_hash(), so we just feed that
648 let hash = self.tcx.def_path_hash(did);
653 impl<'a, 'gcx, 'tcx, W> TypeVisitor<'tcx> for TypeIdHasher<'a, 'gcx, 'tcx, W>
654 where W: StableHasherResult
656 fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool {
657 // Distinguish between the Ty variants uniformly.
658 self.hash_discriminant_u8(&ty.sty);
661 TyInt(i) => self.hash(i),
662 TyUint(u) => self.hash(u),
663 TyFloat(f) => self.hash(f),
664 TyArray(_, n) => self.hash(n),
666 TyRef(_, m) => self.hash(m.mutbl),
667 TyClosure(def_id, _) |
669 TyFnDef(def_id, ..) => self.def_id(def_id),
670 TyAdt(d, _) => self.def_id(d.did),
672 self.hash(f.unsafety());
674 self.hash(f.variadic());
675 self.hash(f.inputs().skip_binder().len());
677 TyDynamic(ref data, ..) => {
678 if let Some(p) = data.principal() {
679 self.def_id(p.def_id());
681 for d in data.auto_traits() {
685 TyTuple(tys, defaulted) => {
686 self.hash(tys.len());
687 self.hash(defaulted);
691 self.hash(p.name.as_str());
693 TyProjection(ref data) => {
694 self.def_id(data.item_def_id);
703 TyInfer(_) => bug!("TypeIdHasher: unexpected type {}", ty)
706 ty.super_visit_with(self)
709 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
710 self.hash_discriminant_u8(r);
715 // No variant fields to hash for these ...
717 ty::ReLateBound(db, ty::BrAnon(i)) => {
721 ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => {
724 ty::ReLateBound(..) |
728 ty::ReSkolemized(..) => {
729 bug!("TypeIdHasher: unexpected region {:?}", r)
735 fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, x: &ty::Binder<T>) -> bool {
736 // Anonymize late-bound regions so that, for example:
737 // `for<'a, b> fn(&'a &'b T)` and `for<'a, b> fn(&'b &'a T)`
738 // result in the same TypeId (the two types are equivalent).
739 self.tcx.anonymize_late_bound_regions(x).super_visit_with(self)
743 impl<'a, 'tcx> ty::TyS<'tcx> {
744 pub fn moves_by_default(&'tcx self,
745 tcx: TyCtxt<'a, 'tcx, 'tcx>,
746 param_env: ty::ParamEnv<'tcx>,
749 !tcx.at(span).is_copy_raw(param_env.and(self))
752 pub fn is_sized(&'tcx self,
753 tcx: TyCtxt<'a, 'tcx, 'tcx>,
754 param_env: ty::ParamEnv<'tcx>,
757 tcx.at(span).is_sized_raw(param_env.and(self))
760 pub fn is_freeze(&'tcx self,
761 tcx: TyCtxt<'a, 'tcx, 'tcx>,
762 param_env: ty::ParamEnv<'tcx>,
765 tcx.at(span).is_freeze_raw(param_env.and(self))
768 /// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely
769 /// non-copy and *might* have a destructor attached; if it returns
770 /// `false`, then `ty` definitely has no destructor (i.e. no drop glue).
772 /// (Note that this implies that if `ty` has a destructor attached,
773 /// then `needs_drop` will definitely return `true` for `ty`.)
775 pub fn needs_drop(&'tcx self,
776 tcx: TyCtxt<'a, 'tcx, 'tcx>,
777 param_env: ty::ParamEnv<'tcx>)
779 tcx.needs_drop_raw(param_env.and(self))
783 pub fn layout<'lcx>(&'tcx self, infcx: &InferCtxt<'a, 'tcx, 'lcx>)
784 -> Result<&'tcx Layout, LayoutError<'tcx>> {
785 let tcx = infcx.tcx.global_tcx();
786 let can_cache = !self.has_param_types() && !self.has_self_ty();
788 if let Some(&cached) = tcx.layout_cache.borrow().get(&self) {
793 let rec_limit = tcx.sess.recursion_limit.get();
794 let depth = tcx.layout_depth.get();
795 if depth > rec_limit {
797 &format!("overflow representing the type `{}`", self));
800 tcx.layout_depth.set(depth+1);
801 let layout = Layout::compute_uncached(self, infcx);
802 tcx.layout_depth.set(depth);
803 let layout = layout?;
805 tcx.layout_cache.borrow_mut().insert(self, layout);
811 /// Check whether a type is representable. This means it cannot contain unboxed
812 /// structural recursion. This check is needed for structs and enums.
813 pub fn is_representable(&'tcx self,
814 tcx: TyCtxt<'a, 'tcx, 'tcx>,
816 -> Representability {
818 // Iterate until something non-representable is found
819 fn fold_repr<It: Iterator<Item=Representability>>(iter: It) -> Representability {
820 iter.fold(Representability::Representable, |r1, r2| {
822 (Representability::SelfRecursive(v1),
823 Representability::SelfRecursive(v2)) => {
824 Representability::SelfRecursive(v1.iter().map(|s| *s).chain(v2).collect())
826 (r1, r2) => cmp::max(r1, r2)
831 fn are_inner_types_recursive<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span,
832 seen: &mut Vec<Ty<'tcx>>, ty: Ty<'tcx>)
833 -> Representability {
835 TyTuple(ref ts, _) => {
836 // Find non representable
837 fold_repr(ts.iter().map(|ty| {
838 is_type_structurally_recursive(tcx, sp, seen, ty)
841 // Fixed-length vectors.
842 // FIXME(#11924) Behavior undecided for zero-length vectors.
844 is_type_structurally_recursive(tcx, sp, seen, ty)
846 TyAdt(def, substs) => {
847 // Find non representable fields with their spans
848 fold_repr(def.all_fields().map(|field| {
849 let ty = field.ty(tcx, substs);
850 let span = tcx.hir.span_if_local(field.did).unwrap_or(sp);
851 match is_type_structurally_recursive(tcx, span, seen, ty) {
852 Representability::SelfRecursive(_) => {
853 Representability::SelfRecursive(vec![span])
860 // this check is run on type definitions, so we don't expect
861 // to see closure types
862 bug!("requires check invoked on inapplicable type: {:?}", ty)
864 _ => Representability::Representable,
868 fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: &'tcx ty::AdtDef) -> bool {
870 TyAdt(ty_def, _) => {
877 fn same_type<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
878 match (&a.sty, &b.sty) {
879 (&TyAdt(did_a, substs_a), &TyAdt(did_b, substs_b)) => {
884 substs_a.types().zip(substs_b.types()).all(|(a, b)| same_type(a, b))
890 // Does the type `ty` directly (without indirection through a pointer)
891 // contain any types on stack `seen`?
892 fn is_type_structurally_recursive<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
894 seen: &mut Vec<Ty<'tcx>>,
895 ty: Ty<'tcx>) -> Representability {
896 debug!("is_type_structurally_recursive: {:?} {:?}", ty, sp);
901 // Iterate through stack of previously seen types.
902 let mut iter = seen.iter();
904 // The first item in `seen` is the type we are actually curious about.
905 // We want to return SelfRecursive if this type contains itself.
906 // It is important that we DON'T take generic parameters into account
907 // for this check, so that Bar<T> in this example counts as SelfRecursive:
910 // struct Bar<T> { x: Bar<Foo> }
912 if let Some(&seen_type) = iter.next() {
913 if same_struct_or_enum(seen_type, def) {
914 debug!("SelfRecursive: {:?} contains {:?}",
917 return Representability::SelfRecursive(vec![sp]);
921 // We also need to know whether the first item contains other types
922 // that are structurally recursive. If we don't catch this case, we
923 // will recurse infinitely for some inputs.
925 // It is important that we DO take generic parameters into account
926 // here, so that code like this is considered SelfRecursive, not
927 // ContainsRecursive:
929 // struct Foo { Option<Option<Foo>> }
931 for &seen_type in iter {
932 if same_type(ty, seen_type) {
933 debug!("ContainsRecursive: {:?} contains {:?}",
936 return Representability::ContainsRecursive;
941 // For structs and enums, track all previously seen types by pushing them
942 // onto the 'seen' stack.
944 let out = are_inner_types_recursive(tcx, sp, seen, ty);
949 // No need to push in other cases.
950 are_inner_types_recursive(tcx, sp, seen, ty)
955 debug!("is_type_representable: {:?}", self);
957 // To avoid a stack overflow when checking an enum variant or struct that
958 // contains a different, structurally recursive type, maintain a stack
959 // of seen types and check recursion for each of them (issues #3008, #3779).
960 let mut seen: Vec<Ty> = Vec::new();
961 let r = is_type_structurally_recursive(tcx, sp, &mut seen, self);
962 debug!("is_type_representable: {:?} is {:?}", self, r);
967 fn is_copy_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
968 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
971 let (param_env, ty) = query.into_parts();
972 let trait_def_id = tcx.require_lang_item(lang_items::CopyTraitLangItem);
973 tcx.infer_ctxt(param_env, Reveal::UserFacing)
974 .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
977 fn is_sized_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
978 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
981 let (param_env, ty) = query.into_parts();
982 let trait_def_id = tcx.require_lang_item(lang_items::SizedTraitLangItem);
983 tcx.infer_ctxt(param_env, Reveal::UserFacing)
984 .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
987 fn is_freeze_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
988 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
991 let (param_env, ty) = query.into_parts();
992 let trait_def_id = tcx.require_lang_item(lang_items::FreezeTraitLangItem);
993 tcx.infer_ctxt(param_env, Reveal::UserFacing)
994 .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
997 fn needs_drop_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
998 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
1001 let (param_env, ty) = query.into_parts();
1003 let needs_drop = |ty: Ty<'tcx>| -> bool {
1004 match ty::queries::needs_drop_raw::try_get(tcx, DUMMY_SP, param_env.and(ty)) {
1007 // Cycles should be reported as an error by `check_representable`.
1009 // Consider the type as not needing drop in the meanwhile to avoid
1016 assert!(!ty.needs_infer());
1019 // Fast-path for primitive types
1020 ty::TyInfer(ty::FreshIntTy(_)) | ty::TyInfer(ty::FreshFloatTy(_)) |
1021 ty::TyBool | ty::TyInt(_) | ty::TyUint(_) | ty::TyFloat(_) | ty::TyNever |
1022 ty::TyFnDef(..) | ty::TyFnPtr(_) | ty::TyChar |
1023 ty::TyRawPtr(_) | ty::TyRef(..) | ty::TyStr => false,
1025 // Issue #22536: We first query type_moves_by_default. It sees a
1026 // normalized version of the type, and therefore will definitely
1027 // know whether the type implements Copy (and thus needs no
1028 // cleanup/drop/zeroing) ...
1029 _ if !ty.moves_by_default(tcx, param_env, DUMMY_SP) => false,
1031 // ... (issue #22536 continued) but as an optimization, still use
1032 // prior logic of asking for the structural "may drop".
1034 // FIXME(#22815): Note that this is a conservative heuristic;
1035 // it may report that the type "may drop" when actual type does
1036 // not actually have a destructor associated with it. But since
1037 // the type absolutely did not have the `Copy` bound attached
1038 // (see above), it is sound to treat it as having a destructor.
1040 // User destructors are the only way to have concrete drop types.
1041 ty::TyAdt(def, _) if def.has_dtor(tcx) => true,
1043 // Can refer to a type which may drop.
1044 // FIXME(eddyb) check this against a ParamEnv.
1045 ty::TyDynamic(..) | ty::TyProjection(..) | ty::TyParam(_) |
1046 ty::TyAnon(..) | ty::TyInfer(_) | ty::TyError => true,
1048 // Structural recursion.
1049 ty::TyArray(ty, _) | ty::TySlice(ty) => needs_drop(ty),
1051 ty::TyClosure(def_id, ref substs) => substs.upvar_tys(def_id, tcx).any(needs_drop),
1053 ty::TyTuple(ref tys, _) => tys.iter().cloned().any(needs_drop),
1055 // unions don't have destructors regardless of the child types
1056 ty::TyAdt(def, _) if def.is_union() => false,
1058 ty::TyAdt(def, substs) =>
1059 def.variants.iter().any(
1060 |variant| variant.fields.iter().any(
1061 |field| needs_drop(field.ty(tcx, substs)))),
1066 pub fn provide(providers: &mut ty::maps::Providers) {
1067 *providers = ty::maps::Providers {