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
14 use hir::def_id::DefId;
15 use hir::map::{DefPathData, Node};
17 use ich::NodeIdHashingMode;
18 use traits::{self, ObligationCause};
19 use ty::{self, Ty, TyCtxt, GenericParamDefKind, TypeFoldable};
20 use ty::subst::{Substs, UnpackedKind};
21 use ty::query::TyCtxtAt;
22 use ty::TypeVariants::*;
23 use ty::layout::{Integer, IntegerExt};
24 use util::common::ErrorReported;
25 use middle::lang_items;
27 use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
28 use rustc_data_structures::fx::FxHashMap;
31 use syntax::attr::{self, SignedInt, UnsignedInt};
32 use syntax_pos::{Span, DUMMY_SP};
34 #[derive(Copy, Clone, Debug)]
35 pub struct Discr<'tcx> {
36 /// bit representation of the discriminant, so `-128i8` is `0xFF_u128`
41 impl<'tcx> fmt::Display for Discr<'tcx> {
42 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
45 let bits = ty::tls::with(|tcx| {
46 Integer::from_attr(tcx, SignedInt(ity)).size().bits()
48 let x = self.val as i128;
49 // sign extend the raw representation to be an i128
50 let x = (x << (128 - bits)) >> (128 - bits);
53 _ => write!(fmt, "{}", self.val),
58 impl<'tcx> Discr<'tcx> {
59 /// Adds 1 to the value and wraps around if the maximum for the type is reached
60 pub fn wrap_incr<'a, 'gcx>(self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Self {
61 self.checked_add(tcx, 1).0
63 pub fn checked_add<'a, 'gcx>(self, tcx: TyCtxt<'a, 'gcx, 'tcx>, n: u128) -> (Self, bool) {
64 let (int, signed) = match self.ty.sty {
65 TyInt(ity) => (Integer::from_attr(tcx, SignedInt(ity)), true),
66 TyUint(uty) => (Integer::from_attr(tcx, UnsignedInt(uty)), false),
67 _ => bug!("non integer discriminant"),
70 let bit_size = int.size().bits();
71 let shift = 128 - bit_size;
77 let min = sext(1_u128 << (bit_size - 1));
78 let max = i128::max_value() >> shift;
79 let val = sext(self.val);
80 assert!(n < (i128::max_value() as u128));
82 let oflo = val > max - n;
84 min + (n - (max - val) - 1)
88 // zero the upper bits
89 let val = val as u128;
90 let val = (val << shift) >> shift;
96 let max = u128::max_value() >> shift;
98 let oflo = val > max - n;
112 pub trait IntTypeExt {
113 fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx>;
114 fn disr_incr<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, val: Option<Discr<'tcx>>)
115 -> Option<Discr<'tcx>>;
116 fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Discr<'tcx>;
119 impl IntTypeExt for attr::IntType {
120 fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
122 SignedInt(ast::IntTy::I8) => tcx.types.i8,
123 SignedInt(ast::IntTy::I16) => tcx.types.i16,
124 SignedInt(ast::IntTy::I32) => tcx.types.i32,
125 SignedInt(ast::IntTy::I64) => tcx.types.i64,
126 SignedInt(ast::IntTy::I128) => tcx.types.i128,
127 SignedInt(ast::IntTy::Isize) => tcx.types.isize,
128 UnsignedInt(ast::UintTy::U8) => tcx.types.u8,
129 UnsignedInt(ast::UintTy::U16) => tcx.types.u16,
130 UnsignedInt(ast::UintTy::U32) => tcx.types.u32,
131 UnsignedInt(ast::UintTy::U64) => tcx.types.u64,
132 UnsignedInt(ast::UintTy::U128) => tcx.types.u128,
133 UnsignedInt(ast::UintTy::Usize) => tcx.types.usize,
137 fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Discr<'tcx> {
144 fn disr_incr<'a, 'tcx>(
146 tcx: TyCtxt<'a, 'tcx, 'tcx>,
147 val: Option<Discr<'tcx>>,
148 ) -> Option<Discr<'tcx>> {
149 if let Some(val) = val {
150 assert_eq!(self.to_ty(tcx), val.ty);
151 let (new, oflo) = val.checked_add(tcx, 1);
158 Some(self.initial_discriminant(tcx))
165 pub enum CopyImplementationError<'tcx> {
166 InfrigingFields(Vec<&'tcx ty::FieldDef>),
171 /// Describes whether a type is representable. For types that are not
172 /// representable, 'SelfRecursive' and 'ContainsRecursive' are used to
173 /// distinguish between types that are recursive with themselves and types that
174 /// contain a different recursive type. These cases can therefore be treated
175 /// differently when reporting errors.
177 /// The ordering of the cases is significant. They are sorted so that cmp::max
178 /// will keep the "more erroneous" of two values.
179 #[derive(Clone, PartialOrd, Ord, Eq, PartialEq, Debug)]
180 pub enum Representability {
183 SelfRecursive(Vec<Span>),
186 impl<'tcx> ty::ParamEnv<'tcx> {
187 pub fn can_type_implement_copy<'a>(self,
188 tcx: TyCtxt<'a, 'tcx, 'tcx>,
190 -> Result<(), CopyImplementationError<'tcx>> {
191 // FIXME: (@jroesch) float this code up
192 tcx.infer_ctxt().enter(|infcx| {
193 let (adt, substs) = match self_type.sty {
194 // These types used to have a builtin impl.
195 // Now libcore provides that impl.
196 ty::TyUint(_) | ty::TyInt(_) | ty::TyBool | ty::TyFloat(_) |
197 ty::TyChar | ty::TyRawPtr(..) | ty::TyNever |
198 ty::TyRef(_, _, hir::MutImmutable) => return Ok(()),
200 ty::TyAdt(adt, substs) => (adt, substs),
202 _ => return Err(CopyImplementationError::NotAnAdt),
205 let mut infringing = Vec::new();
206 for variant in &adt.variants {
207 for field in &variant.fields {
208 let span = tcx.def_span(field.did);
209 let ty = field.ty(tcx, substs);
210 if ty.references_error() {
213 let cause = ObligationCause { span, ..ObligationCause::dummy() };
214 let ctx = traits::FulfillmentContext::new();
215 match traits::fully_normalize(&infcx, ctx, cause, self, &ty) {
216 Ok(ty) => if infcx.type_moves_by_default(self, ty, span) {
217 infringing.push(field);
220 infcx.report_fulfillment_errors(&errors, None, false);
225 if !infringing.is_empty() {
226 return Err(CopyImplementationError::InfrigingFields(infringing));
228 if adt.has_dtor(tcx) {
229 return Err(CopyImplementationError::HasDestructor);
237 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
238 /// Creates a hash of the type `Ty` which will be the same no matter what crate
239 /// context it's calculated within. This is used by the `type_id` intrinsic.
240 pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
241 let mut hasher = StableHasher::new();
242 let mut hcx = self.create_stable_hashing_context();
244 // We want the type_id be independent of the types free regions, so we
245 // erase them. The erase_regions() call will also anonymize bound
246 // regions, which is desirable too.
247 let ty = self.erase_regions(&ty);
249 hcx.while_hashing_spans(false, |hcx| {
250 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
251 ty.hash_stable(hcx, &mut hasher);
258 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
259 pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
261 ty::TyAdt(def, substs) => {
262 for field in def.all_fields() {
263 let field_ty = field.ty(self, substs);
264 if let TyError = field_ty.sty {
274 /// Returns the deeply last field of nested structures, or the same type,
275 /// if not a structure at all. Corresponds to the only possible unsized
276 /// field, and its type can be used to determine unsizing strategy.
277 pub fn struct_tail(self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
280 ty::TyAdt(def, substs) => {
281 if !def.is_struct() {
284 match def.non_enum_variant().fields.last() {
285 Some(f) => ty = f.ty(self, substs),
290 ty::TyTuple(tys) => {
291 if let Some((&last_ty, _)) = tys.split_last() {
306 /// Same as applying struct_tail on `source` and `target`, but only
307 /// keeps going as long as the two types are instances of the same
308 /// structure definitions.
309 /// For `(Foo<Foo<T>>, Foo<Trait>)`, the result will be `(Foo<T>, Trait)`,
310 /// whereas struct_tail produces `T`, and `Trait`, respectively.
311 pub fn struct_lockstep_tails(self,
314 -> (Ty<'tcx>, Ty<'tcx>) {
315 let (mut a, mut b) = (source, target);
317 match (&a.sty, &b.sty) {
318 (&TyAdt(a_def, a_substs), &TyAdt(b_def, b_substs))
319 if a_def == b_def && a_def.is_struct() => {
320 if let Some(f) = a_def.non_enum_variant().fields.last() {
321 a = f.ty(self, a_substs);
322 b = f.ty(self, b_substs);
327 (&TyTuple(a_tys), &TyTuple(b_tys))
328 if a_tys.len() == b_tys.len() => {
329 if let Some(a_last) = a_tys.last() {
331 b = b_tys.last().unwrap();
342 /// Given a set of predicates that apply to an object type, returns
343 /// the region bounds that the (erased) `Self` type must
344 /// outlive. Precisely *because* the `Self` type is erased, the
345 /// parameter `erased_self_ty` must be supplied to indicate what type
346 /// has been used to represent `Self` in the predicates
347 /// themselves. This should really be a unique type; `FreshTy(0)` is a
350 /// NB: in some cases, particularly around higher-ranked bounds,
351 /// this function returns a kind of conservative approximation.
352 /// That is, all regions returned by this function are definitely
353 /// required, but there may be other region bounds that are not
354 /// returned, as well as requirements like `for<'a> T: 'a`.
356 /// Requires that trait definitions have been processed so that we can
357 /// elaborate predicates and walk supertraits.
359 /// FIXME callers may only have a &[Predicate], not a Vec, so that's
360 /// what this code should accept.
361 pub fn required_region_bounds(self,
362 erased_self_ty: Ty<'tcx>,
363 predicates: Vec<ty::Predicate<'tcx>>)
364 -> Vec<ty::Region<'tcx>> {
365 debug!("required_region_bounds(erased_self_ty={:?}, predicates={:?})",
369 assert!(!erased_self_ty.has_escaping_regions());
371 traits::elaborate_predicates(self, predicates)
372 .filter_map(|predicate| {
374 ty::Predicate::Projection(..) |
375 ty::Predicate::Trait(..) |
376 ty::Predicate::Subtype(..) |
377 ty::Predicate::WellFormed(..) |
378 ty::Predicate::ObjectSafe(..) |
379 ty::Predicate::ClosureKind(..) |
380 ty::Predicate::RegionOutlives(..) |
381 ty::Predicate::ConstEvaluatable(..) => {
384 ty::Predicate::TypeOutlives(predicate) => {
385 // Search for a bound of the form `erased_self_ty
386 // : 'a`, but be wary of something like `for<'a>
387 // erased_self_ty : 'a` (we interpret a
388 // higher-ranked bound like that as 'static,
389 // though at present the code in `fulfill.rs`
390 // considers such bounds to be unsatisfiable, so
391 // it's kind of a moot point since you could never
392 // construct such an object, but this seems
393 // correct even if that code changes).
394 let ty::OutlivesPredicate(ref t, ref r) = predicate.skip_binder();
395 if t == &erased_self_ty && !r.has_escaping_regions() {
406 /// Calculate the destructor of a given type.
407 pub fn calculate_dtor(
410 validate: &mut dyn FnMut(Self, DefId) -> Result<(), ErrorReported>
411 ) -> Option<ty::Destructor> {
412 let drop_trait = if let Some(def_id) = self.lang_items().drop_trait() {
418 ty::query::queries::coherent_trait::ensure(self, drop_trait);
420 let mut dtor_did = None;
421 let ty = self.type_of(adt_did);
422 self.for_each_relevant_impl(drop_trait, ty, |impl_did| {
423 if let Some(item) = self.associated_items(impl_did).next() {
424 if let Ok(()) = validate(self, impl_did) {
425 dtor_did = Some(item.def_id);
430 Some(ty::Destructor { did: dtor_did? })
433 /// Return the set of types that are required to be alive in
434 /// order to run the destructor of `def` (see RFCs 769 and
437 /// Note that this returns only the constraints for the
438 /// destructor of `def` itself. For the destructors of the
439 /// contents, you need `adt_dtorck_constraint`.
440 pub fn destructor_constraints(self, def: &'tcx ty::AdtDef)
441 -> Vec<ty::subst::Kind<'tcx>>
443 let dtor = match def.destructor(self) {
445 debug!("destructor_constraints({:?}) - no dtor", def.did);
448 Some(dtor) => dtor.did
451 // RFC 1238: if the destructor method is tagged with the
452 // attribute `unsafe_destructor_blind_to_params`, then the
453 // compiler is being instructed to *assume* that the
454 // destructor will not access borrowed data,
455 // even if such data is otherwise reachable.
457 // Such access can be in plain sight (e.g. dereferencing
458 // `*foo.0` of `Foo<'a>(&'a u32)`) or indirectly hidden
459 // (e.g. calling `foo.0.clone()` of `Foo<T:Clone>`).
460 if self.has_attr(dtor, "unsafe_destructor_blind_to_params") {
461 debug!("destructor_constraint({:?}) - blind", def.did);
465 let impl_def_id = self.associated_item(dtor).container.id();
466 let impl_generics = self.generics_of(impl_def_id);
468 // We have a destructor - all the parameters that are not
469 // pure_wrt_drop (i.e, don't have a #[may_dangle] attribute)
472 // We need to return the list of parameters from the ADTs
473 // generics/substs that correspond to impure parameters on the
474 // impl's generics. This is a bit ugly, but conceptually simple:
476 // Suppose our ADT looks like the following
478 // struct S<X, Y, Z>(X, Y, Z);
482 // impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
484 // We want to return the parameters (X, Y). For that, we match
485 // up the item-substs <X, Y, Z> with the substs on the impl ADT,
486 // <P1, P2, P0>, and then look up which of the impl substs refer to
487 // parameters marked as pure.
489 let impl_substs = match self.type_of(impl_def_id).sty {
490 ty::TyAdt(def_, substs) if def_ == def => substs,
494 let item_substs = match self.type_of(def.did).sty {
495 ty::TyAdt(def_, substs) if def_ == def => substs,
499 let result = item_substs.iter().zip(impl_substs.iter())
502 UnpackedKind::Lifetime(&ty::RegionKind::ReEarlyBound(ref ebr)) => {
503 !impl_generics.region_param(ebr, self).pure_wrt_drop
505 UnpackedKind::Type(&ty::TyS {
506 sty: ty::TypeVariants::TyParam(ref pt), ..
508 !impl_generics.type_param(pt, self).pure_wrt_drop
510 UnpackedKind::Lifetime(_) | UnpackedKind::Type(_) => {
511 // not a type or region param - this should be reported
516 }).map(|(&item_param, _)| item_param).collect();
517 debug!("destructor_constraint({:?}) = {:?}", def.did, result);
521 pub fn is_closure(self, def_id: DefId) -> bool {
522 self.def_key(def_id).disambiguated_data.data == DefPathData::ClosureExpr
525 /// True if this def-id refers to the implicit constructor for
526 /// a tuple struct like `struct Foo(u32)`.
527 pub fn is_struct_constructor(self, def_id: DefId) -> bool {
528 self.def_key(def_id).disambiguated_data.data == DefPathData::StructCtor
531 /// Given the `DefId` of a fn or closure, returns the `DefId` of
532 /// the innermost fn item that the closure is contained within.
533 /// This is a significant def-id because, when we do
534 /// type-checking, we type-check this fn item and all of its
535 /// (transitive) closures together. Therefore, when we fetch the
536 /// `typeck_tables_of` the closure, for example, we really wind up
537 /// fetching the `typeck_tables_of` the enclosing fn item.
538 pub fn closure_base_def_id(self, def_id: DefId) -> DefId {
539 let mut def_id = def_id;
540 while self.is_closure(def_id) {
541 def_id = self.parent_def_id(def_id).unwrap_or_else(|| {
542 bug!("closure {:?} has no parent", def_id);
548 /// Given the def-id and substs a closure, creates the type of
549 /// `self` argument that the closure expects. For example, for a
550 /// `Fn` closure, this would return a reference type `&T` where
553 /// Returns `None` if this closure's kind has not yet been inferred.
554 /// This should only be possible during type checking.
556 /// Note that the return value is a late-bound region and hence
557 /// wrapped in a binder.
558 pub fn closure_env_ty(self,
559 closure_def_id: DefId,
560 closure_substs: ty::ClosureSubsts<'tcx>)
561 -> Option<ty::Binder<Ty<'tcx>>>
563 let closure_ty = self.mk_closure(closure_def_id, closure_substs);
564 let env_region = ty::ReLateBound(ty::INNERMOST, ty::BrEnv);
565 let closure_kind_ty = closure_substs.closure_kind_ty(closure_def_id, self);
566 let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
567 let env_ty = match closure_kind {
568 ty::ClosureKind::Fn => self.mk_imm_ref(self.mk_region(env_region), closure_ty),
569 ty::ClosureKind::FnMut => self.mk_mut_ref(self.mk_region(env_region), closure_ty),
570 ty::ClosureKind::FnOnce => closure_ty,
572 Some(ty::Binder::bind(env_ty))
575 /// Given the def-id of some item that has no type parameters, make
576 /// a suitable "empty substs" for it.
577 pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> &'tcx Substs<'tcx> {
578 Substs::for_item(self, item_def_id, |param, _| {
580 GenericParamDefKind::Lifetime => self.types.re_erased.into(),
581 GenericParamDefKind::Type {..} => {
582 bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
588 /// Return whether the node pointed to by def_id is a static item, and its mutability
589 pub fn is_static(&self, def_id: DefId) -> Option<hir::Mutability> {
590 if let Some(node) = self.hir.get_if_local(def_id) {
592 Node::NodeItem(&hir::Item {
593 node: hir::ItemStatic(_, mutbl, _), ..
595 Node::NodeForeignItem(&hir::ForeignItem {
596 node: hir::ForeignItemStatic(_, is_mutbl), ..
599 hir::Mutability::MutMutable
601 hir::Mutability::MutImmutable
606 match self.describe_def(def_id) {
607 Some(Def::Static(_, is_mutbl)) =>
609 hir::Mutability::MutMutable
611 hir::Mutability::MutImmutable
619 impl<'a, 'tcx> ty::TyS<'tcx> {
620 pub fn moves_by_default(&'tcx self,
621 tcx: TyCtxt<'a, 'tcx, 'tcx>,
622 param_env: ty::ParamEnv<'tcx>,
625 !tcx.at(span).is_copy_raw(param_env.and(self))
628 pub fn is_sized(&'tcx self,
629 tcx_at: TyCtxtAt<'a, 'tcx, 'tcx>,
630 param_env: ty::ParamEnv<'tcx>)-> bool
632 tcx_at.is_sized_raw(param_env.and(self))
635 pub fn is_freeze(&'tcx self,
636 tcx: TyCtxt<'a, 'tcx, 'tcx>,
637 param_env: ty::ParamEnv<'tcx>,
640 tcx.at(span).is_freeze_raw(param_env.and(self))
643 /// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely
644 /// non-copy and *might* have a destructor attached; if it returns
645 /// `false`, then `ty` definitely has no destructor (i.e. no drop glue).
647 /// (Note that this implies that if `ty` has a destructor attached,
648 /// then `needs_drop` will definitely return `true` for `ty`.)
650 pub fn needs_drop(&'tcx self,
651 tcx: TyCtxt<'a, 'tcx, 'tcx>,
652 param_env: ty::ParamEnv<'tcx>)
654 tcx.needs_drop_raw(param_env.and(self))
657 /// Check whether a type is representable. This means it cannot contain unboxed
658 /// structural recursion. This check is needed for structs and enums.
659 pub fn is_representable(&'tcx self,
660 tcx: TyCtxt<'a, 'tcx, 'tcx>,
662 -> Representability {
664 // Iterate until something non-representable is found
665 fn fold_repr<It: Iterator<Item=Representability>>(iter: It) -> Representability {
666 iter.fold(Representability::Representable, |r1, r2| {
668 (Representability::SelfRecursive(v1),
669 Representability::SelfRecursive(v2)) => {
670 Representability::SelfRecursive(v1.iter().map(|s| *s).chain(v2).collect())
672 (r1, r2) => cmp::max(r1, r2)
677 fn are_inner_types_recursive<'a, 'tcx>(
678 tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span,
679 seen: &mut Vec<Ty<'tcx>>,
680 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
686 // Find non representable
687 fold_repr(ts.iter().map(|ty| {
688 is_type_structurally_recursive(tcx, sp, seen, representable_cache, ty)
691 // Fixed-length vectors.
692 // FIXME(#11924) Behavior undecided for zero-length vectors.
694 is_type_structurally_recursive(tcx, sp, seen, representable_cache, ty)
696 TyAdt(def, substs) => {
697 // Find non representable fields with their spans
698 fold_repr(def.all_fields().map(|field| {
699 let ty = field.ty(tcx, substs);
700 let span = tcx.hir.span_if_local(field.did).unwrap_or(sp);
701 match is_type_structurally_recursive(tcx, span, seen,
702 representable_cache, ty)
704 Representability::SelfRecursive(_) => {
705 Representability::SelfRecursive(vec![span])
712 // this check is run on type definitions, so we don't expect
713 // to see closure types
714 bug!("requires check invoked on inapplicable type: {:?}", ty)
716 _ => Representability::Representable,
720 fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: &'tcx ty::AdtDef) -> bool {
722 TyAdt(ty_def, _) => {
729 fn same_type<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
730 match (&a.sty, &b.sty) {
731 (&TyAdt(did_a, substs_a), &TyAdt(did_b, substs_b)) => {
736 substs_a.types().zip(substs_b.types()).all(|(a, b)| same_type(a, b))
742 // Does the type `ty` directly (without indirection through a pointer)
743 // contain any types on stack `seen`?
744 fn is_type_structurally_recursive<'a, 'tcx>(
745 tcx: TyCtxt<'a, 'tcx, 'tcx>,
747 seen: &mut Vec<Ty<'tcx>>,
748 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
749 ty: Ty<'tcx>) -> Representability
751 debug!("is_type_structurally_recursive: {:?} {:?}", ty, sp);
752 if let Some(representability) = representable_cache.get(ty) {
753 debug!("is_type_structurally_recursive: {:?} {:?} - (cached) {:?}",
754 ty, sp, representability);
755 return representability.clone();
758 let representability = is_type_structurally_recursive_inner(
759 tcx, sp, seen, representable_cache, ty);
761 representable_cache.insert(ty, representability.clone());
765 fn is_type_structurally_recursive_inner<'a, 'tcx>(
766 tcx: TyCtxt<'a, 'tcx, 'tcx>,
768 seen: &mut Vec<Ty<'tcx>>,
769 representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
770 ty: Ty<'tcx>) -> Representability
775 // Iterate through stack of previously seen types.
776 let mut iter = seen.iter();
778 // The first item in `seen` is the type we are actually curious about.
779 // We want to return SelfRecursive if this type contains itself.
780 // It is important that we DON'T take generic parameters into account
781 // for this check, so that Bar<T> in this example counts as SelfRecursive:
784 // struct Bar<T> { x: Bar<Foo> }
786 if let Some(&seen_type) = iter.next() {
787 if same_struct_or_enum(seen_type, def) {
788 debug!("SelfRecursive: {:?} contains {:?}",
791 return Representability::SelfRecursive(vec![sp]);
795 // We also need to know whether the first item contains other types
796 // that are structurally recursive. If we don't catch this case, we
797 // will recurse infinitely for some inputs.
799 // It is important that we DO take generic parameters into account
800 // here, so that code like this is considered SelfRecursive, not
801 // ContainsRecursive:
803 // struct Foo { Option<Option<Foo>> }
805 for &seen_type in iter {
806 if same_type(ty, seen_type) {
807 debug!("ContainsRecursive: {:?} contains {:?}",
810 return Representability::ContainsRecursive;
815 // For structs and enums, track all previously seen types by pushing them
816 // onto the 'seen' stack.
818 let out = are_inner_types_recursive(tcx, sp, seen, representable_cache, ty);
823 // No need to push in other cases.
824 are_inner_types_recursive(tcx, sp, seen, representable_cache, ty)
829 debug!("is_type_representable: {:?}", self);
831 // To avoid a stack overflow when checking an enum variant or struct that
832 // contains a different, structurally recursive type, maintain a stack
833 // of seen types and check recursion for each of them (issues #3008, #3779).
834 let mut seen: Vec<Ty> = Vec::new();
835 let mut representable_cache = FxHashMap();
836 let r = is_type_structurally_recursive(
837 tcx, sp, &mut seen, &mut representable_cache, self);
838 debug!("is_type_representable: {:?} is {:?}", self, r);
843 fn is_copy_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
844 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
847 let (param_env, ty) = query.into_parts();
848 let trait_def_id = tcx.require_lang_item(lang_items::CopyTraitLangItem);
850 .enter(|infcx| traits::type_known_to_meet_bound(&infcx,
857 fn is_sized_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
858 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
861 let (param_env, ty) = query.into_parts();
862 let trait_def_id = tcx.require_lang_item(lang_items::SizedTraitLangItem);
864 .enter(|infcx| traits::type_known_to_meet_bound(&infcx,
871 fn is_freeze_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
872 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
875 let (param_env, ty) = query.into_parts();
876 let trait_def_id = tcx.require_lang_item(lang_items::FreezeTraitLangItem);
878 .enter(|infcx| traits::type_known_to_meet_bound(&infcx,
885 fn needs_drop_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
886 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
889 let (param_env, ty) = query.into_parts();
891 let needs_drop = |ty: Ty<'tcx>| -> bool {
892 match tcx.try_needs_drop_raw(DUMMY_SP, param_env.and(ty)) {
895 // Cycles should be reported as an error by `check_representable`.
897 // Consider the type as not needing drop in the meanwhile to
898 // avoid further errors.
900 // In case we forgot to emit a bug elsewhere, delay our
901 // diagnostic to get emitted as a compiler bug.
908 assert!(!ty.needs_infer());
911 // Fast-path for primitive types
912 ty::TyInfer(ty::FreshIntTy(_)) | ty::TyInfer(ty::FreshFloatTy(_)) |
913 ty::TyBool | ty::TyInt(_) | ty::TyUint(_) | ty::TyFloat(_) | ty::TyNever |
914 ty::TyFnDef(..) | ty::TyFnPtr(_) | ty::TyChar | ty::TyGeneratorWitness(..) |
915 ty::TyRawPtr(_) | ty::TyRef(..) | ty::TyStr => false,
917 // Foreign types can never have destructors
918 ty::TyForeign(..) => false,
920 // Issue #22536: We first query type_moves_by_default. It sees a
921 // normalized version of the type, and therefore will definitely
922 // know whether the type implements Copy (and thus needs no
923 // cleanup/drop/zeroing) ...
924 _ if !ty.moves_by_default(tcx, param_env, DUMMY_SP) => false,
926 // ... (issue #22536 continued) but as an optimization, still use
927 // prior logic of asking for the structural "may drop".
929 // FIXME(#22815): Note that this is a conservative heuristic;
930 // it may report that the type "may drop" when actual type does
931 // not actually have a destructor associated with it. But since
932 // the type absolutely did not have the `Copy` bound attached
933 // (see above), it is sound to treat it as having a destructor.
935 // User destructors are the only way to have concrete drop types.
936 ty::TyAdt(def, _) if def.has_dtor(tcx) => true,
938 // Can refer to a type which may drop.
939 // FIXME(eddyb) check this against a ParamEnv.
940 ty::TyDynamic(..) | ty::TyProjection(..) | ty::TyParam(_) |
941 ty::TyAnon(..) | ty::TyInfer(_) | ty::TyError => true,
943 // Structural recursion.
944 ty::TyArray(ty, _) | ty::TySlice(ty) => needs_drop(ty),
946 ty::TyClosure(def_id, ref substs) => substs.upvar_tys(def_id, tcx).any(needs_drop),
948 // Pessimistically assume that all generators will require destructors
949 // as we don't know if a destructor is a noop or not until after the MIR
950 // state transformation pass
951 ty::TyGenerator(..) => true,
953 ty::TyTuple(ref tys) => tys.iter().cloned().any(needs_drop),
955 // unions don't have destructors regardless of the child types
956 ty::TyAdt(def, _) if def.is_union() => false,
958 ty::TyAdt(def, substs) =>
959 def.variants.iter().any(
960 |variant| variant.fields.iter().any(
961 |field| needs_drop(field.ty(tcx, substs)))),
965 pub enum ExplicitSelf<'tcx> {
967 ByReference(ty::Region<'tcx>, hir::Mutability),
968 ByRawPointer(hir::Mutability),
973 impl<'tcx> ExplicitSelf<'tcx> {
974 /// Categorizes an explicit self declaration like `self: SomeType`
975 /// into either `self`, `&self`, `&mut self`, `Box<self>`, or
977 /// This is mainly used to require the arbitrary_self_types feature
978 /// in the case of `Other`, to improve error messages in the common cases,
979 /// and to make `Other` non-object-safe.
984 /// impl<'a> Foo for &'a T {
985 /// // Legal declarations:
986 /// fn method1(self: &&'a T); // ExplicitSelf::ByReference
987 /// fn method2(self: &'a T); // ExplicitSelf::ByValue
988 /// fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox
989 /// fn method4(self: Rc<&'a T>); // ExplicitSelf::Other
991 /// // Invalid cases will be caught by `check_method_receiver`:
992 /// fn method_err1(self: &'a mut T); // ExplicitSelf::Other
993 /// fn method_err2(self: &'static T) // ExplicitSelf::ByValue
994 /// fn method_err3(self: &&T) // ExplicitSelf::ByReference
999 self_arg_ty: Ty<'tcx>,
1001 ) -> ExplicitSelf<'tcx>
1003 P: Fn(Ty<'tcx>) -> bool
1005 use self::ExplicitSelf::*;
1007 match self_arg_ty.sty {
1008 _ if is_self_ty(self_arg_ty) => ByValue,
1009 ty::TyRef(region, ty, mutbl) if is_self_ty(ty) => {
1010 ByReference(region, mutbl)
1012 ty::TyRawPtr(ty::TypeAndMut { ty, mutbl }) if is_self_ty(ty) => {
1015 ty::TyAdt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => {
1023 pub fn provide(providers: &mut ty::query::Providers) {
1024 *providers = ty::query::Providers {