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, TypeAndMut, TypeFlags, TypeFoldable};
19 use ty::ParameterEnvironment;
20 use ty::fold::TypeVisitor;
21 use ty::layout::{Layout, LayoutError};
22 use ty::TypeVariants::*;
23 use util::common::ErrorReported;
24 use util::nodemap::FxHashMap;
25 use middle::lang_items;
27 use rustc_const_math::{ConstInt, ConstIsize, ConstUsize};
28 use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
30 use std::cell::RefCell;
34 use syntax::ast::{self, Name};
35 use syntax::attr::{self, SignedInt, UnsignedInt};
36 use syntax_pos::{Span, DUMMY_SP};
42 pub trait IntTypeExt {
43 fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx>;
44 fn disr_incr<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, val: Option<Disr>)
46 fn assert_ty_matches(&self, val: Disr);
47 fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Disr;
51 macro_rules! typed_literal {
52 ($tcx:expr, $ty:expr, $lit:expr) => {
54 SignedInt(ast::IntTy::I8) => ConstInt::I8($lit),
55 SignedInt(ast::IntTy::I16) => ConstInt::I16($lit),
56 SignedInt(ast::IntTy::I32) => ConstInt::I32($lit),
57 SignedInt(ast::IntTy::I64) => ConstInt::I64($lit),
58 SignedInt(ast::IntTy::I128) => ConstInt::I128($lit),
59 SignedInt(ast::IntTy::Is) => match $tcx.sess.target.int_type {
60 ast::IntTy::I16 => ConstInt::Isize(ConstIsize::Is16($lit)),
61 ast::IntTy::I32 => ConstInt::Isize(ConstIsize::Is32($lit)),
62 ast::IntTy::I64 => ConstInt::Isize(ConstIsize::Is64($lit)),
65 UnsignedInt(ast::UintTy::U8) => ConstInt::U8($lit),
66 UnsignedInt(ast::UintTy::U16) => ConstInt::U16($lit),
67 UnsignedInt(ast::UintTy::U32) => ConstInt::U32($lit),
68 UnsignedInt(ast::UintTy::U64) => ConstInt::U64($lit),
69 UnsignedInt(ast::UintTy::U128) => ConstInt::U128($lit),
70 UnsignedInt(ast::UintTy::Us) => match $tcx.sess.target.uint_type {
71 ast::UintTy::U16 => ConstInt::Usize(ConstUsize::Us16($lit)),
72 ast::UintTy::U32 => ConstInt::Usize(ConstUsize::Us32($lit)),
73 ast::UintTy::U64 => ConstInt::Usize(ConstUsize::Us64($lit)),
80 impl IntTypeExt for attr::IntType {
81 fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
83 SignedInt(ast::IntTy::I8) => tcx.types.i8,
84 SignedInt(ast::IntTy::I16) => tcx.types.i16,
85 SignedInt(ast::IntTy::I32) => tcx.types.i32,
86 SignedInt(ast::IntTy::I64) => tcx.types.i64,
87 SignedInt(ast::IntTy::I128) => tcx.types.i128,
88 SignedInt(ast::IntTy::Is) => tcx.types.isize,
89 UnsignedInt(ast::UintTy::U8) => tcx.types.u8,
90 UnsignedInt(ast::UintTy::U16) => tcx.types.u16,
91 UnsignedInt(ast::UintTy::U32) => tcx.types.u32,
92 UnsignedInt(ast::UintTy::U64) => tcx.types.u64,
93 UnsignedInt(ast::UintTy::U128) => tcx.types.u128,
94 UnsignedInt(ast::UintTy::Us) => tcx.types.usize,
98 fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Disr {
99 typed_literal!(tcx, *self, 0)
102 fn assert_ty_matches(&self, val: Disr) {
104 (SignedInt(ast::IntTy::I8), ConstInt::I8(_)) => {},
105 (SignedInt(ast::IntTy::I16), ConstInt::I16(_)) => {},
106 (SignedInt(ast::IntTy::I32), ConstInt::I32(_)) => {},
107 (SignedInt(ast::IntTy::I64), ConstInt::I64(_)) => {},
108 (SignedInt(ast::IntTy::I128), ConstInt::I128(_)) => {},
109 (SignedInt(ast::IntTy::Is), ConstInt::Isize(_)) => {},
110 (UnsignedInt(ast::UintTy::U8), ConstInt::U8(_)) => {},
111 (UnsignedInt(ast::UintTy::U16), ConstInt::U16(_)) => {},
112 (UnsignedInt(ast::UintTy::U32), ConstInt::U32(_)) => {},
113 (UnsignedInt(ast::UintTy::U64), ConstInt::U64(_)) => {},
114 (UnsignedInt(ast::UintTy::U128), ConstInt::U128(_)) => {},
115 (UnsignedInt(ast::UintTy::Us), ConstInt::Usize(_)) => {},
116 _ => bug!("disr type mismatch: {:?} vs {:?}", self, val),
120 fn disr_incr<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, val: Option<Disr>)
122 if let Some(val) = val {
123 self.assert_ty_matches(val);
124 (val + typed_literal!(tcx, *self, 1)).ok()
126 Some(self.initial_discriminant(tcx))
132 #[derive(Copy, Clone)]
133 pub enum CopyImplementationError<'tcx> {
134 InfrigingField(&'tcx ty::FieldDef),
139 /// Describes whether a type is representable. For types that are not
140 /// representable, 'SelfRecursive' and 'ContainsRecursive' are used to
141 /// distinguish between types that are recursive with themselves and types that
142 /// contain a different recursive type. These cases can therefore be treated
143 /// differently when reporting errors.
145 /// The ordering of the cases is significant. They are sorted so that cmp::max
146 /// will keep the "more erroneous" of two values.
147 #[derive(Copy, Clone, PartialOrd, Ord, Eq, PartialEq, Debug)]
148 pub enum Representability {
154 impl<'tcx> ParameterEnvironment<'tcx> {
155 pub fn can_type_implement_copy<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
156 self_type: Ty<'tcx>, span: Span)
157 -> Result<(), CopyImplementationError> {
158 // FIXME: (@jroesch) float this code up
159 tcx.infer_ctxt(self.clone(), Reveal::UserFacing).enter(|infcx| {
160 let (adt, substs) = match self_type.sty {
161 ty::TyAdt(adt, substs) => (adt, substs),
162 _ => return Err(CopyImplementationError::NotAnAdt),
165 let field_implements_copy = |field: &ty::FieldDef| {
166 let cause = traits::ObligationCause::dummy();
167 match traits::fully_normalize(&infcx, cause, &field.ty(tcx, substs)) {
168 Ok(ty) => !infcx.type_moves_by_default(ty, span),
173 for variant in &adt.variants {
174 for field in &variant.fields {
175 if !field_implements_copy(field) {
176 return Err(CopyImplementationError::InfrigingField(field));
181 if adt.has_dtor(tcx) {
182 return Err(CopyImplementationError::HasDestructor);
190 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
191 /// Creates a hash of the type `Ty` which will be the same no matter what crate
192 /// context it's calculated within. This is used by the `type_id` intrinsic.
193 pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
194 let mut hasher = StableHasher::new();
195 let mut hcx = StableHashingContext::new(self);
197 hcx.while_hashing_spans(false, |hcx| {
198 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
199 ty.hash_stable(hcx, &mut hasher);
206 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
207 pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
209 ty::TyAdt(def, substs) => {
210 for field in def.all_fields() {
211 let field_ty = field.ty(self, substs);
212 if let TyError = field_ty.sty {
222 /// Returns the type of element at index `i` in tuple or tuple-like type `t`.
223 /// For an enum `t`, `variant` is None only if `t` is a univariant enum.
224 pub fn positional_element_ty(self,
227 variant: Option<DefId>) -> Option<Ty<'tcx>> {
228 match (&ty.sty, variant) {
229 (&TyAdt(adt, substs), Some(vid)) => {
230 adt.variant_with_id(vid).fields.get(i).map(|f| f.ty(self, substs))
232 (&TyAdt(adt, substs), None) => {
233 // Don't use `struct_variant`, this may be a univariant enum.
234 adt.variants[0].fields.get(i).map(|f| f.ty(self, substs))
236 (&TyTuple(ref v, _), None) => v.get(i).cloned(),
241 /// Returns the type of element at field `n` in struct or struct-like type `t`.
242 /// For an enum `t`, `variant` must be some def id.
243 pub fn named_element_ty(self,
246 variant: Option<DefId>) -> Option<Ty<'tcx>> {
247 match (&ty.sty, variant) {
248 (&TyAdt(adt, substs), Some(vid)) => {
249 adt.variant_with_id(vid).find_field_named(n).map(|f| f.ty(self, substs))
251 (&TyAdt(adt, substs), None) => {
252 adt.struct_variant().find_field_named(n).map(|f| f.ty(self, substs))
258 /// Returns the deeply last field of nested structures, or the same type,
259 /// if not a structure at all. Corresponds to the only possible unsized
260 /// field, and its type can be used to determine unsizing strategy.
261 pub fn struct_tail(self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
262 while let TyAdt(def, substs) = ty.sty {
263 if !def.is_struct() {
266 match def.struct_variant().fields.last() {
267 Some(f) => ty = f.ty(self, substs),
274 /// Same as applying struct_tail on `source` and `target`, but only
275 /// keeps going as long as the two types are instances of the same
276 /// structure definitions.
277 /// For `(Foo<Foo<T>>, Foo<Trait>)`, the result will be `(Foo<T>, Trait)`,
278 /// whereas struct_tail produces `T`, and `Trait`, respectively.
279 pub fn struct_lockstep_tails(self,
282 -> (Ty<'tcx>, Ty<'tcx>) {
283 let (mut a, mut b) = (source, target);
284 while let (&TyAdt(a_def, a_substs), &TyAdt(b_def, b_substs)) = (&a.sty, &b.sty) {
285 if a_def != b_def || !a_def.is_struct() {
288 match a_def.struct_variant().fields.last() {
290 a = f.ty(self, a_substs);
291 b = f.ty(self, b_substs);
299 /// Given a set of predicates that apply to an object type, returns
300 /// the region bounds that the (erased) `Self` type must
301 /// outlive. Precisely *because* the `Self` type is erased, the
302 /// parameter `erased_self_ty` must be supplied to indicate what type
303 /// has been used to represent `Self` in the predicates
304 /// themselves. This should really be a unique type; `FreshTy(0)` is a
307 /// NB: in some cases, particularly around higher-ranked bounds,
308 /// this function returns a kind of conservative approximation.
309 /// That is, all regions returned by this function are definitely
310 /// required, but there may be other region bounds that are not
311 /// returned, as well as requirements like `for<'a> T: 'a`.
313 /// Requires that trait definitions have been processed so that we can
314 /// elaborate predicates and walk supertraits.
315 pub fn required_region_bounds(self,
316 erased_self_ty: Ty<'tcx>,
317 predicates: Vec<ty::Predicate<'tcx>>)
318 -> Vec<&'tcx ty::Region> {
319 debug!("required_region_bounds(erased_self_ty={:?}, predicates={:?})",
323 assert!(!erased_self_ty.has_escaping_regions());
325 traits::elaborate_predicates(self, predicates)
326 .filter_map(|predicate| {
328 ty::Predicate::Projection(..) |
329 ty::Predicate::Trait(..) |
330 ty::Predicate::Equate(..) |
331 ty::Predicate::WellFormed(..) |
332 ty::Predicate::ObjectSafe(..) |
333 ty::Predicate::ClosureKind(..) |
334 ty::Predicate::RegionOutlives(..) => {
337 ty::Predicate::TypeOutlives(ty::Binder(ty::OutlivesPredicate(t, r))) => {
338 // Search for a bound of the form `erased_self_ty
339 // : 'a`, but be wary of something like `for<'a>
340 // erased_self_ty : 'a` (we interpret a
341 // higher-ranked bound like that as 'static,
342 // though at present the code in `fulfill.rs`
343 // considers such bounds to be unsatisfiable, so
344 // it's kind of a moot point since you could never
345 // construct such an object, but this seems
346 // correct even if that code changes).
347 if t == erased_self_ty && !r.has_escaping_regions() {
358 /// Calculate the destructor of a given type.
359 pub fn calculate_dtor(
362 validate: &mut FnMut(Self, DefId) -> Result<(), ErrorReported>
363 ) -> Option<ty::Destructor> {
364 let drop_trait = if let Some(def_id) = self.lang_items.drop_trait() {
370 ty::queries::coherent_trait::get(self, DUMMY_SP, (LOCAL_CRATE, drop_trait));
372 let mut dtor_did = None;
373 let ty = self.item_type(adt_did);
374 self.lookup_trait_def(drop_trait).for_each_relevant_impl(self, ty, |impl_did| {
375 if let Some(item) = self.associated_items(impl_did).next() {
376 if let Ok(()) = validate(self, impl_did) {
377 dtor_did = Some(item.def_id);
382 let dtor_did = match dtor_did {
387 // RFC 1238: if the destructor method is tagged with the
388 // attribute `unsafe_destructor_blind_to_params`, then the
389 // compiler is being instructed to *assume* that the
390 // destructor will not access borrowed data,
391 // even if such data is otherwise reachable.
393 // Such access can be in plain sight (e.g. dereferencing
394 // `*foo.0` of `Foo<'a>(&'a u32)`) or indirectly hidden
395 // (e.g. calling `foo.0.clone()` of `Foo<T:Clone>`).
396 let is_dtorck = !self.has_attr(dtor_did, "unsafe_destructor_blind_to_params");
397 Some(ty::Destructor { did: dtor_did, is_dtorck: is_dtorck })
400 pub fn closure_base_def_id(&self, def_id: DefId) -> DefId {
401 let mut def_id = def_id;
402 while self.def_key(def_id).disambiguated_data.data == DefPathData::ClosureExpr {
403 def_id = self.parent_def_id(def_id).unwrap_or_else(|| {
404 bug!("closure {:?} has no parent", def_id);
410 /// Given the def-id of some item that has no type parameters, make
411 /// a suitable "empty substs" for it.
412 pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> &'tcx ty::Substs<'tcx> {
413 ty::Substs::for_item(self, item_def_id,
414 |_, _| self.mk_region(ty::ReErased),
416 bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
421 pub struct TypeIdHasher<'a, 'gcx: 'a+'tcx, 'tcx: 'a, W> {
422 tcx: TyCtxt<'a, 'gcx, 'tcx>,
423 state: StableHasher<W>,
426 impl<'a, 'gcx, 'tcx, W> TypeIdHasher<'a, 'gcx, 'tcx, W>
427 where W: StableHasherResult
429 pub fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Self {
430 TypeIdHasher { tcx: tcx, state: StableHasher::new() }
433 pub fn finish(self) -> W {
437 pub fn hash<T: Hash>(&mut self, x: T) {
438 x.hash(&mut self.state);
441 fn hash_discriminant_u8<T>(&mut self, x: &T) {
443 intrinsics::discriminant_value(x)
446 assert_eq!(v, b as u64);
450 fn def_id(&mut self, did: DefId) {
451 // Hash the DefPath corresponding to the DefId, which is independent
452 // of compiler internal state. We already have a stable hash value of
453 // all DefPaths available via tcx.def_path_hash(), so we just feed that
455 let hash = self.tcx.def_path_hash(did);
460 impl<'a, 'gcx, 'tcx, W> TypeVisitor<'tcx> for TypeIdHasher<'a, 'gcx, 'tcx, W>
461 where W: StableHasherResult
463 fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool {
464 // Distinguish between the Ty variants uniformly.
465 self.hash_discriminant_u8(&ty.sty);
468 TyInt(i) => self.hash(i),
469 TyUint(u) => self.hash(u),
470 TyFloat(f) => self.hash(f),
471 TyArray(_, n) => self.hash(n),
473 TyRef(_, m) => self.hash(m.mutbl),
474 TyClosure(def_id, _) |
476 TyFnDef(def_id, ..) => self.def_id(def_id),
477 TyAdt(d, _) => self.def_id(d.did),
479 self.hash(f.unsafety());
481 self.hash(f.variadic());
482 self.hash(f.inputs().skip_binder().len());
484 TyDynamic(ref data, ..) => {
485 if let Some(p) = data.principal() {
486 self.def_id(p.def_id());
488 for d in data.auto_traits() {
492 TyTuple(tys, defaulted) => {
493 self.hash(tys.len());
494 self.hash(defaulted);
498 self.hash(p.name.as_str());
500 TyProjection(ref data) => {
501 self.def_id(data.trait_ref.def_id);
502 self.hash(data.item_name.as_str());
511 TyInfer(_) => bug!("TypeIdHasher: unexpected type {}", ty)
514 ty.super_visit_with(self)
517 fn visit_region(&mut self, r: &'tcx ty::Region) -> bool {
518 self.hash_discriminant_u8(r);
523 // No variant fields to hash for these ...
525 ty::ReLateBound(db, ty::BrAnon(i)) => {
529 ty::ReEarlyBound(ty::EarlyBoundRegion { index, name }) => {
531 self.hash(name.as_str());
533 ty::ReLateBound(..) |
537 ty::ReSkolemized(..) => {
538 bug!("TypeIdHasher: unexpected region {:?}", r)
544 fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, x: &ty::Binder<T>) -> bool {
545 // Anonymize late-bound regions so that, for example:
546 // `for<'a, b> fn(&'a &'b T)` and `for<'a, b> fn(&'b &'a T)`
547 // result in the same TypeId (the two types are equivalent).
548 self.tcx.anonymize_late_bound_regions(x).super_visit_with(self)
552 impl<'a, 'tcx> ty::TyS<'tcx> {
553 fn impls_bound(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
554 param_env: &ParameterEnvironment<'tcx>,
556 cache: &RefCell<FxHashMap<Ty<'tcx>, bool>>,
559 if self.has_param_types() || self.has_self_ty() {
560 if let Some(result) = cache.borrow().get(self) {
565 tcx.infer_ctxt(param_env.clone(), Reveal::UserFacing)
567 traits::type_known_to_meet_bound(&infcx, self, def_id, span)
569 if self.has_param_types() || self.has_self_ty() {
570 cache.borrow_mut().insert(self, result);
575 // FIXME (@jroesch): I made this public to use it, not sure if should be private
576 pub fn moves_by_default(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
577 param_env: &ParameterEnvironment<'tcx>,
578 span: Span) -> bool {
579 if self.flags.get().intersects(TypeFlags::MOVENESS_CACHED) {
580 return self.flags.get().intersects(TypeFlags::MOVES_BY_DEFAULT);
583 assert!(!self.needs_infer());
585 // Fast-path for primitive types
586 let result = match self.sty {
587 TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) | TyNever |
588 TyRawPtr(..) | TyFnDef(..) | TyFnPtr(_) | TyRef(_, TypeAndMut {
589 mutbl: hir::MutImmutable, ..
592 TyStr | TyRef(_, TypeAndMut {
593 mutbl: hir::MutMutable, ..
596 TyArray(..) | TySlice(..) | TyDynamic(..) | TyTuple(..) |
597 TyClosure(..) | TyAdt(..) | TyAnon(..) |
598 TyProjection(..) | TyParam(..) | TyInfer(..) | TyError => None
599 }.unwrap_or_else(|| {
600 !self.impls_bound(tcx, param_env,
601 tcx.require_lang_item(lang_items::CopyTraitLangItem),
602 ¶m_env.is_copy_cache, span) });
604 if !self.has_param_types() && !self.has_self_ty() {
605 self.flags.set(self.flags.get() | if result {
606 TypeFlags::MOVENESS_CACHED | TypeFlags::MOVES_BY_DEFAULT
608 TypeFlags::MOVENESS_CACHED
616 pub fn is_sized(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
617 param_env: &ParameterEnvironment<'tcx>,
620 if self.flags.get().intersects(TypeFlags::SIZEDNESS_CACHED) {
621 return self.flags.get().intersects(TypeFlags::IS_SIZED);
624 self.is_sized_uncached(tcx, param_env, span)
627 fn is_sized_uncached(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
628 param_env: &ParameterEnvironment<'tcx>,
629 span: Span) -> bool {
630 assert!(!self.needs_infer());
632 // Fast-path for primitive types
633 let result = match self.sty {
634 TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) |
635 TyRawPtr(..) | TyRef(..) | TyFnDef(..) | TyFnPtr(_) |
636 TyArray(..) | TyTuple(..) | TyClosure(..) | TyNever => Some(true),
638 TyStr | TyDynamic(..) | TySlice(_) => Some(false),
640 TyAdt(..) | TyProjection(..) | TyParam(..) |
641 TyInfer(..) | TyAnon(..) | TyError => None
642 }.unwrap_or_else(|| {
643 self.impls_bound(tcx, param_env, tcx.require_lang_item(lang_items::SizedTraitLangItem),
644 ¶m_env.is_sized_cache, span) });
646 if !self.has_param_types() && !self.has_self_ty() {
647 self.flags.set(self.flags.get() | if result {
648 TypeFlags::SIZEDNESS_CACHED | TypeFlags::IS_SIZED
650 TypeFlags::SIZEDNESS_CACHED
658 pub fn layout<'lcx>(&'tcx self, infcx: &InferCtxt<'a, 'tcx, 'lcx>)
659 -> Result<&'tcx Layout, LayoutError<'tcx>> {
660 let tcx = infcx.tcx.global_tcx();
661 let can_cache = !self.has_param_types() && !self.has_self_ty();
663 if let Some(&cached) = tcx.layout_cache.borrow().get(&self) {
668 let rec_limit = tcx.sess.recursion_limit.get();
669 let depth = tcx.layout_depth.get();
670 if depth > rec_limit {
672 &format!("overflow representing the type `{}`", self));
675 tcx.layout_depth.set(depth+1);
676 let layout = Layout::compute_uncached(self, infcx);
677 tcx.layout_depth.set(depth);
678 let layout = layout?;
680 tcx.layout_cache.borrow_mut().insert(self, layout);
686 /// Check whether a type is representable. This means it cannot contain unboxed
687 /// structural recursion. This check is needed for structs and enums.
688 pub fn is_representable(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span)
689 -> Representability {
691 // Iterate until something non-representable is found
692 fn find_nonrepresentable<'a, 'tcx, It>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
694 seen: &mut Vec<Ty<'tcx>>,
697 where It: Iterator<Item=Ty<'tcx>> {
698 iter.fold(Representability::Representable,
699 |r, ty| cmp::max(r, is_type_structurally_recursive(tcx, sp, seen, ty)))
702 fn are_inner_types_recursive<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span,
703 seen: &mut Vec<Ty<'tcx>>, ty: Ty<'tcx>)
704 -> Representability {
706 TyTuple(ref ts, _) => {
707 find_nonrepresentable(tcx, sp, seen, ts.iter().cloned())
709 // Fixed-length vectors.
710 // FIXME(#11924) Behavior undecided for zero-length vectors.
712 is_type_structurally_recursive(tcx, sp, seen, ty)
714 TyAdt(def, substs) => {
715 find_nonrepresentable(tcx,
718 def.all_fields().map(|f| f.ty(tcx, substs)))
721 // this check is run on type definitions, so we don't expect
722 // to see closure types
723 bug!("requires check invoked on inapplicable type: {:?}", ty)
725 _ => Representability::Representable,
729 fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: &'tcx ty::AdtDef) -> bool {
731 TyAdt(ty_def, _) => {
738 fn same_type<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
739 match (&a.sty, &b.sty) {
740 (&TyAdt(did_a, substs_a), &TyAdt(did_b, substs_b)) => {
745 substs_a.types().zip(substs_b.types()).all(|(a, b)| same_type(a, b))
751 // Does the type `ty` directly (without indirection through a pointer)
752 // contain any types on stack `seen`?
753 fn is_type_structurally_recursive<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
755 seen: &mut Vec<Ty<'tcx>>,
756 ty: Ty<'tcx>) -> Representability {
757 debug!("is_type_structurally_recursive: {:?}", ty);
762 // Iterate through stack of previously seen types.
763 let mut iter = seen.iter();
765 // The first item in `seen` is the type we are actually curious about.
766 // We want to return SelfRecursive if this type contains itself.
767 // It is important that we DON'T take generic parameters into account
768 // for this check, so that Bar<T> in this example counts as SelfRecursive:
771 // struct Bar<T> { x: Bar<Foo> }
773 if let Some(&seen_type) = iter.next() {
774 if same_struct_or_enum(seen_type, def) {
775 debug!("SelfRecursive: {:?} contains {:?}",
778 return Representability::SelfRecursive;
782 // We also need to know whether the first item contains other types
783 // that are structurally recursive. If we don't catch this case, we
784 // will recurse infinitely for some inputs.
786 // It is important that we DO take generic parameters into account
787 // here, so that code like this is considered SelfRecursive, not
788 // ContainsRecursive:
790 // struct Foo { Option<Option<Foo>> }
792 for &seen_type in iter {
793 if same_type(ty, seen_type) {
794 debug!("ContainsRecursive: {:?} contains {:?}",
797 return Representability::ContainsRecursive;
802 // For structs and enums, track all previously seen types by pushing them
803 // onto the 'seen' stack.
805 let out = are_inner_types_recursive(tcx, sp, seen, ty);
810 // No need to push in other cases.
811 are_inner_types_recursive(tcx, sp, seen, ty)
816 debug!("is_type_representable: {:?}", self);
818 // To avoid a stack overflow when checking an enum variant or struct that
819 // contains a different, structurally recursive type, maintain a stack
820 // of seen types and check recursion for each of them (issues #3008, #3779).
821 let mut seen: Vec<Ty> = Vec::new();
822 let r = is_type_structurally_recursive(tcx, sp, &mut seen, self);
823 debug!("is_type_representable: {:?} is {:?}", self, r);