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 hir::map as hir_map;
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, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
191 pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
193 ty::TyAdt(def, substs) => {
194 for field in def.all_fields() {
195 let field_ty = field.ty(self, substs);
196 if let TyError = field_ty.sty {
206 /// Returns the type of element at index `i` in tuple or tuple-like type `t`.
207 /// For an enum `t`, `variant` is None only if `t` is a univariant enum.
208 pub fn positional_element_ty(self,
211 variant: Option<DefId>) -> Option<Ty<'tcx>> {
212 match (&ty.sty, variant) {
213 (&TyAdt(adt, substs), Some(vid)) => {
214 adt.variant_with_id(vid).fields.get(i).map(|f| f.ty(self, substs))
216 (&TyAdt(adt, substs), None) => {
217 // Don't use `struct_variant`, this may be a univariant enum.
218 adt.variants[0].fields.get(i).map(|f| f.ty(self, substs))
220 (&TyTuple(ref v, _), None) => v.get(i).cloned(),
225 /// Returns the type of element at field `n` in struct or struct-like type `t`.
226 /// For an enum `t`, `variant` must be some def id.
227 pub fn named_element_ty(self,
230 variant: Option<DefId>) -> Option<Ty<'tcx>> {
231 match (&ty.sty, variant) {
232 (&TyAdt(adt, substs), Some(vid)) => {
233 adt.variant_with_id(vid).find_field_named(n).map(|f| f.ty(self, substs))
235 (&TyAdt(adt, substs), None) => {
236 adt.struct_variant().find_field_named(n).map(|f| f.ty(self, substs))
242 /// Returns the deeply last field of nested structures, or the same type,
243 /// if not a structure at all. Corresponds to the only possible unsized
244 /// field, and its type can be used to determine unsizing strategy.
245 pub fn struct_tail(self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
246 while let TyAdt(def, substs) = ty.sty {
247 if !def.is_struct() {
250 match def.struct_variant().fields.last() {
251 Some(f) => ty = f.ty(self, substs),
258 /// Same as applying struct_tail on `source` and `target`, but only
259 /// keeps going as long as the two types are instances of the same
260 /// structure definitions.
261 /// For `(Foo<Foo<T>>, Foo<Trait>)`, the result will be `(Foo<T>, Trait)`,
262 /// whereas struct_tail produces `T`, and `Trait`, respectively.
263 pub fn struct_lockstep_tails(self,
266 -> (Ty<'tcx>, Ty<'tcx>) {
267 let (mut a, mut b) = (source, target);
268 while let (&TyAdt(a_def, a_substs), &TyAdt(b_def, b_substs)) = (&a.sty, &b.sty) {
269 if a_def != b_def || !a_def.is_struct() {
272 match a_def.struct_variant().fields.last() {
274 a = f.ty(self, a_substs);
275 b = f.ty(self, b_substs);
283 /// Given a set of predicates that apply to an object type, returns
284 /// the region bounds that the (erased) `Self` type must
285 /// outlive. Precisely *because* the `Self` type is erased, the
286 /// parameter `erased_self_ty` must be supplied to indicate what type
287 /// has been used to represent `Self` in the predicates
288 /// themselves. This should really be a unique type; `FreshTy(0)` is a
291 /// NB: in some cases, particularly around higher-ranked bounds,
292 /// this function returns a kind of conservative approximation.
293 /// That is, all regions returned by this function are definitely
294 /// required, but there may be other region bounds that are not
295 /// returned, as well as requirements like `for<'a> T: 'a`.
297 /// Requires that trait definitions have been processed so that we can
298 /// elaborate predicates and walk supertraits.
299 pub fn required_region_bounds(self,
300 erased_self_ty: Ty<'tcx>,
301 predicates: Vec<ty::Predicate<'tcx>>)
302 -> Vec<&'tcx ty::Region> {
303 debug!("required_region_bounds(erased_self_ty={:?}, predicates={:?})",
307 assert!(!erased_self_ty.has_escaping_regions());
309 traits::elaborate_predicates(self, predicates)
310 .filter_map(|predicate| {
312 ty::Predicate::Projection(..) |
313 ty::Predicate::Trait(..) |
314 ty::Predicate::Equate(..) |
315 ty::Predicate::WellFormed(..) |
316 ty::Predicate::ObjectSafe(..) |
317 ty::Predicate::ClosureKind(..) |
318 ty::Predicate::RegionOutlives(..) => {
321 ty::Predicate::TypeOutlives(ty::Binder(ty::OutlivesPredicate(t, r))) => {
322 // Search for a bound of the form `erased_self_ty
323 // : 'a`, but be wary of something like `for<'a>
324 // erased_self_ty : 'a` (we interpret a
325 // higher-ranked bound like that as 'static,
326 // though at present the code in `fulfill.rs`
327 // considers such bounds to be unsatisfiable, so
328 // it's kind of a moot point since you could never
329 // construct such an object, but this seems
330 // correct even if that code changes).
331 if t == erased_self_ty && !r.has_escaping_regions() {
342 /// Creates a hash of the type `Ty` which will be the same no matter what crate
343 /// context it's calculated within. This is used by the `type_id` intrinsic.
344 pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
345 let mut hasher = TypeIdHasher::new(self);
350 /// Calculate the destructor of a given type.
351 pub fn calculate_dtor(
354 validate: &mut FnMut(Self, DefId) -> Result<(), ErrorReported>
355 ) -> Option<ty::Destructor> {
356 let drop_trait = if let Some(def_id) = self.lang_items.drop_trait() {
362 ty::queries::coherent_trait::get(self, DUMMY_SP, (LOCAL_CRATE, drop_trait));
364 let mut dtor_did = None;
365 let ty = self.item_type(adt_did);
366 self.lookup_trait_def(drop_trait).for_each_relevant_impl(self, ty, |impl_did| {
367 if let Some(item) = self.associated_items(impl_did).next() {
368 if let Ok(()) = validate(self, impl_did) {
369 dtor_did = Some(item.def_id);
374 let dtor_did = match dtor_did {
379 // RFC 1238: if the destructor method is tagged with the
380 // attribute `unsafe_destructor_blind_to_params`, then the
381 // compiler is being instructed to *assume* that the
382 // destructor will not access borrowed data,
383 // even if such data is otherwise reachable.
385 // Such access can be in plain sight (e.g. dereferencing
386 // `*foo.0` of `Foo<'a>(&'a u32)`) or indirectly hidden
387 // (e.g. calling `foo.0.clone()` of `Foo<T:Clone>`).
388 let is_dtorck = !self.has_attr(dtor_did, "unsafe_destructor_blind_to_params");
389 Some(ty::Destructor { did: dtor_did, is_dtorck: is_dtorck })
392 pub fn closure_base_def_id(&self, def_id: DefId) -> DefId {
393 let mut def_id = def_id;
394 while self.def_key(def_id).disambiguated_data.data == DefPathData::ClosureExpr {
395 def_id = self.parent_def_id(def_id).unwrap_or_else(|| {
396 bug!("closure {:?} has no parent", def_id);
402 /// Given the def-id of some item that has no type parameters, make
403 /// a suitable "empty substs" for it.
404 pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> &'tcx ty::Substs<'tcx> {
405 ty::Substs::for_item(self, item_def_id,
406 |_, _| self.mk_region(ty::ReErased),
408 bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
413 pub struct TypeIdHasher<'a, 'gcx: 'a+'tcx, 'tcx: 'a, W> {
414 tcx: TyCtxt<'a, 'gcx, 'tcx>,
415 state: StableHasher<W>,
418 impl<'a, 'gcx, 'tcx, W> TypeIdHasher<'a, 'gcx, 'tcx, W>
419 where W: StableHasherResult
421 pub fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Self {
422 TypeIdHasher { tcx: tcx, state: StableHasher::new() }
425 pub fn finish(self) -> W {
429 pub fn hash<T: Hash>(&mut self, x: T) {
430 x.hash(&mut self.state);
433 fn hash_discriminant_u8<T>(&mut self, x: &T) {
435 intrinsics::discriminant_value(x)
438 assert_eq!(v, b as u64);
442 fn def_id(&mut self, did: DefId) {
443 // Hash the DefPath corresponding to the DefId, which is independent
444 // of compiler internal state.
445 let path = self.tcx.def_path(did);
449 pub fn def_path(&mut self, def_path: &hir_map::DefPath) {
450 def_path.deterministic_hash_to(self.tcx, &mut self.state);
454 impl<'a, 'gcx, 'tcx, W> TypeVisitor<'tcx> for TypeIdHasher<'a, 'gcx, 'tcx, W>
455 where W: StableHasherResult
457 fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool {
458 // Distinguish between the Ty variants uniformly.
459 self.hash_discriminant_u8(&ty.sty);
462 TyInt(i) => self.hash(i),
463 TyUint(u) => self.hash(u),
464 TyFloat(f) => self.hash(f),
465 TyArray(_, n) => self.hash(n),
467 TyRef(_, m) => self.hash(m.mutbl),
468 TyClosure(def_id, _) |
470 TyFnDef(def_id, ..) => self.def_id(def_id),
471 TyAdt(d, _) => self.def_id(d.did),
473 self.hash(f.unsafety());
475 self.hash(f.variadic());
476 self.hash(f.inputs().skip_binder().len());
478 TyDynamic(ref data, ..) => {
479 if let Some(p) = data.principal() {
480 self.def_id(p.def_id());
482 for d in data.auto_traits() {
486 TyTuple(tys, defaulted) => {
487 self.hash(tys.len());
488 self.hash(defaulted);
492 self.hash(p.name.as_str());
494 TyProjection(ref data) => {
495 self.def_id(data.trait_ref.def_id);
496 self.hash(data.item_name.as_str());
505 TyInfer(_) => bug!("TypeIdHasher: unexpected type {}", ty)
508 ty.super_visit_with(self)
511 fn visit_region(&mut self, r: &'tcx ty::Region) -> bool {
512 self.hash_discriminant_u8(r);
517 // No variant fields to hash for these ...
519 ty::ReLateBound(db, ty::BrAnon(i)) => {
523 ty::ReEarlyBound(ty::EarlyBoundRegion { index, name }) => {
525 self.hash(name.as_str());
527 ty::ReLateBound(..) |
531 ty::ReSkolemized(..) => {
532 bug!("TypeIdHasher: unexpected region {:?}", r)
538 fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, x: &ty::Binder<T>) -> bool {
539 // Anonymize late-bound regions so that, for example:
540 // `for<'a, b> fn(&'a &'b T)` and `for<'a, b> fn(&'b &'a T)`
541 // result in the same TypeId (the two types are equivalent).
542 self.tcx.anonymize_late_bound_regions(x).super_visit_with(self)
546 impl<'a, 'tcx> ty::TyS<'tcx> {
547 fn impls_bound(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
548 param_env: &ParameterEnvironment<'tcx>,
550 cache: &RefCell<FxHashMap<Ty<'tcx>, bool>>,
553 if self.has_param_types() || self.has_self_ty() {
554 if let Some(result) = cache.borrow().get(self) {
559 tcx.infer_ctxt(param_env.clone(), Reveal::UserFacing)
561 traits::type_known_to_meet_bound(&infcx, self, def_id, span)
563 if self.has_param_types() || self.has_self_ty() {
564 cache.borrow_mut().insert(self, result);
569 // FIXME (@jroesch): I made this public to use it, not sure if should be private
570 pub fn moves_by_default(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
571 param_env: &ParameterEnvironment<'tcx>,
572 span: Span) -> bool {
573 if self.flags.get().intersects(TypeFlags::MOVENESS_CACHED) {
574 return self.flags.get().intersects(TypeFlags::MOVES_BY_DEFAULT);
577 assert!(!self.needs_infer());
579 // Fast-path for primitive types
580 let result = match self.sty {
581 TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) | TyNever |
582 TyRawPtr(..) | TyFnDef(..) | TyFnPtr(_) | TyRef(_, TypeAndMut {
583 mutbl: hir::MutImmutable, ..
586 TyStr | TyRef(_, TypeAndMut {
587 mutbl: hir::MutMutable, ..
590 TyArray(..) | TySlice(..) | TyDynamic(..) | TyTuple(..) |
591 TyClosure(..) | TyAdt(..) | TyAnon(..) |
592 TyProjection(..) | TyParam(..) | TyInfer(..) | TyError => None
593 }.unwrap_or_else(|| {
594 !self.impls_bound(tcx, param_env,
595 tcx.require_lang_item(lang_items::CopyTraitLangItem),
596 ¶m_env.is_copy_cache, span) });
598 if !self.has_param_types() && !self.has_self_ty() {
599 self.flags.set(self.flags.get() | if result {
600 TypeFlags::MOVENESS_CACHED | TypeFlags::MOVES_BY_DEFAULT
602 TypeFlags::MOVENESS_CACHED
610 pub fn is_sized(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
611 param_env: &ParameterEnvironment<'tcx>,
614 if self.flags.get().intersects(TypeFlags::SIZEDNESS_CACHED) {
615 return self.flags.get().intersects(TypeFlags::IS_SIZED);
618 self.is_sized_uncached(tcx, param_env, span)
621 fn is_sized_uncached(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
622 param_env: &ParameterEnvironment<'tcx>,
623 span: Span) -> bool {
624 assert!(!self.needs_infer());
626 // Fast-path for primitive types
627 let result = match self.sty {
628 TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) |
629 TyRawPtr(..) | TyRef(..) | TyFnDef(..) | TyFnPtr(_) |
630 TyArray(..) | TyTuple(..) | TyClosure(..) | TyNever => Some(true),
632 TyStr | TyDynamic(..) | TySlice(_) => Some(false),
634 TyAdt(..) | TyProjection(..) | TyParam(..) |
635 TyInfer(..) | TyAnon(..) | TyError => None
636 }.unwrap_or_else(|| {
637 self.impls_bound(tcx, param_env, tcx.require_lang_item(lang_items::SizedTraitLangItem),
638 ¶m_env.is_sized_cache, span) });
640 if !self.has_param_types() && !self.has_self_ty() {
641 self.flags.set(self.flags.get() | if result {
642 TypeFlags::SIZEDNESS_CACHED | TypeFlags::IS_SIZED
644 TypeFlags::SIZEDNESS_CACHED
652 pub fn layout<'lcx>(&'tcx self, infcx: &InferCtxt<'a, 'tcx, 'lcx>)
653 -> Result<&'tcx Layout, LayoutError<'tcx>> {
654 let tcx = infcx.tcx.global_tcx();
655 let can_cache = !self.has_param_types() && !self.has_self_ty();
657 if let Some(&cached) = tcx.layout_cache.borrow().get(&self) {
662 let rec_limit = tcx.sess.recursion_limit.get();
663 let depth = tcx.layout_depth.get();
664 if depth > rec_limit {
666 &format!("overflow representing the type `{}`", self));
669 tcx.layout_depth.set(depth+1);
670 let layout = Layout::compute_uncached(self, infcx);
671 tcx.layout_depth.set(depth);
672 let layout = layout?;
674 tcx.layout_cache.borrow_mut().insert(self, layout);
680 /// Check whether a type is representable. This means it cannot contain unboxed
681 /// structural recursion. This check is needed for structs and enums.
682 pub fn is_representable(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span)
683 -> Representability {
685 // Iterate until something non-representable is found
686 fn find_nonrepresentable<'a, 'tcx, It>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
688 seen: &mut Vec<Ty<'tcx>>,
691 where It: Iterator<Item=Ty<'tcx>> {
692 iter.fold(Representability::Representable,
693 |r, ty| cmp::max(r, is_type_structurally_recursive(tcx, sp, seen, ty)))
696 fn are_inner_types_recursive<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span,
697 seen: &mut Vec<Ty<'tcx>>, ty: Ty<'tcx>)
698 -> Representability {
700 TyTuple(ref ts, _) => {
701 find_nonrepresentable(tcx, sp, seen, ts.iter().cloned())
703 // Fixed-length vectors.
704 // FIXME(#11924) Behavior undecided for zero-length vectors.
706 is_type_structurally_recursive(tcx, sp, seen, ty)
708 TyAdt(def, substs) => {
709 find_nonrepresentable(tcx,
712 def.all_fields().map(|f| f.ty(tcx, substs)))
715 // this check is run on type definitions, so we don't expect
716 // to see closure types
717 bug!("requires check invoked on inapplicable type: {:?}", ty)
719 _ => Representability::Representable,
723 fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: &'tcx ty::AdtDef) -> bool {
725 TyAdt(ty_def, _) => {
732 fn same_type<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
733 match (&a.sty, &b.sty) {
734 (&TyAdt(did_a, substs_a), &TyAdt(did_b, substs_b)) => {
739 substs_a.types().zip(substs_b.types()).all(|(a, b)| same_type(a, b))
745 // Does the type `ty` directly (without indirection through a pointer)
746 // contain any types on stack `seen`?
747 fn is_type_structurally_recursive<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
749 seen: &mut Vec<Ty<'tcx>>,
750 ty: Ty<'tcx>) -> Representability {
751 debug!("is_type_structurally_recursive: {:?}", ty);
756 // Iterate through stack of previously seen types.
757 let mut iter = seen.iter();
759 // The first item in `seen` is the type we are actually curious about.
760 // We want to return SelfRecursive if this type contains itself.
761 // It is important that we DON'T take generic parameters into account
762 // for this check, so that Bar<T> in this example counts as SelfRecursive:
765 // struct Bar<T> { x: Bar<Foo> }
767 if let Some(&seen_type) = iter.next() {
768 if same_struct_or_enum(seen_type, def) {
769 debug!("SelfRecursive: {:?} contains {:?}",
772 return Representability::SelfRecursive;
776 // We also need to know whether the first item contains other types
777 // that are structurally recursive. If we don't catch this case, we
778 // will recurse infinitely for some inputs.
780 // It is important that we DO take generic parameters into account
781 // here, so that code like this is considered SelfRecursive, not
782 // ContainsRecursive:
784 // struct Foo { Option<Option<Foo>> }
786 for &seen_type in iter {
787 if same_type(ty, seen_type) {
788 debug!("ContainsRecursive: {:?} contains {:?}",
791 return Representability::ContainsRecursive;
796 // For structs and enums, track all previously seen types by pushing them
797 // onto the 'seen' stack.
799 let out = are_inner_types_recursive(tcx, sp, seen, ty);
804 // No need to push in other cases.
805 are_inner_types_recursive(tcx, sp, seen, ty)
810 debug!("is_type_representable: {:?}", self);
812 // To avoid a stack overflow when checking an enum variant or struct that
813 // contains a different, structurally recursive type, maintain a stack
814 // of seen types and check recursion for each of them (issues #3008, #3779).
815 let mut seen: Vec<Ty> = Vec::new();
816 let r = is_type_structurally_recursive(tcx, sp, &mut seen, self);
817 debug!("is_type_representable: {:?} is {:?}", self, r);