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 middle::const_eval::{self, ConstVal, ErrKind};
15 use middle::const_eval::EvalHint::UncheckedExprHint;
16 use middle::def_id::DefId;
17 use middle::subst::{self, Subst, Substs};
21 use middle::ty::{self, Ty, TypeAndMut, TypeFlags, TypeFoldable};
22 use middle::ty::{Disr, ParameterEnvironment};
23 use middle::ty::TypeVariants::*;
24 use util::num::ToPrimitive;
27 use std::hash::{Hash, SipHasher, Hasher};
29 use syntax::ast::{self, Name};
30 use syntax::attr::{self, AttrMetaMethods, SignedInt, UnsignedInt};
31 use syntax::codemap::Span;
35 pub trait IntTypeExt {
36 fn to_ty<'tcx>(&self, cx: &ty::ctxt<'tcx>) -> Ty<'tcx>;
37 fn i64_to_disr(&self, val: i64) -> Option<Disr>;
38 fn u64_to_disr(&self, val: u64) -> Option<Disr>;
39 fn disr_incr(&self, val: Disr) -> Option<Disr>;
40 fn disr_string(&self, val: Disr) -> String;
41 fn disr_wrap_incr(&self, val: Option<Disr>) -> Disr;
44 impl IntTypeExt for attr::IntType {
45 fn to_ty<'tcx>(&self, cx: &ty::ctxt<'tcx>) -> Ty<'tcx> {
47 SignedInt(ast::TyI8) => cx.types.i8,
48 SignedInt(ast::TyI16) => cx.types.i16,
49 SignedInt(ast::TyI32) => cx.types.i32,
50 SignedInt(ast::TyI64) => cx.types.i64,
51 SignedInt(ast::TyIs) => cx.types.isize,
52 UnsignedInt(ast::TyU8) => cx.types.u8,
53 UnsignedInt(ast::TyU16) => cx.types.u16,
54 UnsignedInt(ast::TyU32) => cx.types.u32,
55 UnsignedInt(ast::TyU64) => cx.types.u64,
56 UnsignedInt(ast::TyUs) => cx.types.usize,
60 fn i64_to_disr(&self, val: i64) -> Option<Disr> {
62 SignedInt(ast::TyI8) => val.to_i8() .map(|v| v as Disr),
63 SignedInt(ast::TyI16) => val.to_i16() .map(|v| v as Disr),
64 SignedInt(ast::TyI32) => val.to_i32() .map(|v| v as Disr),
65 SignedInt(ast::TyI64) => val.to_i64() .map(|v| v as Disr),
66 UnsignedInt(ast::TyU8) => val.to_u8() .map(|v| v as Disr),
67 UnsignedInt(ast::TyU16) => val.to_u16() .map(|v| v as Disr),
68 UnsignedInt(ast::TyU32) => val.to_u32() .map(|v| v as Disr),
69 UnsignedInt(ast::TyU64) => val.to_u64() .map(|v| v as Disr),
71 UnsignedInt(ast::TyUs) |
72 SignedInt(ast::TyIs) => unreachable!(),
76 fn u64_to_disr(&self, val: u64) -> Option<Disr> {
78 SignedInt(ast::TyI8) => val.to_i8() .map(|v| v as Disr),
79 SignedInt(ast::TyI16) => val.to_i16() .map(|v| v as Disr),
80 SignedInt(ast::TyI32) => val.to_i32() .map(|v| v as Disr),
81 SignedInt(ast::TyI64) => val.to_i64() .map(|v| v as Disr),
82 UnsignedInt(ast::TyU8) => val.to_u8() .map(|v| v as Disr),
83 UnsignedInt(ast::TyU16) => val.to_u16() .map(|v| v as Disr),
84 UnsignedInt(ast::TyU32) => val.to_u32() .map(|v| v as Disr),
85 UnsignedInt(ast::TyU64) => val.to_u64() .map(|v| v as Disr),
87 UnsignedInt(ast::TyUs) |
88 SignedInt(ast::TyIs) => unreachable!(),
92 fn disr_incr(&self, val: Disr) -> Option<Disr> {
94 ($e:expr) => { $e.and_then(|v|v.checked_add(1)).map(|v| v as Disr) }
97 // SignedInt repr means we *want* to reinterpret the bits
98 // treating the highest bit of Disr as a sign-bit, so
99 // cast to i64 before range-checking.
100 SignedInt(ast::TyI8) => add1!((val as i64).to_i8()),
101 SignedInt(ast::TyI16) => add1!((val as i64).to_i16()),
102 SignedInt(ast::TyI32) => add1!((val as i64).to_i32()),
103 SignedInt(ast::TyI64) => add1!(Some(val as i64)),
105 UnsignedInt(ast::TyU8) => add1!(val.to_u8()),
106 UnsignedInt(ast::TyU16) => add1!(val.to_u16()),
107 UnsignedInt(ast::TyU32) => add1!(val.to_u32()),
108 UnsignedInt(ast::TyU64) => add1!(Some(val)),
110 UnsignedInt(ast::TyUs) |
111 SignedInt(ast::TyIs) => unreachable!(),
115 // This returns a String because (1.) it is only used for
116 // rendering an error message and (2.) a string can represent the
117 // full range from `i64::MIN` through `u64::MAX`.
118 fn disr_string(&self, val: Disr) -> String {
120 SignedInt(ast::TyI8) => format!("{}", val as i8 ),
121 SignedInt(ast::TyI16) => format!("{}", val as i16),
122 SignedInt(ast::TyI32) => format!("{}", val as i32),
123 SignedInt(ast::TyI64) => format!("{}", val as i64),
124 UnsignedInt(ast::TyU8) => format!("{}", val as u8 ),
125 UnsignedInt(ast::TyU16) => format!("{}", val as u16),
126 UnsignedInt(ast::TyU32) => format!("{}", val as u32),
127 UnsignedInt(ast::TyU64) => format!("{}", val as u64),
129 UnsignedInt(ast::TyUs) |
130 SignedInt(ast::TyIs) => unreachable!(),
134 fn disr_wrap_incr(&self, val: Option<Disr>) -> Disr {
136 ($e:expr) => { ($e).wrapping_add(1) as Disr }
138 let val = val.unwrap_or(ty::INITIAL_DISCRIMINANT_VALUE);
140 SignedInt(ast::TyI8) => add1!(val as i8 ),
141 SignedInt(ast::TyI16) => add1!(val as i16),
142 SignedInt(ast::TyI32) => add1!(val as i32),
143 SignedInt(ast::TyI64) => add1!(val as i64),
144 UnsignedInt(ast::TyU8) => add1!(val as u8 ),
145 UnsignedInt(ast::TyU16) => add1!(val as u16),
146 UnsignedInt(ast::TyU32) => add1!(val as u32),
147 UnsignedInt(ast::TyU64) => add1!(val as u64),
149 UnsignedInt(ast::TyUs) |
150 SignedInt(ast::TyIs) => unreachable!(),
156 #[derive(Copy, Clone)]
157 pub enum CopyImplementationError {
158 InfrigingField(Name),
159 InfrigingVariant(Name),
164 /// Describes whether a type is representable. For types that are not
165 /// representable, 'SelfRecursive' and 'ContainsRecursive' are used to
166 /// distinguish between types that are recursive with themselves and types that
167 /// contain a different recursive type. These cases can therefore be treated
168 /// differently when reporting errors.
170 /// The ordering of the cases is significant. They are sorted so that cmp::max
171 /// will keep the "more erroneous" of two values.
172 #[derive(Copy, Clone, PartialOrd, Ord, Eq, PartialEq, Debug)]
173 pub enum Representability {
179 impl<'a, 'tcx> ParameterEnvironment<'a, 'tcx> {
180 pub fn can_type_implement_copy(&self, self_type: Ty<'tcx>, span: Span)
181 -> Result<(),CopyImplementationError> {
184 // FIXME: (@jroesch) float this code up
185 let infcx = infer::new_infer_ctxt(tcx, &tcx.tables, Some(self.clone()));
187 let adt = match self_type.sty {
188 ty::TyStruct(struct_def, substs) => {
189 for field in struct_def.all_fields() {
190 let field_ty = field.ty(tcx, substs);
191 if infcx.type_moves_by_default(field_ty, span) {
192 return Err(CopyImplementationError::InfrigingField(
198 ty::TyEnum(enum_def, substs) => {
199 for variant in &enum_def.variants {
200 for field in &variant.fields {
201 let field_ty = field.ty(tcx, substs);
202 if infcx.type_moves_by_default(field_ty, span) {
203 return Err(CopyImplementationError::InfrigingVariant(
210 _ => return Err(CopyImplementationError::NotAnAdt),
214 return Err(CopyImplementationError::HasDestructor)
221 impl<'tcx> ty::ctxt<'tcx> {
222 pub fn pat_contains_ref_binding(&self, pat: &hir::Pat) -> Option<hir::Mutability> {
223 pat_util::pat_contains_ref_binding(&self.def_map, pat)
226 pub fn arm_contains_ref_binding(&self, arm: &hir::Arm) -> Option<hir::Mutability> {
227 pat_util::arm_contains_ref_binding(&self.def_map, arm)
230 /// Returns the type of element at index `i` in tuple or tuple-like type `t`.
231 /// For an enum `t`, `variant` is None only if `t` is a univariant enum.
232 pub fn positional_element_ty(&self,
235 variant: Option<DefId>) -> Option<Ty<'tcx>> {
236 match (&ty.sty, variant) {
237 (&TyStruct(def, substs), None) => {
238 def.struct_variant().fields.get(i).map(|f| f.ty(self, substs))
240 (&TyEnum(def, substs), Some(vid)) => {
241 def.variant_with_id(vid).fields.get(i).map(|f| f.ty(self, substs))
243 (&TyEnum(def, substs), None) => {
244 assert!(def.is_univariant());
245 def.variants[0].fields.get(i).map(|f| f.ty(self, substs))
247 (&TyTuple(ref v), None) => v.get(i).cloned(),
252 /// Returns the type of element at field `n` in struct or struct-like type `t`.
253 /// For an enum `t`, `variant` must be some def id.
254 pub fn named_element_ty(&self,
257 variant: Option<DefId>) -> Option<Ty<'tcx>> {
258 match (&ty.sty, variant) {
259 (&TyStruct(def, substs), None) => {
260 def.struct_variant().find_field_named(n).map(|f| f.ty(self, substs))
262 (&TyEnum(def, substs), Some(vid)) => {
263 def.variant_with_id(vid).find_field_named(n).map(|f| f.ty(self, substs))
269 /// Returns `(normalized_type, ty)`, where `normalized_type` is the
270 /// IntType representation of one of {i64,i32,i16,i8,u64,u32,u16,u8},
271 /// and `ty` is the original type (i.e. may include `isize` or
273 pub fn enum_repr_type(&self, opt_hint: Option<&attr::ReprAttr>)
274 -> (attr::IntType, Ty<'tcx>) {
275 let repr_type = match opt_hint {
276 // Feed in the given type
277 Some(&attr::ReprInt(_, int_t)) => int_t,
278 // ... but provide sensible default if none provided
280 // NB. Historically `fn enum_variants` generate i64 here, while
281 // rustc_typeck::check would generate isize.
282 _ => SignedInt(ast::TyIs),
285 let repr_type_ty = repr_type.to_ty(self);
286 let repr_type = match repr_type {
287 SignedInt(ast::TyIs) =>
288 SignedInt(self.sess.target.int_type),
289 UnsignedInt(ast::TyUs) =>
290 UnsignedInt(self.sess.target.uint_type),
294 (repr_type, repr_type_ty)
297 /// Returns the deeply last field of nested structures, or the same type,
298 /// if not a structure at all. Corresponds to the only possible unsized
299 /// field, and its type can be used to determine unsizing strategy.
300 pub fn struct_tail(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
301 while let TyStruct(def, substs) = ty.sty {
302 match def.struct_variant().fields.last() {
303 Some(f) => ty = f.ty(self, substs),
310 /// Same as applying struct_tail on `source` and `target`, but only
311 /// keeps going as long as the two types are instances of the same
312 /// structure definitions.
313 /// For `(Foo<Foo<T>>, Foo<Trait>)`, the result will be `(Foo<T>, Trait)`,
314 /// whereas struct_tail produces `T`, and `Trait`, respectively.
315 pub fn struct_lockstep_tails(&self,
318 -> (Ty<'tcx>, Ty<'tcx>) {
319 let (mut a, mut b) = (source, target);
320 while let (&TyStruct(a_def, a_substs), &TyStruct(b_def, b_substs)) = (&a.sty, &b.sty) {
324 if let Some(f) = a_def.struct_variant().fields.last() {
325 a = f.ty(self, a_substs);
326 b = f.ty(self, b_substs);
334 /// Returns the repeat count for a repeating vector expression.
335 pub fn eval_repeat_count(&self, count_expr: &hir::Expr) -> usize {
336 let hint = UncheckedExprHint(self.types.usize);
337 match const_eval::eval_const_expr_partial(self, count_expr, hint, None) {
339 let found = match val {
340 ConstVal::Uint(count) => return count as usize,
341 ConstVal::Int(count) if count >= 0 => return count as usize,
342 const_val => const_val.description(),
344 span_err!(self.sess, count_expr.span, E0306,
345 "expected positive integer for repeat count, found {}",
349 let err_msg = match count_expr.node {
350 hir::ExprPath(None, hir::Path {
354 }) if segments.len() == 1 =>
355 format!("found variable"),
356 _ => match err.kind {
357 ErrKind::MiscCatchAll => format!("but found {}", err.description()),
358 _ => format!("but {}", err.description())
361 span_err!(self.sess, count_expr.span, E0307,
362 "expected constant integer for repeat count, {}", err_msg);
368 /// Given a set of predicates that apply to an object type, returns
369 /// the region bounds that the (erased) `Self` type must
370 /// outlive. Precisely *because* the `Self` type is erased, the
371 /// parameter `erased_self_ty` must be supplied to indicate what type
372 /// has been used to represent `Self` in the predicates
373 /// themselves. This should really be a unique type; `FreshTy(0)` is a
376 /// NB: in some cases, particularly around higher-ranked bounds,
377 /// this function returns a kind of conservative approximation.
378 /// That is, all regions returned by this function are definitely
379 /// required, but there may be other region bounds that are not
380 /// returned, as well as requirements like `for<'a> T: 'a`.
382 /// Requires that trait definitions have been processed so that we can
383 /// elaborate predicates and walk supertraits.
384 pub fn required_region_bounds(&self,
385 erased_self_ty: Ty<'tcx>,
386 predicates: Vec<ty::Predicate<'tcx>>)
388 debug!("required_region_bounds(erased_self_ty={:?}, predicates={:?})",
392 assert!(!erased_self_ty.has_escaping_regions());
394 traits::elaborate_predicates(self, predicates)
395 .filter_map(|predicate| {
397 ty::Predicate::Projection(..) |
398 ty::Predicate::Trait(..) |
399 ty::Predicate::Equate(..) |
400 ty::Predicate::WellFormed(..) |
401 ty::Predicate::ObjectSafe(..) |
402 ty::Predicate::RegionOutlives(..) => {
405 ty::Predicate::TypeOutlives(ty::Binder(ty::OutlivesPredicate(t, r))) => {
406 // Search for a bound of the form `erased_self_ty
407 // : 'a`, but be wary of something like `for<'a>
408 // erased_self_ty : 'a` (we interpret a
409 // higher-ranked bound like that as 'static,
410 // though at present the code in `fulfill.rs`
411 // considers such bounds to be unsatisfiable, so
412 // it's kind of a moot point since you could never
413 // construct such an object, but this seems
414 // correct even if that code changes).
415 if t == erased_self_ty && !r.has_escaping_regions() {
426 /// Creates a hash of the type `Ty` which will be the same no matter what crate
427 /// context it's calculated within. This is used by the `type_id` intrinsic.
428 pub fn hash_crate_independent(&self, ty: Ty<'tcx>, svh: &Svh) -> u64 {
429 let mut state = SipHasher::new();
430 helper(self, ty, svh, &mut state);
431 return state.finish();
433 fn helper<'tcx>(tcx: &ty::ctxt<'tcx>, ty: Ty<'tcx>, svh: &Svh,
434 state: &mut SipHasher) {
435 macro_rules! byte { ($b:expr) => { ($b as u8).hash(state) } }
436 macro_rules! hash { ($e:expr) => { $e.hash(state) } }
438 let region = |state: &mut SipHasher, r: ty::Region| {
441 ty::ReLateBound(db, ty::BrAnon(i)) => {
446 ty::ReEarlyBound(..) |
447 ty::ReLateBound(..) |
451 ty::ReSkolemized(..) => {
452 tcx.sess.bug("unexpected region found when hashing a type")
456 let did = |state: &mut SipHasher, did: DefId| {
457 let h = if did.is_local() {
460 tcx.sess.cstore.crate_hash(did.krate)
462 h.as_str().hash(state);
463 did.index.hash(state);
465 let mt = |state: &mut SipHasher, mt: TypeAndMut| {
466 mt.mutbl.hash(state);
468 let fn_sig = |state: &mut SipHasher, sig: &ty::Binder<ty::FnSig<'tcx>>| {
469 let sig = tcx.anonymize_late_bound_regions(sig).0;
470 for a in &sig.inputs { helper(tcx, *a, svh, state); }
471 if let ty::FnConverging(output) = sig.output {
472 helper(tcx, output, svh, state);
517 TyBareFn(opt_def_id, ref b) => {
522 fn_sig(state, &b.sig);
525 TyTrait(ref data) => {
527 did(state, data.principal_def_id());
530 let principal = tcx.anonymize_late_bound_regions(&data.principal).0;
531 for subty in &principal.substs.types {
532 helper(tcx, subty, svh, state);
541 TyTuple(ref inner) => {
549 hash!(p.name.as_str());
551 TyInfer(_) => unreachable!(),
552 TyError => byte!(21),
557 TyProjection(ref data) => {
559 did(state, data.trait_ref.def_id);
560 hash!(data.item_name.as_str());
568 /// Returns true if this ADT is a dtorck type.
570 /// Invoking the destructor of a dtorck type during usual cleanup
571 /// (e.g. the glue emitted for stack unwinding) requires all
572 /// lifetimes in the type-structure of `adt` to strictly outlive
573 /// the adt value itself.
575 /// If `adt` is not dtorck, then the adt's destructor can be
576 /// invoked even when there are lifetimes in the type-structure of
577 /// `adt` that do not strictly outlive the adt value itself.
578 /// (This allows programs to make cyclic structures without
579 /// resorting to unasfe means; see RFCs 769 and 1238).
580 pub fn is_adt_dtorck(&self, adt: ty::AdtDef<'tcx>) -> bool {
581 let dtor_method = match adt.destructor() {
586 // RFC 1238: if the destructor method is tagged with the
587 // attribute `unsafe_destructor_blind_to_params`, then the
588 // compiler is being instructed to *assume* that the
589 // destructor will not access borrowed data,
590 // even if such data is otherwise reachable.
592 // Such access can be in plain sight (e.g. dereferencing
593 // `*foo.0` of `Foo<'a>(&'a u32)`) or indirectly hidden
594 // (e.g. calling `foo.0.clone()` of `Foo<T:Clone>`).
595 return !self.has_attr(dtor_method, "unsafe_destructor_blind_to_params");
600 pub struct ImplMethod<'tcx> {
601 pub method: Rc<ty::Method<'tcx>>,
602 pub substs: Substs<'tcx>,
603 pub is_provided: bool
606 impl<'tcx> ty::ctxt<'tcx> {
607 pub fn get_impl_method(&self,
609 substs: Substs<'tcx>,
613 // there don't seem to be nicer accessors to these:
614 let impl_or_trait_items_map = self.impl_or_trait_items.borrow();
616 for impl_item in &self.impl_items.borrow()[&impl_def_id] {
617 if let ty::MethodTraitItem(ref meth) =
618 impl_or_trait_items_map[&impl_item.def_id()] {
619 if meth.name == name {
621 method: meth.clone(),
629 // It is not in the impl - get the default from the trait.
630 let trait_ref = self.impl_trait_ref(impl_def_id).unwrap();
631 for trait_item in self.trait_items(trait_ref.def_id).iter() {
632 if let &ty::MethodTraitItem(ref meth) = trait_item {
633 if meth.name == name {
634 let impl_to_trait_substs = self
635 .make_substs_for_receiver_types(&trait_ref, meth);
637 method: meth.clone(),
638 substs: impl_to_trait_substs.subst(self, &substs),
645 self.sess.bug(&format!("method {:?} not found in {:?}",
650 impl<'tcx> ty::TyS<'tcx> {
651 fn impls_bound<'a>(&'tcx self, param_env: &ParameterEnvironment<'a,'tcx>,
652 bound: ty::BuiltinBound,
656 let tcx = param_env.tcx;
657 let infcx = infer::new_infer_ctxt(tcx, &tcx.tables, Some(param_env.clone()));
659 let is_impld = traits::type_known_to_meet_builtin_bound(&infcx,
662 debug!("Ty::impls_bound({:?}, {:?}) = {:?}",
663 self, bound, is_impld);
668 // FIXME (@jroesch): I made this public to use it, not sure if should be private
669 pub fn moves_by_default<'a>(&'tcx self, param_env: &ParameterEnvironment<'a,'tcx>,
670 span: Span) -> bool {
671 if self.flags.get().intersects(TypeFlags::MOVENESS_CACHED) {
672 return self.flags.get().intersects(TypeFlags::MOVES_BY_DEFAULT);
675 assert!(!self.needs_infer());
677 // Fast-path for primitive types
678 let result = match self.sty {
679 TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) |
680 TyRawPtr(..) | TyBareFn(..) | TyRef(_, TypeAndMut {
681 mutbl: hir::MutImmutable, ..
684 TyStr | TyBox(..) | TyRef(_, TypeAndMut {
685 mutbl: hir::MutMutable, ..
688 TyArray(..) | TySlice(_) | TyTrait(..) | TyTuple(..) |
689 TyClosure(..) | TyEnum(..) | TyStruct(..) |
690 TyProjection(..) | TyParam(..) | TyInfer(..) | TyError => None
691 }.unwrap_or_else(|| !self.impls_bound(param_env, ty::BoundCopy, span));
693 if !self.has_param_types() && !self.has_self_ty() {
694 self.flags.set(self.flags.get() | if result {
695 TypeFlags::MOVENESS_CACHED | TypeFlags::MOVES_BY_DEFAULT
697 TypeFlags::MOVENESS_CACHED
705 pub fn is_sized<'a>(&'tcx self, param_env: &ParameterEnvironment<'a,'tcx>,
708 if self.flags.get().intersects(TypeFlags::SIZEDNESS_CACHED) {
709 return self.flags.get().intersects(TypeFlags::IS_SIZED);
712 self.is_sized_uncached(param_env, span)
715 fn is_sized_uncached<'a>(&'tcx self, param_env: &ParameterEnvironment<'a,'tcx>,
716 span: Span) -> bool {
717 assert!(!self.needs_infer());
719 // Fast-path for primitive types
720 let result = match self.sty {
721 TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) |
722 TyBox(..) | TyRawPtr(..) | TyRef(..) | TyBareFn(..) |
723 TyArray(..) | TyTuple(..) | TyClosure(..) => Some(true),
725 TyStr | TyTrait(..) | TySlice(_) => Some(false),
727 TyEnum(..) | TyStruct(..) | TyProjection(..) | TyParam(..) |
728 TyInfer(..) | TyError => None
729 }.unwrap_or_else(|| self.impls_bound(param_env, ty::BoundSized, span));
731 if !self.has_param_types() && !self.has_self_ty() {
732 self.flags.set(self.flags.get() | if result {
733 TypeFlags::SIZEDNESS_CACHED | TypeFlags::IS_SIZED
735 TypeFlags::SIZEDNESS_CACHED
743 /// Check whether a type is representable. This means it cannot contain unboxed
744 /// structural recursion. This check is needed for structs and enums.
745 pub fn is_representable(&'tcx self, cx: &ty::ctxt<'tcx>, sp: Span) -> Representability {
747 // Iterate until something non-representable is found
748 fn find_nonrepresentable<'tcx, It: Iterator<Item=Ty<'tcx>>>(cx: &ty::ctxt<'tcx>,
750 seen: &mut Vec<Ty<'tcx>>,
752 -> Representability {
753 iter.fold(Representability::Representable,
754 |r, ty| cmp::max(r, is_type_structurally_recursive(cx, sp, seen, ty)))
757 fn are_inner_types_recursive<'tcx>(cx: &ty::ctxt<'tcx>, sp: Span,
758 seen: &mut Vec<Ty<'tcx>>, ty: Ty<'tcx>)
759 -> Representability {
762 find_nonrepresentable(cx, sp, seen, ts.iter().cloned())
764 // Fixed-length vectors.
765 // FIXME(#11924) Behavior undecided for zero-length vectors.
767 is_type_structurally_recursive(cx, sp, seen, ty)
769 TyStruct(def, substs) | TyEnum(def, substs) => {
770 find_nonrepresentable(cx,
773 def.all_fields().map(|f| f.ty(cx, substs)))
776 // this check is run on type definitions, so we don't expect
777 // to see closure types
778 cx.sess.bug(&format!("requires check invoked on inapplicable type: {:?}", ty))
780 _ => Representability::Representable,
784 fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: ty::AdtDef<'tcx>) -> bool {
786 TyStruct(ty_def, _) | TyEnum(ty_def, _) => {
793 fn same_type<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
794 match (&a.sty, &b.sty) {
795 (&TyStruct(did_a, ref substs_a), &TyStruct(did_b, ref substs_b)) |
796 (&TyEnum(did_a, ref substs_a), &TyEnum(did_b, ref substs_b)) => {
801 let types_a = substs_a.types.get_slice(subst::TypeSpace);
802 let types_b = substs_b.types.get_slice(subst::TypeSpace);
804 let mut pairs = types_a.iter().zip(types_b);
806 pairs.all(|(&a, &b)| same_type(a, b))
814 // Does the type `ty` directly (without indirection through a pointer)
815 // contain any types on stack `seen`?
816 fn is_type_structurally_recursive<'tcx>(cx: &ty::ctxt<'tcx>,
818 seen: &mut Vec<Ty<'tcx>>,
819 ty: Ty<'tcx>) -> Representability {
820 debug!("is_type_structurally_recursive: {:?}", ty);
823 TyStruct(def, _) | TyEnum(def, _) => {
825 // Iterate through stack of previously seen types.
826 let mut iter = seen.iter();
828 // The first item in `seen` is the type we are actually curious about.
829 // We want to return SelfRecursive if this type contains itself.
830 // It is important that we DON'T take generic parameters into account
831 // for this check, so that Bar<T> in this example counts as SelfRecursive:
834 // struct Bar<T> { x: Bar<Foo> }
837 Some(&seen_type) => {
838 if same_struct_or_enum(seen_type, def) {
839 debug!("SelfRecursive: {:?} contains {:?}",
842 return Representability::SelfRecursive;
848 // We also need to know whether the first item contains other types
849 // that are structurally recursive. If we don't catch this case, we
850 // will recurse infinitely for some inputs.
852 // It is important that we DO take generic parameters into account
853 // here, so that code like this is considered SelfRecursive, not
854 // ContainsRecursive:
856 // struct Foo { Option<Option<Foo>> }
858 for &seen_type in iter {
859 if same_type(ty, seen_type) {
860 debug!("ContainsRecursive: {:?} contains {:?}",
863 return Representability::ContainsRecursive;
868 // For structs and enums, track all previously seen types by pushing them
869 // onto the 'seen' stack.
871 let out = are_inner_types_recursive(cx, sp, seen, ty);
876 // No need to push in other cases.
877 are_inner_types_recursive(cx, sp, seen, ty)
882 debug!("is_type_representable: {:?}", self);
884 // To avoid a stack overflow when checking an enum variant or struct that
885 // contains a different, structurally recursive type, maintain a stack
886 // of seen types and check recursion for each of them (issues #3008, #3779).
887 let mut seen: Vec<Ty> = Vec::new();
888 let r = is_type_structurally_recursive(cx, sp, &mut seen, self);
889 debug!("is_type_representable: {:?} is {:?}", self, r);