1 // Copyright 2012-2013 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 //! Generalized type relating mechanism. A type relation R relates a
12 //! pair of values (A, B). A and B are usually types or regions but
13 //! can be other things. Examples of type relations are subtyping,
14 //! type equality, etc.
16 use hir::def_id::DefId;
17 use ty::subst::Substs;
18 use ty::{self, Ty, TyCtxt, TypeFoldable};
19 use ty::error::{ExpectedFound, TypeError};
24 pub type RelateResult<'tcx, T> = Result<T, TypeError<'tcx>>;
26 #[derive(Clone, Debug)]
28 ExistentialRegionBound, // relating an existential region bound
31 pub trait TypeRelation<'a, 'gcx: 'a+'tcx, 'tcx: 'a> : Sized {
32 fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx>;
34 /// Returns a static string we can use for printouts.
35 fn tag(&self) -> &'static str;
37 /// Returns true if the value `a` is the "expected" type in the
38 /// relation. Just affects error messages.
39 fn a_is_expected(&self) -> bool;
41 fn with_cause<F,R>(&mut self, _cause: Cause, f: F) -> R
42 where F: FnOnce(&mut Self) -> R
47 /// Generic relation routine suitable for most anything.
48 fn relate<T: Relate<'tcx>>(&mut self, a: &T, b: &T) -> RelateResult<'tcx, T> {
49 Relate::relate(self, a, b)
52 /// Relete elements of two slices pairwise.
53 fn relate_zip<T: Relate<'tcx>>(&mut self, a: &[T], b: &[T]) -> RelateResult<'tcx, Vec<T>> {
54 assert_eq!(a.len(), b.len());
55 a.iter().zip(b).map(|(a, b)| self.relate(a, b)).collect()
58 /// Switch variance for the purpose of relating `a` and `b`.
59 fn relate_with_variance<T: Relate<'tcx>>(&mut self,
60 variance: ty::Variance,
63 -> RelateResult<'tcx, T>;
65 // Overrideable relations. You shouldn't typically call these
66 // directly, instead call `relate()`, which in turn calls
67 // these. This is both more uniform but also allows us to add
68 // additional hooks for other types in the future if needed
69 // without making older code, which called `relate`, obsolete.
71 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>)
72 -> RelateResult<'tcx, Ty<'tcx>>;
74 fn regions(&mut self, a: ty::Region, b: ty::Region)
75 -> RelateResult<'tcx, ty::Region>;
77 fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>)
78 -> RelateResult<'tcx, ty::Binder<T>>
79 where T: Relate<'tcx>;
82 pub trait Relate<'tcx>: TypeFoldable<'tcx> {
83 fn relate<'a, 'gcx, R>(relation: &mut R, a: &Self, b: &Self)
84 -> RelateResult<'tcx, Self>
85 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a;
88 ///////////////////////////////////////////////////////////////////////////
91 impl<'tcx> Relate<'tcx> for ty::TypeAndMut<'tcx> {
92 fn relate<'a, 'gcx, R>(relation: &mut R,
93 a: &ty::TypeAndMut<'tcx>,
94 b: &ty::TypeAndMut<'tcx>)
95 -> RelateResult<'tcx, ty::TypeAndMut<'tcx>>
96 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
98 debug!("{}.mts({:?}, {:?})",
102 if a.mutbl != b.mutbl {
103 Err(TypeError::Mutability)
106 let variance = match mutbl {
107 ast::Mutability::MutImmutable => ty::Covariant,
108 ast::Mutability::MutMutable => ty::Invariant,
110 let ty = relation.relate_with_variance(variance, &a.ty, &b.ty)?;
111 Ok(ty::TypeAndMut {ty: ty, mutbl: mutbl})
116 // substitutions are not themselves relatable without more context,
117 // but they is an important subroutine for things that ARE relatable,
119 fn relate_item_substs<'a, 'gcx, 'tcx, R>(relation: &mut R,
121 a_subst: &'tcx Substs<'tcx>,
122 b_subst: &'tcx Substs<'tcx>)
123 -> RelateResult<'tcx, &'tcx Substs<'tcx>>
124 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
126 debug!("substs: item_def_id={:?} a_subst={:?} b_subst={:?}",
132 let opt_variances = if relation.tcx().variance_computed.get() {
133 variances = relation.tcx().item_variances(item_def_id);
138 relate_substs(relation, opt_variances, a_subst, b_subst)
141 pub fn relate_substs<'a, 'gcx, 'tcx, R>(relation: &mut R,
142 variances: Option<&ty::ItemVariances>,
143 a_subst: &'tcx Substs<'tcx>,
144 b_subst: &'tcx Substs<'tcx>)
145 -> RelateResult<'tcx, &'tcx Substs<'tcx>>
146 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
148 let tcx = relation.tcx();
150 let types = a_subst.types().zip(b_subst.types()).enumerate().map(|(i, (a_ty, b_ty))| {
151 let variance = variances.map_or(ty::Invariant, |v| v.types[i]);
152 relation.relate_with_variance(variance, a_ty, b_ty)
153 }).collect::<Result<_, _>>()?;
155 let regions = a_subst.regions().zip(b_subst.regions()).enumerate().map(|(i, (a_r, b_r))| {
156 let variance = variances.map_or(ty::Invariant, |v| v.regions[i]);
157 relation.relate_with_variance(variance, a_r, b_r)
158 }).collect::<Result<_, _>>()?;
160 Ok(Substs::new(tcx, types, regions))
163 impl<'tcx> Relate<'tcx> for &'tcx ty::BareFnTy<'tcx> {
164 fn relate<'a, 'gcx, R>(relation: &mut R,
165 a: &&'tcx ty::BareFnTy<'tcx>,
166 b: &&'tcx ty::BareFnTy<'tcx>)
167 -> RelateResult<'tcx, &'tcx ty::BareFnTy<'tcx>>
168 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
170 let unsafety = relation.relate(&a.unsafety, &b.unsafety)?;
171 let abi = relation.relate(&a.abi, &b.abi)?;
172 let sig = relation.relate(&a.sig, &b.sig)?;
173 Ok(relation.tcx().mk_bare_fn(ty::BareFnTy {
181 impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> {
182 fn relate<'a, 'gcx, R>(relation: &mut R,
185 -> RelateResult<'tcx, ty::FnSig<'tcx>>
186 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
188 if a.variadic != b.variadic {
189 return Err(TypeError::VariadicMismatch(
190 expected_found(relation, &a.variadic, &b.variadic)));
193 let inputs = relate_arg_vecs(relation,
196 let output = relation.relate(&a.output, &b.output)?;
198 Ok(ty::FnSig {inputs: inputs,
200 variadic: a.variadic})
204 fn relate_arg_vecs<'a, 'gcx, 'tcx, R>(relation: &mut R,
207 -> RelateResult<'tcx, Vec<Ty<'tcx>>>
208 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
210 if a_args.len() != b_args.len() {
211 return Err(TypeError::ArgCount);
214 a_args.iter().zip(b_args)
215 .map(|(a, b)| relation.relate_with_variance(ty::Contravariant, a, b))
219 impl<'tcx> Relate<'tcx> for ast::Unsafety {
220 fn relate<'a, 'gcx, R>(relation: &mut R,
223 -> RelateResult<'tcx, ast::Unsafety>
224 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
227 Err(TypeError::UnsafetyMismatch(expected_found(relation, a, b)))
234 impl<'tcx> Relate<'tcx> for abi::Abi {
235 fn relate<'a, 'gcx, R>(relation: &mut R,
238 -> RelateResult<'tcx, abi::Abi>
239 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
244 Err(TypeError::AbiMismatch(expected_found(relation, a, b)))
249 impl<'tcx> Relate<'tcx> for ty::ProjectionTy<'tcx> {
250 fn relate<'a, 'gcx, R>(relation: &mut R,
251 a: &ty::ProjectionTy<'tcx>,
252 b: &ty::ProjectionTy<'tcx>)
253 -> RelateResult<'tcx, ty::ProjectionTy<'tcx>>
254 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
256 if a.item_name != b.item_name {
257 Err(TypeError::ProjectionNameMismatched(
258 expected_found(relation, &a.item_name, &b.item_name)))
260 let trait_ref = relation.relate(&a.trait_ref, &b.trait_ref)?;
261 Ok(ty::ProjectionTy { trait_ref: trait_ref, item_name: a.item_name })
266 impl<'tcx> Relate<'tcx> for ty::ExistentialProjection<'tcx> {
267 fn relate<'a, 'gcx, R>(relation: &mut R,
268 a: &ty::ExistentialProjection<'tcx>,
269 b: &ty::ExistentialProjection<'tcx>)
270 -> RelateResult<'tcx, ty::ExistentialProjection<'tcx>>
271 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
273 if a.item_name != b.item_name {
274 Err(TypeError::ProjectionNameMismatched(
275 expected_found(relation, &a.item_name, &b.item_name)))
277 let trait_ref = relation.relate(&a.trait_ref, &b.trait_ref)?;
278 let ty = relation.relate(&a.ty, &b.ty)?;
279 Ok(ty::ExistentialProjection {
280 trait_ref: trait_ref,
281 item_name: a.item_name,
288 impl<'tcx> Relate<'tcx> for Vec<ty::PolyExistentialProjection<'tcx>> {
289 fn relate<'a, 'gcx, R>(relation: &mut R,
290 a: &Vec<ty::PolyExistentialProjection<'tcx>>,
291 b: &Vec<ty::PolyExistentialProjection<'tcx>>)
292 -> RelateResult<'tcx, Vec<ty::PolyExistentialProjection<'tcx>>>
293 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
295 // To be compatible, `a` and `b` must be for precisely the
296 // same set of traits and item names. We always require that
297 // projection bounds lists are sorted by trait-def-id and item-name,
298 // so we can just iterate through the lists pairwise, so long as they are the
300 if a.len() != b.len() {
301 Err(TypeError::ProjectionBoundsLength(expected_found(relation, &a.len(), &b.len())))
304 .map(|(a, b)| relation.relate(a, b))
310 impl<'tcx> Relate<'tcx> for ty::BuiltinBounds {
311 fn relate<'a, 'gcx, R>(relation: &mut R,
312 a: &ty::BuiltinBounds,
313 b: &ty::BuiltinBounds)
314 -> RelateResult<'tcx, ty::BuiltinBounds>
315 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
317 // Two sets of builtin bounds are only relatable if they are
318 // precisely the same (but see the coercion code).
320 Err(TypeError::BuiltinBoundsMismatch(expected_found(relation, a, b)))
327 impl<'tcx> Relate<'tcx> for ty::TraitRef<'tcx> {
328 fn relate<'a, 'gcx, R>(relation: &mut R,
329 a: &ty::TraitRef<'tcx>,
330 b: &ty::TraitRef<'tcx>)
331 -> RelateResult<'tcx, ty::TraitRef<'tcx>>
332 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
334 // Different traits cannot be related
335 if a.def_id != b.def_id {
336 Err(TypeError::Traits(expected_found(relation, &a.def_id, &b.def_id)))
338 let substs = relate_item_substs(relation, a.def_id, a.substs, b.substs)?;
339 Ok(ty::TraitRef { def_id: a.def_id, substs: substs })
344 impl<'tcx> Relate<'tcx> for ty::ExistentialTraitRef<'tcx> {
345 fn relate<'a, 'gcx, R>(relation: &mut R,
346 a: &ty::ExistentialTraitRef<'tcx>,
347 b: &ty::ExistentialTraitRef<'tcx>)
348 -> RelateResult<'tcx, ty::ExistentialTraitRef<'tcx>>
349 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
351 // Different traits cannot be related
352 if a.def_id != b.def_id {
353 Err(TypeError::Traits(expected_found(relation, &a.def_id, &b.def_id)))
355 let substs = relate_item_substs(relation, a.def_id, a.substs, b.substs)?;
356 Ok(ty::ExistentialTraitRef { def_id: a.def_id, substs: substs })
361 impl<'tcx> Relate<'tcx> for Ty<'tcx> {
362 fn relate<'a, 'gcx, R>(relation: &mut R,
365 -> RelateResult<'tcx, Ty<'tcx>>
366 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
372 /// The main "type relation" routine. Note that this does not handle
373 /// inference artifacts, so you should filter those out before calling
375 pub fn super_relate_tys<'a, 'gcx, 'tcx, R>(relation: &mut R,
378 -> RelateResult<'tcx, Ty<'tcx>>
379 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
381 let tcx = relation.tcx();
384 debug!("super_tys: a_sty={:?} b_sty={:?}", a_sty, b_sty);
385 match (a_sty, b_sty) {
386 (&ty::TyInfer(_), _) |
387 (_, &ty::TyInfer(_)) =>
389 // The caller should handle these cases!
390 bug!("var types encountered in super_relate_tys")
393 (&ty::TyError, _) | (_, &ty::TyError) =>
402 (&ty::TyUint(_), _) |
403 (&ty::TyFloat(_), _) |
410 (&ty::TyParam(ref a_p), &ty::TyParam(ref b_p))
411 if a_p.idx == b_p.idx =>
416 (&ty::TyEnum(a_def, a_substs), &ty::TyEnum(b_def, b_substs))
419 let substs = relate_item_substs(relation, a_def.did, a_substs, b_substs)?;
420 Ok(tcx.mk_enum(a_def, substs))
423 (&ty::TyTrait(ref a_obj), &ty::TyTrait(ref b_obj)) =>
425 let principal = relation.relate(&a_obj.principal, &b_obj.principal)?;
428 Cause::ExistentialRegionBound,
429 |relation| relation.relate_with_variance(ty::Contravariant,
431 &b_obj.region_bound))?;
432 let nb = relation.relate(&a_obj.builtin_bounds, &b_obj.builtin_bounds)?;
433 let pb = relation.relate(&a_obj.projection_bounds, &b_obj.projection_bounds)?;
434 Ok(tcx.mk_trait(ty::TraitObject {
435 principal: principal,
438 projection_bounds: pb
442 (&ty::TyStruct(a_def, a_substs), &ty::TyStruct(b_def, b_substs))
445 let substs = relate_item_substs(relation, a_def.did, a_substs, b_substs)?;
446 Ok(tcx.mk_struct(a_def, substs))
449 (&ty::TyClosure(a_id, a_substs),
450 &ty::TyClosure(b_id, b_substs))
453 // All TyClosure types with the same id represent
454 // the (anonymous) type of the same closure expression. So
455 // all of their regions should be equated.
456 let substs = relation.relate(&a_substs, &b_substs)?;
457 Ok(tcx.mk_closure_from_closure_substs(a_id, substs))
460 (&ty::TyBox(a_inner), &ty::TyBox(b_inner)) =>
462 let typ = relation.relate(&a_inner, &b_inner)?;
466 (&ty::TyRawPtr(ref a_mt), &ty::TyRawPtr(ref b_mt)) =>
468 let mt = relation.relate(a_mt, b_mt)?;
472 (&ty::TyRef(a_r, ref a_mt), &ty::TyRef(b_r, ref b_mt)) =>
474 let r = relation.relate_with_variance(ty::Contravariant, a_r, b_r)?;
475 let mt = relation.relate(a_mt, b_mt)?;
476 Ok(tcx.mk_ref(tcx.mk_region(r), mt))
479 (&ty::TyArray(a_t, sz_a), &ty::TyArray(b_t, sz_b)) =>
481 let t = relation.relate(&a_t, &b_t)?;
483 Ok(tcx.mk_array(t, sz_a))
485 Err(TypeError::FixedArraySize(expected_found(relation, &sz_a, &sz_b)))
489 (&ty::TySlice(a_t), &ty::TySlice(b_t)) =>
491 let t = relation.relate(&a_t, &b_t)?;
495 (&ty::TyTuple(as_), &ty::TyTuple(bs)) =>
497 if as_.len() == bs.len() {
498 let ts = as_.iter().zip(bs)
499 .map(|(a, b)| relation.relate(a, b))
500 .collect::<Result<_, _>>()?;
502 } else if !(as_.is_empty() || bs.is_empty()) {
503 Err(TypeError::TupleSize(
504 expected_found(relation, &as_.len(), &bs.len())))
506 Err(TypeError::Sorts(expected_found(relation, &a, &b)))
510 (&ty::TyFnDef(a_def_id, a_substs, a_fty),
511 &ty::TyFnDef(b_def_id, b_substs, b_fty))
512 if a_def_id == b_def_id =>
514 let substs = relate_substs(relation, None, a_substs, b_substs)?;
515 let fty = relation.relate(&a_fty, &b_fty)?;
516 Ok(tcx.mk_fn_def(a_def_id, substs, fty))
519 (&ty::TyFnPtr(a_fty), &ty::TyFnPtr(b_fty)) =>
521 let fty = relation.relate(&a_fty, &b_fty)?;
522 Ok(tcx.mk_fn_ptr(fty))
525 (&ty::TyProjection(ref a_data), &ty::TyProjection(ref b_data)) =>
527 let projection_ty = relation.relate(a_data, b_data)?;
528 Ok(tcx.mk_projection(projection_ty.trait_ref, projection_ty.item_name))
531 (&ty::TyAnon(a_def_id, a_substs), &ty::TyAnon(b_def_id, b_substs))
532 if a_def_id == b_def_id =>
534 let substs = relate_substs(relation, None, a_substs, b_substs)?;
535 Ok(tcx.mk_anon(a_def_id, substs))
540 Err(TypeError::Sorts(expected_found(relation, &a, &b)))
545 impl<'tcx> Relate<'tcx> for ty::ClosureSubsts<'tcx> {
546 fn relate<'a, 'gcx, R>(relation: &mut R,
547 a: &ty::ClosureSubsts<'tcx>,
548 b: &ty::ClosureSubsts<'tcx>)
549 -> RelateResult<'tcx, ty::ClosureSubsts<'tcx>>
550 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
552 let substs = relate_substs(relation, None, a.func_substs, b.func_substs)?;
553 let upvar_tys = relation.relate_zip(&a.upvar_tys, &b.upvar_tys)?;
554 Ok(ty::ClosureSubsts {
556 upvar_tys: relation.tcx().mk_type_list(upvar_tys)
561 impl<'tcx> Relate<'tcx> for &'tcx Substs<'tcx> {
562 fn relate<'a, 'gcx, R>(relation: &mut R,
563 a: &&'tcx Substs<'tcx>,
564 b: &&'tcx Substs<'tcx>)
565 -> RelateResult<'tcx, &'tcx Substs<'tcx>>
566 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
568 relate_substs(relation, None, a, b)
572 impl<'tcx> Relate<'tcx> for ty::Region {
573 fn relate<'a, 'gcx, R>(relation: &mut R,
576 -> RelateResult<'tcx, ty::Region>
577 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
579 relation.regions(*a, *b)
583 impl<'tcx, T: Relate<'tcx>> Relate<'tcx> for ty::Binder<T> {
584 fn relate<'a, 'gcx, R>(relation: &mut R,
587 -> RelateResult<'tcx, ty::Binder<T>>
588 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
590 relation.binders(a, b)
594 impl<'tcx, T: Relate<'tcx>> Relate<'tcx> for Rc<T> {
595 fn relate<'a, 'gcx, R>(relation: &mut R,
598 -> RelateResult<'tcx, Rc<T>>
599 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
603 Ok(Rc::new(relation.relate(a, b)?))
607 impl<'tcx, T: Relate<'tcx>> Relate<'tcx> for Box<T> {
608 fn relate<'a, 'gcx, R>(relation: &mut R,
611 -> RelateResult<'tcx, Box<T>>
612 where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
616 Ok(Box::new(relation.relate(a, b)?))
620 ///////////////////////////////////////////////////////////////////////////
623 pub fn expected_found<'a, 'gcx, 'tcx, R, T>(relation: &mut R,
627 where R: TypeRelation<'a, 'gcx, 'tcx>, T: Clone, 'gcx: 'a+'tcx, 'tcx: 'a
629 expected_found_bool(relation.a_is_expected(), a, b)
632 pub fn expected_found_bool<T>(a_is_expected: bool,
641 ExpectedFound {expected: a, found: b}
643 ExpectedFound {expected: b, found: a}