1 use rustc_errors
::DiagnosticBuilder
;
3 use smallvec
::smallvec
;
4 use smallvec
::SmallVec
;
6 use rustc_data_structures
::fx
::FxHashSet
;
7 use rustc_hir
::def_id
::DefId
;
8 use rustc_middle
::ty
::subst
::{GenericArg, Subst, SubstsRef}
;
9 use rustc_middle
::ty
::{self, ToPredicate, Ty, TyCtxt, WithConstness}
;
11 use super::{Normalized, Obligation, ObligationCause, PredicateObligation, SelectionContext}
;
12 pub use rustc_infer
::traits
::util
::*;
14 ///////////////////////////////////////////////////////////////////////////
15 // `TraitAliasExpander` iterator
16 ///////////////////////////////////////////////////////////////////////////
18 /// "Trait alias expansion" is the process of expanding a sequence of trait
19 /// references into another sequence by transitively following all trait
20 /// aliases. e.g. If you have bounds like `Foo + Send`, a trait alias
21 /// `trait Foo = Bar + Sync;`, and another trait alias
22 /// `trait Bar = Read + Write`, then the bounds would expand to
23 /// `Read + Write + Sync + Send`.
24 /// Expansion is done via a DFS (depth-first search), and the `visited` field
25 /// is used to avoid cycles.
26 pub struct TraitAliasExpander
<'tcx
> {
28 stack
: Vec
<TraitAliasExpansionInfo
<'tcx
>>,
31 /// Stores information about the expansion of a trait via a path of zero or more trait aliases.
32 #[derive(Debug, Clone)]
33 pub struct TraitAliasExpansionInfo
<'tcx
> {
34 pub path
: SmallVec
<[(ty
::PolyTraitRef
<'tcx
>, Span
); 4]>,
37 impl<'tcx
> TraitAliasExpansionInfo
<'tcx
> {
38 fn new(trait_ref
: ty
::PolyTraitRef
<'tcx
>, span
: Span
) -> Self {
39 Self { path: smallvec![(trait_ref, span)] }
42 /// Adds diagnostic labels to `diag` for the expansion path of a trait through all intermediate
44 pub fn label_with_exp_info(
46 diag
: &mut DiagnosticBuilder
<'_
>,
50 diag
.span_label(self.top().1, top_label
);
51 if self.path
.len() > 1 {
52 for (_
, sp
) in self.path
.iter().rev().skip(1).take(self.path
.len() - 2) {
53 diag
.span_label(*sp
, format
!("referenced here ({})", use_desc
));
58 format
!("trait alias used in trait object type ({})", use_desc
),
62 pub fn trait_ref(&self) -> &ty
::PolyTraitRef
<'tcx
> {
66 pub fn top(&self) -> &(ty
::PolyTraitRef
<'tcx
>, Span
) {
67 self.path
.last().unwrap()
70 pub fn bottom(&self) -> &(ty
::PolyTraitRef
<'tcx
>, Span
) {
71 self.path
.first().unwrap()
74 fn clone_and_push(&self, trait_ref
: ty
::PolyTraitRef
<'tcx
>, span
: Span
) -> Self {
75 let mut path
= self.path
.clone();
76 path
.push((trait_ref
, span
));
82 pub fn expand_trait_aliases
<'tcx
>(
84 trait_refs
: impl Iterator
<Item
= (ty
::PolyTraitRef
<'tcx
>, Span
)>,
85 ) -> TraitAliasExpander
<'tcx
> {
87 trait_refs
.map(|(trait_ref
, span
)| TraitAliasExpansionInfo
::new(trait_ref
, span
)).collect();
88 TraitAliasExpander { tcx, stack: items }
91 impl<'tcx
> TraitAliasExpander
<'tcx
> {
92 /// If `item` is a trait alias and its predicate has not yet been visited, then expands `item`
93 /// to the definition, pushes the resulting expansion onto `self.stack`, and returns `false`.
94 /// Otherwise, immediately returns `true` if `item` is a regular trait, or `false` if it is a
96 /// The return value indicates whether `item` should be yielded to the user.
97 fn expand(&mut self, item
: &TraitAliasExpansionInfo
<'tcx
>) -> bool
{
99 let trait_ref
= item
.trait_ref();
100 let pred
= trait_ref
.without_const().to_predicate(tcx
);
102 debug
!("expand_trait_aliases: trait_ref={:?}", trait_ref
);
104 // Don't recurse if this bound is not a trait alias.
105 let is_alias
= tcx
.is_trait_alias(trait_ref
.def_id());
110 // Don't recurse if this trait alias is already on the stack for the DFS search.
111 let anon_pred
= anonymize_predicate(tcx
, pred
);
112 if item
.path
.iter().rev().skip(1).any(|(tr
, _
)| {
113 anonymize_predicate(tcx
, tr
.without_const().to_predicate(tcx
)) == anon_pred
118 // Get components of trait alias.
119 let predicates
= tcx
.super_predicates_of(trait_ref
.def_id());
121 let items
= predicates
.predicates
.iter().rev().filter_map(|(pred
, span
)| {
122 pred
.subst_supertrait(tcx
, &trait_ref
)
123 .to_opt_poly_trait_ref()
124 .map(|trait_ref
| item
.clone_and_push(trait_ref
, *span
))
126 debug
!("expand_trait_aliases: items={:?}", items
.clone());
128 self.stack
.extend(items
);
134 impl<'tcx
> Iterator
for TraitAliasExpander
<'tcx
> {
135 type Item
= TraitAliasExpansionInfo
<'tcx
>;
137 fn size_hint(&self) -> (usize, Option
<usize>) {
138 (self.stack
.len(), None
)
141 fn next(&mut self) -> Option
<TraitAliasExpansionInfo
<'tcx
>> {
142 while let Some(item
) = self.stack
.pop() {
143 if self.expand(&item
) {
151 ///////////////////////////////////////////////////////////////////////////
152 // Iterator over def-IDs of supertraits
153 ///////////////////////////////////////////////////////////////////////////
155 pub struct SupertraitDefIds
<'tcx
> {
158 visited
: FxHashSet
<DefId
>,
161 pub fn supertrait_def_ids(tcx
: TyCtxt
<'_
>, trait_def_id
: DefId
) -> SupertraitDefIds
<'_
> {
164 stack
: vec
![trait_def_id
],
165 visited
: Some(trait_def_id
).into_iter().collect(),
169 impl Iterator
for SupertraitDefIds
<'tcx
> {
172 fn next(&mut self) -> Option
<DefId
> {
173 let def_id
= self.stack
.pop()?
;
174 let predicates
= self.tcx
.super_predicates_of(def_id
);
175 let visited
= &mut self.visited
;
180 .filter_map(|(pred
, _
)| pred
.to_opt_poly_trait_ref())
181 .map(|trait_ref
| trait_ref
.def_id())
182 .filter(|&super_def_id
| visited
.insert(super_def_id
)),
188 ///////////////////////////////////////////////////////////////////////////
190 ///////////////////////////////////////////////////////////////////////////
192 /// Instantiate all bound parameters of the impl with the given substs,
193 /// returning the resulting trait ref and all obligations that arise.
194 /// The obligations are closed under normalization.
195 pub fn impl_trait_ref_and_oblig
<'a
, 'tcx
>(
196 selcx
: &mut SelectionContext
<'a
, 'tcx
>,
197 param_env
: ty
::ParamEnv
<'tcx
>,
199 impl_substs
: SubstsRef
<'tcx
>,
200 ) -> (ty
::TraitRef
<'tcx
>, impl Iterator
<Item
= PredicateObligation
<'tcx
>>) {
201 let impl_trait_ref
= selcx
.tcx().impl_trait_ref(impl_def_id
).unwrap();
202 let impl_trait_ref
= impl_trait_ref
.subst(selcx
.tcx(), impl_substs
);
203 let Normalized { value: impl_trait_ref, obligations: normalization_obligations1 }
=
204 super::normalize(selcx
, param_env
, ObligationCause
::dummy(), &impl_trait_ref
);
206 let predicates
= selcx
.tcx().predicates_of(impl_def_id
);
207 let predicates
= predicates
.instantiate(selcx
.tcx(), impl_substs
);
208 let Normalized { value: predicates, obligations: normalization_obligations2 }
=
209 super::normalize(selcx
, param_env
, ObligationCause
::dummy(), &predicates
);
210 let impl_obligations
=
211 predicates_for_generics(ObligationCause
::dummy(), 0, param_env
, predicates
);
213 let impl_obligations
= impl_obligations
214 .chain(normalization_obligations1
.into_iter())
215 .chain(normalization_obligations2
.into_iter());
217 (impl_trait_ref
, impl_obligations
)
220 pub fn predicates_for_generics
<'tcx
>(
221 cause
: ObligationCause
<'tcx
>,
222 recursion_depth
: usize,
223 param_env
: ty
::ParamEnv
<'tcx
>,
224 generic_bounds
: ty
::InstantiatedPredicates
<'tcx
>,
225 ) -> impl Iterator
<Item
= PredicateObligation
<'tcx
>> {
226 debug
!("predicates_for_generics(generic_bounds={:?})", generic_bounds
);
228 generic_bounds
.predicates
.into_iter().map(move |predicate
| Obligation
{
229 cause
: cause
.clone(),
236 pub fn predicate_for_trait_ref
<'tcx
>(
238 cause
: ObligationCause
<'tcx
>,
239 param_env
: ty
::ParamEnv
<'tcx
>,
240 trait_ref
: ty
::TraitRef
<'tcx
>,
241 recursion_depth
: usize,
242 ) -> PredicateObligation
<'tcx
> {
247 predicate
: trait_ref
.without_const().to_predicate(tcx
),
251 pub fn predicate_for_trait_def(
253 param_env
: ty
::ParamEnv
<'tcx
>,
254 cause
: ObligationCause
<'tcx
>,
256 recursion_depth
: usize,
258 params
: &[GenericArg
<'tcx
>],
259 ) -> PredicateObligation
<'tcx
> {
261 ty
::TraitRef { def_id: trait_def_id, substs: tcx.mk_substs_trait(self_ty, params) }
;
262 predicate_for_trait_ref(tcx
, cause
, param_env
, trait_ref
, recursion_depth
)
265 /// Casts a trait reference into a reference to one of its super
266 /// traits; returns `None` if `target_trait_def_id` is not a
268 pub fn upcast_choices(
270 source_trait_ref
: ty
::PolyTraitRef
<'tcx
>,
271 target_trait_def_id
: DefId
,
272 ) -> Vec
<ty
::PolyTraitRef
<'tcx
>> {
273 if source_trait_ref
.def_id() == target_trait_def_id
{
274 return vec
![source_trait_ref
]; // Shortcut the most common case.
277 supertraits(tcx
, source_trait_ref
).filter(|r
| r
.def_id() == target_trait_def_id
).collect()
280 /// Given a trait `trait_ref`, returns the number of vtable entries
281 /// that come from `trait_ref`, excluding its supertraits. Used in
282 /// computing the vtable base for an upcast trait of a trait object.
283 pub fn count_own_vtable_entries(tcx
: TyCtxt
<'tcx
>, trait_ref
: ty
::PolyTraitRef
<'tcx
>) -> usize {
285 // Count number of methods and add them to the total offset.
286 // Skip over associated types and constants.
287 for trait_item
in tcx
.associated_items(trait_ref
.def_id()).in_definition_order() {
288 if trait_item
.kind
== ty
::AssocKind
::Fn
{
295 /// Given an upcast trait object described by `object`, returns the
296 /// index of the method `method_def_id` (which should be part of
297 /// `object.upcast_trait_ref`) within the vtable for `object`.
298 pub fn get_vtable_index_of_object_method
<N
>(
300 object
: &super::VtableObjectData
<'tcx
, N
>,
301 method_def_id
: DefId
,
303 // Count number of methods preceding the one we are selecting and
304 // add them to the total offset.
305 // Skip over associated types and constants.
306 let mut entries
= object
.vtable_base
;
307 for trait_item
in tcx
.associated_items(object
.upcast_trait_ref
.def_id()).in_definition_order() {
308 if trait_item
.def_id
== method_def_id
{
309 // The item with the ID we were given really ought to be a method.
310 assert_eq
!(trait_item
.kind
, ty
::AssocKind
::Fn
);
313 if trait_item
.kind
== ty
::AssocKind
::Fn
{
318 bug
!("get_vtable_index_of_object_method: {:?} was not found", method_def_id
);
321 pub fn closure_trait_ref_and_return_type(
323 fn_trait_def_id
: DefId
,
325 sig
: ty
::PolyFnSig
<'tcx
>,
326 tuple_arguments
: TupleArgumentsFlag
,
327 ) -> ty
::Binder
<(ty
::TraitRef
<'tcx
>, Ty
<'tcx
>)> {
328 let arguments_tuple
= match tuple_arguments
{
329 TupleArgumentsFlag
::No
=> sig
.skip_binder().inputs()[0],
330 TupleArgumentsFlag
::Yes
=> tcx
.intern_tup(sig
.skip_binder().inputs()),
332 let trait_ref
= ty
::TraitRef
{
333 def_id
: fn_trait_def_id
,
334 substs
: tcx
.mk_substs_trait(self_ty
, &[arguments_tuple
.into()]),
336 ty
::Binder
::bind((trait_ref
, sig
.skip_binder().output()))
339 pub fn generator_trait_ref_and_outputs(
341 fn_trait_def_id
: DefId
,
343 sig
: ty
::PolyGenSig
<'tcx
>,
344 ) -> ty
::Binder
<(ty
::TraitRef
<'tcx
>, Ty
<'tcx
>, Ty
<'tcx
>)> {
345 let trait_ref
= ty
::TraitRef
{
346 def_id
: fn_trait_def_id
,
347 substs
: tcx
.mk_substs_trait(self_ty
, &[sig
.skip_binder().resume_ty
.into()]),
349 ty
::Binder
::bind((trait_ref
, sig
.skip_binder().yield_ty
, sig
.skip_binder().return_ty
))
352 pub fn impl_item_is_final(tcx
: TyCtxt
<'_
>, assoc_item
: &ty
::AssocItem
) -> bool
{
353 assoc_item
.defaultness
.is_final() && tcx
.impl_defaultness(assoc_item
.container
.id()).is_final()
356 pub enum TupleArgumentsFlag
{