rustc_trait_selection/solve/
delegate.rs1use std::ops::Deref;
2
3use rustc_data_structures::fx::FxHashSet;
4use rustc_hir::LangItem;
5use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
6use rustc_infer::infer::canonical::query_response::make_query_region_constraints;
7use rustc_infer::infer::canonical::{
8 Canonical, CanonicalExt as _, CanonicalQueryInput, CanonicalVarKind, CanonicalVarValues,
9};
10use rustc_infer::infer::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TyCtxtInferExt};
11use rustc_infer::traits::solve::Goal;
12use rustc_middle::traits::query::NoSolution;
13use rustc_middle::traits::solve::Certainty;
14use rustc_middle::ty::{
15 self, Ty, TyCtxt, TypeFlags, TypeFoldable, TypeVisitableExt as _, TypingMode,
16};
17use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
18
19use crate::traits::{EvaluateConstErr, ObligationCause, specialization_graph};
20
21#[repr(transparent)]
22pub struct SolverDelegate<'tcx>(InferCtxt<'tcx>);
23
24impl<'a, 'tcx> From<&'a InferCtxt<'tcx>> for &'a SolverDelegate<'tcx> {
25 fn from(infcx: &'a InferCtxt<'tcx>) -> Self {
26 unsafe { std::mem::transmute(infcx) }
28 }
29}
30
31impl<'tcx> Deref for SolverDelegate<'tcx> {
32 type Target = InferCtxt<'tcx>;
33
34 fn deref(&self) -> &Self::Target {
35 &self.0
36 }
37}
38
39impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<'tcx> {
40 type Infcx = InferCtxt<'tcx>;
41 type Interner = TyCtxt<'tcx>;
42
43 fn cx(&self) -> TyCtxt<'tcx> {
44 self.0.tcx
45 }
46
47 fn build_with_canonical<V>(
48 interner: TyCtxt<'tcx>,
49 canonical: &CanonicalQueryInput<'tcx, V>,
50 ) -> (Self, V, CanonicalVarValues<'tcx>)
51 where
52 V: TypeFoldable<TyCtxt<'tcx>>,
53 {
54 let (infcx, value, vars) = interner
55 .infer_ctxt()
56 .with_next_trait_solver(true)
57 .build_with_canonical(DUMMY_SP, canonical);
58 (SolverDelegate(infcx), value, vars)
59 }
60
61 fn compute_goal_fast_path(
62 &self,
63 goal: Goal<'tcx, ty::Predicate<'tcx>>,
64 span: Span,
65 ) -> Option<Certainty> {
66 if let Some(trait_pred) = goal.predicate.as_trait_clause() {
67 if self.shallow_resolve(trait_pred.self_ty().skip_binder()).is_ty_var()
68 && self.inner.borrow_mut().opaque_types().is_empty()
73 {
74 return Some(Certainty::AMBIGUOUS);
75 }
76
77 if trait_pred.polarity() == ty::PredicatePolarity::Positive {
78 match self.0.tcx.as_lang_item(trait_pred.def_id()) {
79 Some(LangItem::Sized)
80 if self
81 .resolve_vars_if_possible(trait_pred.self_ty().skip_binder())
82 .is_trivially_sized(self.0.tcx) =>
83 {
84 return Some(Certainty::Yes);
85 }
86 Some(LangItem::Copy | LangItem::Clone) => {
87 let self_ty =
88 self.resolve_vars_if_possible(trait_pred.self_ty().skip_binder());
89 if !self_ty
95 .has_type_flags(TypeFlags::HAS_FREE_REGIONS | TypeFlags::HAS_INFER)
96 && self_ty.is_trivially_pure_clone_copy()
97 {
98 return Some(Certainty::Yes);
99 }
100 }
101 _ => {}
102 }
103 }
104 }
105
106 let pred = goal.predicate.kind();
107 match pred.no_bound_vars()? {
108 ty::PredicateKind::DynCompatible(def_id) if self.0.tcx.is_dyn_compatible(def_id) => {
109 Some(Certainty::Yes)
110 }
111 ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(outlives)) => {
112 self.0.sub_regions(
113 SubregionOrigin::RelateRegionParamBound(span, None),
114 outlives.1,
115 outlives.0,
116 );
117 Some(Certainty::Yes)
118 }
119 ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(outlives)) => {
120 self.0.register_type_outlives_constraint(
121 outlives.0,
122 outlives.1,
123 &ObligationCause::dummy_with_span(span),
124 );
125
126 Some(Certainty::Yes)
127 }
128 ty::PredicateKind::Subtype(ty::SubtypePredicate { a, b, .. })
129 | ty::PredicateKind::Coerce(ty::CoercePredicate { a, b }) => {
130 if self.shallow_resolve(a).is_ty_var() && self.shallow_resolve(b).is_ty_var() {
131 Some(Certainty::AMBIGUOUS)
135 } else {
136 None
137 }
138 }
139 _ => None,
140 }
141 }
142
143 fn fresh_var_for_kind_with_span(
144 &self,
145 arg: ty::GenericArg<'tcx>,
146 span: Span,
147 ) -> ty::GenericArg<'tcx> {
148 match arg.kind() {
149 ty::GenericArgKind::Lifetime(_) => {
150 self.next_region_var(RegionVariableOrigin::MiscVariable(span)).into()
151 }
152 ty::GenericArgKind::Type(_) => self.next_ty_var(span).into(),
153 ty::GenericArgKind::Const(_) => self.next_const_var(span).into(),
154 }
155 }
156
157 fn leak_check(&self, max_input_universe: ty::UniverseIndex) -> Result<(), NoSolution> {
158 self.0.leak_check(max_input_universe, None).map_err(|_| NoSolution)
159 }
160
161 fn evaluate_const(
162 &self,
163 param_env: ty::ParamEnv<'tcx>,
164 uv: ty::UnevaluatedConst<'tcx>,
165 ) -> Option<ty::Const<'tcx>> {
166 let ct = ty::Const::new_unevaluated(self.tcx, uv);
167
168 match crate::traits::try_evaluate_const(&self.0, ct, param_env) {
169 Ok(ct) => Some(ct),
170 Err(EvaluateConstErr::EvaluationFailure(e)) => Some(ty::Const::new_error(self.tcx, e)),
171 Err(
172 EvaluateConstErr::InvalidConstParamTy(_) | EvaluateConstErr::HasGenericsOrInfers,
173 ) => None,
174 }
175 }
176
177 fn well_formed_goals(
178 &self,
179 param_env: ty::ParamEnv<'tcx>,
180 term: ty::Term<'tcx>,
181 ) -> Option<Vec<Goal<'tcx, ty::Predicate<'tcx>>>> {
182 crate::traits::wf::unnormalized_obligations(
183 &self.0,
184 param_env,
185 term,
186 DUMMY_SP,
187 CRATE_DEF_ID,
188 )
189 .map(|obligations| obligations.into_iter().map(|obligation| obligation.as_goal()).collect())
190 }
191
192 fn make_deduplicated_outlives_constraints(
193 &self,
194 ) -> Vec<ty::OutlivesPredicate<'tcx, ty::GenericArg<'tcx>>> {
195 let region_obligations = self.0.inner.borrow().region_obligations().to_owned();
198 let region_constraints = self.0.with_region_constraints(|region_constraints| {
199 make_query_region_constraints(
200 self.tcx,
201 region_obligations
202 .iter()
203 .map(|r_o| (r_o.sup_type, r_o.sub_region, r_o.origin.to_constraint_category())),
204 region_constraints,
205 )
206 });
207
208 let mut seen = FxHashSet::default();
209 region_constraints
210 .outlives
211 .into_iter()
212 .filter(|&(outlives, _)| seen.insert(outlives))
213 .map(|(outlives, _)| outlives)
214 .collect()
215 }
216
217 fn instantiate_canonical<V>(
218 &self,
219 canonical: Canonical<'tcx, V>,
220 values: CanonicalVarValues<'tcx>,
221 ) -> V
222 where
223 V: TypeFoldable<TyCtxt<'tcx>>,
224 {
225 canonical.instantiate(self.tcx, &values)
226 }
227
228 fn instantiate_canonical_var_with_infer(
229 &self,
230 kind: CanonicalVarKind<'tcx>,
231 span: Span,
232 universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
233 ) -> ty::GenericArg<'tcx> {
234 self.0.instantiate_canonical_var(span, kind, universe_map)
235 }
236
237 fn add_item_bounds_for_hidden_type(
238 &self,
239 def_id: DefId,
240 args: ty::GenericArgsRef<'tcx>,
241 param_env: ty::ParamEnv<'tcx>,
242 hidden_ty: Ty<'tcx>,
243 goals: &mut Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
244 ) {
245 self.0.add_item_bounds_for_hidden_type(def_id, args, param_env, hidden_ty, goals);
246 }
247
248 fn fetch_eligible_assoc_item(
249 &self,
250 goal_trait_ref: ty::TraitRef<'tcx>,
251 trait_assoc_def_id: DefId,
252 impl_def_id: DefId,
253 ) -> Result<Option<DefId>, ErrorGuaranteed> {
254 let node_item = specialization_graph::assoc_def(self.tcx, impl_def_id, trait_assoc_def_id)?;
255
256 let eligible = if node_item.is_final() {
257 true
259 } else {
260 match self.typing_mode() {
265 TypingMode::Coherence
266 | TypingMode::Analysis { .. }
267 | TypingMode::Borrowck { .. }
268 | TypingMode::PostBorrowckAnalysis { .. } => false,
269 TypingMode::PostAnalysis => {
270 let poly_trait_ref = self.resolve_vars_if_possible(goal_trait_ref);
271 !poly_trait_ref.still_further_specializable()
272 }
273 }
274 };
275
276 if eligible { Ok(Some(node_item.item.def_id)) } else { Ok(None) }
278 }
279
280 fn is_transmutable(
283 &self,
284 dst: Ty<'tcx>,
285 src: Ty<'tcx>,
286 assume: ty::Const<'tcx>,
287 ) -> Result<Certainty, NoSolution> {
288 let (dst, src) = self.tcx.erase_regions((dst, src));
291
292 let Some(assume) = rustc_transmute::Assume::from_const(self.tcx, assume) else {
293 return Err(NoSolution);
294 };
295
296 match rustc_transmute::TransmuteTypeEnv::new(self.0.tcx)
298 .is_transmutable(rustc_transmute::Types { src, dst }, assume)
299 {
300 rustc_transmute::Answer::Yes => Ok(Certainty::Yes),
301 rustc_transmute::Answer::No(_) | rustc_transmute::Answer::If(_) => Err(NoSolution),
302 }
303 }
304}