1 //! Defines a Chalk-based `TraitEngine`
3 use crate::infer::canonical::OriginalQueryValues;
4 use crate::infer::InferCtxt;
5 use crate::traits::query::NoSolution;
7 ChalkEnvironmentAndGoal, FulfillmentError, FulfillmentErrorCode, ObligationCause,
8 PredicateObligation, SelectionError, TraitEngine,
10 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
11 use rustc_middle::ty::{self, Ty, TypeVisitable};
13 pub struct FulfillmentContext<'tcx> {
14 obligations: FxIndexSet<PredicateObligation<'tcx>>,
16 relationships: FxHashMap<ty::TyVid, ty::FoundRelationships>,
19 impl FulfillmentContext<'_> {
20 pub(crate) fn new() -> Self {
22 obligations: FxIndexSet::default(),
23 relationships: FxHashMap::default(),
28 impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
29 fn normalize_projection_type(
31 infcx: &InferCtxt<'_, 'tcx>,
32 _param_env: ty::ParamEnv<'tcx>,
33 projection_ty: ty::ProjectionTy<'tcx>,
34 _cause: ObligationCause<'tcx>,
36 infcx.tcx.mk_ty(ty::Projection(projection_ty))
39 fn register_predicate_obligation(
41 infcx: &InferCtxt<'_, 'tcx>,
42 obligation: PredicateObligation<'tcx>,
44 assert!(!infcx.is_in_snapshot());
45 let obligation = infcx.resolve_vars_if_possible(obligation);
47 super::relationships::update(self, infcx, &obligation);
49 self.obligations.insert(obligation);
52 fn select_all_or_error(&mut self, infcx: &InferCtxt<'_, 'tcx>) -> Vec<FulfillmentError<'tcx>> {
54 let errors = self.select_where_possible(infcx);
56 if !errors.is_empty() {
61 // any remaining obligations are errors
64 .map(|obligation| FulfillmentError {
65 obligation: obligation.clone(),
66 code: FulfillmentErrorCode::CodeAmbiguity,
67 // FIXME - does Chalk have a notation of 'root obligation'?
68 // This is just for diagnostics, so it's okay if this is wrong
69 root_obligation: obligation.clone(),
74 fn select_where_possible(
76 infcx: &InferCtxt<'_, 'tcx>,
77 ) -> Vec<FulfillmentError<'tcx>> {
78 assert!(!infcx.is_in_snapshot());
80 let mut errors = Vec::new();
81 let mut next_round = FxIndexSet::default();
82 let mut making_progress;
85 making_progress = false;
87 // We iterate over all obligations, and record if we are able
88 // to unambiguously prove at least one obligation.
89 for obligation in self.obligations.drain(..) {
90 let obligation = infcx.resolve_vars_if_possible(obligation);
91 let environment = obligation.param_env.caller_bounds();
92 let goal = ChalkEnvironmentAndGoal { environment, goal: obligation.predicate };
93 let mut orig_values = OriginalQueryValues::default();
94 if goal.references_error() {
99 infcx.canonicalize_query_preserving_universes(goal, &mut orig_values);
101 match infcx.tcx.evaluate_goal(canonical_goal) {
103 if response.is_proven() {
104 making_progress = true;
106 match infcx.instantiate_query_response_and_region_obligations(
108 obligation.param_env,
112 Ok(infer_ok) => next_round.extend(
113 infer_ok.obligations.into_iter().map(|obligation| {
114 assert!(!infcx.is_in_snapshot());
115 infcx.resolve_vars_if_possible(obligation)
119 Err(_err) => errors.push(FulfillmentError {
120 obligation: obligation.clone(),
121 code: FulfillmentErrorCode::CodeSelectionError(
122 SelectionError::Unimplemented,
124 // FIXME - does Chalk have a notation of 'root obligation'?
125 // This is just for diagnostics, so it's okay if this is wrong
126 root_obligation: obligation,
130 // Ambiguous: retry at next round.
131 next_round.insert(obligation);
135 Err(NoSolution) => errors.push(FulfillmentError {
136 obligation: obligation.clone(),
137 code: FulfillmentErrorCode::CodeSelectionError(
138 SelectionError::Unimplemented,
140 // FIXME - does Chalk have a notation of 'root obligation'?
141 // This is just for diagnostics, so it's okay if this is wrong
142 root_obligation: obligation,
146 next_round = std::mem::replace(&mut self.obligations, next_round);
148 if !making_progress {
156 fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
157 self.obligations.iter().cloned().collect()
160 fn relationships(&mut self) -> &mut FxHashMap<ty::TyVid, ty::FoundRelationships> {
161 &mut self.relationships