|
| 1 | +use traits::{ |
| 2 | + Environment, |
| 3 | + InEnvironment, |
| 4 | + TraitEngine, |
| 5 | + ObligationCause, |
| 6 | + PredicateObligation, |
| 7 | + FulfillmentError, |
| 8 | + FulfillmentErrorCode, |
| 9 | + SelectionError, |
| 10 | +}; |
| 11 | +use traits::query::NoSolution; |
| 12 | +use infer::InferCtxt; |
| 13 | +use infer::canonical::{Canonical, OriginalQueryValues}; |
| 14 | +use ty::{self, Ty}; |
| 15 | +use rustc_data_structures::fx::FxHashSet; |
| 16 | + |
| 17 | +pub type CanonicalGoal<'tcx> = Canonical<'tcx, InEnvironment<'tcx, ty::Predicate<'tcx>>>; |
| 18 | + |
| 19 | +pub struct FulfillmentContext<'tcx> { |
| 20 | + obligations: FxHashSet<InEnvironment<'tcx, PredicateObligation<'tcx>>>, |
| 21 | +} |
| 22 | + |
| 23 | +impl FulfillmentContext<'tcx> { |
| 24 | + crate fn new() -> Self { |
| 25 | + FulfillmentContext { |
| 26 | + obligations: FxHashSet::default(), |
| 27 | + } |
| 28 | + } |
| 29 | +} |
| 30 | + |
| 31 | +fn in_environment( |
| 32 | + infcx: &InferCtxt<'_, 'gcx, 'tcx>, |
| 33 | + obligation: PredicateObligation<'tcx> |
| 34 | +) -> InEnvironment<'tcx, PredicateObligation<'tcx>> { |
| 35 | + assert!(!infcx.is_in_snapshot()); |
| 36 | + let obligation = infcx.resolve_type_vars_if_possible(&obligation); |
| 37 | + |
| 38 | + let environment = match obligation.param_env.def_id { |
| 39 | + Some(def_id) => infcx.tcx.environment(def_id), |
| 40 | + None if obligation.param_env.caller_bounds.is_empty() => Environment { |
| 41 | + clauses: ty::List::empty(), |
| 42 | + }, |
| 43 | + _ => bug!("non-empty `ParamEnv` with no def-id"), |
| 44 | + }; |
| 45 | + |
| 46 | + InEnvironment { |
| 47 | + environment, |
| 48 | + goal: obligation, |
| 49 | + } |
| 50 | +} |
| 51 | + |
| 52 | +impl TraitEngine<'tcx> for FulfillmentContext<'tcx> { |
| 53 | + fn normalize_projection_type( |
| 54 | + &mut self, |
| 55 | + infcx: &InferCtxt<'_, 'gcx, 'tcx>, |
| 56 | + _param_env: ty::ParamEnv<'tcx>, |
| 57 | + projection_ty: ty::ProjectionTy<'tcx>, |
| 58 | + _cause: ObligationCause<'tcx>, |
| 59 | + ) -> Ty<'tcx> { |
| 60 | + infcx.tcx.mk_ty(ty::Projection(projection_ty)) |
| 61 | + } |
| 62 | + |
| 63 | + fn register_predicate_obligation( |
| 64 | + &mut self, |
| 65 | + infcx: &InferCtxt<'_, 'gcx, 'tcx>, |
| 66 | + obligation: PredicateObligation<'tcx>, |
| 67 | + ) { |
| 68 | + self.obligations.insert(in_environment(infcx, obligation)); |
| 69 | + } |
| 70 | + |
| 71 | + fn select_all_or_error( |
| 72 | + &mut self, |
| 73 | + infcx: &InferCtxt<'_, 'gcx, 'tcx>, |
| 74 | + ) -> Result<(), Vec<FulfillmentError<'tcx>>> { |
| 75 | + self.select_where_possible(infcx)?; |
| 76 | + |
| 77 | + if self.obligations.is_empty() { |
| 78 | + Ok(()) |
| 79 | + } else { |
| 80 | + let errors = self.obligations.iter() |
| 81 | + .map(|obligation| FulfillmentError { |
| 82 | + obligation: obligation.goal.clone(), |
| 83 | + code: FulfillmentErrorCode::CodeAmbiguity, |
| 84 | + }) |
| 85 | + .collect(); |
| 86 | + Err(errors) |
| 87 | + } |
| 88 | + } |
| 89 | + |
| 90 | + fn select_where_possible( |
| 91 | + &mut self, |
| 92 | + infcx: &InferCtxt<'_, 'gcx, 'tcx>, |
| 93 | + ) -> Result<(), Vec<FulfillmentError<'tcx>>> { |
| 94 | + let mut errors = Vec::new(); |
| 95 | + let mut next_round = FxHashSet::default(); |
| 96 | + let mut making_progress; |
| 97 | + |
| 98 | + loop { |
| 99 | + making_progress = false; |
| 100 | + |
| 101 | + // We iterate over all obligations, and record if we are able |
| 102 | + // to unambiguously prove at least one obligation. |
| 103 | + for obligation in self.obligations.drain() { |
| 104 | + let mut orig_values = OriginalQueryValues::default(); |
| 105 | + let canonical_goal = infcx.canonicalize_query(&InEnvironment { |
| 106 | + environment: obligation.environment, |
| 107 | + goal: obligation.goal.predicate, |
| 108 | + }, &mut orig_values); |
| 109 | + |
| 110 | + match infcx.tcx.global_tcx().evaluate_goal(canonical_goal) { |
| 111 | + Ok(response) => { |
| 112 | + if response.is_proven() { |
| 113 | + making_progress = true; |
| 114 | + |
| 115 | + match infcx.instantiate_query_response_and_region_obligations( |
| 116 | + &obligation.goal.cause, |
| 117 | + obligation.goal.param_env, |
| 118 | + &orig_values, |
| 119 | + &response |
| 120 | + ) { |
| 121 | + Ok(infer_ok) => next_round.extend( |
| 122 | + infer_ok.obligations |
| 123 | + .into_iter() |
| 124 | + .map(|obligation| in_environment(infcx, obligation)) |
| 125 | + ), |
| 126 | + |
| 127 | + Err(_err) => errors.push(FulfillmentError { |
| 128 | + obligation: obligation.goal, |
| 129 | + code: FulfillmentErrorCode::CodeSelectionError( |
| 130 | + SelectionError::Unimplemented |
| 131 | + ), |
| 132 | + }), |
| 133 | + } |
| 134 | + } else { |
| 135 | + // Ambiguous: retry at next round. |
| 136 | + next_round.insert(obligation); |
| 137 | + } |
| 138 | + } |
| 139 | + |
| 140 | + Err(NoSolution) => errors.push(FulfillmentError { |
| 141 | + obligation: obligation.goal, |
| 142 | + code: FulfillmentErrorCode::CodeSelectionError( |
| 143 | + SelectionError::Unimplemented |
| 144 | + ), |
| 145 | + }) |
| 146 | + } |
| 147 | + } |
| 148 | + next_round = std::mem::replace(&mut self.obligations, next_round); |
| 149 | + |
| 150 | + if !making_progress { |
| 151 | + break; |
| 152 | + } |
| 153 | + } |
| 154 | + |
| 155 | + if errors.is_empty() { |
| 156 | + Ok(()) |
| 157 | + } else { |
| 158 | + Err(errors) |
| 159 | + } |
| 160 | + } |
| 161 | + |
| 162 | + fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> { |
| 163 | + self.obligations.iter().map(|obligation| obligation.goal.clone()).collect() |
| 164 | + } |
| 165 | +} |
0 commit comments