| use crate::traits::{ |
| Environment, |
| InEnvironment, |
| TraitEngine, |
| ObligationCause, |
| PredicateObligation, |
| FulfillmentError, |
| FulfillmentErrorCode, |
| SelectionError, |
| }; |
| use crate::traits::query::NoSolution; |
| use crate::infer::InferCtxt; |
| use crate::infer::canonical::{Canonical, OriginalQueryValues}; |
| use crate::ty::{self, Ty}; |
| use rustc_data_structures::fx::FxHashSet; |
| |
| pub type CanonicalGoal<'tcx> = Canonical<'tcx, InEnvironment<'tcx, ty::Predicate<'tcx>>>; |
| |
| pub struct FulfillmentContext<'tcx> { |
| obligations: FxHashSet<InEnvironment<'tcx, PredicateObligation<'tcx>>>, |
| } |
| |
| impl FulfillmentContext<'tcx> { |
| crate fn new() -> Self { |
| FulfillmentContext { |
| obligations: FxHashSet::default(), |
| } |
| } |
| } |
| |
| fn in_environment( |
| infcx: &InferCtxt<'_, 'tcx>, |
| obligation: PredicateObligation<'tcx>, |
| ) -> InEnvironment<'tcx, PredicateObligation<'tcx>> { |
| assert!(!infcx.is_in_snapshot()); |
| let obligation = infcx.resolve_vars_if_possible(&obligation); |
| |
| let environment = match obligation.param_env.def_id { |
| Some(def_id) => infcx.tcx.environment(def_id), |
| None if obligation.param_env.caller_bounds.is_empty() => Environment { |
| clauses: ty::List::empty(), |
| }, |
| _ => bug!("non-empty `ParamEnv` with no def-id"), |
| }; |
| |
| InEnvironment { |
| environment, |
| goal: obligation, |
| } |
| } |
| |
| impl TraitEngine<'tcx> for FulfillmentContext<'tcx> { |
| fn normalize_projection_type( |
| &mut self, |
| infcx: &InferCtxt<'_, 'tcx>, |
| _param_env: ty::ParamEnv<'tcx>, |
| projection_ty: ty::ProjectionTy<'tcx>, |
| _cause: ObligationCause<'tcx>, |
| ) -> Ty<'tcx> { |
| infcx.tcx.mk_ty(ty::Projection(projection_ty)) |
| } |
| |
| fn register_predicate_obligation( |
| &mut self, |
| infcx: &InferCtxt<'_, 'tcx>, |
| obligation: PredicateObligation<'tcx>, |
| ) { |
| self.obligations.insert(in_environment(infcx, obligation)); |
| } |
| |
| fn select_all_or_error( |
| &mut self, |
| infcx: &InferCtxt<'_, 'tcx>, |
| ) -> Result<(), Vec<FulfillmentError<'tcx>>> { |
| self.select_where_possible(infcx)?; |
| |
| if self.obligations.is_empty() { |
| Ok(()) |
| } else { |
| let errors = self.obligations.iter() |
| .map(|obligation| FulfillmentError { |
| obligation: obligation.goal.clone(), |
| code: FulfillmentErrorCode::CodeAmbiguity, |
| }) |
| .collect(); |
| Err(errors) |
| } |
| } |
| |
| fn select_where_possible( |
| &mut self, |
| infcx: &InferCtxt<'_, 'tcx>, |
| ) -> Result<(), Vec<FulfillmentError<'tcx>>> { |
| let mut errors = Vec::new(); |
| let mut next_round = FxHashSet::default(); |
| let mut making_progress; |
| |
| loop { |
| making_progress = false; |
| |
| // We iterate over all obligations, and record if we are able |
| // to unambiguously prove at least one obligation. |
| for obligation in self.obligations.drain() { |
| let mut orig_values = OriginalQueryValues::default(); |
| let canonical_goal = infcx.canonicalize_query(&InEnvironment { |
| environment: obligation.environment, |
| goal: obligation.goal.predicate, |
| }, &mut orig_values); |
| |
| match infcx.tcx.global_tcx().evaluate_goal(canonical_goal) { |
| Ok(response) => { |
| if response.is_proven() { |
| making_progress = true; |
| |
| match infcx.instantiate_query_response_and_region_obligations( |
| &obligation.goal.cause, |
| obligation.goal.param_env, |
| &orig_values, |
| &response |
| ) { |
| Ok(infer_ok) => next_round.extend( |
| infer_ok.obligations |
| .into_iter() |
| .map(|obligation| in_environment(infcx, obligation)) |
| ), |
| |
| Err(_err) => errors.push(FulfillmentError { |
| obligation: obligation.goal, |
| code: FulfillmentErrorCode::CodeSelectionError( |
| SelectionError::Unimplemented |
| ), |
| }), |
| } |
| } else { |
| // Ambiguous: retry at next round. |
| next_round.insert(obligation); |
| } |
| } |
| |
| Err(NoSolution) => errors.push(FulfillmentError { |
| obligation: obligation.goal, |
| code: FulfillmentErrorCode::CodeSelectionError( |
| SelectionError::Unimplemented |
| ), |
| }) |
| } |
| } |
| next_round = std::mem::replace(&mut self.obligations, next_round); |
| |
| if !making_progress { |
| break; |
| } |
| } |
| |
| if errors.is_empty() { |
| Ok(()) |
| } else { |
| Err(errors) |
| } |
| } |
| |
| fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> { |
| self.obligations.iter().map(|obligation| obligation.goal.clone()).collect() |
| } |
| } |