Struct rustc_trait_selection::traits::fulfill::FulfillmentContext

pub struct FulfillmentContext<'tcx> {
    predicates: ObligationForest<PendingPredicateObligation<'tcx>>,
    usable_in_snapshot: usize,
}

The fulfillment context is used to drive trait resolution. It consists of a list of obligations that must be (eventually) satisfied. The job is to track which are satisfied, which yielded errors, and which are still pending. At any point, users can call select_where_possible, and the fulfillment context will try to do selection, retaining only those obligations that remain ambiguous. This may be helpful in pushing type inference along. Once all type inference constraints have been generated, the method select_all_or_error can be used to report any remaining ambiguous cases as errors.

Fields

predicates: ObligationForest<PendingPredicateObligation<'tcx>>

A list of all obligations that have been registered with this fulfillment context.

usable_in_snapshot: usize

The snapshot in which this context was created. Using the context outside of this snapshot leads to subtle bugs if the snapshot gets rolled back. Because of this we explicitly check that we only use the context in exactly this snapshot.

Implementations

impl<'tcx> FulfillmentContext<'tcx>

pub(super) fn new(infcx: &InferCtxt<'tcx>) -> FulfillmentContext<'tcx>

Creates a new fulfillment context.

fn select( &mut self, selcx: SelectionContext<'_, 'tcx> ) -> Vec<FulfillmentError<'tcx>>

Attempts to select obligations using selcx.

Trait Implementations

impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx>

fn register_predicate_obligation( &mut self, infcx: &InferCtxt<'tcx>, obligation: PredicateObligation<'tcx> )

fn collect_remaining_errors( &mut self, _infcx: &InferCtxt<'tcx> ) -> Vec<FulfillmentError<'tcx>>

fn select_where_possible( &mut self, infcx: &InferCtxt<'tcx> ) -> Vec<FulfillmentError<'tcx>>

fn drain_unstalled_obligations( &mut self, infcx: &InferCtxt<'tcx> ) -> Vec<PredicateObligation<'tcx>>

Among all pending obligations, collect those are stalled on a inference variable which has changed since the last call to select_where_possible. Those obligations are marked as successful and returned.

fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>

fn register_bound( &mut self, infcx: &InferCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>, def_id: DefId, cause: ObligationCause<'tcx> )

Requires that ty must implement the trait with def_id in the given environment. This trait must not have any type parameters (except for Self).

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 160 bytes