Struct rustc_trait_selection::traits::FulfillmentContext

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

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>>

register_region_obligations: bool

usable_in_snapshot: bool

Implementations

impl<'a, 'tcx> FulfillmentContext<'tcx>

pub fn new() -> FulfillmentContext<'tcx>

Creates a new fulfillment context.

pub fn new_in_snapshot() -> FulfillmentContext<'tcx>

pub fn new_ignoring_regions() -> FulfillmentContext<'tcx>

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

Attempts to select obligations using selcx.

Trait Implementations

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

fn normalize_projection_type(
    &mut self,
    infcx: &InferCtxt<'_, 'tcx>,
    param_env: ParamEnv<'tcx>,
    projection_ty: ProjectionTy<'tcx>,
    cause: ObligationCause<'tcx>
) -> Ty<'tcx>

“Normalize” a projection type <SomeType as SomeTrait>::X by creating a fresh type variable $0 as well as a projection predicate <SomeType as SomeTrait>::X == $0. When the inference engine runs, it will attempt to find an impl of SomeTrait or a where-clause that lets us unify $0 with something concrete. If this fails, we’ll unify $0 with projection_ty again.

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

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

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

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

fn register_bound(
    &mut self,
    infcx: &InferCtxt<'_, 'tcx>,
    param_env: ParamEnv<'tcx>,
    ty: &'tcx TyS<'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).