Trait rustc_trait_selection::traits::query::type_op::QueryTypeOp
source · pub trait QueryTypeOp<'tcx>: Debug + Copy + TypeFoldable<TyCtxt<'tcx>> + 'tcx {
type QueryResponse: TypeFoldable<TyCtxt<'tcx>>;
// Required methods
fn try_fast_path(
tcx: TyCtxt<'tcx>,
key: &ParamEnvAnd<'tcx, Self>
) -> Option<Self::QueryResponse>;
fn perform_query(
tcx: TyCtxt<'tcx>,
canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Self>>
) -> Fallible<CanonicalQueryResponse<'tcx, Self::QueryResponse>>;
// Provided method
fn fully_perform_into(
query_key: ParamEnvAnd<'tcx, Self>,
infcx: &InferCtxt<'tcx>,
output_query_region_constraints: &mut QueryRegionConstraints<'tcx>
) -> Fallible<(Self::QueryResponse, Option<Canonical<'tcx, ParamEnvAnd<'tcx, Self>>>, PredicateObligations<'tcx>, Certainty)> { ... }
}Expand description
“Query type ops” are type ops that are implemented using a
canonical query. The Self type here contains the kernel of
information needed to do the operation – TypeOp is actually
implemented for ParamEnvAnd<Self>, since we always need to bring
along a parameter environment as well. For query type-ops, we will
first canonicalize the key and then invoke the query on the tcx,
which produces the resulting query region constraints.
Required Associated Types§
type QueryResponse: TypeFoldable<TyCtxt<'tcx>>
Required Methods§
sourcefn try_fast_path(
tcx: TyCtxt<'tcx>,
key: &ParamEnvAnd<'tcx, Self>
) -> Option<Self::QueryResponse>
fn try_fast_path( tcx: TyCtxt<'tcx>, key: &ParamEnvAnd<'tcx, Self> ) -> Option<Self::QueryResponse>
Give query the option for a simple fast path that never
actually hits the tcx cache lookup etc. Return Some(r) with
a final result or None to do the full path.
sourcefn perform_query(
tcx: TyCtxt<'tcx>,
canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Self>>
) -> Fallible<CanonicalQueryResponse<'tcx, Self::QueryResponse>>
fn perform_query( tcx: TyCtxt<'tcx>, canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Self>> ) -> Fallible<CanonicalQueryResponse<'tcx, Self::QueryResponse>>
Performs the actual query with the canonicalized key – the
real work happens here. This method is not given an infcx
because it shouldn’t need one – and if it had access to one,
it might do things like invoke sub_regions, which would be
bad, because it would create subregion relationships that are
not captured in the return value.