src/librustc/traits/query/type_op/outlives.rs

   1 use crate::infer::canonical::{Canonicalized, CanonicalizedQueryResponse};
   2 use crate::traits::query::dropck_outlives::{DropckOutlivesResult, trivial_dropck_outlives};
   3 use crate::traits::query::Fallible;
   4 use crate::ty::{ParamEnvAnd, Ty, TyCtxt};
   5
   6 #[derive(Copy, Clone, Debug, TypeFoldable, Lift)]
   7 pub struct DropckOutlives<'tcx> {
   8     dropped_ty: Ty<'tcx>,
   9 }
  10
  11 impl<'tcx> DropckOutlives<'tcx> {
  12     pub fn new(dropped_ty: Ty<'tcx>) -> Self {
  13         DropckOutlives { dropped_ty }
  14     }
  15 }
  16
  17 impl super::QueryTypeOp<'tcx> for DropckOutlives<'tcx> {
  18     type QueryResponse = DropckOutlivesResult<'tcx>;
  19
  20     fn try_fast_path(
  21         tcx: TyCtxt<'tcx>,
  22         key: &ParamEnvAnd<'tcx, Self>,
  23     ) -> Option<Self::QueryResponse> {
  24         if trivial_dropck_outlives(tcx, key.value.dropped_ty) {
  25             Some(DropckOutlivesResult::default())
  26         } else {
  27             None
  28         }
  29     }
  30
  31     fn perform_query(
  32         tcx: TyCtxt<'tcx>,
  33         canonicalized: Canonicalized<'tcx, ParamEnvAnd<'tcx, Self>>,
  34     ) -> Fallible<CanonicalizedQueryResponse<'tcx, Self::QueryResponse>> {
  35         // Subtle: note that we are not invoking
  36         // `infcx.at(...).dropck_outlives(...)` here, but rather the
  37         // underlying `dropck_outlives` query. This same underlying
  38         // query is also used by the
  39         // `infcx.at(...).dropck_outlives(...)` fn. Avoiding the
  40         // wrapper means we don't need an infcx in this code, which is
  41         // good because the interface doesn't give us one (so that we
  42         // know we are not registering any subregion relations or
  43         // other things).
  44
  45         // FIXME convert to the type expected by the `dropck_outlives`
  46         // query. This should eventually be fixed by changing the
  47         // *underlying query*.
  48         let canonicalized = canonicalized.unchecked_map(|ParamEnvAnd { param_env, value }| {
  49             let DropckOutlives { dropped_ty } = value;
  50             param_env.and(dropped_ty)
  51         });
  52
  53         tcx.dropck_outlives(canonicalized)
  54     }
  55 }
  56
  57 impl_stable_hash_for! {
  58     struct DropckOutlives<'tcx> { dropped_ty }
  59 }