compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs

   1 use crate::infer::canonical::{Canonicalized, CanonicalizedQueryResponse};
   2 use crate::traits::query::Fallible;
   3 use rustc_infer::traits::query::OutlivesBound;
   4 use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt};
   5
   6 #[derive(Copy, Clone, Debug, HashStable, TypeFoldable, TypeVisitable, Lift)]
   7 pub struct ImpliedOutlivesBounds<'tcx> {
   8     pub ty: Ty<'tcx>,
   9 }
  10
  11 impl<'tcx> super::QueryTypeOp<'tcx> for ImpliedOutlivesBounds<'tcx> {
  12     type QueryResponse = Vec<OutlivesBound<'tcx>>;
  13
  14     fn try_fast_path(
  15         _tcx: TyCtxt<'tcx>,
  16         key: &ParamEnvAnd<'tcx, Self>,
  17     ) -> Option<Self::QueryResponse> {
  18         // Don't go into the query for things that can't possibly have lifetimes.
  19         match key.value.ty.kind() {
  20             ty::Tuple(elems) if elems.is_empty() => Some(vec![]),
  21             ty::Never | ty::Str | ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) => {
  22                 Some(vec![])
  23             }
  24             _ => None,
  25         }
  26     }
  27
  28     fn perform_query(
  29         tcx: TyCtxt<'tcx>,
  30         canonicalized: Canonicalized<'tcx, ParamEnvAnd<'tcx, Self>>,
  31     ) -> Fallible<CanonicalizedQueryResponse<'tcx, Self::QueryResponse>> {
  32         // FIXME this `unchecked_map` is only necessary because the
  33         // query is defined as taking a `ParamEnvAnd<Ty>`; it should
  34         // take an `ImpliedOutlivesBounds` instead
  35         let canonicalized = canonicalized.unchecked_map(|ParamEnvAnd { param_env, value }| {
  36             let ImpliedOutlivesBounds { ty } = value;
  37             param_env.and(ty)
  38         });
  39
  40         tcx.implied_outlives_bounds(canonicalized)
  41     }
  42 }