src/librustc_trait_selection/traits/query/type_op/prove_predicate.rs

   1 use crate::infer::canonical::{Canonicalized, CanonicalizedQueryResponse};
   2 use crate::traits::query::Fallible;
   3 use rustc_middle::ty::{ParamEnvAnd, Predicate, TyCtxt};
   4
   5 pub use rustc_middle::traits::query::type_op::ProvePredicate;
   6
   7 impl<'tcx> super::QueryTypeOp<'tcx> for ProvePredicate<'tcx> {
   8     type QueryResponse = ();
   9
  10     fn try_fast_path(
  11         tcx: TyCtxt<'tcx>,
  12         key: &ParamEnvAnd<'tcx, Self>,
  13     ) -> Option<Self::QueryResponse> {
  14         // Proving Sized, very often on "obviously sized" types like
  15         // `&T`, accounts for about 60% percentage of the predicates
  16         // we have to prove. No need to canonicalize and all that for
  17         // such cases.
  18         if let Predicate::Trait(trait_ref, _) = key.value.predicate {
  19             if let Some(sized_def_id) = tcx.lang_items().sized_trait() {
  20                 if trait_ref.def_id() == sized_def_id {
  21                     if trait_ref.skip_binder().self_ty().is_trivially_sized(tcx) {
  22                         return Some(());
  23                     }
  24                 }
  25             }
  26         }
  27
  28         None
  29     }
  30
  31     fn perform_query(
  32         tcx: TyCtxt<'tcx>,
  33         canonicalized: Canonicalized<'tcx, ParamEnvAnd<'tcx, Self>>,
  34     ) -> Fallible<CanonicalizedQueryResponse<'tcx, ()>> {
  35         tcx.type_op_prove_predicate(canonicalized)
  36     }
  37 }