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

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use infer::canonical::{Canonical, Canonicalized, CanonicalizedQueryResult, QueryResult};
  12 use traits::query::Fallible;
  13 use ty::{ParamEnvAnd, Ty, TyCtxt};
  14
  15 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
  16 pub struct Subtype<'tcx> {
  17     pub sub: Ty<'tcx>,
  18     pub sup: Ty<'tcx>,
  19 }
  20
  21 impl<'tcx> Subtype<'tcx> {
  22     pub fn new(sub: Ty<'tcx>, sup: Ty<'tcx>) -> Self {
  23         Self {
  24             sub,
  25             sup,
  26         }
  27     }
  28 }
  29
  30 impl<'gcx: 'tcx, 'tcx> super::QueryTypeOp<'gcx, 'tcx> for Subtype<'tcx> {
  31     type QueryResult = ();
  32
  33     fn try_fast_path(_tcx: TyCtxt<'_, 'gcx, 'tcx>, key: &ParamEnvAnd<'tcx, Self>) -> Option<()> {
  34         if key.value.sub == key.value.sup {
  35             Some(())
  36         } else {
  37             None
  38         }
  39     }
  40
  41     fn perform_query(
  42         tcx: TyCtxt<'_, 'gcx, 'tcx>,
  43         canonicalized: Canonicalized<'gcx, ParamEnvAnd<'tcx, Self>>,
  44     ) -> Fallible<CanonicalizedQueryResult<'gcx, ()>> {
  45         tcx.type_op_subtype(canonicalized)
  46     }
  47
  48     fn shrink_to_tcx_lifetime(
  49         v: &'a CanonicalizedQueryResult<'gcx, ()>,
  50     ) -> &'a Canonical<'tcx, QueryResult<'tcx, ()>> {
  51         v
  52     }
  53 }
  54
  55 BraceStructTypeFoldableImpl! {
  56     impl<'tcx> TypeFoldable<'tcx> for Subtype<'tcx> {
  57         sub,
  58         sup,
  59     }
  60 }
  61
  62 BraceStructLiftImpl! {
  63     impl<'a, 'tcx> Lift<'tcx> for Subtype<'a> {
  64         type Lifted = Subtype<'tcx>;
  65         sub,
  66         sup,
  67     }
  68 }
  69
  70 impl_stable_hash_for! {
  71     struct Subtype<'tcx> { sub, sup }
  72 }