src/librustc/ty/normalize_erasing_regions.rs

   1 //! Methods for normalizing when you don't care about regions (and
   2 //! aren't doing type inference). If either of those things don't
   3 //! apply to you, use `infcx.normalize(...)`.
   4 //!
   5 //! The methods in this file use a `TypeFolder` to recursively process
   6 //! contents, invoking the underlying
   7 //! `normalize_ty_after_erasing_regions` query for each type found
   8 //! within. (This underlying query is what is cached.)
   9
  10 use crate::ty::fold::{TypeFoldable, TypeFolder};
  11 use crate::ty::subst::{Subst, SubstsRef};
  12 use crate::ty::{self, Ty, TyCtxt};
  13
  14 impl<'tcx> TyCtxt<'tcx> {
  15     /// Erase the regions in `value` and then fully normalize all the
  16     /// types found within. The result will also have regions erased.
  17     ///
  18     /// This is appropriate to use only after type-check: it assumes
  19     /// that normalization will succeed, for example.
  20     pub fn normalize_erasing_regions<T>(self, param_env: ty::ParamEnv<'tcx>, value: T) -> T
  21     where
  22         T: TypeFoldable<'tcx>,
  23     {
  24         debug!(
  25             "normalize_erasing_regions::<{}>(value={:?}, param_env={:?})",
  26             ::std::any::type_name::<T>(),
  27             value,
  28             param_env,
  29         );
  30
  31         // Erase first before we do the real query -- this keeps the
  32         // cache from being too polluted.
  33         let value = self.erase_regions(&value);
  34         if !value.has_projections() {
  35             value
  36         } else {
  37             value.fold_with(&mut NormalizeAfterErasingRegionsFolder {
  38                 tcx: self,
  39                 param_env: param_env,
  40             })
  41         }
  42     }
  43
  44     /// If you have a `Binder<T>`, you can do this to strip out the
  45     /// late-bound regions and then normalize the result, yielding up
  46     /// a `T` (with regions erased). This is appropriate when the
  47     /// binder is being instantiated at the call site.
  48     ///
  49     /// N.B., currently, higher-ranked type bounds inhibit
  50     /// normalization. Therefore, each time we erase them in
  51     /// codegen, we need to normalize the contents.
  52     pub fn normalize_erasing_late_bound_regions<T>(
  53         self,
  54         param_env: ty::ParamEnv<'tcx>,
  55         value: &ty::Binder<T>,
  56     ) -> T
  57     where
  58         T: TypeFoldable<'tcx>,
  59     {
  60         assert!(!value.needs_subst());
  61         let value = self.erase_late_bound_regions(value);
  62         self.normalize_erasing_regions(param_env, value)
  63     }
  64
  65     /// Monomorphizes a type from the AST by first applying the
  66     /// in-scope substitutions and then normalizing any associated
  67     /// types.
  68     pub fn subst_and_normalize_erasing_regions<T>(
  69         self,
  70         param_substs: SubstsRef<'tcx>,
  71         param_env: ty::ParamEnv<'tcx>,
  72         value: &T,
  73     ) -> T
  74     where
  75         T: TypeFoldable<'tcx>,
  76     {
  77         debug!(
  78             "subst_and_normalize_erasing_regions(\
  79              param_substs={:?}, \
  80              value={:?}, \
  81              param_env={:?})",
  82             param_substs, value, param_env,
  83         );
  84         let substituted = value.subst(self, param_substs);
  85         self.normalize_erasing_regions(param_env, substituted)
  86     }
  87 }
  88
  89 struct NormalizeAfterErasingRegionsFolder<'tcx> {
  90     tcx: TyCtxt<'tcx>,
  91     param_env: ty::ParamEnv<'tcx>,
  92 }
  93
  94 impl TypeFolder<'tcx> for NormalizeAfterErasingRegionsFolder<'tcx> {
  95     fn tcx(&self) -> TyCtxt<'tcx> {
  96         self.tcx
  97     }
  98
  99     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
 100         self.tcx.normalize_ty_after_erasing_regions(self.param_env.and(ty))
 101     }
 102 }