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 { tcx: self, param_env })
  38         }
  39     }
  40
  41     /// If you have a `Binder<T>`, you can do this to strip out the
  42     /// late-bound regions and then normalize the result, yielding up
  43     /// a `T` (with regions erased). This is appropriate when the
  44     /// binder is being instantiated at the call site.
  45     ///
  46     /// N.B., currently, higher-ranked type bounds inhibit
  47     /// normalization. Therefore, each time we erase them in
  48     /// codegen, we need to normalize the contents.
  49     pub fn normalize_erasing_late_bound_regions<T>(
  50         self,
  51         param_env: ty::ParamEnv<'tcx>,
  52         value: &ty::Binder<T>,
  53     ) -> T
  54     where
  55         T: TypeFoldable<'tcx>,
  56     {
  57         assert!(!value.needs_subst());
  58         let value = self.erase_late_bound_regions(value);
  59         self.normalize_erasing_regions(param_env, value)
  60     }
  61
  62     /// Monomorphizes a type from the AST by first applying the
  63     /// in-scope substitutions and then normalizing any associated
  64     /// types.
  65     pub fn subst_and_normalize_erasing_regions<T>(
  66         self,
  67         param_substs: SubstsRef<'tcx>,
  68         param_env: ty::ParamEnv<'tcx>,
  69         value: &T,
  70     ) -> T
  71     where
  72         T: TypeFoldable<'tcx>,
  73     {
  74         debug!(
  75             "subst_and_normalize_erasing_regions(\
  76              param_substs={:?}, \
  77              value={:?}, \
  78              param_env={:?})",
  79             param_substs, value, param_env,
  80         );
  81         let substituted = value.subst(self, param_substs);
  82         self.normalize_erasing_regions(param_env, substituted)
  83     }
  84 }
  85
  86 struct NormalizeAfterErasingRegionsFolder<'tcx> {
  87     tcx: TyCtxt<'tcx>,
  88     param_env: ty::ParamEnv<'tcx>,
  89 }
  90
  91 impl TypeFolder<'tcx> for NormalizeAfterErasingRegionsFolder<'tcx> {
  92     fn tcx(&self) -> TyCtxt<'tcx> {
  93         self.tcx
  94     }
  95
  96     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
  97         self.tcx.normalize_ty_after_erasing_regions(self.param_env.and(ty))
  98     }
  99 }