1 files changed, 283 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
new file mode 100644
index 000000000..9d8a81165
--- /dev/null
+++ b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
@@ -0,0 +1,283 @@
+//! Methods for normalizing when you don't care about regions (and
+//! aren't doing type inference). If either of those things don't
+//! apply to you, use `infcx.normalize(...)`.
+//!
+//! The methods in this file use a `TypeFolder` to recursively process
+//! contents, invoking the underlying
+//! `normalize_generic_arg_after_erasing_regions` query for each type
+//! or constant found within. (This underlying query is what is cached.)
+
+use crate::mir;
+use crate::traits::query::NoSolution;
+use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder};
+use crate::ty::subst::{Subst, SubstsRef};
+use crate::ty::{self, EarlyBinder, Ty, TyCtxt};
+
+#[derive(Debug, Copy, Clone, HashStable, TyEncodable, TyDecodable)]
+pub enum NormalizationError<'tcx> {
+    Type(Ty<'tcx>),
+    Const(ty::Const<'tcx>),
+    ConstantKind(mir::ConstantKind<'tcx>),
+}
+
+impl<'tcx> NormalizationError<'tcx> {
+    pub fn get_type_for_failure(&self) -> String {
+        match self {
+            NormalizationError::Type(t) => format!("{}", t),
+            NormalizationError::Const(c) => format!("{}", c),
+            NormalizationError::ConstantKind(ck) => format!("{}", ck),
+        }
+    }
+}
+
+impl<'tcx> TyCtxt<'tcx> {
+    /// Erase the regions in `value` and then fully normalize all the
+    /// types found within. The result will also have regions erased.
+    ///
+    /// This should only be used outside of type inference. For example,
+    /// it assumes that normalization will succeed.
+    pub fn normalize_erasing_regions<T>(self, param_env: ty::ParamEnv<'tcx>, value: T) -> T
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        debug!(
+            "normalize_erasing_regions::<{}>(value={:?}, param_env={:?})",
+            std::any::type_name::<T>(),
+            value,
+            param_env,
+        );
+
+        // Erase first before we do the real query -- this keeps the
+        // cache from being too polluted.
+        let value = self.erase_regions(value);
+        debug!(?value);
+
+        if !value.has_projections() {
+            value
+        } else {
+            value.fold_with(&mut NormalizeAfterErasingRegionsFolder { tcx: self, param_env })
+        }
+    }
+
+    /// Tries to erase the regions in `value` and then fully normalize all the
+    /// types found within. The result will also have regions erased.
+    ///
+    /// Contrary to `normalize_erasing_regions` this function does not assume that normalization
+    /// succeeds.
+    pub fn try_normalize_erasing_regions<T>(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        value: T,
+    ) -> Result<T, NormalizationError<'tcx>>
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        debug!(
+            "try_normalize_erasing_regions::<{}>(value={:?}, param_env={:?})",
+            std::any::type_name::<T>(),
+            value,
+            param_env,
+        );
+
+        // Erase first before we do the real query -- this keeps the
+        // cache from being too polluted.
+        let value = self.erase_regions(value);
+        debug!(?value);
+
+        if !value.has_projections() {
+            Ok(value)
+        } else {
+            let mut folder = TryNormalizeAfterErasingRegionsFolder::new(self, param_env);
+            value.try_fold_with(&mut folder)
+        }
+    }
+
+    /// If you have a `Binder<'tcx, T>`, you can do this to strip out the
+    /// late-bound regions and then normalize the result, yielding up
+    /// a `T` (with regions erased). This is appropriate when the
+    /// binder is being instantiated at the call site.
+    ///
+    /// N.B., currently, higher-ranked type bounds inhibit
+    /// normalization. Therefore, each time we erase them in
+    /// codegen, we need to normalize the contents.
+    pub fn normalize_erasing_late_bound_regions<T>(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        value: ty::Binder<'tcx, T>,
+    ) -> T
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        let value = self.erase_late_bound_regions(value);
+        self.normalize_erasing_regions(param_env, value)
+    }
+
+    /// If you have a `Binder<'tcx, T>`, you can do this to strip out the
+    /// late-bound regions and then normalize the result, yielding up
+    /// a `T` (with regions erased). This is appropriate when the
+    /// binder is being instantiated at the call site.
+    ///
+    /// N.B., currently, higher-ranked type bounds inhibit
+    /// normalization. Therefore, each time we erase them in
+    /// codegen, we need to normalize the contents.
+    pub fn try_normalize_erasing_late_bound_regions<T>(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        value: ty::Binder<'tcx, T>,
+    ) -> Result<T, NormalizationError<'tcx>>
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        let value = self.erase_late_bound_regions(value);
+        self.try_normalize_erasing_regions(param_env, value)
+    }
+
+    /// Monomorphizes a type from the AST by first applying the
+    /// in-scope substitutions and then normalizing any associated
+    /// types.
+    /// Panics if normalization fails. In case normalization might fail
+    /// use `try_subst_and_normalize_erasing_regions` instead.
+    pub fn subst_and_normalize_erasing_regions<T>(
+        self,
+        param_substs: SubstsRef<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        value: T,
+    ) -> T
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        debug!(
+            "subst_and_normalize_erasing_regions(\
+             param_substs={:?}, \
+             value={:?}, \
+             param_env={:?})",
+            param_substs, value, param_env,
+        );
+        let substituted = EarlyBinder(value).subst(self, param_substs);
+        self.normalize_erasing_regions(param_env, substituted)
+    }
+
+    /// Monomorphizes a type from the AST by first applying the
+    /// in-scope substitutions and then trying to normalize any associated
+    /// types. Contrary to `subst_and_normalize_erasing_regions` this does
+    /// not assume that normalization succeeds.
+    pub fn try_subst_and_normalize_erasing_regions<T>(
+        self,
+        param_substs: SubstsRef<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        value: T,
+    ) -> Result<T, NormalizationError<'tcx>>
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        debug!(
+            "subst_and_normalize_erasing_regions(\
+             param_substs={:?}, \
+             value={:?}, \
+             param_env={:?})",
+            param_substs, value, param_env,
+        );
+        let substituted = EarlyBinder(value).subst(self, param_substs);
+        self.try_normalize_erasing_regions(param_env, substituted)
+    }
+}
+
+struct NormalizeAfterErasingRegionsFolder<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+}
+
+impl<'tcx> NormalizeAfterErasingRegionsFolder<'tcx> {
+    #[instrument(skip(self), level = "debug")]
+    fn normalize_generic_arg_after_erasing_regions(
+        &self,
+        arg: ty::GenericArg<'tcx>,
+    ) -> ty::GenericArg<'tcx> {
+        let arg = self.param_env.and(arg);
+        debug!(?arg);
+
+        self.tcx.try_normalize_generic_arg_after_erasing_regions(arg).unwrap_or_else(|_| bug!(
+                "Failed to normalize {:?}, maybe try to call `try_normalize_erasing_regions` instead",
+                arg.value
+            ))
+    }
+}
+
+impl<'tcx> TypeFolder<'tcx> for NormalizeAfterErasingRegionsFolder<'tcx> {
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        self.normalize_generic_arg_after_erasing_regions(ty.into()).expect_ty()
+    }
+
+    fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> {
+        self.normalize_generic_arg_after_erasing_regions(c.into()).expect_const()
+    }
+
+    #[inline]
+    fn fold_mir_const(&mut self, c: mir::ConstantKind<'tcx>) -> mir::ConstantKind<'tcx> {
+        // FIXME: This *probably* needs canonicalization too!
+        let arg = self.param_env.and(c);
+        self.tcx
+            .try_normalize_mir_const_after_erasing_regions(arg)
+            .unwrap_or_else(|_| bug!("failed to normalize {:?}", c))
+    }
+}
+
+struct TryNormalizeAfterErasingRegionsFolder<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+}
+
+impl<'tcx> TryNormalizeAfterErasingRegionsFolder<'tcx> {
+    fn new(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self {
+        TryNormalizeAfterErasingRegionsFolder { tcx, param_env }
+    }
+
+    #[instrument(skip(self), level = "debug")]
+    fn try_normalize_generic_arg_after_erasing_regions(
+        &self,
+        arg: ty::GenericArg<'tcx>,
+    ) -> Result<ty::GenericArg<'tcx>, NoSolution> {
+        let arg = self.param_env.and(arg);
+        debug!(?arg);
+
+        self.tcx.try_normalize_generic_arg_after_erasing_regions(arg)
+    }
+}
+
+impl<'tcx> FallibleTypeFolder<'tcx> for TryNormalizeAfterErasingRegionsFolder<'tcx> {
+    type Error = NormalizationError<'tcx>;
+
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
+        match self.try_normalize_generic_arg_after_erasing_regions(ty.into()) {
+            Ok(t) => Ok(t.expect_ty()),
+            Err(_) => Err(NormalizationError::Type(ty)),
+        }
+    }
+
+    fn try_fold_const(&mut self, c: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
+        match self.try_normalize_generic_arg_after_erasing_regions(c.into()) {
+            Ok(t) => Ok(t.expect_const()),
+            Err(_) => Err(NormalizationError::Const(c)),
+        }
+    }
+
+    fn try_fold_mir_const(
+        &mut self,
+        c: mir::ConstantKind<'tcx>,
+    ) -> Result<mir::ConstantKind<'tcx>, Self::Error> {
+        // FIXME: This *probably* needs canonicalization too!
+        let arg = self.param_env.and(c);
+        match self.tcx.try_normalize_mir_const_after_erasing_regions(arg) {
+            Ok(c) => Ok(c),
+            Err(_) => Err(NormalizationError::ConstantKind(c)),
+        }
+    }
+}