1 files changed, 196 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics/type_name.rs b/compiler/rustc_const_eval/src/interpret/intrinsics/type_name.rs
new file mode 100644
index 000000000..f9847742f
--- /dev/null
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics/type_name.rs
@@ -0,0 +1,196 @@
+use rustc_data_structures::intern::Interned;
+use rustc_hir::def_id::CrateNum;
+use rustc_hir::definitions::DisambiguatedDefPathData;
+use rustc_middle::mir::interpret::{Allocation, ConstAllocation};
+use rustc_middle::ty::{
+    self,
+    print::{PrettyPrinter, Print, Printer},
+    subst::{GenericArg, GenericArgKind},
+    Ty, TyCtxt,
+};
+use std::fmt::Write;
+
+struct AbsolutePathPrinter<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    path: String,
+}
+
+impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
+    type Error = std::fmt::Error;
+
+    type Path = Self;
+    type Region = Self;
+    type Type = Self;
+    type DynExistential = Self;
+    type Const = Self;
+
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
+        Ok(self)
+    }
+
+    fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
+        match *ty.kind() {
+            // Types without identity.
+            ty::Bool
+            | ty::Char
+            | ty::Int(_)
+            | ty::Uint(_)
+            | ty::Float(_)
+            | ty::Str
+            | ty::Array(_, _)
+            | ty::Slice(_)
+            | ty::RawPtr(_)
+            | ty::Ref(_, _, _)
+            | ty::FnPtr(_)
+            | ty::Never
+            | ty::Tuple(_)
+            | ty::Dynamic(_, _) => self.pretty_print_type(ty),
+
+            // Placeholders (all printed as `_` to uniformize them).
+            ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => {
+                write!(self, "_")?;
+                Ok(self)
+            }
+
+            // Types with identity (print the module path).
+            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), substs)
+            | ty::FnDef(def_id, substs)
+            | ty::Opaque(def_id, substs)
+            | ty::Projection(ty::ProjectionTy { item_def_id: def_id, substs })
+            | ty::Closure(def_id, substs)
+            | ty::Generator(def_id, substs, _) => self.print_def_path(def_id, substs),
+            ty::Foreign(def_id) => self.print_def_path(def_id, &[]),
+
+            ty::GeneratorWitness(_) => bug!("type_name: unexpected `GeneratorWitness`"),
+        }
+    }
+
+    fn print_const(self, ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
+        self.pretty_print_const(ct, false)
+    }
+
+    fn print_dyn_existential(
+        mut self,
+        predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
+    ) -> Result<Self::DynExistential, Self::Error> {
+        let mut first = true;
+        for p in predicates {
+            if !first {
+                write!(self, "+")?;
+            }
+            first = false;
+            self = p.print(self)?;
+        }
+        Ok(self)
+    }
+
+    fn path_crate(mut self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
+        self.path.push_str(self.tcx.crate_name(cnum).as_str());
+        Ok(self)
+    }
+
+    fn path_qualified(
+        self,
+        self_ty: Ty<'tcx>,
+        trait_ref: Option<ty::TraitRef<'tcx>>,
+    ) -> Result<Self::Path, Self::Error> {
+        self.pretty_path_qualified(self_ty, trait_ref)
+    }
+
+    fn path_append_impl(
+        self,
+        print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+        _disambiguated_data: &DisambiguatedDefPathData,
+        self_ty: Ty<'tcx>,
+        trait_ref: Option<ty::TraitRef<'tcx>>,
+    ) -> Result<Self::Path, Self::Error> {
+        self.pretty_path_append_impl(
+            |mut cx| {
+                cx = print_prefix(cx)?;
+
+                cx.path.push_str("::");
+
+                Ok(cx)
+            },
+            self_ty,
+            trait_ref,
+        )
+    }
+
+    fn path_append(
+        mut self,
+        print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+        disambiguated_data: &DisambiguatedDefPathData,
+    ) -> Result<Self::Path, Self::Error> {
+        self = print_prefix(self)?;
+
+        write!(self.path, "::{}", disambiguated_data.data).unwrap();
+
+        Ok(self)
+    }
+
+    fn path_generic_args(
+        mut self,
+        print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+        args: &[GenericArg<'tcx>],
+    ) -> Result<Self::Path, Self::Error> {
+        self = print_prefix(self)?;
+        let args =
+            args.iter().cloned().filter(|arg| !matches!(arg.unpack(), GenericArgKind::Lifetime(_)));
+        if args.clone().next().is_some() {
+            self.generic_delimiters(|cx| cx.comma_sep(args))
+        } else {
+            Ok(self)
+        }
+    }
+}
+
+impl<'tcx> PrettyPrinter<'tcx> for AbsolutePathPrinter<'tcx> {
+    fn should_print_region(&self, _region: ty::Region<'_>) -> bool {
+        false
+    }
+    fn comma_sep<T>(mut self, mut elems: impl Iterator<Item = T>) -> Result<Self, Self::Error>
+    where
+        T: Print<'tcx, Self, Output = Self, Error = Self::Error>,
+    {
+        if let Some(first) = elems.next() {
+            self = first.print(self)?;
+            for elem in elems {
+                self.path.push_str(", ");
+                self = elem.print(self)?;
+            }
+        }
+        Ok(self)
+    }
+
+    fn generic_delimiters(
+        mut self,
+        f: impl FnOnce(Self) -> Result<Self, Self::Error>,
+    ) -> Result<Self, Self::Error> {
+        write!(self, "<")?;
+
+        self = f(self)?;
+
+        write!(self, ">")?;
+
+        Ok(self)
+    }
+}
+
+impl Write for AbsolutePathPrinter<'_> {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        self.path.push_str(s);
+        Ok(())
+    }
+}
+
+/// Directly returns an `Allocation` containing an absolute path representation of the given type.
+pub(crate) fn alloc_type_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ConstAllocation<'tcx> {
+    let path = AbsolutePathPrinter { tcx, path: String::new() }.print_type(ty).unwrap().path;
+    let alloc = Allocation::from_bytes_byte_aligned_immutable(path.into_bytes());
+    tcx.intern_const_alloc(alloc)
+}