Move BoundTy to ty::TyKind

scalexm · scalexm · commit 1003b7f85e75 · 2018-11-03T11:33:14.000+01:00
diff --git a/src/librustc/ich/impls_ty.rs b/src/librustc/ich/impls_ty.rs
@@ -852,6 +852,9 @@ for ty::TyKind<'gcx>
             Param(param_ty) => {
                 param_ty.hash_stable(hcx, hasher);
             }
+            Bound(bound_ty) => {
+                bound_ty.hash_stable(hcx, hasher);
+            }
             Foreign(def_id) => {
                 def_id.hash_stable(hcx, hasher);
             }
@@ -869,7 +872,6 @@ impl_stable_hash_for!(enum ty::InferTy {
     FreshTy(a),
     FreshIntTy(a),
     FreshFloatTy(a),
-    BoundTy(a),
 });
 
 impl<'a, 'gcx> HashStable<StableHashingContext<'a>>
diff --git a/src/librustc/infer/canonical/canonicalizer.rs b/src/librustc/infer/canonical/canonicalizer.rs
@@ -337,8 +337,8 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Canonicalizer<'cx, 'gcx, 'tcx>
                 bug!("encountered a fresh type during canonicalization")
             }
 
-            ty::Infer(ty::BoundTy(_)) => {
-                bug!("encountered a canonical type during canonicalization")
+            ty::Bound(_) => {
+                bug!("encountered a bound type during canonicalization")
             }
 
             ty::Closure(..)
@@ -455,7 +455,7 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
     /// or returns an existing variable if `kind` has already been
     /// seen. `kind` is expected to be an unbound variable (or
     /// potentially a free region).
-    fn canonical_var(&mut self, info: CanonicalVarInfo, kind: Kind<'tcx>) -> BoundTy {
+    fn canonical_var(&mut self, info: CanonicalVarInfo, kind: Kind<'tcx>) -> BoundTyIndex {
         let Canonicalizer {
             variables,
             query_state,
@@ -506,10 +506,7 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
             })
         };
 
-        BoundTy {
-            level: ty::INNERMOST,
-            var,
-        }
+        var
     }
 
     /// Shorthand helper that creates a canonical region variable for
@@ -552,9 +549,8 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
         info: CanonicalVarInfo,
         r: ty::Region<'tcx>,
     ) -> ty::Region<'tcx> {
-        let b = self.canonical_var(info, r.into());
-        debug_assert_eq!(ty::INNERMOST, b.level);
-        self.tcx().mk_region(ty::ReCanonical(b.var))
+        let var = self.canonical_var(info, r.into());
+        self.tcx().mk_region(ty::ReCanonical(var))
     }
 
     /// Given a type variable `ty_var` of the given kind, first check
@@ -570,9 +566,8 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
             let info = CanonicalVarInfo {
                 kind: CanonicalVarKind::Ty(ty_kind),
             };
-            let b = self.canonical_var(info, ty_var.into());
-            debug_assert_eq!(ty::INNERMOST, b.level);
-            self.tcx().mk_infer(ty::InferTy::BoundTy(b))
+            let var = self.canonical_var(info, ty_var.into());
+            self.tcx().mk_ty(ty::Bound(BoundTy::new(ty::INNERMOST, var)))
         }
     }
 }
diff --git a/src/librustc/infer/canonical/query_response.rs b/src/librustc/infer/canonical/query_response.rs
@@ -432,7 +432,7 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
             match result_value.unpack() {
                 UnpackedKind::Type(result_value) => {
                     // e.g., here `result_value` might be `?0` in the example above...
-                    if let ty::Infer(ty::InferTy::BoundTy(b)) = result_value.sty {
+                    if let ty::Bound(b) = result_value.sty {
                         // in which case we would set `canonical_vars[0]` to `Some(?U)`.
                         opt_values[b.var] = Some(*original_value);
                     }
diff --git a/src/librustc/infer/canonical/substitute.rs b/src/librustc/infer/canonical/substitute.rs
@@ -85,8 +85,7 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for CanonicalVarValuesSubst<'cx, 'g
 
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
         match t.sty {
-            ty::Infer(ty::InferTy::BoundTy(b)) => {
-                debug_assert_eq!(ty::INNERMOST, b.level);
+            ty::Bound(b) => {
                 match self.var_values.var_values[b.var].unpack() {
                     UnpackedKind::Type(ty) => ty,
                     r => bug!("{:?} is a type but value is {:?}", b, r),
diff --git a/src/librustc/infer/freshen.rs b/src/librustc/infer/freshen.rs
@@ -171,8 +171,8 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
                 t
             }
 
-            ty::Infer(ty::BoundTy(..)) =>
-                bug!("encountered canonical ty during freshening"),
+            ty::Bound(..) =>
+                bug!("encountered bound ty during freshening"),
 
             ty::Generator(..) |
             ty::Bool |
diff --git a/src/librustc/traits/coherence.rs b/src/librustc/traits/coherence.rs
@@ -455,7 +455,7 @@ fn ty_is_local_constructor(ty: Ty<'_>, in_crate: InCrate) -> bool {
             false
         }
 
-        ty::Infer(..) => match in_crate {
+        ty::Bound(..) | ty::Infer(..) => match in_crate {
             InCrate::Local => false,
             // The inference variable might be unified with a local
             // type in that remote crate.
diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs
@@ -280,7 +280,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 ty::Generator(..) => Some(18),
                 ty::Foreign(..) => Some(19),
                 ty::GeneratorWitness(..) => Some(20),
-                ty::Infer(..) | ty::Error => None,
+                ty::Bound(..) | ty::Infer(..) | ty::Error => None,
                 ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
             }
         }
diff --git a/src/librustc/traits/query/dropck_outlives.rs b/src/librustc/traits/query/dropck_outlives.rs
@@ -252,6 +252,7 @@ pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'_, '_, 'tcx>, ty: Ty<'tcx>) ->
         | ty::Param(_)
         | ty::Opaque(..)
         | ty::Infer(_)
+        | ty::Bound(..)
         | ty::Generator(..) => false,
 
         ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
@@ -2445,7 +2445,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             ty::Infer(ty::TyVar(_)) => Ambiguous,
 
             ty::UnnormalizedProjection(..)
-            | ty::Infer(ty::BoundTy(_))
+            | ty::Bound(_)
             | ty::Infer(ty::FreshTy(_))
             | ty::Infer(ty::FreshIntTy(_))
             | ty::Infer(ty::FreshFloatTy(_)) => {
@@ -2530,7 +2530,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             }
 
             ty::UnnormalizedProjection(..)
-            | ty::Infer(ty::BoundTy(_))
+            | ty::Bound(_)
             | ty::Infer(ty::FreshTy(_))
             | ty::Infer(ty::FreshIntTy(_))
             | ty::Infer(ty::FreshFloatTy(_)) => {
@@ -2573,7 +2573,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             | ty::Param(..)
             | ty::Foreign(..)
             | ty::Projection(..)
-            | ty::Infer(ty::BoundTy(_))
+            | ty::Bound(_)
             | ty::Infer(ty::TyVar(_))
             | ty::Infer(ty::FreshTy(_))
             | ty::Infer(ty::FreshIntTy(_))
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
@@ -2243,7 +2243,7 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
         sty_debug_print!(
             self,
             Adt, Array, Slice, RawPtr, Ref, FnDef, FnPtr,
-            Generator, GeneratorWitness, Dynamic, Closure, Tuple,
+            Generator, GeneratorWitness, Dynamic, Closure, Tuple, Bound,
             Param, Infer, UnnormalizedProjection, Projection, Opaque, Foreign);
 
         println!("Substs interner: #{}", self.interners.substs.borrow().len());
diff --git a/src/librustc/ty/error.rs b/src/librustc/ty/error.rs
@@ -212,7 +212,7 @@ impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
             ty::Infer(ty::TyVar(_)) => "inferred type".into(),
             ty::Infer(ty::IntVar(_)) => "integral variable".into(),
             ty::Infer(ty::FloatVar(_)) => "floating-point variable".into(),
-            ty::Infer(ty::BoundTy(_)) |
+            ty::Bound(_) |
             ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
             ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
             ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
diff --git a/src/librustc/ty/fast_reject.rs b/src/librustc/ty/fast_reject.rs
@@ -122,7 +122,7 @@ pub fn simplify_type<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
         ty::Foreign(def_id) => {
             Some(ForeignSimplifiedType(def_id))
         }
-        ty::Infer(_) | ty::Error => None,
+        ty::Bound(..) | ty::Infer(_) | ty::Error => None,
     }
 }
 
diff --git a/src/librustc/ty/flags.rs b/src/librustc/ty/flags.rs
@@ -115,14 +115,15 @@ impl FlagComputation {
                 self.add_substs(&substs.substs);
             }
 
+            &ty::Bound(_) => self.add_flags(TypeFlags::HAS_CANONICAL_VARS),
+
             &ty::Infer(infer) => {
                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES); // it might, right?
                 self.add_flags(TypeFlags::HAS_TY_INFER);
                 match infer {
                     ty::FreshTy(_) |
                     ty::FreshIntTy(_) |
-                    ty::FreshFloatTy(_) |
-                    ty::BoundTy(_) => {
+                    ty::FreshFloatTy(_) => {
                         self.add_flags(TypeFlags::HAS_CANONICAL_VARS);
                     }
 
diff --git a/src/librustc/ty/item_path.rs b/src/librustc/ty/item_path.rs
@@ -519,6 +519,7 @@ pub fn characteristic_def_id_of_type(ty: Ty<'_>) -> Option<DefId> {
         ty::Param(_) |
         ty::Opaque(..) |
         ty::Infer(_) |
+        ty::Bound(..) |
         ty::Error |
         ty::GeneratorWitness(..) |
         ty::Never |
diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
@@ -1124,9 +1124,14 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
                 }
                 tcx.layout_raw(param_env.and(normalized))?
             }
-            ty::UnnormalizedProjection(..) | ty::GeneratorWitness(..) | ty::Infer(_) => {
+
+            ty::Bound(..) |
+            ty::UnnormalizedProjection(..) |
+            ty::GeneratorWitness(..) |
+            ty::Infer(_) => {
                 bug!("LayoutDetails::compute: unexpected type `{}`", ty)
             }
+
             ty::Param(_) | ty::Error => {
                 return Err(LayoutError::Unknown(ty));
             }
@@ -1703,7 +1708,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
                 }
             }
 
-            ty::Projection(_) | ty::UnnormalizedProjection(..) |
+            ty::Projection(_) | ty::UnnormalizedProjection(..) | ty::Bound(..) |
             ty::Opaque(..) | ty::Param(_) | ty::Infer(_) | ty::Error => {
                 bug!("TyLayout::field_type: unexpected type `{}`", this.ty)
             }
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
@@ -63,7 +63,7 @@ use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
 
 use hir;
 
-pub use self::sty::{Binder, BoundTy, BoundTyIndex, DebruijnIndex, INNERMOST};
+pub use self::sty::{Binder, BoundTy, BoundTyKind, BoundTyIndex, DebruijnIndex, INNERMOST};
 pub use self::sty::{FnSig, GenSig, CanonicalPolyFnSig, PolyFnSig, PolyGenSig};
 pub use self::sty::{InferTy, ParamTy, ProjectionTy, ExistentialPredicate};
 pub use self::sty::{ClosureSubsts, GeneratorSubsts, UpvarSubsts, TypeAndMut};
@@ -2378,6 +2378,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
                 }
             }
 
+            Bound(..) |
             Infer(..) => {
                 bug!("unexpected type `{:?}` in sized_constraint_for_ty",
                      ty)
diff --git a/src/librustc/ty/outlives.rs b/src/librustc/ty/outlives.rs
@@ -156,6 +156,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             ty::FnDef(..) |       // OutlivesFunction (*)
             ty::FnPtr(_) |        // OutlivesFunction (*)
             ty::Dynamic(..) |       // OutlivesObject, OutlivesFragment (*)
+            ty::Bound(..) |
             ty::Error => {
                 // (*) Bare functions and traits are both binders. In the
                 // RFC, this means we would add the bound regions to the
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
@@ -734,9 +734,19 @@ impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
                 ty::UnnormalizedProjection(data.fold_with(folder))
             }
             ty::Opaque(did, substs) => ty::Opaque(did, substs.fold_with(folder)),
-            ty::Bool | ty::Char | ty::Str | ty::Int(_) |
-            ty::Uint(_) | ty::Float(_) | ty::Error | ty::Infer(_) |
-            ty::Param(..) | ty::Never | ty::Foreign(..) => return self
+
+            ty::Bool |
+            ty::Char |
+            ty::Str |
+            ty::Int(_) |
+            ty::Uint(_) |
+            ty::Float(_) |
+            ty::Error |
+            ty::Infer(_) |
+            ty::Param(..) |
+            ty::Bound(..) |
+            ty::Never |
+            ty::Foreign(..) => return self
         };
 
         if self.sty == sty {
@@ -771,9 +781,19 @@ impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
                 data.visit_with(visitor)
             }
             ty::Opaque(_, ref substs) => substs.visit_with(visitor),
-            ty::Bool | ty::Char | ty::Str | ty::Int(_) |
-            ty::Uint(_) | ty::Float(_) | ty::Error | ty::Infer(_) |
-            ty::Param(..) | ty::Never | ty::Foreign(..) => false,
+
+            ty::Bool |
+            ty::Char |
+            ty::Str |
+            ty::Int(_) |
+            ty::Uint(_) |
+            ty::Float(_) |
+            ty::Error |
+            ty::Infer(_) |
+            ty::Bound(..) |
+            ty::Param(..) |
+            ty::Never |
+            ty::Foreign(..) => false,
         }
     }
 
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
@@ -188,6 +188,9 @@ pub enum TyKind<'tcx> {
     /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
     Param(ParamTy),
 
+    /// Bound type variable, used only when preparing a trait query.
+    Bound(BoundTy),
+
     /// A type variable used during type checking.
     Infer(InferTy),
 
@@ -1219,9 +1222,6 @@ pub enum InferTy {
     FreshTy(u32),
     FreshIntTy(u32),
     FreshFloatTy(u32),
-
-    /// Bound type variable, used only when preparing a trait query.
-    BoundTy(BoundTy),
 }
 
 newtype_index! {
@@ -1232,9 +1232,28 @@ newtype_index! {
 pub struct BoundTy {
     pub level: DebruijnIndex,
     pub var: BoundTyIndex,
+    pub kind: BoundTyKind,
 }
 
-impl_stable_hash_for!(struct BoundTy { level, var });
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
+pub enum BoundTyKind {
+    Anon,
+    Param(InternedString),
+}
+
+impl_stable_hash_for!(struct BoundTy { level, var, kind });
+impl_stable_hash_for!(enum self::BoundTyKind { Anon, Param(a) });
+
+impl BoundTy {
+    pub fn new(level: DebruijnIndex, var: BoundTyIndex) -> Self {
+        debug_assert_eq!(ty::INNERMOST, level);
+        BoundTy {
+            level,
+            var,
+            kind: BoundTyKind::Anon,
+        }
+    }
+}
 
 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
@@ -1865,6 +1884,7 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
             Tuple(..) |
             Foreign(..) |
             Param(_) |
+            Bound(..) |
             Infer(_) |
             Error => {
                 vec![]
@@ -1930,7 +1950,7 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
 
             ty::Infer(ty::TyVar(_)) => false,
 
-            ty::Infer(ty::BoundTy(_)) |
+            ty::Bound(_) |
             ty::Infer(ty::FreshTy(_)) |
             ty::Infer(ty::FreshIntTy(_)) |
             ty::Infer(ty::FreshFloatTy(_)) =>
diff --git a/src/librustc/ty/subst.rs b/src/librustc/ty/subst.rs
@@ -556,7 +556,7 @@ impl CanonicalUserSubsts<'tcx> {
         self.value.substs.iter().zip(BoundTyIndex::new(0)..).all(|(kind, cvar)| {
             match kind.unpack() {
                 UnpackedKind::Type(ty) => match ty.sty {
-                    ty::Infer(ty::BoundTy(ref b)) => cvar == b.var,
+                    ty::Bound(ref b) => cvar == b.var,
                     _ => false,
                 },
 
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
@@ -951,7 +951,7 @@ fn needs_drop_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
         // Can refer to a type which may drop.
         // FIXME(eddyb) check this against a ParamEnv.
-        ty::Dynamic(..) | ty::Projection(..) | ty::Param(_) |
+        ty::Dynamic(..) | ty::Projection(..) | ty::Param(_) | ty::Bound(..) |
         ty::Opaque(..) | ty::Infer(_) | ty::Error => true,
 
         ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
diff --git a/src/librustc/ty/walk.rs b/src/librustc/ty/walk.rs
@@ -82,7 +82,7 @@ fn push_subtypes<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent_ty: Ty<'tcx>) {
     match parent_ty.sty {
         ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) |
         ty::Str | ty::Infer(_) | ty::Param(_) | ty::Never | ty::Error |
-        ty::Foreign(..) => {
+        ty::Bound(..) | ty::Foreign(..) => {
         }
         ty::Array(ty, len) => {
             push_const(stack, len);
diff --git a/src/librustc/ty/wf.rs b/src/librustc/ty/wf.rs
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
diff --git a/src/librustc_codegen_llvm/debuginfo/type_names.rs b/src/librustc_codegen_llvm/debuginfo/type_names.rs
diff --git a/src/librustc_lint/types.rs b/src/librustc_lint/types.rs
diff --git a/src/librustc_mir/monomorphize/item.rs b/src/librustc_mir/monomorphize/item.rs
diff --git a/src/librustc_traits/chalk_context.rs b/src/librustc_traits/chalk_context.rs
diff --git a/src/librustc_traits/dropck_outlives.rs b/src/librustc_traits/dropck_outlives.rs
diff --git a/src/librustc_traits/lowering/environment.rs b/src/librustc_traits/lowering/environment.rs
diff --git a/src/librustc_typeck/check/cast.rs b/src/librustc_typeck/check/cast.rs
diff --git a/src/librustc_typeck/variance/constraints.rs b/src/librustc_typeck/variance/constraints.rs
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs

Original file line number	Diff line number	Diff line change
`@@ -432,7 +432,7 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {`
`432`	`432`	`match result_value.unpack() {`
`433`	`433`	`UnpackedKind::Type(result_value) => {`
`434`	`434`	// e.g., here `result_value` might be `?0` in the example above...
`435`		`- if let ty::Infer(ty::InferTy::BoundTy(b)) = result_value.sty {`
	`435`	`+ if let ty::Bound(b) = result_value.sty {`
`436`	`436`	// in which case we would set `canonical_vars[0]` to `Some(?U)`.
`437`	`437`	`opt_values[b.var] = Some(*original_value);`
`438`	`438`	`}`
Original file line number	Diff line number	Diff line change
`@@ -171,8 +171,8 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {`
`171`	`171`	`t`
`172`	`172`	`}`
`173`	`173`
`174`		`- ty::Infer(ty::BoundTy(..)) =>`
`175`		`- bug!("encountered canonical ty during freshening"),`
	`174`	`+ ty::Bound(..) =>`
	`175`	`+ bug!("encountered bound ty during freshening"),`
`176`	`176`
`177`	`177`	`ty::Generator(..) \|`
`178`	`178`	`ty::Bool \|`
Original file line number	Diff line number	Diff line change
`@@ -455,7 +455,7 @@ fn ty_is_local_constructor(ty: Ty<'_>, in_crate: InCrate) -> bool {`
`455`	`455`	`false`
`456`	`456`	`}`
`457`	`457`
`458`		`- ty::Infer(..) => match in_crate {`
	`458`	`+ ty::Bound(..) \| ty::Infer(..) => match in_crate {`
`459`	`459`	`InCrate::Local => false,`
`460`	`460`	`// The inference variable might be unified with a local`
`461`	`461`	`// type in that remote crate.`
Original file line number	Diff line number	Diff line change
`@@ -280,7 +280,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {`
`280`	`280`	`ty::Generator(..) => Some(18),`
`281`	`281`	`ty::Foreign(..) => Some(19),`
`282`	`282`	`ty::GeneratorWitness(..) => Some(20),`
`283`		`- ty::Infer(..) \| ty::Error => None,`
	`283`	`+ ty::Bound(..) \| ty::Infer(..) \| ty::Error => None,`
`284`	`284`	`ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),`
`285`	`285`	`}`
`286`	`286`	`}`