Document and rename the new wrapper type

7 files changed, 54 insertions, 33 deletions

diff --git a/compiler/rustc_data_structures/src/intern.rs b/compiler/rustc_data_structures/src/intern.rs
index bd62f30372e..009b5d5340a 100644
--- a/compiler/rustc_data_structures/src/intern.rs
+++ b/compiler/rustc_data_structures/src/intern.rs
@@ -115,34 +115,41 @@ pub trait InternedHashingContext {
     fn with_def_path_and_no_spans(&mut self, f: impl FnOnce(&mut Self));
 }
 
+/// A helper type that you can wrap round your own type in order to automatically
+/// cache the stable hash on creation and not recompute it whenever the stable hash
+/// of the type is computed.
+/// This is only done in incremental mode. You can also opt out of caching by using
+/// StableHash::ZERO for the hash, in which case the hash gets computed each time.
+/// This is useful if you have values that you intern but never (can?) use for stable
+/// hashing.
 #[derive(Copy, Clone)]
-pub struct InTy<T> {
+pub struct WithStableHash<T> {
     pub internee: T,
     pub stable_hash: Fingerprint,
 }
 
-impl<T: PartialEq> PartialEq for InTy<T> {
+impl<T: PartialEq> PartialEq for WithStableHash<T> {
     #[inline]
     fn eq(&self, other: &Self) -> bool {
         self.internee.eq(&other.internee)
     }
 }
 
-impl<T: Eq> Eq for InTy<T> {}
+impl<T: Eq> Eq for WithStableHash<T> {}
 
-impl<T: Ord> PartialOrd for InTy<T> {
-    fn partial_cmp(&self, other: &InTy<T>) -> Option<Ordering> {
+impl<T: Ord> PartialOrd for WithStableHash<T> {
+    fn partial_cmp(&self, other: &WithStableHash<T>) -> Option<Ordering> {
         Some(self.internee.cmp(&other.internee))
     }
 }
 
-impl<T: Ord> Ord for InTy<T> {
-    fn cmp(&self, other: &InTy<T>) -> Ordering {
+impl<T: Ord> Ord for WithStableHash<T> {
+    fn cmp(&self, other: &WithStableHash<T>) -> Ordering {
         self.internee.cmp(&other.internee)
     }
 }
 
-impl<T> Deref for InTy<T> {
+impl<T> Deref for WithStableHash<T> {
     type Target = T;
 
     #[inline]
@@ -151,14 +158,14 @@ impl<T> Deref for InTy<T> {
     }
 }
 
-impl<T: Hash> Hash for InTy<T> {
+impl<T: Hash> Hash for WithStableHash<T> {
     #[inline]
     fn hash<H: Hasher>(&self, s: &mut H) {
         self.internee.hash(s)
     }
 }
 
-impl<T: HashStable<CTX>, CTX: InternedHashingContext> HashStable<CTX> for InTy<T> {
+impl<T: HashStable<CTX>, CTX: InternedHashingContext> HashStable<CTX> for WithStableHash<T> {
     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
         if self.stable_hash == Fingerprint::ZERO || cfg!(debug_assertions) {
             // No cached hash available. This can only mean that incremental is disabled.
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index 5141d5beb7d..7c90cbb9092 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -87,7 +87,7 @@ macro_rules! arena_types {
             [] hir_id_set: rustc_hir::HirIdSet,
 
             // Interned types
-            [] tys: rustc_data_structures::intern::InTy<rustc_middle::ty::TyS<'tcx>>,
+            [] tys: rustc_data_structures::intern::WithStableHash<rustc_middle::ty::TyS<'tcx>>,
             [] predicates: rustc_middle::ty::PredicateS<'tcx>,
             [] consts: rustc_middle::ty::ConstS<'tcx>,
 
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index bc077a673f3..acca24a79f4 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -26,7 +26,7 @@ use crate::ty::{
 use rustc_ast as ast;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_data_structures::intern::{InTy, Interned};
+use rustc_data_structures::intern::{Interned, WithStableHash};
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_data_structures::sharded::{IntoPointer, ShardedHashMap};
@@ -105,7 +105,7 @@ pub struct CtxtInterners<'tcx> {
 
     // Specifically use a speedy hash algorithm for these hash sets, since
     // they're accessed quite often.
-    type_: InternedSet<'tcx, InTy<TyS<'tcx>>>,
+    type_: InternedSet<'tcx, WithStableHash<TyS<'tcx>>>,
     substs: InternedSet<'tcx, InternalSubsts<'tcx>>,
     canonical_var_infos: InternedSet<'tcx, List<CanonicalVarInfo<'tcx>>>,
     region: InternedSet<'tcx, RegionKind>,
@@ -180,7 +180,9 @@ impl<'tcx> CtxtInterners<'tcx> {
                         outer_exclusive_binder: flags.outer_exclusive_binder,
                     };
 
-                    InternedInSet(self.arena.alloc(InTy { internee: ty_struct, stable_hash }))
+                    InternedInSet(
+                        self.arena.alloc(WithStableHash { internee: ty_struct, stable_hash }),
+                    )
                 })
                 .0,
         ))
@@ -2047,23 +2049,23 @@ impl<'tcx, T: 'tcx + ?Sized> IntoPointer for InternedInSet<'tcx, T> {
 }
 
 #[allow(rustc::usage_of_ty_tykind)]
-impl<'tcx> Borrow<TyKind<'tcx>> for InternedInSet<'tcx, InTy<TyS<'tcx>>> {
+impl<'tcx> Borrow<TyKind<'tcx>> for InternedInSet<'tcx, WithStableHash<TyS<'tcx>>> {
     fn borrow<'a>(&'a self) -> &'a TyKind<'tcx> {
         &self.0.kind
     }
 }
 
-impl<'tcx> PartialEq for InternedInSet<'tcx, InTy<TyS<'tcx>>> {
-    fn eq(&self, other: &InternedInSet<'tcx, InTy<TyS<'tcx>>>) -> bool {
+impl<'tcx> PartialEq for InternedInSet<'tcx, WithStableHash<TyS<'tcx>>> {
+    fn eq(&self, other: &InternedInSet<'tcx, WithStableHash<TyS<'tcx>>>) -> bool {
         // The `Borrow` trait requires that `x.borrow() == y.borrow()` equals
         // `x == y`.
         self.0.kind == other.0.kind
     }
 }
 
-impl<'tcx> Eq for InternedInSet<'tcx, InTy<TyS<'tcx>>> {}
+impl<'tcx> Eq for InternedInSet<'tcx, WithStableHash<TyS<'tcx>>> {}
 
-impl<'tcx> Hash for InternedInSet<'tcx, InTy<TyS<'tcx>>> {
+impl<'tcx> Hash for InternedInSet<'tcx, WithStableHash<TyS<'tcx>>> {
     fn hash<H: Hasher>(&self, s: &mut H) {
         // The `Borrow` trait requires that `x.borrow().hash(s) == x.hash(s)`.
         self.0.kind.hash(s)
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 482460c0fe9..a4a9fef4515 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -31,7 +31,7 @@ use crate::ty::util::Discr;
 use rustc_ast as ast;
 use rustc_attr as attr;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
-use rustc_data_structures::intern::{InTy, Interned};
+use rustc_data_structures::intern::{Interned, WithStableHash};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
 use rustc_hir as hir;
@@ -439,15 +439,22 @@ crate struct TyS<'tcx> {
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 static_assert_size!(TyS<'_>, 40);
 
+// We are actually storing a stable hash cache next to the type, so let's
+// also check the full size
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+static_assert_size!(WithStableHash<TyS<'_>>, 56);
+
 /// Use this rather than `TyS`, whenever possible.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
 #[rustc_diagnostic_item = "Ty"]
 #[rustc_pass_by_value]
-pub struct Ty<'tcx>(Interned<'tcx, InTy<TyS<'tcx>>>);
+pub struct Ty<'tcx>(Interned<'tcx, WithStableHash<TyS<'tcx>>>);
 
 // Statics only used for internal testing.
-pub static BOOL_TY: Ty<'static> =
-    Ty(Interned::new_unchecked(&InTy { internee: BOOL_TYS, stable_hash: Fingerprint::ZERO }));
+pub static BOOL_TY: Ty<'static> = Ty(Interned::new_unchecked(&WithStableHash {
+    internee: BOOL_TYS,
+    stable_hash: Fingerprint::ZERO,
+}));
 const BOOL_TYS: TyS<'static> = TyS {
     kind: ty::Bool,
     flags: TypeFlags::empty(),
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 7e0b0ace8c0..1a843a47323 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -3,7 +3,7 @@ use crate::ty::subst::{GenericArg, GenericArgKind, Subst};
 use crate::ty::{self, ConstInt, DefIdTree, ParamConst, ScalarInt, Term, Ty, TyCtxt, TypeFoldable};
 use rustc_apfloat::ieee::{Double, Single};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::intern::{InTy, Interned};
+use rustc_data_structures::intern::{Interned, WithStableHash};
 use rustc_data_structures::sso::SsoHashSet;
 use rustc_hir as hir;
 use rustc_hir::def::{self, CtorKind, DefKind, Namespace};
@@ -1266,13 +1266,13 @@ pub trait PrettyPrinter<'tcx>:
             ty::Ref(
                 _,
                 Ty(Interned(
-                    InTy {
+                    WithStableHash {
                         internee:
                             ty::TyS {
                                 kind:
                                     ty::Array(
                                         Ty(Interned(
-                                            InTy {
+                                            WithStableHash {
                                                 internee:
                                                     ty::TyS { kind: ty::Uint(ty::UintTy::U8), .. },
                                                 ..
@@ -1452,7 +1452,10 @@ pub trait PrettyPrinter<'tcx>:
                 ConstValue::Slice { data, start, end },
                 ty::Ref(
                     _,
-                    Ty(Interned(InTy { internee: ty::TyS { kind: ty::Slice(t), .. }, .. }, _)),
+                    Ty(Interned(
+                        WithStableHash { internee: ty::TyS { kind: ty::Slice(t), .. }, .. },
+                        _,
+                    )),
                     _,
                 ),
             ) if *t == u8_type => {
@@ -1467,7 +1470,7 @@ pub trait PrettyPrinter<'tcx>:
                 ConstValue::Slice { data, start, end },
                 ty::Ref(
                     _,
-                    Ty(Interned(InTy { internee: ty::TyS { kind: ty::Str, .. }, .. }, _)),
+                    Ty(Interned(WithStableHash { internee: ty::TyS { kind: ty::Str, .. }, .. }, _)),
                     _,
                 ),
             ) => {
diff --git a/compiler/rustc_middle/src/ty/subst.rs b/compiler/rustc_middle/src/ty/subst.rs
index 50357877c0a..46b938ea93b 100644
--- a/compiler/rustc_middle/src/ty/subst.rs
+++ b/compiler/rustc_middle/src/ty/subst.rs
@@ -6,7 +6,7 @@ use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeVisitor}
 use crate::ty::sty::{ClosureSubsts, GeneratorSubsts, InlineConstSubsts};
 use crate::ty::{self, Lift, List, ParamConst, Ty, TyCtxt};
 
-use rustc_data_structures::intern::{InTy, Interned};
+use rustc_data_structures::intern::{Interned, WithStableHash};
 use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
 use rustc_serialize::{self, Decodable, Encodable};
@@ -85,7 +85,7 @@ impl<'tcx> GenericArgKind<'tcx> {
             GenericArgKind::Type(ty) => {
                 // Ensure we can use the tag bits.
                 assert_eq!(mem::align_of_val(ty.0.0) & TAG_MASK, 0);
-                (TYPE_TAG, ty.0.0 as *const InTy<ty::TyS<'tcx>> as usize)
+                (TYPE_TAG, ty.0.0 as *const WithStableHash<ty::TyS<'tcx>> as usize)
             }
             GenericArgKind::Const(ct) => {
                 // Ensure we can use the tag bits.
@@ -154,7 +154,7 @@ impl<'tcx> GenericArg<'tcx> {
                     &*((ptr & !TAG_MASK) as *const ty::RegionKind),
                 ))),
                 TYPE_TAG => GenericArgKind::Type(Ty(Interned::new_unchecked(
-                    &*((ptr & !TAG_MASK) as *const InTy<ty::TyS<'tcx>>),
+                    &*((ptr & !TAG_MASK) as *const WithStableHash<ty::TyS<'tcx>>),
                 ))),
                 CONST_TAG => GenericArgKind::Const(ty::Const(Interned::new_unchecked(
                     &*((ptr & !TAG_MASK) as *const ty::ConstS<'tcx>),
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index a5cc730813f..29a38853879 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -13,7 +13,7 @@ use rustc_apfloat::Float as _;
 use rustc_ast as ast;
 use rustc_attr::{self as attr, SignedInt, UnsignedInt};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_data_structures::intern::{InTy, Interned};
+use rustc_data_structures::intern::{Interned, WithStableHash};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
@@ -427,7 +427,9 @@ impl<'tcx> TyCtxt<'tcx> {
                         !impl_generics.region_param(ebr, self).pure_wrt_drop
                     }
                     GenericArgKind::Type(Ty(Interned(
-                        InTy { internee: ty::TyS { kind: ty::Param(ref pt), .. }, .. },
+                        WithStableHash {
+                            internee: ty::TyS { kind: ty::Param(ref pt), .. }, ..
+                        },
                         _,
                     ))) => !impl_generics.type_param(pt, self).pure_wrt_drop,
                     GenericArgKind::Const(Const(Interned(