1 files changed, 135 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/impls_ty.rs b/compiler/rustc_middle/src/ty/impls_ty.rs
new file mode 100644
index 000000000..cd00b26b8
--- /dev/null
+++ b/compiler/rustc_middle/src/ty/impls_ty.rs
@@ -0,0 +1,135 @@
+//! This module contains `HashStable` implementations for various data types
+//! from `rustc_middle::ty` in no particular order.
+
+use crate::middle::region;
+use crate::mir;
+use crate::ty;
+use crate::ty::fast_reject::SimplifiedType;
+use rustc_data_structures::fingerprint::Fingerprint;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::stable_hasher::HashingControls;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
+use rustc_query_system::ich::StableHashingContext;
+use std::cell::RefCell;
+
+impl<'a, 'tcx, T> HashStable<StableHashingContext<'a>> for &'tcx ty::List<T>
+where
+    T: HashStable<StableHashingContext<'a>>,
+{
+    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
+        thread_local! {
+            static CACHE: RefCell<FxHashMap<(usize, usize, HashingControls), Fingerprint>> =
+                RefCell::new(Default::default());
+        }
+
+        let hash = CACHE.with(|cache| {
+            let key = (self.as_ptr() as usize, self.len(), hcx.hashing_controls());
+            if let Some(&hash) = cache.borrow().get(&key) {
+                return hash;
+            }
+
+            let mut hasher = StableHasher::new();
+            (&self[..]).hash_stable(hcx, &mut hasher);
+
+            let hash: Fingerprint = hasher.finish();
+            cache.borrow_mut().insert(key, hash);
+            hash
+        });
+
+        hash.hash_stable(hcx, hasher);
+    }
+}
+
+impl<'a, 'tcx, T> ToStableHashKey<StableHashingContext<'a>> for &'tcx ty::List<T>
+where
+    T: HashStable<StableHashingContext<'a>>,
+{
+    type KeyType = Fingerprint;
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &StableHashingContext<'a>) -> Fingerprint {
+        let mut hasher = StableHasher::new();
+        let mut hcx: StableHashingContext<'a> = hcx.clone();
+        self.hash_stable(&mut hcx, &mut hasher);
+        hasher.finish()
+    }
+}
+
+impl<'a> ToStableHashKey<StableHashingContext<'a>> for SimplifiedType {
+    type KeyType = Fingerprint;
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &StableHashingContext<'a>) -> Fingerprint {
+        let mut hasher = StableHasher::new();
+        let mut hcx: StableHashingContext<'a> = hcx.clone();
+        self.hash_stable(&mut hcx, &mut hasher);
+        hasher.finish()
+    }
+}
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArg<'tcx> {
+    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
+        self.unpack().hash_stable(hcx, hasher);
+    }
+}
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArgKind<'tcx> {
+    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
+        match self {
+            // WARNING: We dedup cache the `HashStable` results for `List`
+            // while ignoring types and freely transmute
+            // between `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>`.
+            // See `fn intern_type_list` for more details.
+            //
+            // We therefore hash types without adding a hash for their discriminant.
+            //
+            // In order to make it very unlikely for the sequence of bytes being hashed for
+            // a `GenericArgKind::Type` to be the same as the sequence of bytes being
+            // hashed for one of the other variants, we hash some very high number instead
+            // of their actual discriminant since `TyKind` should never start with anything
+            // that high.
+            ty::subst::GenericArgKind::Type(ty) => ty.hash_stable(hcx, hasher),
+            ty::subst::GenericArgKind::Const(ct) => {
+                0xF3u8.hash_stable(hcx, hasher);
+                ct.hash_stable(hcx, hasher);
+            }
+            ty::subst::GenericArgKind::Lifetime(lt) => {
+                0xF5u8.hash_stable(hcx, hasher);
+                lt.hash_stable(hcx, hasher);
+            }
+        }
+    }
+}
+
+// AllocIds get resolved to whatever they point to (to be stable)
+impl<'a> HashStable<StableHashingContext<'a>> for mir::interpret::AllocId {
+    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
+        ty::tls::with_opt(|tcx| {
+            trace!("hashing {:?}", *self);
+            let tcx = tcx.expect("can't hash AllocIds during hir lowering");
+            tcx.try_get_global_alloc(*self).hash_stable(hcx, hasher);
+        });
+    }
+}
+
+// `Relocations` with default type parameters is a sorted map.
+impl<'a, Prov> HashStable<StableHashingContext<'a>> for mir::interpret::Relocations<Prov>
+where
+    Prov: HashStable<StableHashingContext<'a>>,
+{
+    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
+        self.len().hash_stable(hcx, hasher);
+        for reloc in self.iter() {
+            reloc.hash_stable(hcx, hasher);
+        }
+    }
+}
+
+impl<'a> ToStableHashKey<StableHashingContext<'a>> for region::Scope {
+    type KeyType = region::Scope;
+
+    #[inline]
+    fn to_stable_hash_key(&self, _: &StableHashingContext<'a>) -> region::Scope {
+        *self
+    }
+}