Use HashStable_Generic in rustc_type_ir

A lot of the types in this crate implemented HashStable directly to
avoid circular dependencies. One way around that is to use
HashStable_Generic. We adopt that here to avoid a lot of boilerplate.

This doesn't update all the types, because some would require
`I: Interner + HashStable`.

5 files changed, 16 insertions, 43 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 68ea8b51c55..90bcc2e4be4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3958,6 +3958,7 @@ dependencies = [
  "rustc_session",
  "rustc_span",
  "rustc_target",
+ "rustc_type_ir",
  "smallvec",
  "thin-vec",
  "tracing",
diff --git a/compiler/rustc_query_system/Cargo.toml b/compiler/rustc_query_system/Cargo.toml
index bafc6b0a082..d7599a56c0b 100644
--- a/compiler/rustc_query_system/Cargo.toml
+++ b/compiler/rustc_query_system/Cargo.toml
@@ -21,6 +21,7 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
+rustc_type_ir = { path = "../rustc_type_ir" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
 thin-vec = "0.2.8"
 tracing = "0.1"
diff --git a/compiler/rustc_query_system/src/ich/impls_syntax.rs b/compiler/rustc_query_system/src/ich/impls_syntax.rs
index d7732cb1825..0bc811eb044 100644
--- a/compiler/rustc_query_system/src/ich/impls_syntax.rs
+++ b/compiler/rustc_query_system/src/ich/impls_syntax.rs
@@ -148,3 +148,5 @@ impl<'tcx> HashStable<StableHashingContext<'tcx>> for rustc_feature::Features {
         });
     }
 }
+
+impl<'ctx> rustc_type_ir::HashStableContext for StableHashingContext<'ctx> {}
diff --git a/compiler/rustc_type_ir/src/lib.rs b/compiler/rustc_type_ir/src/lib.rs
index 5488bca8f47..da30344ef7e 100644
--- a/compiler/rustc_type_ir/src/lib.rs
+++ b/compiler/rustc_type_ir/src/lib.rs
@@ -23,6 +23,9 @@ pub mod sty;
 pub use codec::*;
 pub use sty::*;
 
+/// Needed so we can use #[derive(HashStable_Generic)]
+pub trait HashStableContext {}
+
 pub trait Interner {
     type AdtDef: Clone + Debug + Hash + PartialEq + Eq + PartialOrd + Ord;
     type SubstsRef: Clone + Debug + Hash + PartialEq + Eq + PartialOrd + Ord;
@@ -295,6 +298,7 @@ rustc_index::newtype_index! {
     /// is the outer fn.
     ///
     /// [dbi]: https://en.wikipedia.org/wiki/De_Bruijn_index
+    #[derive(HashStable_Generic)]
     pub struct DebruijnIndex {
         DEBUG_FORMAT = "DebruijnIndex({})",
         const INNERMOST = 0,
@@ -366,7 +370,7 @@ impl DebruijnIndex {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
-#[derive(Encodable, Decodable)]
+#[derive(Encodable, Decodable, HashStable_Generic)]
 pub enum IntTy {
     Isize,
     I8,
@@ -413,7 +417,7 @@ impl IntTy {
 }
 
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Copy, Debug)]
-#[derive(Encodable, Decodable)]
+#[derive(Encodable, Decodable, HashStable_Generic)]
 pub enum UintTy {
     Usize,
     U8,
@@ -460,7 +464,7 @@ impl UintTy {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
-#[derive(Encodable, Decodable)]
+#[derive(Encodable, Decodable, HashStable_Generic)]
 pub enum FloatTy {
     F32,
     F64,
@@ -597,7 +601,7 @@ impl UnifyKey for FloatVid {
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Decodable, Encodable, Hash)]
+#[derive(Copy, Clone, PartialEq, Decodable, Encodable, Hash, HashStable_Generic)]
 #[rustc_pass_by_value]
 pub enum Variance {
     Covariant,     // T<A> <: T<B> iff A <: B -- e.g., function return type
@@ -666,30 +670,6 @@ impl Variance {
     }
 }
 
-impl<CTX> HashStable<CTX> for DebruijnIndex {
-    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        self.as_u32().hash_stable(ctx, hasher);
-    }
-}
-
-impl<CTX> HashStable<CTX> for IntTy {
-    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        discriminant(self).hash_stable(ctx, hasher);
-    }
-}
-
-impl<CTX> HashStable<CTX> for UintTy {
-    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        discriminant(self).hash_stable(ctx, hasher);
-    }
-}
-
-impl<CTX> HashStable<CTX> for FloatTy {
-    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        discriminant(self).hash_stable(ctx, hasher);
-    }
-}
-
 impl<CTX> HashStable<CTX> for InferTy {
     fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
         use InferTy::*;
@@ -703,12 +683,6 @@ impl<CTX> HashStable<CTX> for InferTy {
     }
 }
 
-impl<CTX> HashStable<CTX> for Variance {
-    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        discriminant(self).hash_stable(ctx, hasher);
-    }
-}
-
 impl fmt::Debug for IntVarValue {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
@@ -811,6 +785,7 @@ rustc_index::newtype_index! {
     /// declared, but a type name in a non-zero universe is a placeholder
     /// type -- an idealized representative of "types in general" that we
     /// use for checking generic functions.
+    #[derive(HashStable_Generic)]
     pub struct UniverseIndex {
         DEBUG_FORMAT = "U{}",
     }
@@ -850,9 +825,3 @@ impl UniverseIndex {
         self.private < other.private
     }
 }
-
-impl<CTX> HashStable<CTX> for UniverseIndex {
-    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        self.private.hash_stable(ctx, hasher);
-    }
-}
diff --git a/compiler/rustc_type_ir/src/sty.rs b/compiler/rustc_type_ir/src/sty.rs
index 74737e30bb4..26e48d2d214 100644
--- a/compiler/rustc_type_ir/src/sty.rs
+++ b/compiler/rustc_type_ir/src/sty.rs
@@ -3,7 +3,6 @@
 use std::cmp::{Eq, Ord, Ordering, PartialEq, PartialOrd};
 use std::{fmt, hash};
 
-use crate::DebruijnIndex;
 use crate::FloatTy;
 use crate::IntTy;
 use crate::Interner;
@@ -11,6 +10,7 @@ use crate::TyDecoder;
 use crate::TyEncoder;
 use crate::UintTy;
 use crate::UniverseIndex;
+use crate::{DebruijnIndex, HashStableContext};
 
 use self::RegionKind::*;
 use self::TyKind::*;
@@ -774,7 +774,7 @@ where
 
 // This is not a derived impl because a derive would require `I: HashStable`
 #[allow(rustc::usage_of_ty_tykind)]
-impl<CTX, I: Interner> HashStable<CTX> for TyKind<I>
+impl<CTX: HashStableContext, I: Interner> HashStable<CTX> for TyKind<I>
 where
     I::AdtDef: HashStable<CTX>,
     I::DefId: HashStable<CTX>,
@@ -1286,7 +1286,7 @@ where
 }
 
 // This is not a derived impl because a derive would require `I: HashStable`
-impl<CTX, I: Interner> HashStable<CTX> for RegionKind<I>
+impl<CTX: HashStableContext, I: Interner> HashStable<CTX> for RegionKind<I>
 where
     I::EarlyBoundRegion: HashStable<CTX>,
     I::BoundRegion: HashStable<CTX>,