Add HashStable_NoContext to simplify HashStable implementations in rustc_type_ir

Author: compiler-errors

compiler/rustc_ast/src/lib.rs

@@ -59,9 +59,7 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 /// Requirements for a `StableHashingContext` to be used in this crate.
 /// This is a hack to allow using the `HashStable_Generic` derive macro
 /// instead of implementing everything in `rustc_middle`.
-pub trait HashStableContext:
-    rustc_type_ir::HashStableContext + rustc_span::HashStableContext
-{
+pub trait HashStableContext: rustc_span::HashStableContext {
     fn hash_attr(&mut self, _: &ast::Attribute, hasher: &mut StableHasher);
 }
 

compiler/rustc_macros/src/hash_stable.rs

@@ -81,6 +81,50 @@ pub fn hash_stable_generic_derive(mut s: synstructure::Structure<'_>) -> proc_ma
     )
 }
 
+pub fn hash_stable_no_context_derive(
+    mut s: synstructure::Structure<'_>,
+) -> proc_macro2::TokenStream {
+    let generic: syn::GenericParam = parse_quote!(__CTX);
+    s.add_bounds(synstructure::AddBounds::Fields);
+    s.add_impl_generic(generic);
+    let body = s.each(|bi| {
+        let attrs = parse_attributes(bi.ast());
+        if attrs.ignore {
+            quote! {}
+        } else if let Some(project) = attrs.project {
+            quote! {
+                (&#bi.#project).hash_stable(__hcx, __hasher);
+            }
+        } else {
+            quote! {
+                #bi.hash_stable(__hcx, __hasher);
+            }
+        }
+    });
+
+    let discriminant = match s.ast().data {
+        syn::Data::Enum(_) => quote! {
+            ::std::mem::discriminant(self).hash_stable(__hcx, __hasher);
+        },
+        syn::Data::Struct(_) => quote! {},
+        syn::Data::Union(_) => panic!("cannot derive on union"),
+    };
+
+    s.bound_impl(
+        quote!(::rustc_data_structures::stable_hasher::HashStable<__CTX>),
+        quote! {
+            #[inline]
+            fn hash_stable(
+                &self,
+                __hcx: &mut __CTX,
+                __hasher: &mut ::rustc_data_structures::stable_hasher::StableHasher) {
+                #discriminant
+                match *self { #body }
+            }
+        },
+    )
+}
+
 pub fn hash_stable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
     let generic: syn::GenericParam = parse_quote!('__ctx);
     s.add_bounds(synstructure::AddBounds::Generics);

compiler/rustc_macros/src/lib.rs

@@ -67,6 +67,13 @@ decl_derive!(
     [HashStable_Generic, attributes(stable_hasher)] =>
     hash_stable::hash_stable_generic_derive
 );
+decl_derive!(
+    [HashStable_NoContext] =>
+    /// `HashStable` implementation that has no `HashStableContext` bound and
+    /// which adds `where` bounds for `HashStable` based off of fields and not
+    /// generics. This is suitable for use in crates like `rustc_type_ir`.
+    hash_stable::hash_stable_no_context_derive
+);
 
 decl_derive!([Decodable] => serialize::decodable_derive);
 decl_derive!([Encodable] => serialize::encodable_derive);

compiler/rustc_query_system/src/ich/impls_syntax.rs

@@ -123,5 +123,3 @@ impl<'tcx> HashStable<StableHashingContext<'tcx>> for rustc_feature::Features {
         });
     }
 }
-
-impl<'ctx> rustc_type_ir::HashStableContext for StableHashingContext<'ctx> {}

compiler/rustc_type_ir/src/canonical.rs

@@ -2,18 +2,16 @@ use std::fmt;
 use std::hash::Hash;
 use std::ops::ControlFlow;
 
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-
 use crate::fold::{FallibleTypeFolder, TypeFoldable};
 use crate::visit::{TypeVisitable, TypeVisitor};
-use crate::{HashStableContext, Interner, UniverseIndex};
+use crate::{Interner, UniverseIndex};
 
 /// A "canonicalized" type `V` is one where all free inference
 /// variables have been rewritten to "canonical vars". These are
 /// numbered starting from 0 in order of first appearance.
 #[derive(derivative::Derivative)]
 #[derivative(Clone(bound = "V: Clone"), Hash(bound = "V: Hash"))]
-#[derive(TyEncodable, TyDecodable)]
+#[derive(TyEncodable, TyDecodable, HashStable_NoContext)]
 pub struct Canonical<I: Interner, V> {
     pub value: V,
     pub max_universe: UniverseIndex,
@@ -60,17 +58,6 @@ impl<I: Interner, V> Canonical<I, V> {
     }
 }
 
-impl<CTX: HashStableContext, I: Interner, V: HashStable<CTX>> HashStable<CTX> for Canonical<I, V>
-where
-    I::CanonicalVars: HashStable<CTX>,
-{
-    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        self.value.hash_stable(hcx, hasher);
-        self.max_universe.hash_stable(hcx, hasher);
-        self.variables.hash_stable(hcx, hasher);
-    }
-}
-
 impl<I: Interner, V: Eq> Eq for Canonical<I, V> {}
 
 impl<I: Interner, V: PartialEq> PartialEq for Canonical<I, V> {

compiler/rustc_type_ir/src/const_kind.rs

@@ -1,8 +1,6 @@
-use rustc_data_structures::stable_hasher::HashStable;
-use rustc_data_structures::stable_hasher::StableHasher;
 use std::fmt;
 
-use crate::{DebruijnIndex, DebugWithInfcx, HashStableContext, InferCtxtLike, Interner, WithInfcx};
+use crate::{DebruijnIndex, DebugWithInfcx, InferCtxtLike, Interner, WithInfcx};
 
 use self::ConstKind::*;
 
@@ -16,7 +14,7 @@ use self::ConstKind::*;
     Ord = "feature_allow_slow_enum",
     Hash(bound = "")
 )]
-#[derive(TyEncodable, TyDecodable)]
+#[derive(TyEncodable, TyDecodable, HashStable_NoContext)]
 pub enum ConstKind<I: Interner> {
     /// A const generic parameter.
     Param(I::ParamConst),
@@ -47,48 +45,6 @@ pub enum ConstKind<I: Interner> {
     Expr(I::ExprConst),
 }
 
-const fn const_kind_discriminant<I: Interner>(value: &ConstKind<I>) -> usize {
-    match value {
-        Param(_) => 0,
-        Infer(_) => 1,
-        Bound(_, _) => 2,
-        Placeholder(_) => 3,
-        Unevaluated(_) => 4,
-        Value(_) => 5,
-        Error(_) => 6,
-        Expr(_) => 7,
-    }
-}
-
-impl<CTX: HashStableContext, I: Interner> HashStable<CTX> for ConstKind<I>
-where
-    I::ParamConst: HashStable<CTX>,
-    I::InferConst: HashStable<CTX>,
-    I::BoundConst: HashStable<CTX>,
-    I::PlaceholderConst: HashStable<CTX>,
-    I::AliasConst: HashStable<CTX>,
-    I::ValueConst: HashStable<CTX>,
-    I::ErrorGuaranteed: HashStable<CTX>,
-    I::ExprConst: HashStable<CTX>,
-{
-    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        const_kind_discriminant(self).hash_stable(hcx, hasher);
-        match self {
-            Param(p) => p.hash_stable(hcx, hasher),
-            Infer(i) => i.hash_stable(hcx, hasher),
-            Bound(d, b) => {
-                d.hash_stable(hcx, hasher);
-                b.hash_stable(hcx, hasher);
-            }
-            Placeholder(p) => p.hash_stable(hcx, hasher),
-            Unevaluated(u) => u.hash_stable(hcx, hasher),
-            Value(v) => v.hash_stable(hcx, hasher),
-            Error(e) => e.hash_stable(hcx, hasher),
-            Expr(e) => e.hash_stable(hcx, hasher),
-        }
-    }
-}
-
 impl<I: Interner> PartialEq for ConstKind<I> {
     fn eq(&self, other: &Self) -> bool {
         match (self, other) {

compiler/rustc_type_ir/src/lib.rs

@@ -47,9 +47,6 @@ pub use region_kind::*;
 pub use ty_info::*;
 pub use ty_kind::*;
 
-/// Needed so we can use #[derive(HashStable_Generic)]
-pub trait HashStableContext {}
-
 rustc_index::newtype_index! {
     /// A [De Bruijn index][dbi] is a standard means of representing
     /// regions (and perhaps later types) in a higher-ranked setting. In
@@ -90,7 +87,7 @@ rustc_index::newtype_index! {
     /// is the outer fn.
     ///
     /// [dbi]: https://en.wikipedia.org/wiki/De_Bruijn_index
-    #[derive(HashStable_Generic)]
+    #[derive(HashStable_NoContext)]
     #[debug_format = "DebruijnIndex({})"]
     pub struct DebruijnIndex {
         const INNERMOST = 0;
@@ -173,7 +170,7 @@ pub fn debug_bound_var<T: std::fmt::Write>(
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Decodable, Encodable, Hash, HashStable_Generic)]
+#[derive(Copy, Clone, PartialEq, Eq, Decodable, Encodable, Hash, HashStable_NoContext)]
 #[rustc_pass_by_value]
 pub enum Variance {
     Covariant,     // T<A> <: T<B> iff A <: B -- e.g., function return type
@@ -289,7 +286,7 @@ 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)]
+    #[derive(HashStable_NoContext)]
     #[debug_format = "U{}"]
     pub struct UniverseIndex {}
 }

compiler/rustc_type_ir/src/predicate_kind.rs

@@ -1,16 +1,15 @@
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use std::fmt;
 use std::ops::ControlFlow;
 
 use crate::fold::{FallibleTypeFolder, TypeFoldable};
 use crate::visit::{TypeVisitable, TypeVisitor};
-use crate::{HashStableContext, Interner};
+use crate::Interner;
 
 /// A clause is something that can appear in where bounds or be inferred
 /// by implied bounds.
 #[derive(derivative::Derivative)]
 #[derivative(Clone(bound = ""), Hash(bound = ""))]
-#[derive(TyEncodable, TyDecodable)]
+#[derive(TyEncodable, TyDecodable, HashStable_NoContext)]
 pub enum ClauseKind<I: Interner> {
     /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
     /// the `Self` type of the trait reference and `A`, `B`, and `C`
@@ -67,45 +66,6 @@ impl<I: Interner> PartialEq for ClauseKind<I> {
 
 impl<I: Interner> Eq for ClauseKind<I> {}
 
-fn clause_kind_discriminant<I: Interner>(value: &ClauseKind<I>) -> usize {
-    match value {
-        ClauseKind::Trait(_) => 0,
-        ClauseKind::RegionOutlives(_) => 1,
-        ClauseKind::TypeOutlives(_) => 2,
-        ClauseKind::Projection(_) => 3,
-        ClauseKind::ConstArgHasType(_, _) => 4,
-        ClauseKind::WellFormed(_) => 5,
-        ClauseKind::ConstEvaluatable(_) => 6,
-    }
-}
-
-impl<CTX: HashStableContext, I: Interner> HashStable<CTX> for ClauseKind<I>
-where
-    I::Ty: HashStable<CTX>,
-    I::Const: HashStable<CTX>,
-    I::GenericArg: HashStable<CTX>,
-    I::TraitPredicate: HashStable<CTX>,
-    I::ProjectionPredicate: HashStable<CTX>,
-    I::TypeOutlivesPredicate: HashStable<CTX>,
-    I::RegionOutlivesPredicate: HashStable<CTX>,
-{
-    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        clause_kind_discriminant(self).hash_stable(hcx, hasher);
-        match self {
-            ClauseKind::Trait(p) => p.hash_stable(hcx, hasher),
-            ClauseKind::RegionOutlives(p) => p.hash_stable(hcx, hasher),
-            ClauseKind::TypeOutlives(p) => p.hash_stable(hcx, hasher),
-            ClauseKind::Projection(p) => p.hash_stable(hcx, hasher),
-            ClauseKind::ConstArgHasType(c, t) => {
-                c.hash_stable(hcx, hasher);
-                t.hash_stable(hcx, hasher);
-            }
-            ClauseKind::WellFormed(t) => t.hash_stable(hcx, hasher),
-            ClauseKind::ConstEvaluatable(c) => c.hash_stable(hcx, hasher),
-        }
-    }
-}
-
 impl<I: Interner> TypeFoldable<I> for ClauseKind<I>
 where
     I::Ty: TypeFoldable<I>,
@@ -161,7 +121,7 @@ where
 
 #[derive(derivative::Derivative)]
 #[derivative(Clone(bound = ""), Hash(bound = ""))]
-#[derive(TyEncodable, TyDecodable)]
+#[derive(TyEncodable, TyDecodable, HashStable_NoContext)]
 pub enum PredicateKind<I: Interner> {
     /// Prove a clause
     Clause(ClauseKind<I>),
@@ -239,56 +199,6 @@ impl<I: Interner> PartialEq for PredicateKind<I> {
 
 impl<I: Interner> Eq for PredicateKind<I> {}
 
-fn predicate_kind_discriminant<I: Interner>(value: &PredicateKind<I>) -> usize {
-    match value {
-        PredicateKind::Clause(_) => 0,
-        PredicateKind::ObjectSafe(_) => 1,
-        PredicateKind::ClosureKind(_, _, _) => 2,
-        PredicateKind::Subtype(_) => 3,
-        PredicateKind::Coerce(_) => 4,
-        PredicateKind::ConstEquate(_, _) => 5,
-        PredicateKind::Ambiguous => 6,
-        PredicateKind::AliasRelate(_, _, _) => 7,
-    }
-}
-
-impl<CTX: HashStableContext, I: Interner> HashStable<CTX> for PredicateKind<I>
-where
-    I::DefId: HashStable<CTX>,
-    I::Const: HashStable<CTX>,
-    I::GenericArgs: HashStable<CTX>,
-    I::Term: HashStable<CTX>,
-    I::CoercePredicate: HashStable<CTX>,
-    I::SubtypePredicate: HashStable<CTX>,
-    I::ClosureKind: HashStable<CTX>,
-    ClauseKind<I>: HashStable<CTX>,
-{
-    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        predicate_kind_discriminant(self).hash_stable(hcx, hasher);
-        match self {
-            PredicateKind::Clause(p) => p.hash_stable(hcx, hasher),
-            PredicateKind::ObjectSafe(d) => d.hash_stable(hcx, hasher),
-            PredicateKind::ClosureKind(d, g, k) => {
-                d.hash_stable(hcx, hasher);
-                g.hash_stable(hcx, hasher);
-                k.hash_stable(hcx, hasher);
-            }
-            PredicateKind::Subtype(p) => p.hash_stable(hcx, hasher),
-            PredicateKind::Coerce(p) => p.hash_stable(hcx, hasher),
-            PredicateKind::ConstEquate(c1, c2) => {
-                c1.hash_stable(hcx, hasher);
-                c2.hash_stable(hcx, hasher);
-            }
-            PredicateKind::Ambiguous => {}
-            PredicateKind::AliasRelate(t1, t2, r) => {
-                t1.hash_stable(hcx, hasher);
-                t2.hash_stable(hcx, hasher);
-                r.hash_stable(hcx, hasher);
-            }
-        }
-    }
-}
-
 impl<I: Interner> TypeFoldable<I> for PredicateKind<I>
 where
     I::DefId: TypeFoldable<I>,
@@ -361,7 +271,7 @@ where
 }
 
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Copy)]
-#[derive(HashStable_Generic, Encodable, Decodable)]
+#[derive(HashStable_NoContext, Encodable, Decodable)]
 pub enum AliasRelationDirection {
     Equate,
     Subtype,

compiler/rustc_type_ir/src/region_kind.rs

@@ -1,8 +1,7 @@
-use rustc_data_structures::stable_hasher::HashStable;
-use rustc_data_structures::stable_hasher::StableHasher;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use std::fmt;
 
-use crate::{DebruijnIndex, DebugWithInfcx, HashStableContext, InferCtxtLike, Interner, WithInfcx};
+use crate::{DebruijnIndex, DebugWithInfcx, InferCtxtLike, Interner, WithInfcx};
 
 use self::RegionKind::*;
 
@@ -250,7 +249,7 @@ impl<I: Interner> fmt::Debug for RegionKind<I> {
 }
 
 // This is not a derived impl because a derive would require `I: HashStable`
-impl<CTX: HashStableContext, I: Interner> HashStable<CTX> for RegionKind<I>
+impl<CTX, I: Interner> HashStable<CTX> for RegionKind<I>
 where
     I::EarlyBoundRegion: HashStable<CTX>,
     I::BoundRegion: HashStable<CTX>,