Inline derived hash function.

Because most of the other derived functions are inlined: `clone`,
`default`, `eq`, `partial_cmp`, `cmp`. The exception is `fmt`, but it
tends to not be on hot paths as much.

Author: nnethercote

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -1,7 +1,7 @@
 use crate::deriving::generic::ty::*;
 use crate::deriving::generic::*;
 use crate::deriving::{path_std, pathvec_std};
-use rustc_ast::{AttrVec, MetaItem, Mutability};
+use rustc_ast::{MetaItem, Mutability};
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
@@ -20,6 +20,7 @@ pub fn expand_deriving_hash(
     let typaram = sym::__H;
 
     let arg = Path::new_local(typaram);
+    let attrs = thin_vec![cx.attr_word(sym::inline, span)];
     let hash_trait_def = TraitDef {
         span,
         path,
@@ -33,7 +34,7 @@ pub fn expand_deriving_hash(
             explicit_self: true,
             nonself_args: vec![(Ref(Box::new(Path(arg)), Mutability::Mut), sym::state)],
             ret_ty: Unit,
-            attributes: AttrVec::new(),
+            attributes: attrs,
             fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
             combine_substructure: combine_substructure(Box::new(|a, b, c| {
                 hash_substructure(a, b, c)

tests/ui/deriving/deriving-all-codegen.stdout

@@ -44,6 +44,7 @@ impl ::core::default::Default for Empty {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Empty {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {}
 }
 #[automatically_derived]
@@ -113,6 +114,7 @@ impl ::core::default::Default for Point {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Point {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.x, state);
         ::core::hash::Hash::hash(&self.y, state)
@@ -198,6 +200,7 @@ impl ::core::default::Default for PackedPoint {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for PackedPoint {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&{ self.x }, state);
         ::core::hash::Hash::hash(&{ self.y }, state)
@@ -301,6 +304,7 @@ impl ::core::default::Default for Big {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Big {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.b1, state);
         ::core::hash::Hash::hash(&self.b2, state);
@@ -478,6 +482,7 @@ impl ::core::fmt::Debug for Unsized {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Unsized {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.0, state)
     }
@@ -529,6 +534,7 @@ impl ::core::fmt::Debug for PackedUnsizedU8 {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for PackedUnsizedU8 {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.0, state)
     }
@@ -584,6 +590,7 @@ impl<T: ::core::default::Default + Trait, U: ::core::default::Default>
 #[automatically_derived]
 impl<T: ::core::hash::Hash + Trait, U: ::core::hash::Hash> ::core::hash::Hash
     for Generic<T, U> where T::A: ::core::hash::Hash {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.t, state);
         ::core::hash::Hash::hash(&self.ta, state);
@@ -701,6 +708,7 @@ impl<T: ::core::hash::Hash + ::core::marker::Copy + Trait,
     U: ::core::hash::Hash + ::core::marker::Copy> ::core::hash::Hash for
     PackedGeneric<T, U> where T::A: ::core::hash::Hash + ::core::marker::Copy
     {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&{ self.0 }, state);
         ::core::hash::Hash::hash(&{ self.1 }, state);
@@ -795,6 +803,7 @@ impl ::core::fmt::Debug for Enum0 {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Enum0 {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         unsafe { ::core::intrinsics::unreachable() }
     }
@@ -861,6 +870,7 @@ impl ::core::fmt::Debug for Enum1 {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Enum1 {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         match self {
             Enum1::Single { x: __self_0 } =>
@@ -937,6 +947,7 @@ impl ::core::default::Default for Fieldless1 {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Fieldless1 {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {}
 }
 #[automatically_derived]
@@ -1004,6 +1015,7 @@ impl ::core::default::Default for Fieldless {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Fieldless {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         let __self_tag = ::core::intrinsics::discriminant_value(self);
         ::core::hash::Hash::hash(&__self_tag, state)
@@ -1095,6 +1107,7 @@ impl ::core::default::Default for Mixed {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Mixed {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         let __self_tag = ::core::intrinsics::discriminant_value(self);
         ::core::hash::Hash::hash(&__self_tag, state);
@@ -1224,6 +1237,7 @@ impl ::core::fmt::Debug for Fielded {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Fielded {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         let __self_tag = ::core::intrinsics::discriminant_value(self);
         ::core::hash::Hash::hash(&__self_tag, state);
@@ -1345,6 +1359,7 @@ impl<T: ::core::fmt::Debug, U: ::core::fmt::Debug> ::core::fmt::Debug for
 #[automatically_derived]
 impl<T: ::core::hash::Hash, U: ::core::hash::Hash> ::core::hash::Hash for
     EnumGeneric<T, U> {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         let __self_tag = ::core::intrinsics::discriminant_value(self);
         ::core::hash::Hash::hash(&__self_tag, state);