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.

1 files changed, 3 insertions, 2 deletions

diff --git a/compiler/rustc_builtin_macros/src/deriving/hash.rs b/compiler/rustc_builtin_macros/src/deriving/hash.rs
index 4eee573db42..6fea50feb2a 100644
--- a/compiler/rustc_builtin_macros/src/deriving/hash.rs
+++ b/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)