Manually implement a more general HashStable for RustcVersion

dtolnay · dtolnay · commit 0fc378a6b3c4 · 2023-10-27T08:54:13.000-07:00
diff --git a/compiler/rustc_attr/src/lib.rs b/compiler/rustc_attr/src/lib.rs
@@ -27,6 +27,6 @@ pub use StabilityLevel::*;
 
 pub use rustc_ast::attr::*;
 
-pub(crate) use rustc_session::HashStableContext;
+pub(crate) use rustc_ast::HashStableContext;
 
 fluent_messages! { "../messages.ftl" }
diff --git a/compiler/rustc_session/src/version.rs b/compiler/rustc_session/src/version.rs
@@ -1,7 +1,8 @@
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use std::fmt::{self, Display};
 
 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[derive(HashStable_Generic)]
+//#[derive(HashStable_Generic)]
 pub struct RustcVersion {
     pub major: u16,
     pub minor: u16,
@@ -17,3 +18,16 @@ impl Display for RustcVersion {
         write!(formatter, "{}.{}.{}", self.major, self.minor, self.patch)
     }
 }
+
+// Handwritten because #[derive(HashStable_Generic)] would generate a stricter
+// `Ctx: rustc_session::HashStableContext` bound.
+impl<Ctx> HashStable<Ctx> for RustcVersion
+where
+    Ctx: rustc_ast::HashStableContext,
+{
+    fn hash_stable(&self, hcx: &mut Ctx, hasher: &mut StableHasher) {
+        self.major.hash_stable(hcx, hasher);
+        self.minor.hash_stable(hcx, hasher);
+        self.patch.hash_stable(hcx, hasher);
+    }
+}
