add a SalsaStructInDb trait

Not currently used anywhere,
but will be implemented by all salsa structs.

components/salsa-2022-macros/src/tracked_struct.rs

@@ -39,6 +39,7 @@ impl TrackedStruct {
         let id_struct = self.id_struct();
         let inherent_impl = self.tracked_inherent_impl();
         let ingredients_for_impl = self.tracked_struct_ingredients(&config_structs);
+        let salsa_struct_in_db_impl = self.salsa_struct_in_db_impl();
         let tracked_struct_in_db_impl = self.tracked_struct_in_db_impl();
         let as_id_impl = self.as_id_impl();
         Ok(quote! {
@@ -46,6 +47,7 @@ impl TrackedStruct {
             #id_struct
             #inherent_impl
             #ingredients_for_impl
+            #salsa_struct_in_db_impl
             #tracked_struct_in_db_impl
             #as_id_impl
             #(#config_impls)*
@@ -205,6 +207,19 @@ impl TrackedStruct {
         }
     }
 
+    /// Implementation of `SalsaStructInDb`.
+    fn salsa_struct_in_db_impl(&self) -> syn::ItemImpl {
+        let ident = self.id_ident();
+        let jar_ty = self.jar_ty();
+        parse_quote! {
+            impl<DB> salsa::salsa_struct::SalsaStructInDb<DB> for #ident
+            where
+                DB: ?Sized + salsa::DbWithJar<#jar_ty>,
+            {
+            }
+        }
+    }
+
     /// Implementation of `TrackedStructInDb`.
     fn tracked_struct_in_db_impl(&self) -> syn::ItemImpl {
         let ident = self.id_ident();

components/salsa-2022/src/lib.rs

@@ -17,6 +17,7 @@ pub mod plumbing;
 pub mod revision;
 pub mod routes;
 pub mod runtime;
+pub mod salsa_struct;
 pub mod storage;
 #[doc(hidden)]
 pub mod tracked_struct;

components/salsa-2022/src/salsa_struct.rs

@@ -0,0 +1,3 @@
+use crate::Database;
+
+pub trait SalsaStructInDb<DB: ?Sized + Database> {}

components/salsa-2022/src/tracked_struct.rs

@@ -4,6 +4,7 @@ use crate::{
     interned::{InternedData, InternedId, InternedIngredient},
     key::{DatabaseKeyIndex, DependencyIndex},
     runtime::{local_state::QueryInputs, Runtime},
+    salsa_struct::SalsaStructInDb,
     Database, IngredientIndex, Revision,
 };
 
@@ -13,7 +14,7 @@ impl<T: InternedId> TrackedStructId for T {}
 pub trait TrackedStructData: InternedData {}
 impl<T: InternedData> TrackedStructData for T {}
 
-pub trait TrackedStructInDb<DB: ?Sized + Database> {
+pub trait TrackedStructInDb<DB: ?Sized + Database>: SalsaStructInDb<DB> {
     fn database_key_index(self, db: &DB) -> DatabaseKeyIndex;
 }