give each function a SalsaStruct assoc type

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

@@ -1,5 +1,6 @@
 pub(crate) struct Configuration {
     pub(crate) jar_ty: syn::Type,
+    pub(crate) salsa_struct_ty: syn::Type,
     pub(crate) key_ty: syn::Type,
     pub(crate) value_ty: syn::Type,
     pub(crate) cycle_strategy: CycleRecoveryStrategy,
@@ -12,6 +13,7 @@ impl Configuration {
     pub(crate) fn to_impl(&self, self_ty: &syn::Type) -> syn::ItemImpl {
         let Configuration {
             jar_ty,
+            salsa_struct_ty,
             key_ty,
             value_ty,
             cycle_strategy,
@@ -22,6 +24,7 @@ impl Configuration {
         parse_quote! {
             impl salsa::function::Configuration for #self_ty {
                 type Jar = #jar_ty;
+                type SalsaStruct = #salsa_struct_ty;
                 type Key = #key_ty;
                 type Value = #value_ty;
                 const CYCLE_STRATEGY: salsa::cycle::CycleRecoveryStrategy = #cycle_strategy;

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

@@ -221,6 +221,7 @@ impl SalsaStruct {
                 let item_impl: syn::ItemImpl = parse_quote! {
                     impl salsa::function::Configuration for #config_name {
                         type Jar = #jar_ty;
+                        type SalsaStruct = #ident;
                         type Key = #ident;
                         type Value = #value_field_ty;
                         const CYCLE_STRATEGY: salsa::cycle::CycleRecoveryStrategy = salsa::cycle::CycleRecoveryStrategy::Panic;

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

@@ -101,10 +101,7 @@ fn configuration_struct(item_fn: &syn::ItemFn) -> syn::ItemStruct {
 
     parse_quote! {
         #[allow(non_camel_case_types)]
-        #visibility struct #fn_name
+        #visibility struct #fn_name {
-        where
-            #salsa_struct_ty: salsa::AsId, // require that the salsa struct is, well, a salsa struct!
-        {
             intern_map: #intern_map,
             function: salsa::function::FunctionIngredient<Self>,
         }
@@ -127,10 +124,11 @@ fn salsa_struct_ty(item_fn: &syn::ItemFn) -> &syn::Type {
 
 fn fn_configuration(args: &Args, item_fn: &syn::ItemFn) -> Configuration {
     let jar_ty = args.jar_ty();
+    let salsa_struct_ty = salsa_struct_ty(item_fn).clone();
     let key_ty = if requires_interning(item_fn) {
         parse_quote!(salsa::id::Id)
     } else {
-        salsa_struct_ty(item_fn).clone()
+        salsa_struct_ty.clone()
     };
     let value_ty = configuration::value_ty(&item_fn.sig);
 
@@ -187,6 +185,7 @@ fn fn_configuration(args: &Args, item_fn: &syn::ItemFn) -> Configuration {
 
     Configuration {
         jar_ty,
+        salsa_struct_ty,
         key_ty,
         value_ty,
         cycle_strategy,

components/salsa-2022/src/function.rs

@@ -9,6 +9,7 @@ use crate::{
     jar::Jar,
     key::{DatabaseKeyIndex, DependencyIndex},
     runtime::local_state::QueryInputs,
+    salsa_struct::SalsaStructInDb,
     Cycle, DbWithJar, Id, Revision,
 };
 
@@ -69,6 +70,11 @@ pub struct FunctionIngredient<C: Configuration> {
 pub trait Configuration {
     type Jar: for<'db> Jar<'db>;
 
+    /// The "salsa struct type" that this function is associated with.
+    /// This can be just `salsa::Id` for functions that intern their arguments
+    /// and are not clearly associated with any one salsa struct.
+    type SalsaStruct: for<'db> SalsaStructInDb<DynDb<'db, Self>>;
+
     /// What key is used to index the memo. Typically a salsa struct id,
     /// but if this memoized function has multiple argments it will be a `salsa::Id`
     /// that results from interning those arguments.