rework interning to have a Configuration

This will permit GATs so that interned values
can carry lifetimes.

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

@@ -55,8 +55,10 @@ impl InternedStruct {
     fn generate_interned(&self) -> syn::Result<TokenStream> {
         self.validate_interned()?;
         let id_struct = self.the_struct_id();
+        let config_struct = self.config_struct();
         let data_struct = self.data_struct();
-        let ingredients_for_impl = self.ingredients_for_impl();
+        let configuration_impl = self.configuration_impl(&data_struct.ident, &config_struct.ident);
+        let ingredients_for_impl = self.ingredients_for_impl(&config_struct.ident);
         let as_id_impl = self.as_id_impl();
         let named_fields_impl = self.inherent_impl_for_named_fields();
         let salsa_struct_in_db_impl = self.salsa_struct_in_db_impl();
@@ -64,6 +66,8 @@ impl InternedStruct {
 
         Ok(quote! {
             #id_struct
+            #config_struct
+            #configuration_impl
             #data_struct
             #ingredients_for_impl
             #as_id_impl
@@ -113,6 +117,20 @@ impl InternedStruct {
         }
     }
 
+    fn configuration_impl(
+        &self,
+        data_struct: &syn::Ident,
+        config_struct: &syn::Ident,
+    ) -> syn::ItemImpl {
+        parse_quote_spanned!(
+            config_struct.span() =>
+
+            impl salsa::interned::Configuration for #config_struct {
+                type Data = #data_struct;
+            }
+        )
+    }
+
     /// If this is an interned struct, then generate methods to access each field,
     /// as well as a `new` method.
     fn inherent_impl_for_named_fields(&self) -> syn::ItemImpl {
@@ -186,15 +204,14 @@ impl InternedStruct {
     /// Generates an impl of `salsa::storage::IngredientsFor`.
     ///
     /// For a memoized type, the only ingredient is an `InternedIngredient`.
-    fn ingredients_for_impl(&self) -> syn::ItemImpl {
+    fn ingredients_for_impl(&self, config_struct: &syn::Ident) -> syn::ItemImpl {
         let id_ident = self.the_ident();
         let debug_name = crate::literal(id_ident);
         let jar_ty = self.jar_ty();
-        let data_ident = self.data_ident();
         parse_quote! {
             impl salsa::storage::IngredientsFor for #id_ident {
                 type Jar = #jar_ty;
-                type Ingredients = salsa::interned::InternedIngredient<#data_ident>;
+                type Ingredients = salsa::interned::InternedIngredient<#config_struct>;
 
                 fn create_ingredients<DB>(
                     routes: &mut salsa::routes::Routes<DB>,

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

@@ -293,6 +293,7 @@ fn fn_struct(args: &FnArgs, item_fn: &syn::ItemFn) -> syn::Result<(syn::Type, To
     let struct_item_ident = &struct_item.ident;
     let config_ty: syn::Type = parse_quote!(#struct_item_ident);
     let configuration_impl = configuration.to_impl(&config_ty);
+    let interned_configuration_impl = interned_configuration_impl(item_fn, &config_ty);
     let ingredients_for_impl = ingredients_for_impl(args, item_fn, &config_ty);
     let item_impl = setter_impl(args, item_fn, &config_ty)?;
 
@@ -301,22 +302,27 @@ fn fn_struct(args: &FnArgs, item_fn: &syn::ItemFn) -> syn::Result<(syn::Type, To
         quote! {
             #struct_item
             #configuration_impl
+            #interned_configuration_impl
             #ingredients_for_impl
             #item_impl
         },
     ))
 }
 
-/// Returns the key type for this tracked function.
-/// This is a tuple of all the argument types (apart from the database).
-fn key_tuple_ty(item_fn: &syn::ItemFn) -> syn::Type {
+fn interned_configuration_impl(item_fn: &syn::ItemFn, config_ty: &syn::Type) -> syn::ItemImpl {
     let arg_tys = item_fn.sig.inputs.iter().skip(1).map(|arg| match arg {
         syn::FnArg::Receiver(_) => unreachable!(),
         syn::FnArg::Typed(pat_ty) => pat_ty.ty.clone(),
     });
 
+    let intern_data_ty: syn::Type = parse_quote!(
+        (#(#arg_tys),*)
+    );
+
     parse_quote!(
-        (#(#arg_tys,)*)
+        impl salsa::interned::Configuration for #config_ty {
+            type Data = #intern_data_ty;
+        }
     )
 }
 
@@ -324,17 +330,15 @@ fn configuration_struct(item_fn: &syn::ItemFn) -> syn::ItemStruct {
     let fn_name = item_fn.sig.ident.clone();
     let visibility = &item_fn.vis;
 
-    let salsa_struct_ty = salsa_struct_ty(item_fn);
     let intern_map: syn::Type = match function_type(item_fn) {
         FunctionType::Constant => {
-            parse_quote! { salsa::interned::IdentityInterner<()> }
+            parse_quote! { salsa::interned::IdentityInterner<Self> }
         }
         FunctionType::SalsaStruct => {
-            parse_quote! { salsa::interned::IdentityInterner<#salsa_struct_ty> }
+            parse_quote! { salsa::interned::IdentityInterner<Self> }
         }
         FunctionType::RequiresInterning => {
-            let key_ty = key_tuple_ty(item_fn);
-            parse_quote! { salsa::interned::InternedIngredient<#key_ty> }
+            parse_quote! { salsa::interned::InternedIngredient<Self> }
         }
     };
 
@@ -389,7 +393,24 @@ fn fn_configuration(args: &FnArgs, item_fn: &syn::ItemFn) -> Configuration {
 
     let fn_ty = item_fn.sig.ident.clone();
 
-    let indices = (0..item_fn.sig.inputs.len() - 1).map(Literal::usize_unsuffixed);
+    // During recovery or execution, we are invoked with a `salsa::Id`
+    // that represents the interned value. We convert it back to a key
+    // which is either a single value (if there is one argument)
+    // or a tuple of values (if multiple arugments). `key_var` is the variable
+    // name that will store this result, and `key_splat` is a set of tokens
+    // that will convert it into one or multiple arguments (e.g., `key_var` if there
+    // is one argument or `key_var.0, key_var.1` if 2) that can be pasted into a function call.
+    let key_var = syn::Ident::new("__key", item_fn.span());
+    let key_fields = item_fn.sig.inputs.len() - 1;
+    let key_splat = if key_fields == 1 {
+        quote!(#key_var)
+    } else {
+        let indices = (0..key_fields)
+            .map(Literal::usize_unsuffixed)
+            .collect::<Vec<_>>();
+        quote!(#(__key.#indices),*)
+    };
+
     let (cycle_strategy, recover_fn) = if let Some(recovery_fn) = &args.recovery_fn {
         // Create the `recover_from_cycle` function, which (a) maps from the interned id to the actual
         // keys and then (b) invokes the recover function itself.
@@ -400,8 +421,8 @@ fn fn_configuration(args: &FnArgs, item_fn: &syn::ItemFn) -> Configuration {
                 let (__jar, __runtime) = <_ as salsa::storage::HasJar<#jar_ty>>::jar(__db);
                 let __ingredients =
                     <_ as salsa::storage::HasIngredientsFor<#fn_ty>>::ingredient(__jar);
-                let __key = __ingredients.intern_map.data(__runtime, __id).clone();
-                #recovery_fn(__db, __cycle, #(__key.#indices),*)
+                let #key_var = __ingredients.intern_map.data(__runtime, __id).clone();
+                #recovery_fn(__db, __cycle, #key_splat)
             }
         };
         (cycle_strategy, cycle_fullback)
@@ -425,7 +446,6 @@ fn fn_configuration(args: &FnArgs, item_fn: &syn::ItemFn) -> Configuration {
 
     // Create the `execute` function, which (a) maps from the interned id to the actual
     // keys and then (b) invokes the function itself (which we embed within).
-    let indices = (0..item_fn.sig.inputs.len() - 1).map(Literal::usize_unsuffixed);
     let execute_fn = parse_quote! {
         fn execute<'db>(__db: &'db salsa::function::DynDb<'db, Self>, __id: salsa::Id) -> Self::Value<'db> {
             #inner_fn
@@ -433,8 +453,8 @@ fn fn_configuration(args: &FnArgs, item_fn: &syn::ItemFn) -> Configuration {
             let (__jar, __runtime) = <_ as salsa::storage::HasJar<#jar_ty>>::jar(__db);
             let __ingredients =
                 <_ as salsa::storage::HasIngredientsFor<#fn_ty>>::ingredient(__jar);
-            let __key = __ingredients.intern_map.data(__runtime, __id).clone();
-            #inner_fn_name(__db, #(__key.#indices),*)
+            let #key_var = __ingredients.intern_map.data(__runtime, __id).clone();
+            #inner_fn_name(__db, #key_splat)
         }
     };
 

components/salsa-2022/src/interned.rs

@@ -18,25 +18,29 @@ use super::ingredient::Ingredient;
 use super::routes::IngredientIndex;
 use super::Revision;
 
+pub trait Configuration {
+    type Data: InternedData;
+}
+
 pub trait InternedData: Sized + Eq + Hash + Clone {}
 impl<T: Eq + Hash + Clone> InternedData for T {}
 
 /// The interned ingredient has the job of hashing values of type `Data` to produce an `Id`.
 /// It used to store interned structs but also to store the id fields of a tracked struct.
 /// Interned values endure until they are explicitly removed in some way.
-pub struct InternedIngredient<Data: InternedData> {
+pub struct InternedIngredient<C: Configuration> {
     /// Index of this ingredient in the database (used to construct database-ids, etc).
     ingredient_index: IngredientIndex,
 
     /// Maps from data to the existing interned id for that data.
     ///
     /// Deadlock requirement: We access `value_map` while holding lock on `key_map`, but not vice versa.
-    key_map: FxDashMap<Data, Id>,
+    key_map: FxDashMap<C::Data, Id>,
 
     /// Maps from an interned id to its data.
     ///
     /// Deadlock requirement: We access `value_map` while holding lock on `key_map`, but not vice versa.
-    value_map: FxDashMap<Id, Box<Data>>,
+    value_map: FxDashMap<Id, Box<C::Data>>,
 
     /// counter for the next id.
     counter: AtomicCell<u32>,
@@ -52,14 +56,14 @@ pub struct InternedIngredient<Data: InternedData> {
     /// references to that data floating about that are tied to the lifetime of some
     /// `&db` reference. This queue itself is not freed until we have an `&mut db` reference,
     /// guaranteeing that there are no more references to it.
-    deleted_entries: SegQueue<Box<Data>>,
+    deleted_entries: SegQueue<Box<C::Data>>,
 
     debug_name: &'static str,
 }
 
-impl<Data> InternedIngredient<Data>
+impl<C> InternedIngredient<C>
 where
-    Data: InternedData,
+    C: Configuration,
 {
     pub fn new(ingredient_index: IngredientIndex, debug_name: &'static str) -> Self {
         Self {
@@ -78,7 +82,7 @@ where
     /// * `id` is the interned id
     /// * `b` is a boolean, `true` indicates this fn call added `data` to the interning table;
     ///   `false` indicates it was already present
-    pub(crate) fn intern_full(&self, runtime: &Runtime, data: Data) -> (Id, bool) {
+    pub(crate) fn intern_full(&self, runtime: &Runtime, data: C::Data) -> (Id, bool) {
         runtime.report_tracked_read(
             DependencyIndex::for_table(self.ingredient_index),
             Durability::MAX,
@@ -109,7 +113,7 @@ where
         }
     }
 
-    pub fn intern(&self, runtime: &Runtime, data: Data) -> Id {
+    pub fn intern(&self, runtime: &Runtime, data: C::Data) -> Id {
         self.intern_full(runtime, data).0
     }
 
@@ -125,7 +129,7 @@ where
     }
 
     #[track_caller]
-    pub fn data<'db>(&'db self, runtime: &'db Runtime, id: Id) -> &'db Data {
+    pub fn data<'db>(&'db self, runtime: &'db Runtime, id: Id) -> &'db C::Data {
         runtime.report_tracked_read(
             DependencyIndex::for_table(self.ingredient_index),
             Durability::MAX,
@@ -187,9 +191,9 @@ where
     }
 }
 
-impl<DB: ?Sized, Data> Ingredient<DB> for InternedIngredient<Data>
+impl<DB: ?Sized, C> Ingredient<DB> for InternedIngredient<C>
 where
-    Data: InternedData,
+    C: Configuration,
 {
     fn ingredient_index(&self) -> IngredientIndex {
         self.ingredient_index
@@ -247,28 +251,36 @@ where
     }
 }
 
-impl<Data> IngredientRequiresReset for InternedIngredient<Data>
+impl<C> IngredientRequiresReset for InternedIngredient<C>
 where
-    Data: InternedData,
+    C: Configuration,
 {
     const RESET_ON_NEW_REVISION: bool = false;
 }
 
-pub struct IdentityInterner<Id: AsId> {
-    data: PhantomData<Id>,
+pub struct IdentityInterner<C>
+where
+    C: Configuration,
+    C::Data: AsId,
+{
+    data: PhantomData<C>,
 }
 
-impl<Id: AsId> IdentityInterner<Id> {
+impl<C> IdentityInterner<C>
+where
+    C: Configuration,
+    C::Data: AsId,
+{
     #[allow(clippy::new_without_default)]
     pub fn new() -> Self {
         IdentityInterner { data: PhantomData }
     }
 
-    pub fn intern(&self, _runtime: &Runtime, id: Id) -> crate::Id {
+    pub fn intern(&self, _runtime: &Runtime, id: C::Data) -> crate::Id {
         id.as_id()
     }
 
-    pub fn data(&self, _runtime: &Runtime, id: crate::Id) -> (Id,) {
-        (Id::from_id(id),)
+    pub fn data(&self, _runtime: &Runtime, id: crate::Id) -> C::Data {
+        <C::Data>::from_id(id)
     }
 }

components/salsa-2022/src/tracked_struct.rs

@@ -110,6 +110,10 @@ struct TrackedStructKey {
     data_hash: u64,
 }
 
+impl crate::interned::Configuration for TrackedStructKey {
+    type Data = TrackedStructKey;
+}
+
 // ANCHOR: TrackedStructValue
 #[derive(Debug)]
 pub struct TrackedStructValue<C>