give fields a lifetime

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

@@ -135,11 +135,11 @@ impl TrackedStruct {
 
         parse_quote! {
             impl salsa::tracked_struct::Configuration for #config_ident {
-                type Fields = ( #(#field_tys,)* );
+                type Fields<'db> = ( #(#field_tys,)* );
                 type Revisions = [salsa::Revision; #arity];
 
                 #[allow(clippy::unused_unit)]
-                fn id_fields(fields: &Self::Fields) -> impl std::hash::Hash {
+                fn id_fields(fields: &Self::Fields<'_>) -> impl std::hash::Hash {
                     ( #( &fields.#id_field_indices ),* )
                 }
 
@@ -151,11 +151,11 @@ impl TrackedStruct {
                     [current_revision; #arity]
                 }
 
-                unsafe fn update_fields(
+                unsafe fn update_fields<'db>(
                     #current_revision: salsa::Revision,
                     #revisions: &mut Self::Revisions,
-                    #old_fields: *mut Self::Fields,
-                    #new_fields: Self::Fields,
+                    #old_fields: *mut Self::Fields<'db>,
+                    #new_fields: Self::Fields<'db>,
                 ) {
                     use salsa::update::helper::Fallback as _;
                     #update_fields

components/salsa-2022/src/tracked_struct.rs

@@ -24,7 +24,7 @@ mod tracked_field;
 /// to a struct.
 pub trait Configuration {
     /// A (possibly empty) tuple of the fields for this struct.
-    type Fields;
+    type Fields<'db>;
 
     /// A array of [`Revision`][] values, one per each of the value fields.
     /// When a struct is re-recreated in a new revision, the corresponding
@@ -32,7 +32,7 @@ pub trait Configuration {
     /// values have changed (or if the field is marked as `#[no_eq]`).
     type Revisions;
 
-    fn id_fields(fields: &Self::Fields) -> impl Hash;
+    fn id_fields(fields: &Self::Fields<'_>) -> impl Hash;
 
     /// Access the revision of a given value field.
     /// `field_index` will be between 0 and the number of value fields.
@@ -62,11 +62,11 @@ pub trait Configuration {
     /// Ensures that `old_fields` is fully updated and valid
     /// after it returns and that `revisions` has been updated
     /// for any field that changed.
-    unsafe fn update_fields(
+    unsafe fn update_fields<'db>(
         current_revision: Revision,
         revisions: &mut Self::Revisions,
-        old_fields: *mut Self::Fields,
-        new_fields: Self::Fields,
+        old_fields: *mut Self::Fields<'db>,
+        new_fields: Self::Fields<'db>,
     );
 }
 // ANCHOR_END: Configuration
@@ -140,7 +140,7 @@ where
 
     /// Fields of this tracked struct. They can change across revisions,
     /// but they do not change within a particular revision.
-    fields: C::Fields,
+    fields: C::Fields<'static>,
 
     /// The revision information for each field: when did this field last change.
     /// When tracked structs are re-created, this revision may be updated to the
@@ -156,6 +156,14 @@ impl<C> TrackedStructIngredient<C>
 where
     C: Configuration,
 {
+    unsafe fn to_static<'db>(&'db self, fields: C::Fields<'db>) -> C::Fields<'static> {
+        unsafe { std::mem::transmute(fields) }
+    }
+
+    unsafe fn to_self_ptr<'db>(&'db self, fields: *mut C::Fields<'static>) -> *mut C::Fields<'db> {
+        unsafe { std::mem::transmute(fields) }
+    }
+
     pub fn new(index: IngredientIndex, debug_name: &'static str) -> Self {
         Self {
             interned: InternedIngredient::new(index, debug_name),
@@ -199,7 +207,7 @@ where
     pub fn new_struct<'db>(
         &'db self,
         runtime: &'db Runtime,
-        fields: C::Fields,
+        fields: C::Fields<'db>,
     ) -> &'db TrackedStructValue<C> {
         let data_hash = crate::hash::hash(&C::id_fields(&fields));
 
@@ -226,7 +234,7 @@ where
                     struct_ingredient_index: self.struct_ingredient_index(),
                     created_at: current_revision,
                     durability: current_deps.durability,
-                    fields,
+                    fields: unsafe { self.to_static(fields) },
                     revisions: C::new_revisions(current_deps.changed_at),
                 },
             )
@@ -254,7 +262,7 @@ where
                         C::update_fields(
                             current_revision,
                             &mut data.revisions,
-                            std::ptr::addr_of_mut!(data.fields),
+                            self.to_self_ptr(std::ptr::addr_of_mut!(data.fields)),
                             fields,
                         );
                     }

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

@@ -31,10 +31,14 @@ impl<C> TrackedFieldIngredient<C>
 where
     C: Configuration,
 {
+    unsafe fn to_self_ref<'db>(&'db self, fields: &'db C::Fields<'static>) -> &'db C::Fields<'db> {
+        unsafe { std::mem::transmute(fields) }
+    }
+
     /// Access to this value field.
     /// Note that this function returns the entire tuple of value fields.
     /// The caller is responible for selecting the appropriate element.
-    pub fn field<'db>(&'db self, runtime: &'db Runtime, id: Id) -> &'db C::Fields {
+    pub fn field<'db>(&'db self, runtime: &'db Runtime, id: Id) -> &'db C::Fields<'db> {
         let data = self.struct_map.get(runtime, id);
 
         let changed_at = C::revision(&data.revisions, self.field_index);
@@ -48,7 +52,7 @@ where
             changed_at,
         );
 
-        &data.fields
+        unsafe { self.to_self_ref(&data.fields) }
     }
 }