Fix returns(deref | as_ref | as_deref) in tracked methods (#857)

Author: MichaReiser

components/salsa-macro-rules/src/setup_input_struct.rs

@@ -110,7 +110,7 @@ macro_rules! setup_input_struct {
 
                 pub fn ingredient_mut(db: &mut dyn $zalsa::Database) -> (&mut $zalsa_struct::IngredientImpl<Self>, &mut $zalsa::Runtime) {
                     let zalsa_mut = db.zalsa_mut();
-                    let current_revision = zalsa_mut.new_revision();
+                    zalsa_mut.new_revision();
                     let index = zalsa_mut.add_or_lookup_jar_by_type::<$zalsa_struct::JarImpl<$Configuration>>();
                     let (ingredient, runtime) = zalsa_mut.lookup_ingredient_mut(index);
                     let ingredient = ingredient.assert_type_mut::<$zalsa_struct::IngredientImpl<Self>>();

components/salsa-macros/src/tracked_impl.rs

@@ -298,7 +298,22 @@ impl Macro {
     ) -> syn::Result<()> {
         if let Some(returns) = &args.returns {
             if let syn::ReturnType::Type(_, t) = &mut sig.output {
-                **t = parse_quote!(& #db_lt #t)
+                if returns == "copy" || returns == "clone" {
+                    // leave as is
+                } else if returns == "ref" {
+                    **t = parse_quote!(& #db_lt #t)
+                } else if returns == "deref" {
+                    **t = parse_quote!(& #db_lt <#t as ::core::ops::Deref>::Target)
+                } else if returns == "as_ref" {
+                    **t = parse_quote!(<#t as ::salsa::SalsaAsRef>::AsRef<#db_lt>)
+                } else if returns == "as_deref" {
+                    **t = parse_quote!(<#t as ::salsa::SalsaAsDeref>::AsDeref<#db_lt>)
+                } else {
+                    return Err(syn::Error::new_spanned(
+                        returns,
+                        format!("Unknown returns mode `{returns}`"),
+                    ));
+                }
             } else {
                 return Err(syn::Error::new_spanned(
                     returns,

tests/tracked_method_inherent_return_deref.rs

@@ -0,0 +1,31 @@
+use salsa::Database;
+
+#[salsa::input]
+struct Input {
+    number: usize,
+}
+
+#[salsa::tracked]
+impl Input {
+    #[salsa::tracked(returns(deref))]
+    fn test(self, db: &dyn salsa::Database) -> Vec<String> {
+        (0..self.number(db)).map(|i| format!("test {i}")).collect()
+    }
+}
+
+#[test]
+fn invoke() {
+    salsa::DatabaseImpl::new().attach(|db| {
+        let input = Input::new(db, 3);
+        let x: &[String] = input.test(db);
+
+        assert_eq!(
+            x,
+            &[
+                "test 0".to_string(),
+                "test 1".to_string(),
+                "test 2".to_string()
+            ]
+        );
+    })
+}