Use #[salsa::tracked] for tracked methods

This changes tracked methods from being annotated with `#[tracked]` to
`#[salsa::tracked]`. This improves consistency and allows outputting a
nicer error message if someone forgets to put the attribute on the impl
block.

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

@@ -18,6 +18,13 @@ pub(crate) fn tracked_fn(
         ));
     }
 
+    if let syn::FnArg::Receiver(receiver) = &item_fn.sig.inputs[0] {
+        return Err(syn::Error::new(
+            receiver.span(),
+            "#[salsa::tracked] must also be applied to the impl block for tracked methods",
+        ));
+    }
+
     if let Some(s) = &args.specify {
         if requires_interning(&item_fn) {
             return Err(syn::Error::new(
@@ -96,10 +103,12 @@ pub(crate) fn tracked_impl(
                 _ => return None,
             };
             let salsa_tracked_attr = item_method.attrs.iter().position(|attr| {
-                attr.path
-                    .get_ident()
-                    .map(|ident| ident == "tracked")
-                    .unwrap_or(false)
+                let path = &attr.path.segments;
+                path.len() == 2
+                    && path[0].arguments == syn::PathArguments::None
+                    && path[0].ident == "salsa"
+                    && path[1].arguments == syn::PathArguments::None
+                    && path[1].ident == "tracked"
             })?;
             let salsa_tracked_attr = item_method.attrs.remove(salsa_tracked_attr);
             let inner_args = if !salsa_tracked_attr.tokens.is_empty() {

salsa-2022-tests/tests/tracked_method.rs

@@ -7,19 +7,19 @@ struct Jar(MyInput, MyInput_tracked_fn, MyInput_tracked_fn_ref);
 
 trait Db: salsa::DbWithJar<Jar> {}
 
-#[salsa::input(jar = Jar)]
+#[salsa::input]
 struct MyInput {
     field: u32,
 }
 
-#[salsa::tracked(jar = Jar)]
+#[salsa::tracked]
 impl MyInput {
-    #[tracked]
+    #[salsa::tracked]
     fn tracked_fn(self, db: &dyn Db) -> u32 {
         self.field(db) * 2
     }
 
-    #[tracked(return_ref)]
+    #[salsa::tracked(return_ref)]
     fn tracked_fn_ref(self, db: &dyn Db) -> u32 {
         self.field(db) * 3
     }