salsa/tests/compile-fail/panic-when-reading-fields-of-tracked-structs-from-older-revisions.rs
Niko Matsakis daaa78056a switch to new database design
Under this design, *all* databases are a
`DatabaseImpl<U>`, where the `U` implements
`UserData` (you can use `()` if there is none).

Code would default to `&dyn salsa::Database` but
if you want to give access to the userdata, you
can define a custom database trait
`MyDatabase: salsa::Databse` so long as you

* annotate `MyDatabase` trait definition of
  impls of `MyDatabase` with `#[salsa::db]`
* implement `MyDatabase` for `DatabaseImpl<U>`
  where `U` is your userdata (this could be a
  blanket impl, if you don't know the precise
  userdata type).

The `tests/common/mod.rs` shows the pattern.
2024-07-28 12:47:50 +00:00

24 lines
525 B
Rust

use salsa::prelude::*;
#[salsa::input]
struct MyInput {
field: u32,
}
#[salsa::tracked]
struct MyTracked<'db> {
field: u32,
}
#[salsa::tracked]
fn tracked_fn<'db>(db: &'db dyn salsa::Database, input: MyInput) -> MyTracked<'db> {
MyTracked::new(db, input.field(db) / 2)
}
fn main() {
let mut db = salsa::DatabaseImpl::new();
let input = MyInput::new(&db, 22);
let tracked = tracked_fn(&db, input);
input.set_field(&mut db).to(24);
tracked.field(&db); // tracked comes from prior revision
}