Go to Rust: 02 diff 01

02-01.diff

@@ -25,17 +24,15 @@
 /// call methods on the singleton. It takes a closure that takes a
 /// &[Controller] and an arg, calls the closure using the singleton,
 /// and returns the result.
-fn run_method<ArgT, ResultT, FnT>(
+fn run_method<ArgT, ResultT, FnT, Fut>(
     f: FnT,
     arg: ArgT,
 ) -> Result<ResultT, Box<dyn Error + Sync + Send>>
 where
-    // 2024-11-27: `async FnOnce` and `AsyncFnOnce` are unstable, and it is not yet decided
-    // which syntax will win. See
-    // - https://blog.rust-lang.org/inside-rust/2024/08/09/async-closures-call-for-testing.html
-    // - https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Async.20closures.20bounds.20syntax
-    FnT: async FnOnce(&Controller, ArgT) -> Result<ResultT, Box<dyn Error + Sync + Send>>,
-    // OR:
+    FnT: FnOnce(&Controller, ArgT) -> Fut,
+    Fut: Future<Output = Result<ResultT, Box<dyn Error + Sync + Send>>>,
+    // Some day, one of these will work:
+    // FnT: async FnOnce(&Controller, ArgT) -> Result<ResultT, Box<dyn Error + Sync + Send>>,
     // FnT: std::ops::AsyncFnOnce(&Controller, ArgT) -> Result<ResultT, Box<dyn Error + Sync + Send>>,
 {
     let lock = CONTROLLER.controller.read().unwrap();