Cut down on macro nonsense

- InertAtomic replaced atomic_inert! for improved tooling support
- atomic_defaults! is easier to type out than to explain in a docstring
- Changed rustfmt config to better support tiny functions such as as_any

src/utils/ddispatch.rs

@@ -0,0 +1,29 @@
+//! A variant of [std::any::Provider]
+
+use std::any::Any;
+
+/// A request for a value of an unknown type
+pub struct Request<'a>(&'a mut dyn Any);
+impl<'a> Request<'a> {
+  pub fn can_serve<T: 'static>(&self) -> bool { self.0.is::<Option<T>>() }
+
+  pub fn serve<T: 'static>(&mut self, value: T) { self.serve_with(|| value) }
+
+  pub fn serve_with<T: 'static>(&mut self, provider: impl FnOnce() -> T) {
+    if let Some(slot) = self.0.downcast_mut() {
+      *slot = provider();
+    }
+  }
+}
+
+/// Trait for objects that can respond to type-erased commands. This trait is
+/// a dependency of `Atomic` but the implementation can be left empty.
+pub trait Responder {
+  fn respond(&self, _request: Request) {}
+}
+
+pub fn request<T: 'static>(responder: &(impl Responder + ?Sized)) -> Option<T> {
+  let mut slot = None;
+  responder.respond(Request(&mut slot));
+  slot
+}