feat(routeify): map `?` span to `route!` for tooling support

Use the span of the `?` token when generating the macro invocation in
the `#[routeify]` transformation, so that rust-analyzer resolves hover
and go-to-definition on `?` to the `route!` macro's documentation

1 files changed, 22 insertions, 0 deletions

diff --git a/mingling_macros/src/lib.rs b/mingling_macros/src/lib.rs
index a85648f..be355cd 100644
--- a/mingling_macros/src/lib.rs
+++ b/mingling_macros/src/lib.rs
@@ -511,6 +511,28 @@ pub fn pack_err_structural(input: TokenStream) -> TokenStream {
 /// directly, while the `Err` value is converted via `Routable::to_chain()` and
 /// returned early.
 ///
+/// ## Interaction with `#[routeify]`
+///
+/// The [`#[routeify]`](attr.routeify.html) attribute macro automatically replaces
+/// every `expr?` inside a function with `route!(expr)`. This means you can use the
+/// familiar `?` syntax in chain functions instead of writing `route!(...)`
+/// explicitly:
+///
+/// ```rust,ignore
+/// use mingling::macros::chain;
+///
+/// #[chain(routeify)]
+/// fn process(prev: SomeEntry) -> Next {
+///     // `?` here expands to `route!(...)` → this macro → the match block
+///     let value = some_fallible_call()?;
+///     value.to_chain()
+/// }
+/// ```
+///
+/// Because `#[routeify]` maps the span of `?` to this macro, hovering over `?` in
+/// a `#[routeify]` function will display this documentation — explaining what
+/// the `?` actually expands to.
+///
 /// # Example
 ///
 /// ```rust,ignore