diff --git a/src/extract.rs b/src/extract.rs index c189bbf9..5289bd7d 100644 --- a/src/extract.rs +++ b/src/extract.rs @@ -193,57 +193,83 @@ impl FromRequest for () { macro_rules! tuple_from_req ({$fut_type:ident, $(($n:tt, $T:ident)),+} => { - /// FromRequest implementation for tuple - #[doc(hidden)] - #[allow(unused_parens)] - impl<$($T: FromRequest + 'static),+> FromRequest for ($($T,)+) - { - type Error = Error; - type Future = $fut_type<$($T),+>; - type Config = ($($T::Config),+); + // This module is a trick to get around the inability of + // `macro_rules!` macros to make new idents. We want to make + // a new `FutWrapper` struct for each distinct invocation of + // this macro. Ideally, we would name it something like + // `FutWrapper_$fut_type`, but this can't be done in a macro_rules + // macro. + // + // Instead, we put everything in a module named `$fut_type`, thus allowing + // us to use the name `FutWrapper` without worrying about conflicts. + // This macro only exists to generate trait impls for tuples - these + // are inherently global, so users don't have to care about this + // weird trick. + #[allow(non_snake_case)] + mod $fut_type { - fn from_request(req: &HttpRequest, payload: &mut Payload) -> Self::Future { - $fut_type { - items: <($(Option<$T>,)+)>::default(), - futs: ($($T::from_request(req, payload),)+), + // Bring everything into scope, so we don't need + // redundant imports + use super::*; + + /// A helper struct to allow us to pin-project through + /// to individual fields + #[pin_project::pin_project] + struct FutWrapper<$($T: FromRequest),+>($(#[pin] $T::Future),+); + + /// FromRequest implementation for tuple + #[doc(hidden)] + #[allow(unused_parens)] + impl<$($T: FromRequest + 'static),+> FromRequest for ($($T,)+) + { + type Error = Error; + type Future = $fut_type<$($T),+>; + type Config = ($($T::Config),+); + + fn from_request(req: &HttpRequest, payload: &mut Payload) -> Self::Future { + $fut_type { + items: <($(Option<$T>,)+)>::default(), + futs: FutWrapper($($T::from_request(req, payload),)+), + } } } - } - #[doc(hidden)] - #[pin_project::pin_project] - pub struct $fut_type<$($T: FromRequest),+> { - items: ($(Option<$T>,)+), - futs: ($($T::Future,)+), - } + #[doc(hidden)] + #[pin_project::pin_project] + pub struct $fut_type<$($T: FromRequest),+> { + items: ($(Option<$T>,)+), + #[pin] + futs: FutWrapper<$($T,)+>, + } - impl<$($T: FromRequest),+> Future for $fut_type<$($T),+> - { - type Output = Result<($($T,)+), Error>; + impl<$($T: FromRequest),+> Future for $fut_type<$($T),+> + { + type Output = Result<($($T,)+), Error>; - fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll { - let this = self.project(); + fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll { + let mut this = self.project(); - let mut ready = true; - $( - if this.items.$n.is_none() { - match unsafe { Pin::new_unchecked(&mut this.futs.$n) }.poll(cx) { - Poll::Ready(Ok(item)) => { - this.items.$n = Some(item); + let mut ready = true; + $( + if this.items.$n.is_none() { + match this.futs.as_mut().project().$n.poll(cx) { + Poll::Ready(Ok(item)) => { + this.items.$n = Some(item); + } + Poll::Pending => ready = false, + Poll::Ready(Err(e)) => return Poll::Ready(Err(e.into())), } - Poll::Pending => ready = false, - Poll::Ready(Err(e)) => return Poll::Ready(Err(e.into())), } - } - )+ + )+ - if ready { - Poll::Ready(Ok( - ($(this.items.$n.take().unwrap(),)+) - )) - } else { - Poll::Pending - } + if ready { + Poll::Ready(Ok( + ($(this.items.$n.take().unwrap(),)+) + )) + } else { + Poll::Pending + } + } } } });