Avoid unhelpful compiler suggestion

[jplatte]

No description provided.

[jplatte]

I think it's actually kind of wrong to say we don't support generic functions, it's just that we can't fully check them. Also we could check input types that don't mention any of the generic parameters, but that's non-trivial and might not be worth the time needed to implement it.

I've had an idea for a while that would make generic handlers pretty much fully checkable, that is:

#[debug_handler(with(T = String, T = u64; U = i8, U = i16; N = 0))]
fn handler<T, U, const N: usize>(extract_t: Path<T>, extract_u: Json<U>, extract_n: Foo<N>)
where
    T: Deserialize,
    U: Deserialize,
{
    // ...
}

could make debug_handler add FromRequest assertions for Path<String>, Path<u64>, Json<i8>, Json<i16> and Foo<0> while also adding Send assertions for the futures returned by

• handler::<String, i8, 0>
• handler::<String, i16, 0>
• handler::<u64, i8, 0>
• handler::<u64, i16, 0>

If we were to do that, we could just require users to add this with() annotation before any parameters are checked on a generic function (even ones that don't mention the generic types) as it should be easy enough.