It is currently not possible to tell if a function or method is a const fn by reading documentation, as rustdoc does not retain the const keyword in const fn declarations

[slightlyoutofphase]

Basically, a function written for example like this:

pub const fn add(a: i32, b: i32) -> i32 {
    a + b
}

is currently documented like this:

pub fn add(a: i32, b: i32) -> i32

but it would be nice if was instead documented like this:

pub const fn add(a: i32, b: i32) -> i32

[tesuji]

Currently, in nightly std:

Stable:

[jonas-schievink]

This should work fine, yeah. The only case in which rustdoc will (deliberately) omit the const is for const-unstable functions.

[slightlyoutofphase]

Hmmm, it's possible this is only a problem with struct member methods, and possibly not in all scenarios? I should have taken a closer look at other documentation first I guess.

That said, for example, in my crate's documentation here, the very first method shown, (specifically, new) is a const fn but is not displayed as such (as are none of the other const fn methods that struct has either).

[jonas-schievink]

Can you provide a minimal reproduction for this to show up?

[slightlyoutofphase]

Sure, I'll put one together later today when I have access to my normal dev setup.

[slightlyoutofphase]

Just opened a new issue, as I narrowed it down to a very specific cause that consistently reproduces the problem.