Function sha1_from_const_slice 

pub const fn sha1_from_const_slice(data: &ConstSlice) -> Digest

A const evaluated sha1 function. The function differs from sha1 in that it uses a ConstSlice which allows for resizing a slice at const evaluation time which is not permitted with built-in slices.

Use

const fn signature() -> const_sha1::Digest {
    const_sha1::sha1_from_const_slice(&const_sha1::ConstSlice::from_slice(stringify!(MyType).as_bytes()))
}