I cannot find where it impl trait `Display`

where-it-impl-Display?

&format!(
    "used non-generic {} `{}` for generic parameter",
    opaque_param.kind.descr(),
    arg,
),

what i did

  1. I went to defination of arg,, it's GenericArg

  2. I check all impl for GenericArg

  3. I don't find Display

  4. but I can use .to_string() on it

How certain are you that it's a -> Region rather than, say, a fn descr(&self) -> &'static str?

2 Likes

That's was my mistake, I fixed the question now, I'm sorry.

The Region in my first edition should be questioned with this LOC

But your link do forwarded me to the answer, thank you.