error: each predicate in a where clause must have at least one bound in it

[emk]

Good morning! One of my Rust builds failed last night with an error in rust-replace-map, and I thought you might like to know:

src/lib.rs:18:7: 18:11 error: each predicate in a `where` clause must have at least one bound in it
src/lib.rs:18 where F: |: T| -> T {
                    ^~~~
src/lib.rs:18:10: 18:11 error: expected `{`, found `|`
src/lib.rs:18 where F: |: T| -> T {
                       ^

I'm not quite sure how where clauses work yet. I need to go look that up. :-)

[emk]

See rust-lang/rust#17454 for one failed attempt to fix this:

pub fn replace_map<'a, T, F>(src: &mut T, prod: F)
where F: FnOnce(T) -> T {

[reem]

Ah, that's because of a change to unboxed closure syntax. It's because |: T| -> T is not a trait anymore.

Why does the above fail?

[reem]

Fixed in latest master.