odd diagnostic with multiple where clauses that only differ by lifetimes

[BoxyUwU]

Given the following code:

trait Foo {}
impl<'a, 'b, T> Foo for T
where
    T: FnMut(&'a ()),
    T: FnMut(&'b ()), {

    }

The current output is:

error[E0283]: type annotations needed
   --> src/lib.rs:4:8
    |
4   |       T: FnMut(&'a ()),
    |          ^^^^^^^^^^^^^ cannot infer type for type parameter `T`
    |
    = note: cannot satisfy `T: FnMut<(&'a (),)>`
help: consider specifying the type arguments in the function call
    |
4   |     T: FnMut(&'a ())::<Self, Args>,
    |                     ^^^^^^^^^^^^^^

error: aborting due to previous error

Ideally the output should look like:

/shrug I expected this to compile but at the very least it shouldn't suggest writing code that doesnt even parse lol