Too long line for function parameter of type impl Trait

[benediktsatalia]

Consider the following function:

fn my_function(
    my_long_impl_trait_parameter: impl Into<MyVeryLongTypeNameThatMakesThisWholeLineOverThe100CharLimit>,
) {
}

The parameter line is too long (105 chars) but rustfmt does not change it, it even reformats to this if we try to fix it manually.

Interestingly, if we add one more character then it breaks correctly:

fn my_function(
    my_long_impl_trait_parameter: impl Into<
        MyVeryLongTypeNameThatMakesThisWholeLineOverThe100CharLimitA,
    >,
) {
}

(I have chosen the example in the extreme case on purpose)

Also if we remove the impl and replace Into with some struct name it correctly formats again. So I think it has to do with the impl , but this is just a wild guess.

[jacobsa]

For the record I think I'm seeing this issue too (Google-internal bug 482888536).

[jacobsa]

Thank you @ytmimi!