Regression in type inference between stable 1.79.0 and nightly-2024-06-19 about rust HOT 5 OPEN

I think this is expected. With the additional implementation of collect() into Box<str>, it's now ambiguous whether Box<_> means Box<[_]> or Box<str>. It's unfortunate to regress existing code that wasn't being explicit, but I think this is an acceptable cost for the additional functionality.

from rust.

Fine by me. Maybe this should be announced as part of the release note to let people know?

from rust.

Minimized a bit:

pub fn parse(input: &str) -> String {
    input
        .split('\n')
        .map(str::trim_end)
        .collect::<Box<_>>()
        .join("\n")
}

from rust.

@rustbot label -needs-triage -regression-untriaged +regression-from-stable-to-nightly +T-compiler +A-inference

from rust.

Bisection points to #99969 cc @dtolnay @calebsander

Can this issue be considered an intended or rather an unintended behaviour?

I can reproduce in beta so I'll flip the regression labels

from rust.