Indexing with `slice::binary_search_by`'s result should not produce panicking branch

In this code:

fn binary_search_repro(needle: &str) -> Option<&str> {
    let haystack = &["a", "b"];
    haystack.binary_search(&needle).ok().map(|i| haystack[i])
}

the compiler should be able to use the hint from slice::binary_search_by in order to elide the length check in the index operation (haystack[i]).

Seems the knowledge from this assert_unchecked is lost somehow:
https://github.com/rust-lang/rust/blob/e10aa8891182378de002bd71bf4d04181fb8231d/library/core/src/slice/mod.rs#L2975

Godbolt: https://rust.godbolt.org/z/8zqq8vrrv

Start with the binary_search_repro example and the linked assert_unchecked in library/core/src/slice/mod.rs. Inspect how the compiler carries the binary-search result into the haystack[i] indexing operation, using the linked Godbolt reproduction to compare generated code. Done means the bounds check is eliminated for this pattern without changing behavior.