explicit_counter_loop false positive with continue statement

[mbrt]

Clippy shows a false positive in this example, asking for an explicit_counter_loop refactor:

    let text = "banana";
    let mut count = 0;
    for ch in text.chars() {
        if ch == 'a' {
            continue;
        }
        count += 1
    }
    println!("{}", count);

But since the continue statement skips the counter, the proposed for (count, ch) in text.char_indices() is not equivalent.

[mcarton]

We could suggest to use filter when the first statement in a for loop is if f(var) { continue }.

[mbrt]

Actually I think that you can simply suppress the suggestion if a continue
statement is present in the loop body. There could be dependencies (in term
of side effects) among the counter and continue and break statements. It's
not easy to detect when they are effectively equivalent.

[Reylak]

I agree with @mbrt, I think this lint in most often wrong whenever the counter update statement can be unreachable because of a continue.

[oli-obk]

Yea let's just bail on continue statements

[JoshMcguigan]

@oli-obk I've added a test case based on the post by @mbrt and submitted PR #3135, but I'm not seeing this example activate a lint, so the test case is passing without any code changes.

Just let me know if I am missing something here.