Function skip_balanced_brackets_back

src/subject_extraction.rs:76–96

Skip backwards past a balanced bracket group `[…]` in a char slice. `pos` must point one past the closing `]`. Returns the index of the opening `[`, or `None` if brackets are unbalanced.

(chars: &[char], pos: usize)

/// `pos` must point one past the closing `]`.  Returns the index of the
/// opening `[`, or `None` if brackets are unbalanced.
fn skip_balanced_brackets_back(chars: &[char], pos: usize) -> Option<usize> {
    if pos == 0 || chars[pos - 1] != ']' {
        return None;
    }
    let mut depth: u32 = 0;
    let mut j = pos;
    while j > 0 {
        j -= 1;
        match chars[j] {
            ']' => depth += 1,
            '[' => {
                depth -= 1;
                if depth == 0 {
                    return Some(j);
                }
            }
            _ => {}
        }
    }
    None
}

/// Check if the `new` keyword (followed by whitespace) appears immediately
/// before the identifier starting at position `ident_start`.