Function extract_simple_variable

src/subject_extraction.rs:628–647

Extract a simple `$variable` or bare identifier ending at position `end` (exclusive). Skips trailing whitespace, then walks backwards through identifier characters. If a `$` prefix is found, includes it (producing e.g. `"$this"`, `"$var"`). Otherwise returns whatever identifier was collected (e.g. `"self"`, `"parent"`), which may be empty.

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

/// `"$this"`, `"$var"`).  Otherwise returns whatever identifier was
/// collected (e.g. `"self"`, `"parent"`), which may be empty.
fn extract_simple_variable(chars: &[char], end: usize) -> String {
    let mut i = end;
    // skip whitespace
    while i > 0 && chars[i - 1] == ' ' {
        i -= 1;
    }
    let var_end = i;
    // walk back through identifier chars
    while i > 0 && (chars[i - 1].is_alphanumeric() || chars[i - 1] == '_') {
        i -= 1;
    }
    // expect `$` prefix
    if i > 0 && chars[i - 1] == '$' {
        i -= 1;
        chars[i..var_end].iter().collect()
    } else {
        // no `$` — return whatever we collected (may be empty)
        chars[i..var_end].iter().collect()
    }
}

/// Extract the identifier/keyword before `::`.
///