Function detect_access_operator

src/subject_extraction.rs:711–767

Detect an access operator (`->`, `?->`, or `::`) before a cursor position in an already-collapsed character slice, and extract the subject expression to the operator's left. The cursor is expected to sit *after* the operator, possibly with a partial identifier already typed (used by completion). # Parameters `chars` — the collapsed line as a char slice. `col` — the cursor's character offset wit

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

/// `Some((subject, AccessKind))` when an operator is found, `None`
/// otherwise.
pub(crate) fn detect_access_operator(chars: &[char], col: usize) -> Option<(String, AccessKind)> {
    let col = col.min(chars.len());

    if chars.is_empty() {
        return None;
    }

    // Walk backwards past any partial identifier the user has typed,
    // then skip whitespace so that `->   ` (operator followed by
    // spaces but no identifier yet) is still detected.
    let operator_end = {
        let mut i = col;
        while i > 0 && (chars[i - 1].is_alphanumeric() || chars[i - 1] == '_') {
            i -= 1;
        }
        // Skip `$` prefix for partially typed static properties
        // (e.g. `Foo::$f` — the `$` is the property sigil, not part
        // of the operator).
        if i > 0 && chars[i - 1] == '$' {
            i -= 1;
        }
        while i > 0 && chars[i - 1] == ' ' {
            i -= 1;
        }
        i
    };

    // Try `::`.
    if operator_end >= 2 && chars[operator_end - 2] == ':' && chars[operator_end - 1] == ':' {
        let subject = extract_double_colon_subject(chars, operator_end - 2);
        if !subject.is_empty() {
            return Some((subject, AccessKind::DoubleColon));
        }
    }

    // Try `->`.
    if operator_end >= 2 && chars[operator_end - 2] == '-' && chars[operator_end - 1] == '>' {
        let subject = extract_arrow_subject(chars, operator_end - 2);
        if !subject.is_empty() {
            return Some((subject, AccessKind::Arrow));
        }
    }

    // Try `?->` (null-safe operator).
    if operator_end >= 3
        && chars[operator_end - 3] == '?'
        && chars[operator_end - 2] == '-'
        && chars[operator_end - 1] == '>'
    {
        let subject = extract_arrow_subject(chars, operator_end - 3);
        if !subject.is_empty() {
            return Some((subject, AccessKind::Arrow));
        }
    }

    None
}