tokenLocation

pub fn tokenLocation(self: Ast, start_offset: ByteOffset, token_index: TokenIndex) Location {
    var loc = Location{
        .line = 0,
        .column = 0,
        .line_start = start_offset,
        .line_end = self.source.len,
    };
    const token_start = self.tokenStart(token_index);

    // Scan to by line until we go past the token start
    while (std.mem.findScalarPos(u8, self.source, loc.line_start, '\n')) |i| {
        if (i >= token_start) {
            break; // Went past
        }
        loc.line += 1;
        loc.line_start = i + 1;
    }

    const offset = loc.line_start;
    for (self.source[offset..], 0..) |c, i| {
        if (i + offset == token_start) {
            loc.line_end = i + offset;
            while (loc.line_end < self.source.len and self.source[loc.line_end] != '\n') {
                loc.line_end += 1;
            }
            return loc;
        }
        if (c == '\n') {
            loc.line += 1;
            loc.column = 0;
            loc.line_start = i + 1;
        } else {
            loc.column += 1;
        }
    }
    return loc;
}