parsePtrModifiers

fn parsePtrModifiers(p: *Parse, align_type: enum { bit_align, byte_align }) !PtrModifiers {
    var result: PtrModifiers = .{
        .align_node = .none,
        .addrspace_node = .none,
        .bit_range_start = .none,
        .bit_range_end = .none,
    };
    while (true) {
        switch (p.tokenTag(p.tok_i)) {
            .keyword_align => {
                if (result.align_node != .none) {
                    try p.warn(.extra_align_qualifier);
                }
                p.tok_i += 1;
                _ = try p.expectToken(.l_paren);
                result.align_node = (try p.expectExpr()).toOptional();

                if (p.eatToken(.colon)) |colon| {
                    if (align_type == .byte_align) {
                        try p.warnMsg(.{ .tag = .invalid_bit_range, .token = colon });
                    }
                    result.bit_range_start = (try p.expectExpr()).toOptional();
                    _ = try p.expectToken(.colon);
                    result.bit_range_end = (try p.expectExpr()).toOptional();
                }

                _ = try p.expectToken(.r_paren);
            },
            .keyword_addrspace => {
                if (result.addrspace_node != .none) {
                    try p.warn(.extra_addrspace_qualifier);
                }
                result.addrspace_node = .fromOptional(try p.parseAddrSpace());
            },
            .keyword_allowzero,
            .keyword_const,
            .keyword_volatile,
            => p.tok_i += 1,
            else => return result,
        }
    }
}