1export fn a() void {
 2    const S = struct {
 3        fn b() struct { usize, usize } {
 4            return .{ 0, 0 };
 5        }
 6    };
 7    const c, _ = S.b();
 8    c += 10;
 9}
10
11// error
12//
13// :8:5: error: cannot assign to constant