append

alias Str = UniqueString!false;

assert(Str(`a`).append('b', 'c')[] == `abc`);
assert(Str(`a`).append(`b`, `c`)[] == `abc`);

const Str x = Str(`a`).append('b', 'c'); // is moved
assert(x[] == `abc`);

Str y = `x`;
Str z = y.append('y', 'z', `w`); // needs dup
assert(y.ptr != z.ptr);
assert(z[] == `xyzw`);