// Swapping POD (plain old data) types:
int a = 42, b = 34;
swap(a, b);
assert(a == 34 && b == 42);

// Swapping structs with indirection:
static struct S { int x; char c; int[] y; }
S s1 = { 0, 'z', [ 1, 2 ] };
S s2 = { 42, 'a', [ 4, 6 ] };
swap(s1, s2);
assert(s1.x == 42);
assert(s1.c == 'a');
assert(s1.y == [ 4, 6 ]);

assert(s2.x == 0);
assert(s2.c == 'z');
assert(s2.y == [ 1, 2 ]);

// Immutables cannot be swapped:
immutable int imm1 = 1, imm2 = 2;
static assert(!__traits(compiles, swap(imm1, imm2)));

int c = imm1 + 0;
int d = imm2 + 0;
swap(c, d);
assert(c == 2);
assert(d == 1);

// Non-copyable types can still be swapped.
static struct NoCopy
{
    this(this) { assert(0); }
    int n;
    string s;
}
NoCopy nc1, nc2;
nc1.n = 127; nc1.s = "abc";
nc2.n = 513; nc2.s = "uvwxyz";

swap(nc1, nc2);
assert(nc1.n == 513 && nc1.s == "uvwxyz");
assert(nc2.n == 127 && nc2.s == "abc");

swap(nc1, nc1);
swap(nc2, nc2);
assert(nc1.n == 513 && nc1.s == "uvwxyz");
assert(nc2.n == 127 && nc2.s == "abc");

// Types containing non-copyable fields can also be swapped.
static struct NoCopyHolder
{
    NoCopy noCopy;
}
NoCopyHolder h1, h2;
h1.noCopy.n = 31; h1.noCopy.s = "abc";
h2.noCopy.n = 65; h2.noCopy.s = null;

swap(h1, h2);
assert(h1.noCopy.n == 65 && h1.noCopy.s == null);
assert(h2.noCopy.n == 31 && h2.noCopy.s == "abc");

swap(h1, h1);
swap(h2, h2);
assert(h1.noCopy.n == 65 && h1.noCopy.s == null);
assert(h2.noCopy.n == 31 && h2.noCopy.s == "abc");

// Const types cannot be swapped.
const NoCopy const1, const2;
assert(const1.n == 0 && const2.n == 0);
static assert(!__traits(compiles, swap(const1, const2)));