wrap

1 interface Quack
2 {
3     int quack();
4     @property int height();
5 }
6 interface Flyer
7 {
8     @property int height();
9 }
10 class Duck : Quack
11 {
12     int quack() { return 1; }
13     @property int height() { return 10; }
14 }
15 class Human
16 {
17     int quack() { return 2; }
18     @property int height() { return 20; }
19 }
20 
21 Duck d1 = new Duck();
22 Human h1 = new Human();
23 
24 interface Refleshable
25 {
26     int reflesh();
27 }
28 
29 // does not have structural conformance
30 static assert(!__traits(compiles, d1.wrap!Refleshable));
31 static assert(!__traits(compiles, h1.wrap!Refleshable));
32 
33 // strict upcast
34 Quack qd = d1.wrap!Quack;
35 assert(qd is d1);
36 assert(qd.quack() == 1);    // calls Duck.quack
37 // strict downcast
38 Duck d2 = qd.unwrap!Duck;
39 assert(d2 is d1);
40 
41 // structural upcast
42 Quack qh = h1.wrap!Quack;
43 assert(qh.quack() == 2);    // calls Human.quack
44 // structural downcast
45 Human h2 = qh.unwrap!Human;
46 assert(h2 is h1);
47 
48 // structural upcast (two steps)
49 Quack qx = h1.wrap!Quack;   // Human -> Quack
50 Flyer fx = qx.wrap!Flyer;   // Quack -> Flyer
51 assert(fx.height == 20);    // calls Human.height
52 // structural downcast (two steps)
53 Quack qy = fx.unwrap!Quack; // Flyer -> Quack
54 Human hy = qy.unwrap!Human; // Quack -> Human
55 assert(hy is h1);
56 // structural downcast (one step)
57 Human hz = fx.unwrap!Human; // Flyer -> Human
58 assert(hz is h1);

1 import std.traits : FunctionAttribute, functionAttributes;
2 interface A { int run(); }
3 interface B { int stop(); @property int status(); }
4 class X
5 {
6     int run() { return 1; }
7     int stop() { return 2; }
8     @property int status() { return 3; }
9 }
10 
11 auto x = new X();
12 auto ab = x.wrap!(A, B);
13 A a = ab;
14 B b = ab;
15 assert(a.run() == 1);
16 assert(b.stop() == 2);
17 assert(b.status == 3);
18 static assert(functionAttributes!(typeof(ab).status) & FunctionAttribute.property);