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Enum member `std.traits.isInstanceOf`

Returns true if T is an instance of the template S.


						
				enum isInstanceOf(alias S, T)
				 = is(T == S!Args, Args...);
						
						
				enum isInstanceOf(alias S, alias T)
				 = impl!T;

Example

static struct Foo(T...) { }
static struct Bar(T...) { }
static struct Doo(T) { }
static struct ABC(int x) { }
static void fun(T)() { }
template templ(T) { }

static assert(isInstanceOf!(Foo, Foo!int));
static assert(!isInstanceOf!(Foo, Bar!int));
static assert(!isInstanceOf!(Foo, int));
static assert(isInstanceOf!(Doo, Doo!int));
static assert(isInstanceOf!(ABC, ABC!1));
static assert(!isInstanceOf!(Foo, Foo));
static assert(isInstanceOf!(fun, fun!int));
static assert(isInstanceOf!(templ, templ!int));

Example

To use isInstanceOf to check the identity of a template while inside of said template, use TemplateOf.

static struct A(T = void)
{
    // doesn't work as expected, only accepts A when T = void
    void func(B)(B b) if (isInstanceOf!(A, B)) {}

    // correct behavior
    void method(B)(B b) if (isInstanceOf!(TemplateOf!(A), B)) {}
}

A!(void) a1;
A!(void) a2;
A!(int) a3;

static assert(!__traits(compiles, a1.func(a3)));
static assert( __traits(compiles, a1.method(a2)));
static assert( __traits(compiles, a1.method(a3)));

Authors

Walter Bright, Tomasz Stachowiak (isExpressions), Andrei Alexandrescu, Shin Fujishiro, Robert Clipsham, David Nadlinger, Kenji Hara, Shoichi Kato

License

Boost License 1.0.

API Documentation

Enum member std.traits.isInstanceOf

Example

Example

Authors

License

Enum member `std.traits.isInstanceOf`