/+dub.sdl:

dependency "sumtype" version="~>0.8.11"

+/

import sumtype;

import std.variant;

​

struct A { int a; }

struct B { int b; }

​

Algebraic!(A, B) alg;

SumType!(A, B) sum;

​

unittest {

    // visit takes a "default" handler with no arguments

    assert(__traits(compiles,

        alg.visit!(

            (A a) => "got A",

            () => "got something"

        )

    ));

​

    // match doesn't

    assert(!__traits(compiles,

        sum.match!(

            (A a) => "got A",

            () => "got something"

        )

    ));

}

​

unittest {

    // visit prioritizes non-template handlers

    assert(__traits(compiles,

        alg.visit!(

            something => "got something",

            (A a) => "got A"

        )

    ));

​

    // match doesn't, so it considers the second

    // handler unreachable and fails to compile

    assert(!__traits(compiles,

        sum.match!(

            something => "got something",

            (A a) => "got A"

        )

    ));

}

​

void main() {}