Eponymous mixin templates

[dlangBugzillaToGithub]

Simen Kjaeraas reported this on 2018-03-10T16:36:31Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=18586

CC List

• Ali Ak
• Mike Franklin

Description

The eponymous template trick is very useful in other cases, but there seems to be an oversight in that mixin templates don't benefit from it.

The usefulness of this lies in a reduced reliance on string mixins, and a decoupling of the mixin template arguments from the name of the mixed-in code. Consider:

struct S {
    int n;
    mixin fun!("myfunction", "return n;");
}

mixin template fun(string funName, string body) {
    mixin("auto "~funName~"() { "~body~" }");
}

unittest {
    auto s = S(3);
    assert(s.myfunction == 3);
}

That's the code you currently have to write to mix in a function with a specific name. With eponymous templates, the function name wouldn't need to be passed:

struct S {
    int n;
    mixin fun!"return n;" myfunction ;
}

mixin template fun(string body) {
    mixin("auto fun() { "~body~" }");
}

unittest {
    auto s = S(3);
    assert(s.myfunction == 3);
}