Re: Subtyping of an enum

[diniz via Digitalmars-d-learn]

Le 15/04/2019 à 10:39, Anton Fediushin via Digitalmars-d-learn a écrit :
This seems to work just fine for assigning and comparisons but passing Enum as a 
function argument does not work:
```
void fun(Enum e) {}
fun(Enum.foo);
---
Error: function fun(Enum e) is not callable using argument types (internal)
Cannot pass argument foo of type internal to parameter Enum e.
```

I don't understand why you just don't call fun with an Enum (struct) param, 
since that is how fun is defined. This works by me (see call in main):

struct Enum {
  private {
    enum internal {
      foo,
      bar
    }
    internal m_enum;
  }
  this (internal i) { m_enum = i; }
  alias m_enum this;
  string toString() {
    switch (this.m_enum) {
        case internal.foo : return "FOO" ;
        case internal.bar : return "BAR" ;
        default : assert(0) ;
    }
  }
}

void fun (Enum e) {
    writeln(e) ;
}

void main() {
    auto e = Enum(Enum.foo) ;
    fun(e) ;    // -> "FOO"
}

[And I wouldn't make the enum (little e) private, this just risks complicating 
code, also eg in testing, I would just not export it.]

--
diniz {la vita e estranj}