At the very top of my module I have this declaration:

static if (__VERSION__ >= 2098)
{
    alias Foo = TypeA;
}
else
{
    alias Foo = TypeB;
}

No problem inside the module itself but this doesn't work when imported from another module:
Error: undefined identifier Foo

While this workaround works:

template getAlias()
{
    static if (__VERSION__ >= 2098)
    {
        alias getAlias = TypeA;
    }
    else
    {
        alias getAlias = TypeB;
    }
}
alias Foo = getAlias!();

Is there a reason for that?

On Tuesday, 18 January 2022 at 04:42:45 UTC, frame wrote:

static if (__VERSION__ >= 2098)
{
    alias Foo = TypeA;
}
else
{
    alias Foo = TypeB;
}

template getAlias()
{
    static if (__VERSION__ >= 2098)
    {
        alias getAlias = TypeA;
    }
    else
    {
        alias getAlias = TypeB;
    }
}
alias Foo = getAlias!();

static ifs and mixins need semantic analysis to expand, but when you import module, the semantic analysis doesn't run yet (depends on order).

Beter workaround is:

import std.traits : Select;

alias Foo  = Select!(__VERSION__ >= 2098, TypeA, TypeB);

On Tuesday, 18 January 2022 at 04:42:45 UTC, frame wrote:

static if (__VERSION__ >= 2098)
{
    alias Foo = TypeA;
}
else
{
    alias Foo = TypeB;
}

Works for me: https://run.dlang.io/is/XZlvQ8

On Tuesday, 18 January 2022 at 12:05:38 UTC, Paul Backus wrote:

static if (__VERSION__ >= 2098)
{
    alias Foo = TypeA;
}
else
{
    alias Foo = TypeB;
}

It works until you have cyclic dependencies:

https://run.dlang.io/is/wDDcK5

On 1/18/22 7:19 AM, vit wrote:

static if (__VERSION__ >= 2098)
{
    alias Foo = TypeA;
}
else
{
    alias Foo = TypeB;
}

Has nothing to do with __VERSION__:

https://run.dlang.io/is/pa8lDy

That does seem like a bug. And it's LDC specific, dmd seems to work fine.

-Steve

On Wednesday, 19 January 2022 at 04:15:54 UTC, Steven Schveighoffer wrote:

static if (__VERSION__ >= 2098)
{
    alias Foo = TypeA;
}
else
{
    alias Foo = TypeB;
}

In dmd is order of module compilation different.
Same problem:

https://run.dlang.io/is/NkySAw

This is not only problem with imports:

class Foo{
    Bar.B b;

    static if(true)
    	alias F = int;

}

class Bar{
    Foo.F f;     //Error: no property `F` for type `onlineapp.Foo`

    static if(true)
    	alias B = int;

}

void main(){}