Compilation of this code:

auto foo(T)()
{
    return T();   // Error: cannot access frame pointer of `onlineapp.main.T`
}

void main()
{
    struct T
    {
        int a=1;
        void argsFunc(int a) {} // (1)
    }

    pragma(msg,foo!T());
}

fails with this error:

onlineapp.d(3): Error: cannot access frame pointer of `onlineapp.main.T`
onlineapp.d(14): Error: template instance `onlineapp.foo!(T)` error instantiating
onlineapp.d(14):        while evaluating `pragma(msg, foo!(T)())`

But when I comment out argsFunc function on line (1), it compiles successfully meaning that there is no issue to access frame pointer.

Is this a bug?

On Sunday, 9 May 2021 at 17:37:40 UTC, Andrey Zherikov wrote:

auto foo(T)()
{
    return T();   // Error: cannot access frame pointer of `onlineapp.main.T`
}

void main()
{
    struct T
    {
        int a=1;
        void argsFunc(int a) {} // (1)
    }

    pragma(msg,foo!T());
}

onlineapp.d(3): Error: cannot access frame pointer of `onlineapp.main.T`
onlineapp.d(14): Error: template instance `onlineapp.foo!(T)` error instantiating
onlineapp.d(14):        while evaluating `pragma(msg, foo!(T)())`

Most likely because function member types have access to the scope, it complains because doing so will escape the scope of that function.

If you make struct static this erorr should go away.

On Sunday, 9 May 2021 at 17:37:40 UTC, Andrey Zherikov wrote:

My best guess is that, since the struct doesn't have any member functions the compiler has decided that the struct doesn't need any access to the main function's context/frame pointer, so the struct has implicitly become a static struct.

Marking the struct static yourself while keeping the member function, will show that it can then compile.

You can also move your foo function into the main function and it'll compile. Oddly the output ends up becoming: T(1, null) which I didn't really expect.

Just a guess though.

On Sunday, 9 May 2021 at 17:37:40 UTC, Andrey Zherikov wrote:

https://run.dlang.io/is/sCUdXe shows this a bit more clearly.

On Sunday, 9 May 2021 at 17:53:07 UTC, SealabJaster wrote:

That's a point! Thanks you!