void popFront(T)(ref T[] a) { a = a[1..$]; }

​

​

enum bool isInputRange(R) = is(typeof(

{

    R r;

    r.popFront();

}));

​

struct DirEntry

{

    @property string name() { return ""; }

    alias name this;

}

pragma(msg, isInputRange!DirEntry);

pragma(msg, isInputRange!(typeof(DirEntry.init.name)));

​

bool isDir(R)(R r) if (isInputRange!R) { return true; }

​

void main()

{

    DirEntry de;

    bool c = isDir(de);

}