I can't tell if this is a bug, I was just playing with it and it's not important to me:

void foo(alias dg)() {
    dg();
}

void test() {
    foo!({ int x; })();
}

void main() {
    test();
}

$ dmd test.d
ok

$ dmd -inline test.d
test.d(3): Error: function test.test.foo!(delegate pure nothrow @safe void()
{
int x = 0;
}
).foo is a nested function and cannot be accessed from main

Note that if I make it a delegate literal it will compile:

void foo(alias dg)() {
    dg();
}

void test() {
    int y;
    foo!({ int x = y; })();
}

void main() {
    test();
}

$ dmd -inline test.d
ok