This deprecated D2 code works with DMD 2.051:


typedef int[1][1] Mat;
void main() {
    Mat m;
    foreach (row; m) {}
}


But this alternative:


struct Mat {
    int[1][1] a;
    alias a this;
}
void main() {
    Mat m;
    foreach (row; m) {} // line 7
}


DMD 2.051 prints:

test.d(7): Error: cannot infer type for row

This is something that I'd like to see work, so structs+alias this are better usable as an alternative of typedef.