Understanding opAssign and 'alias this'

[Maxim Fomin]

On Monday, 14 October 2013 at 09:17:12 UTC, John Colvin wrote:
> Everything is working fine except for the error on [2] when xxx 
> == true, which I think is a bug.
>
> minimised test:
>
> struct A
> {
>         void opAssign(A a) {}
> }
>
> struct B {
>         A a;
>         alias a this;
> }
>
> void main() {
>         A a;
>         B b;
>         b = a;
> }
>
> Error: function assign.B.opAssign (B p) is not callable using 
> argument types (A)

This does not work (and need not) because compiler generates 
default function B.opAssign(B) which is really not callable using 
argument types (A).