the behavior of opAssign

[Simen Kjærås]

On Monday, 29 January 2018 at 09:23:55 UTC, Sobaya wrote:
> I found a strange behavior.
>
> class A {
>     void opAssign(int v) {}
> }
>
> class Test {
>     A a;
>     this() {
>         a = new A(); // removing this causes compile error.
>         a = 3; // cannot implicitly convert expression `3` of 
> `int` to `A`
>     }
> }
>
> void main() {
>     // this is allowed.
>     A a;
>     a = 3;
> }

The first assignment in the constructor isn't actually a call to 
opAssign, it's a constructor call. In the same way, this will not 
compile:

A a = 3;

Also, since classes are reference types, you will need to 
construct an instance before assigning an int to it. The code in 
your main() will crash at runtime because the 'this' reference is 
null inside opAssign.

--
   Simen