Safe to cast to immutable and return?

[Timoses]

On Thursday, 5 July 2018 at 12:15:35 UTC, vit wrote:
>
> Try pure functions:
>
> class A {}
> A getA()pure @safe  //pure whitout mutable parameters 
> guarantees that function doesn't leak data.
> {
>      A a;
>      // .. do stuff with a
>      // not leaking a to any functions
>
>      // is this safe????
>      return a;
> }
> A getA2(A x)pure @safe  //pure with mutable param
> {
>      A a;
>      // .. do stuff with a
>      // not leaking a to any functions
>
>      // is this safe????
>      return a;
> }
>
> void test()@safe{
>     immutable(A) a1 = getA();        //ok
>     immutable(A) a2 = getA2(null);   //ok
>     immutable(A) a3 = getA2(new A);  //ok
>     immutable(A) a4 = getA2(a3);    //error in theory can leak
> }

Very nice!
I assume the @safe is not a must?

Good read:
https://dlang.org/spec/function.html#pure-functions