On Friday, 27 July 2018 at 14:52:20 UTC, Steven Schveighoffer
wrote:
On 7/23/18 2:39 PM, aliak wrote:
Hi,
I'm playing around with an Optional wrapper type. It stores a
type T and a bool that defines whether a value is defined or
not:
struct Optional(T) {
T value;
bool defined = false;
this(U : T)(auto ref inout(U) value) inout {
this.value = value;
this.defined = true;
}
}
Don't use inout here. The point of inout on the constructor is
to *transfer* the mutability of the parameter to the struct
instance. But you want to simply copy the type into the struct
(an immutable(Optional!T) is quite useless, no?)
Just use U, not inout(U), and don't put inout on the
constructor.
-Steve
But then it only works for mutable Optional right? Why would an
immutable(Optional!T) be useless? Data can be "forever" empty or
a certain value.
