import std.traits: isMutable;
struct S {
    immutable int i = 3;
}

pragma(msg, isMutable!S);

void main() {
    S s;
    s = S();
}

And is there a trait that takes the transitivity of immutability in to account?

Cheers,
- Ali

On 7/27/18 9:10 AM, aliak wrote:
> import std.traits: isMutable;
> struct S {
>      immutable int i = 3;
> }
> 
> pragma(msg, isMutable!S);
> 
> void main() {
>      S s;
>      s = S();
> }

isMutable only takes the type into account, it doesn't look to see if all the internals are mutable.

It literally is this:

enum bool isMutable(T) = !is(T == const) && !is(T == immutable) && !is(T == inout);

> And is there a trait that takes the transitivity of immutability in to account?

I think you are looking for https://dlang.org/phobos/std_traits.html#isAssignable

-Steve

On Friday, 27 July 2018 at 14:48:06 UTC, Steven Schveighoffer wrote:
> On 7/27/18 9:10 AM, aliak wrote:
>> import std.traits: isMutable;
>> struct S {
>>      immutable int i = 3;
>> }
>> 
>> pragma(msg, isMutable!S);
>> 
>> void main() {
>>      S s;
>>      s = S();
>> }
>
> isMutable only takes the type into account, it doesn't look to see if all the internals are mutable.
>
> It literally is this:
>
> enum bool isMutable(T) = !is(T == const) && !is(T == immutable) && !is(T == inout);
>
>> And is there a trait that takes the transitivity of immutability in to account?
>
> I think you are looking for https://dlang.org/phobos/std_traits.html#isAssignable
>
> -Steve

Ah! Yes I think I am. Thanks!