• =?UTF-8?B?Tm9yZGzDtnc=?= (4/4) Oct 09 2016 Now that we have isCopyable from
• James Buren (3/7) Oct 09 2016 I would imagine that an intermediate value, or other lvalue, may
• Jonathan M Davis via Digitalmars-d-learn (6/15) Oct 09 2016 Yes, but isCopyable is checking a type, not a value, so that doesn't ent...
• Jonathan M Davis via Digitalmars-d-learn (9/13) Oct 09 2016 If it's const or immutable, it could be copyable but not assignable. Als...

=?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

Now that we have isCopyable from

https://github.com/dlang/phobos/pull/4706

can somebody briefly outline when something fulfills `isCopyable` 
but not `isAssignable` and vice versa?

James Buren <ryu0 ymail.com> writes:

On Sunday, 9 October 2016 at 07:23:05 UTC, Nordlöw wrote:
 Now that we have isCopyable from

 https://github.com/dlang/phobos/pull/4706

 can somebody briefly outline when something fulfills 
 `isCopyable` but not `isAssignable` and vice versa?

I would imagine that an intermediate value, or other lvalue, may 
be copyable, but not assignable.

Jonathan M Davis via Digitalmars-d-learn writes:

On Sunday, October 09, 2016 07:27:38 James Buren via Digitalmars-d-learn 
wrote:
 On Sunday, 9 October 2016 at 07:23:05 UTC, Nordlöw wrote:
 Now that we have isCopyable from

 https://github.com/dlang/phobos/pull/4706

 can somebody briefly outline when something fulfills
 `isCopyable` but not `isAssignable` and vice versa?

 I would imagine that an intermediate value, or other lvalue, may
 be copyable, but not assignable.

Yes, but isCopyable is checking a type, not a value, so that doesn't enter
into it. To check any kind of value with isCopyable, you'd have to use
typeof on it.

- Jonathan M Davis

Jonathan M Davis via Digitalmars-d-learn writes:

On Sunday, October 09, 2016 07:23:05 Nordlöw via Digitalmars-d-learn wrote:
 Now that we have isCopyable from

 https://github.com/dlang/phobos/pull/4706

 can somebody briefly outline when something fulfills `isCopyable`
 but not `isAssignable` and vice versa?

If it's const or immutable, it could be copyable but not assignable. Also,
someone could specifically  disable opAssign while still allowing copying,
though I don't know why anyone would want to do that.

As for the reverse,  disabling the postblit constructor would disable
copying, and if opAssign takes its argument by ref, then assignment should
still work (though I'm not sure whether it would still work if you didn't
explicitly overload opAssign).

- Jonathan M Davis