On 08/07/2015 03:24 PM, Marek Janukowicz wrote:> This program works fine:
>
> import std.concurrency;
>
> struct A {
> string a,b;
> }
>
> void main () {
> immutable A a = immutable A( "blah" );
> send( thisTid, a );
> }
>
> But if change struct A declaration to:
>
> struct A {
> string a,b,c;
> }
>
> I get this error during compilation:
> /opt/dmd2/linux/bin64/../../src/phobos/std/variant.d(653): Error: cannot
> modify immutable expression *p
> /opt/dmd2/linux/bin64/../../src/phobos/std/variant.d(580): Error:
template
> instance std.variant.VariantN!32LU.VariantN.opAssign!(immutable(A)) error
> instantiating
> /opt/dmd2/linux/bin64/../../src/phobos/std/concurrency.d(117):
> instantiated from here: __ctor!(immutable(A))
> /opt/dmd2/linux/bin64/../../src/phobos/std/concurrency.d(628):
> instantiated from here: __ctor!(immutable(A))
> /opt/dmd2/linux/bin64/../../src/phobos/std/concurrency.d(618):
> instantiated from here: _send!(immutable(A))
> /opt/dmd2/linux/bin64/../../src/phobos/std/concurrency.d(594):
> instantiated from here: _send!(immutable(A))
>
> Is this is a bug?
Yes, it is a bug. The reason the number of members makes a difference is
that Variant's implementation does different things depending on T.sizeof:
https://github.com/D-Programming-Language/phobos/blob/master/std/variant.d#L608
> On a related note - sometimes when sending a shared struct I get a
> compilation error similar to this:
Variant has a number of open bugs. Unfortunately, Variant reduces the
quality of std.concurrency as Variant is used as a catch-all type by
that module.
Ali
