Bug 13930 – std.concurrency can't send immutable AA to another thread

cat > bug.d << CODE import std.concurrency; void main() { immutable aa = ["0":0]; thisTid.send(aa); } CODE dmd -c bug ---- Trying to send an immutable associative array to another thread fails with this error messsage. Looks like a problem with copying in Variant or so. Hash tables are basic types so this should be supported. ---- /usr/include/dmd/phobos/std/variant.d(621): Error: template instance std.variant.VariantN!32LU.VariantN.handler!(immutable(int[string])) error instantiating /usr/include/dmd/phobos/std/variant.d(571): instantiated from here: opAssign!(immutable(int[string])) /usr/include/dmd/phobos/std/concurrency.d(109): instantiated from here: __ctor!(immutable(int[string])) /usr/include/dmd/phobos/std/concurrency.d(588): instantiated from here: __ctor!(immutable(int[string])) /usr/include/dmd/phobos/std/concurrency.d(578): instantiated from here: _send!(immutable(int[string])) /usr/include/dmd/phobos/std/concurrency.d(556): instantiated from here: _send!(immutable(int[string])) bug.d(6): instantiated from here: send!(immutable(int[string])) ----

Receiving immutable AAs doesn't work either. cat > bug.d << CODE import std.concurrency; void main() { auto aa = receiveOnly!(immutable string[string]); } CODE dmd -c bug DPL/dmd/src/../../phobos/std/concurrency.d(760): Error: cannot modify immutable expression ret.__expand_field_0 bug.d(5): Error: template instance std.concurrency.receiveOnly!(immutable(string[string])) error instantiating

Is there any easy workaround? Shared AAs can't be sent either[1]. [1]: http://melpon.org/wandbox/permlink/hoZTHJGgnWrnjxzw

I guess this issue contains two distinct problems. The example in the first comment is about the problem of the `send` function. I guess it was already solved by issue 21296 because the following test works without errors (I used phobos commit:f85ca8db in which issue 21296 was fixed): ``` @system unittest { immutable aa = ["0":0]; thisTid.send(aa); } ``` The example in the second comment is about the problem of the `receiveOnly` function (same as issue 19345). This problem only happens with `receiveOnly` but does not happen with other `receive` family such as `receive` and `receiveTimeout`. I confirmed the following tests work without errors (I used phobos commit:f85ca8db): ``` @system unittest { immutable aa = ["0":0]; thisTid.send(aa); receive((immutable int[string] val) {}); } @system unittest { immutable aa = ["0":0]; thisTid.send(aa); receiveTimeout(10.seconds, (immutable int[string] val) {}); } ``` Note: I did not test the case of shared.

@tom-tan created dlang/phobos pull request #7655 "Fix `receiveOnly` for non-assignable types (issue 13930, issue 19345)" mentioning this issue: - Fix receiveOnly for non-assignable types - Fix issue 13930 - std.concurrency can't send immutable AA to another thread - Fix issue 19345 - std.concurrency does not work with structs of const value type https://github.com/dlang/phobos/pull/7655

dlang/phobos pull request #7655 "Fix issue 13930, 19345 - Fix `receiveOnly` for non-assignable types " was merged into master: - d86c1f605995b423dd1a467b2c1c530dc52adb1e by Tomoya Tanjo: Fix issue 13930, 19345 - Fix receiveOnly for non-assignable types https://github.com/dlang/phobos/pull/7655

dlang/phobos pull request #7657 "Revert "Fix issue 13930, 19345 - Fix `receiveOnly` for non-assignable types "" was merged into master: - 756242350896019ffc7a7cbe05e838538a559f5a by Mathias LANG: Revert "Fix issue 13930, 19345 - Fix receiveOnly for non-assignable types" This reverts commit 4f4fef19400ff85eb4699d569b02b21299b254cc. https://github.com/dlang/phobos/pull/7657