Issue 697

[jClaireCodesStuff]

Wrote a test case. It demonstrates that the master sends !Send results, and fails to compile after my changes. The existing 12 tests pass.

Removed unsafe impl of Sync and Send for ScopeFuture. Replaced it with:

• Send bounds for the return types of the user's Future
• a newtype wrapping ScopeHandle with unsafe impl Send

Now the only other type in the crate with unsafe impl is ScopeFutureWrapped.

I need help transforming the test into one that expects a compiler error.

I did not investigate whether sending ScopeHandle is sound.

[cuviper]

I do think you're right that this needs Send, but we also plan to just deprecate and remove the rayon-futures crate, since it's based on old futures. New integration will probably be added directly to rayon-core, something like #679.

This PR constitutes a breaking change, though it's to fix soundness, which we've allowed without a semver bump before. Plus rayon-futures requires the nasty --cfg=rayon_unstable anyway. So I'm thinking of pushing your changes to a new branch, along with publishing a new release that pins the compatible rayon-core minor version and marks rayon-futures deprecated. Then I will remove it for the new rayon-core minor version coming to the master branch.

Does this sound OK?

[cuviper]

I published rayon-futures 0.1.1 with this change.