Make Generic UnwindSafe even if its error type isn't
#204
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`std::io::Error` does not implement `UnwindSafe` on account of its ability to wrap a `Box<dyn Error + Send + Sync>`. This infects `Generic` which in turn infects `Channel`, which is inconvenient because it means you can't construct a channel pair, pass the receiver side to a child thread, and then handles panics in the child. But this is silly, because the error parameter to `Generic` is just a phantom. We aren't really wrapping an error at all, let alone downcasting it to a mutable reference and mucking with the referent. This patch changes the `PhantomData<E>` to `PhantomData<AssertUnwindSafe<E>>` so that `Generic<F, E>` can be `UnwindSafe` as long as `F` is.
Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## master #204 +/- ##
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+ Coverage 85.44% 86.20% +0.75%
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Files 13 15 +2
Lines 1876 2066 +190
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+ Hits 1603 1781 +178
- Misses 273 285 +12
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std::io::Errordoes not implementUnwindSafeon account of its ability to wrap aBox<dyn Error + Send + Sync>. This infectsGenericwhich in turn infectsChannel, which is inconvenient because it means you can't construct a channel pair, pass the receiver side to a child thread, and then handles panics in the child.But this is silly, because the error parameter to
Genericis just a phantom. We aren't really wrapping an error at all, let alone downcasting it to a mutable reference and mucking with the referent. This patch changes thePhantomData<E>toPhantomData<AssertUnwindSafe<E>>so thatGeneric<F, E>can beUnwindSafeas long asFis.