Collapse the 'rooted' field into the ptr #17
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| impl<T: ?Sized> !marker::Send for Gc<T> {} | ||
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| impl<T: ?Sized> !marker::Sync for Gc<T> {} | ||
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| impl<T: Trace + ?Sized + marker::Unsize<U>, U: Trace + ?Sized> CoerceUnsized<Gc<U>> for Gc<T> {} |
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This PR is broken up into two commits. The first one leaves CoerceUnsigned, but doesn't have UnsafeCell.
I don't know how to get one without removing the other. Maybe it can be done? Maybe it needs support in the standard lib?
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I believe that the CoerceUnsized constraints are a bit too strong in rustc. I believe NonZero allows for the CoerceUnsize because of this: https://github.com/rust-lang/rust/blob/f9b8c49cdb75fb571c7b3ea4af90b0e96929276c/src/libcore/nonzero.rs#L78. UnsafeCell doesn't have such an impl for it (although I believe it would be safe for it to have one).
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Implement `CoerceUnsized` for `{Cell, RefCell, UnsafeCell}`
These impls are analogous to the one for `NonZero`. It's occasionally useful to be able to coerce the cell types when they're being used inside another abstraction. See Manishearth/rust-gc#17 for an example.
r? @eddyb
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Fixed by #40 |
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Gc now stores the "rooted" state in the least-significant bit in the data pointer.