[derive] Derive TryFromBytes on unions #800
Merged
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The implementation itself is very straightforward, but it requires a few prerequisite changes:
Ptr::project
method now requires that it only be called on struct and union typesAsInitialized
invariant property is changed in a subtle but important way. Previously, a byte offset in a type was required to be initialized if, in every instance of that type, it was initialized. Now, this is required if the byte is initialized in /any/ instance of the type. Without this change, it would be possible to invokeTryFromBytes::is_bit_valid
on a byte sequence where an uninitialized byte appears which is valid for one union field but not valid for another. Since we check bit validity for all union fields, uninitialized bytes may only appear which are compatible with /all/ union fields.