Add a (short) chapter on Kind
#282
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oli-obk
reviewed
Feb 16, 2019
| `UnpackedKind`s first. This is done by calling the `.unpack()` method. | ||
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| ```rust | ||
| // An example of unpacking and packing a kind. |
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you need imports here in order to make the example compile and pass travis
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Can you make this example compile and pass without importing the whole compiler? Usually, I just add rust,ignore...
eddyb
reviewed
Mar 14, 2019
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| ## `Kind` | ||
| The actual `Kind` struct is optimised for space, storing the type, lifetime or | ||
| const as an interned pointer containing a mask identifying its kind (in the |
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The lowest 2 bits are the "tag", a (bit) "mask" is what you use to "mask out" bits other than the ones you're interested in (e.g. let (tag, ptr) = (x & 0b11, x & !0b11); uses 0b11 to get the lowest 2 bits and !0b11 for everything else).
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This chapter briefly describes the use of
Kind,UnpackedKindandSubst.This has been delayed long enough that I think it's worth getting something in the guide, just to provide some explanation. We can always extend this in the future with more examples.
Fixes #97.