Document metadata of ptrs to indirectly unsized types#2289
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We say that pointers to DSTs store metadata and what that metadata is for pointers to slices, `str`, and trait objects. But a struct or tuple with an unsized tail is itself a DST, and we hadn't said what the metadata is for pointers to these unsized types. Now that we've defined *metadata* and *unsized tail*, let's complete this enumeration.
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This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed. Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers. |
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We say that pointers to DSTs store metadata and what that metadata is for pointers to slices,
str, and trait objects. But a struct or tuple with an unsized tail is itself a DST, and we hadn't said what the metadata is for pointers to these unsized types.Now that we've defined metadata and unsized tail, let's complete this enumeration.
I'm breaking this out from #2282 so that we can merge the prerequisites before considering the new lang guarantees.
This is stacked on #2286 and #2287 and #2288 and #2290 (yes, that one is out of order) and those should be merged first.
cc @ehuss @RalfJung @Mark-Simulacrum