Omit discriminant from nullary univariant enums.#4866
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jld wants to merge 1 commit intorust-lang:incomingfrom
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Omit discriminant from nullary univariant enums.#4866jld wants to merge 1 commit intorust-lang:incomingfrom
jld wants to merge 1 commit intorust-lang:incomingfrom
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If an enum is isomorphic to unit, there's no need to use any bits to represent it. The only obvious reason this wasn't the case was because the enum could be C-like and have a user-specified discriminant -- but that value is constant, so it doesn't need to be stored. This change means that all newtype-like enums have the same size (and layout) as their underlying type, which might be a useful property to have, at least in terms of making programs' low-level behavior less surprising.
bors
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Feb 10, 2013
If an enum is isomorphic to unit, there's no need to use any bits to represent it. The only obvious reason this wasn't the case was because the enum could be C-like and have a user-specified discriminant -- but that value is constant, so it doesn't need to be stored. This change means that all newtype-like enums have the same size (and layout) as their underlying type, which might be a useful property to have, at least in terms of making programs' low-level behavior less surprising.
RalfJung
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Mar 4, 2026
Fix typo in tracing.md for `tracing_separate_thread`
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If an enum is isomorphic to unit, there's no need to use any bits to
represent it. The only obvious reason this wasn't the case was because
the enum could be C-like and have a user-specified discriminant -- but
that value is constant, so it doesn't need to be stored.
This change means that all newtype-like enums have the same size (and
layout) as their underlying type, which might be a useful property to
have, at least in terms of making programs' low-level behavior less
surprising.