Add proposal for enhanced enums in C# #9713
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Updated enum syntax to include 'class' or 'struct' keywords and clarified rules for shape enums.
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| Each case with a parameter list generates a nested record type. `enum class` generates `sealed record class` types; `enum struct` generates `readonly record struct` types. While these are the generated types, the union implementation may optimize internal storage. | ||
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| TODO: Should the structs be readonly? Seems like that goes against normal structs (including `record struct`). Seems like that could be opt in with `readonly enum struct X`. |
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This is an interesting question. I want to note that giving out refs to the fields which implement the case payloads can be problematic, especially mutable refs.
If an enum struct member, wants to be mutable, e.g. reassign the whole this to implement StateMachine.Transition(input), mutating the receiver variable, that is probably ok.
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Yup. This def seems like an ldm question. Inline with tuples and record-structs, i'm leanign toward this being mutable. Basically, we could just say that you get records, and the behavior that comes with them. Then if you really awnt readonly, you opt in, just like with record sstructs.
Co-authored-by: Rikki Gibson <[email protected]>
| enum class Result<T> | ||
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| Success(T value), | ||
| Error(string message); |
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I find this mix of commas and semicolons exceptionally unwieldy in Java enums.
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One thing i didn't fully understand; is that an alternative proposal to unions, or in addition to?
Logically they feel very similar - and thus is an alternative - but the way it's worded at times ("Shape enums inherit all union pattern matching behavior:") seems to imply unions already exist in the spec
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| Each case with a parameter list generates a nested record type. `enum class` generates `sealed record class` types; `enum struct` generates `readonly record struct` types. While these are the generated types, the union implementation may optimize internal storage. | ||
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| TODO: Should the structs be readonly? Seems like that goes against normal structs (including `record struct`). Seems like that could be opt in with `readonly enum struct X`. |
In addition to. As the spec states, these can just compile down to unions. |
Co-authored-by: Rikki Gibson <[email protected]>
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