[swift-evolution] Ad hoc enums / options

Austin Zheng austinzheng at gmail.com
Tue May 31 23:24:18 CDT 2016

I admire the desire of this proposal to increase the readability of code.
I'm -1 to the proposal itself, though:

- It breaks the ability to pass in a variable containing the desired value,
rather than the literal value itself. (Unless you actually want a
not-so-anonymous enum type whose definition happens to live in a function
signature rather than somewhere you'd usually expect a type definition to
- It breaks the ability to store a reference to the function in a variable
of function type (ditto).
- Almost every time I've wanted to use one of these "anonymous enums" in my
code, I've ended up needing to use that same enum elsewhere. In my
experience, 'lightweight enums' don't end up saving much time compared to a
full-fledged one.

Like Brent said, I have to say no to any proposal that tries to make enums
synonyms for numerical values. What happens if you rearrange your anonymous
enum cases between library versions? Do you somehow store an opaque
case-to-UInt8 table somewhere for every anonymous enum you define for
resilience? What happens when people start bringing back terrible C
patterns, like doing arithmetic or bitwise ops on the underlying case
values? At least you have to try pretty hard as it is to abuse Swift's


On Tue, May 31, 2016 at 8:25 PM, Brent Royal-Gordon via swift-evolution <
swift-evolution at swift.org> wrote:

> > And the obvious answer is you can have up to 255 of these babies for the
> anonymous enum type, and be able to pass numerical equivalents UInt8 with
> compile time substitution. That the ad-hoc enumeration is basically a
> syntactic shorthand for UInt8, with an enforced upper bound compile time
> check simplifies everything including switch statements.
> If I wanted a language like that, I'd be writing C, not Swift.
> --
> Brent Royal-Gordon
> Architechies
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
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