> On Jun 21, 2016, at 12:45 PM, Joe Groff via swift-evolution
> <[email protected]> wrote:
>
> Regarding the issue of existential metatypes with sizeof:
>
> Pyry Jahkola points out one instance where the memorySize(type(of: …))
> workaround won't work. When the value is an existential, it's illegal to ask
> for the size of its dynamic type: the result can't be retrieved at compile
> time:
>
> let i = 123
> let c: CustomStringConvertible = i
> print(sizeof(c.dynamicType)) // error: cannot invoke 'sizeof' with an
> argument list of type '(CustomStringCo
> This could be enabled by having sizeof and friends formally take an Any.Type
> instead of <T> T.Type. (This might need some tweaking of the underlying
> builtins to be able to open existential metatypes, but it seems
> implementable.)
While I'm not a huge fan of Dave A's generic struct approach (for reasons
detailed in the proposal), this could resolve one major issue I currently have
with his alternative.
-- E
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