On Thu, Aug 11, 2022 at 7:40 PM 'Matt Rosencrantz' via golang-nuts <
golang-nuts@googlegroups.com> wrote:
> I'd really love to be able to do:
>
> type allowedTypes{
> int64|float64|string
> }
>
> func Foo[T allowedTypes](arg T) {
> switch t := arg {
> case int64:
> // something
> case string:
> // something completely different
> }
> }
>
>
As a way of having the type checker disallow other types from being passed
> so I don't have to return an error for incorrect types. I guess this would
> be the same as asking for typesets to be allowed in normal interfaces like:
>
> func Foo(arg allowedTypes) {...}
>
> Is there another way to achieve this? Is there a reason it is not possible?
>
The type-parameters proposal discusses this a little.
You can cast your arg to an interface-type before type-asserting.
https://go.googlesource.com/proposal/+/HEAD/design/43651-type-parameters.md#identifying-the-matched-predeclared-type
Note that the design uses the interface{} syntax, while you can now use
"any" when converting to an interface.
Worth noting: you'll still have a runtime cost to the type-switch.
> Thanks!
> Matt
>
>
>
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