Feature Request: Infer the other way.

[ivands]

The Infer function is great because it allows us to get the output types of a given struct.
However, it would also be great to be able to get the input types of a given struct.
I'll give an example of the difference:

The following struct will always output a number.

const MyNumber = coerce(number(), string(), (value) => parseFloat(value))
type OutputType = number // generated by Infer

However, it can accept numbers & strings.
So the input type would be:

type InputType = string | number

I need a way to Infer the input type of a struct.
Also, I think this would be a great addition to the already great lib.

[ianstormtaylor]

Very cool idea, I'd be open to a pull request that implements this! Feel free to talk through the implementation here too to see if it will work or what the gotchas might be.

[ivands]

Sadly I'm just learning typescript, so I'm not sure if I can be much help atm. (This might change in the future XD)
However, I do know Zod already has a way to infer the input type of a given struct.
Maybe we can learn something from their implementation.
Superstruct still has a superior API tho, because of its tree-shakeablitity, making it ideal for serverless functions.

[ziad-saab]

@ianstormtaylor I took a stab at this here: #1181

It's probably not mergeable as-is, but lmk what you think.

[ivands]

Cool work @ziad-saab 👍.
I hope it can be merged soon because we really need this feature at the moment.

@ianstormtaylor What do you think?

[hmalik88]

Bump, would like this change to be added in. Have you had a change to look? @ianstormtaylor