[justinmchase]

I mostly agree, having every single type checked all the time like other static languages is not appropriate and probably not even a good idea but on the other hand it is also kind of annoying to have your validation code be divorced from your types totally.

For example suppose I have a web request coming in and I have essentially just a string of input coming in on the body. I have an expectation of what it needs to be but there is a step where it is of type `unknown` and I need to convert it into `IMyHandlerInput`. Just casting it is obviously a bad idea and so now I need to essentially use some kind of library such as ajv to do json schema or jtd validation, _then_ I can cast it into my interface.

This is all fine but it definitely feels redundant to me. It would be a cool _ecmascript_ feature to essentially support, not runtime types per-se but syntactic _validation_ which can also be used by typescript to derive types automatically.

This is totally hypothetical but I'm imagining something like this for example:

```ts schema Example { @min 0 id: number

  @pattern /^\w+ \w+$/
  name: string

  @future
  expiresAt: Date

}

const data: Example = new Example(JSON.parse(body)) ```

Something that the JS runtime can use to allow developers to opt-in to extensible validation which can also be used by the typescript interpreter to essentially derive types.