JSXv4: Nested component definitions yields confusing error

[glennsl]

Repro

module Outer = {
  @react.component
  let make = () => {
    module Inner = {
      @react.component
      let make = () => <div />
    }

    <Inner />
  }
}

causes the error:

React: props need to be labelled arguments.
  If you are working with refs be sure to wrap with React.forwardRef.
  If your component doesn't have any props use () or _ instead of a name.

without any location information.

This used to work in JSX v3.

[cristianoc]

This is a "fun" one: the transform uses an ast mapper, which transforms the inner component before the outer one.
The inner component transformation leaves behind @react.component after applying the transformation.
When the outer component is transformed, its body is processed again and the inner component transformed again after having already been transformed, leading to the weird error observed here.

I have a fix I'll put into a PR.