Implicit type conversion?

Hello,
I’m exploring rescript-react and noticed a peculiar behaviour. Here’s my test code:

module MyComponent = {
  @react.component
  let make = () => {
    let (value, setValue) = React.useState(_ => 0)
    <>
      <div> {React.string(string_of_int(value))} </div>
      <input
        onChange={evt => {
          let x = ReactEvent.Form.target(evt)["value"] // 1
          setValue(_ => x) // 2
        }}
      />
    </>
  }
}

What I noticed is that on the line marked with // 1 the type of x is 'a, but on line // 2 hovering over x shows the type int. Why is that? I would expect the compiler to ask me to decode the value of x.

Thank you in advance!

P.S.

• Playground
• a thread on the forum

Start with the ReactEvent.Form.target(evt)["value"] expression and the useState setter in the supplied component, then reproduce the behavior using the linked Playground. Compare the result with the linked forum thread and determine whether the inferred type is intentional; done means the behavior is clarified or a concrete repository change is identified.