JsValue to wasm_bindgen defined type

Suppose we have

#[wasm_bindgen::prelude::wasm_bindgen]
extern "C" {
    pub type Msg_Inner;

Is there a way to force a JsValue into a Msg_Inner ?

I.e. we have x: JsValue, and as programmer, I know for a fact that x is a TypeScript Msg_Inner. Is there a way to force cast a x into a Msg_Inner ?