Where in the source is useState defined?

useState is defined in [packages/react/src/ReactHooks.js:L66-L72].

Here's the implementation:

export function useState<S>(
  initialState: (() => S) | S,
): [S, Dispatch<BasicStateAction<S>>] {
  const dispatcher = resolveDispatcher();
  return dispatcher.useState(initialState);
}

The function accepts an initial state (either a value or a function that returns a value) and delegates to the dispatcher's useState method. The dispatcher is resolved at runtime via resolveDispatcher(), which allows React to use different implementations depending on the environment (like during rendering vs. outside of a component).

FOLLOW_UPS:

• What does resolveDispatcher function do?
• How does useState handle initial state functions?
• What is the Dispatch type signature?