TS2440

error TS2440: Import declaration conflicts with local declaration of ‘React‘.

Broken Code ❌

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import React from 'react';

declare module React {
  type MyCustomType<P> = void;
}

Fixed Code ✔️

You cannot redeclare a module that you are importing, but you can outsource your additional typings to a declaration file in order to apply declaration merging:

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declare namespace React {
  type MyCustomType<P> = void;
}