Parameterizing Types with Options in TypeScript

type MyTypeOptions = {
  fieldIsRequired: boolean;
};
type MyType<T extends MyTypeOptions> = {
  field: T['fieldIsRequired'] extends true ? string : string | null;
};

const one: MyType<{ fieldIsRequired: true }> = {
  // @ts-expect-error
  field: null,
};

const two: MyType<{ fieldIsRequired: true }> = {
  field: 'value',
};

const three: MyType<{ fieldIsRequired: false }> = {
  field: null,
};