So far I was able to get around this error by manually specifying error types: sequenceS(E.either as E.as apply.Apply2C< 'Either', ValidateEmailError | ValidatePasswordError)({ email: validateEmail(email), password: validatePassword(password), }) But it still is not pretty.

The problem with this code: sequenceS(E.either)({ email: validateEmail(email), password: validatePassword(password), }) Is if validateEmail and validatePassword has different left types it wont compile. Is there a way around this?