What is the reason for it passing the type check?

I'm really struggling to understand this part:

import axios from 'axios'
import * as TE from 'fp-ts/lib/TaskEither'

export const getIntent = (sessionId: string, input: string) => process.env.INTENT_URL
  ? TE.tryCatch(
      () => axios.post(`${process.env.INTENT_URL}`,{sessionId, input}),
      reason => String(reason))
  : TE.left(Error("No INTENT_URL")
)

It seems like Left is being assigned a value of type String and/or Error, even though they are not the same. How does this code pass type checking???

typescripttypescript-typingstypecheckingfp-ts

Answer №1

Similar to why this code successfully compiles:

export const getResult = () => process.env.RESULT_URL
  ? true
  : "false"

The absence of a return type declaration in your function prompts typescript to widen the return type as a union type to encompass all possible return values.

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