partial application typing fail with custom error type

[samuela]

Bug Report

🔎 Search Terms

partial application, currying, type inference, higher-order functions, polymorphism

🕗 Version & Regression Information

Affects [email protected] and v4.5.0-beta.

• I was unable to test this on prior versions because of the following error:

❯ npm i -D typescript@next
npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR! 
npm ERR! Found: [email protected]
npm ERR! node_modules/typescript
npm ERR!   dev typescript@"4.6.0-dev.20211105" from the root project
npm ERR! 
npm ERR! Could not resolve dependency:
npm ERR! peerOptional typescript@">=3.3.1" from [email protected]
npm ERR! node_modules/eslint-config-next
npm ERR!   dev eslint-config-next@"12.0.2" from the root project
npm ERR! 
npm ERR! Fix the upstream dependency conflict, or retry
npm ERR! this command with --force, or --legacy-peer-deps
npm ERR! to accept an incorrect (and potentially broken) dependency resolution.
npm ERR! 
npm ERR! See /Users/skainswo/.npm/eresolve-report.txt for a full report.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/skainswo/.npm/_logs/2021-11-05T19_54_53_547Z-debug.log

⏯ Playground Link

Playground link with relevant code

💻 Code

// See https://github.com/Microsoft/TypeScript/issues/7556.
type ErrorT = { new (message: string): Error };

function _notNull<T>(errorType: ErrorT, v: T | null | undefined): T {
  if (v === null || v === undefined) {
    throw new errorType("error message");
  }
  return v;
}

const partial =
  <A, B, T>(f: (a: A, b: B) => T, a: A) =>
  (b: B) =>
    f(a, b);

function partial2<A, B, T>(f: (a: A, b: B) => T, a: A) {
  return (b: B) => f(a, b);
}

// good: (b: number) => number
const sumPartial = partial((a: number, b: number) => a + b, 5);
const sumPartial2 = partial2((a: number, b: number) => a + b, 5);

// good: <T>(v: T | null | undefined) => T
const notNull = <T>(v: T | null | undefined) => _notNull(Error, v);

// bad: (v: unknown) => unknown
const notNull2 = _notNull.bind(null, Error);
const notNull3 = partial(_notNull, Error);
const notNull4 = partial2(_notNull, Error);

export {};

🙁 Actual behavior

_notNull.bind(null, Error), partial(_notNull, Error), and partial2(_notNull, Error) are typed unhelpfully as (v: unknown) => unknown. I can understand that bind is messy to infer types on, but I don't understand the trouble with partial and partial2 which are defined with simple type signatures.

🙂 Expected behavior

For everything to have the type <T>(v: T | null | undefined) => T.

[andrewbranch]

Duplicate of #30727 (different example, same problem)

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.