TypeScript 管道/组合函数时输入错误

Question

When piping data that varies in type, I receive typing errors. How can I satisfy TypeScript?

const square = (x: number) => x * x

console.log(
  R.pipe(
    R.add, // two values
    square // one value
  )(1, 2)
)

[tsserver 2769] [E] No overload matches this call.The last overload gave the following error.

Argument of type '(x: number) => number' is not assignable to parameter of type '(x: (b: number) => number) => number'.

Types of parameters 'x' and 'x' are incompatible.

Type '(b: number) => number' is not assignable to type 'number'.

I have @types/ramda installed.

Answer 1

This is an unsatisfying solution, but it does work. I temporarily replaced R.add with a locally defined function of simpler type:

const add = (a: number, b: number) => a + b
const square = (x: number) => x * x

console.log(
  R.pipe(
    add, // two values
    square // one value
  )(1, 2)
)

Observing the instantiation of R.pipe in your original non-compiling example ( <number, number> ) vs. this simplified example ( <number, number, number, number> ), I realized that TypeScript was incorrectly choosing the curried overload of R.add and getting confused from there. If we explicitly instantiate R.pipe with the correct total arity, the compiler makes the right decision:

const square = (x: number) => x * x

console.log(
  R.pipe<number, number, number, number>(
    R.add, // two values
    square // one value
  )(1, 2)
)