Composition and generics

[wclr]

This errors:

R.compose(R.fromPairs)([['1','A'], ['2','B'], ['3','C']])

[ts] Argument of type '[string, string][]' is not assignable to parameter of type 'KeyValuePair<number, any>[]'.
  Type '[string, string]' is not assignable to type 'KeyValuePair<number, any>'.
    Types of property '0' are incompatible.
      Type 'string' is not assignable to type 'number'.

Though this works as it should (without compose and with numbered index)

R.fromPairs([['1','A'], ['2','B'], ['3','C']])

R.compose(R.fromPairs)([[1,'A'], [2,'B'], [3,'C']])

[KiaraGrouwstra]

Thank you for posting this.
From what I can see, this issue relates to interaction between composition and functions with generics. The more recent thread #92 appeared to be about the same problem. I currently intend to track this issue in #78, about currying rather than composition but otherwise seemingly the same issue. I've integrated your example into the test suite, so we won't forget.
I agree inference failing here is a significant issue, and I hope we can find a solution.

[KiaraGrouwstra]

Minimum reproduction: R.pipe(R.identity) kills generics, degenerating to {} => {}.

[KiaraGrouwstra]

Comes down to microsoft/TypeScript#16072 (comment). May get viable after microsoft/TypeScript#6606.