Equivalent arguments typed with tuples aren't assignable to the same functions with overloads when the same function is recursively referenced

Bug Report

🔎 Search Terms

arguments, overloads, function, tuple

🕗 Version & Regression Information

All versions with support for tuple arguments (upto v4.5.0-dev.20210815).

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about function overloading (there is nothing in the FAQ about tuples)

⏯ Playground Link

Playground link with relevant code

💻 Code

type START = 0
type DATA = 1

type Args<In, Out> =
  | [t: START, other: FnWithArgs<Out, In>]
  | [t: DATA]

type FnWithArgs<In, Out> = (...args: Args<In, Out>) => void

interface FnWithOverloads<In, Out> {
  (t: START, other: FnWithOverloads<Out, In>): void;
  (t: DATA): void;
}

declare const withArgs: FnWithArgs<1, 2>

// these should be assignable to one another, but aren't:
const assertion: FnWithOverloads<1, 2> = withArgs

🙁 Actual behavior

Two types that should be functionally equivalent aren’t assignable to one another:

Type 'FnWithArgs<1, 2>' is not assignable to type 'FnWithOverloads<1, 2>'.
  Types of parameters 'args' and 't' are incompatible.
    Type '[t: 0, other: FnWithOverloads<2, 1>]' is not assignable to type 'Args<1, 2>'.
      Type '[t: 0, other: FnWithOverloads<2, 1>]' is not assignable to type '[t: 0, other: FnWithArgs<2, 1>]'.
        Type at position 1 in source is not compatible with type at position 1 in target.
          Type 'FnWithOverloads<2, 1>' is not assignable to type 'FnWithArgs<2, 1>'.
            Types of parameters 't' and 'args' are incompatible.
              Type 'Args<2, 1>' is not assignable to type '[t: 0, other: FnWithOverloads<1, 2>]'.
                Type '[t: 1]' is not assignable to type '[t: 0, other: FnWithOverloads<1, 2>]'.
                  Source has 1 element(s) but target requires 2.

I’ve tried simplifying the example, and this issue doesn’t seem to occur when the parameters of the function don’t reference themselves in their signature.

🙂 Expected behavior

No error, types should be assignable to one another.

Related issues

• https://github.com/microsoft/TypeScript/issues/29732
• https://github.com/microsoft/TypeScript/issues/32164

[RyanCavanaugh]

The root of the issue seems to be that TS wants to be able to “choose” a specific overload

This is a correct analysis of what’s going wrong, but also a frequent source of complaint. Barring the problems of combinatorial explosion, this “should” work but doesn’t.

[andrewbranch]

It means we’d like to see how many people 👍 this issue and comment with other solutions and ideas before considering it more.