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Comment by brlewis | Hacker News Reader

"For this function named `call`, the first argument must be a function `fn`, and subsequent arguments must be the type of arguments that `fn` expects. The return value of `call` is the same type as the return value of `fn`."

How would you recommend communicating all that in an extended version of ECMAscript?

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I like TypeScript's syntax, but I think the way function types are declared is ugly.

If you have a function from A to B, you have to declare its type as

    type MyFunction = (arg1: A) => B

instead of

    type MyFunction = A => B

Here's that syntax applied to the example from GP:

    function call<TS extends any[], R>(fn: (...args: TS) => R, ...args: TS): R { return fn(...args); }

vs.

    function call<TS extends any[], R>(fn: ...TS => R, ...args: TS): R { return fn(...args); }

The syntax is probably meant to differentiate between a function expression and a function type declaration.

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