Spread operator on function call won't work if the spreaded parameter is not the last

[avshyz]

TypeScript Version: 3.9.2

Search Terms: spread, rest operator, function call

Code

function foo(x: number, y: number, z: number, f: number, aleph: number) { }
function baz(x: number, y: number, z: number) { }

const args: [number, number, number] = [0, 1, 2];

baz(...args);        // working
foo(3, 1, ...args);  // working
foo(1, ...args, 2);  // COMPILER ERROR - Expected 5 arguments, but got 2 or more.(2556)
foo(...args, 3, 2);  // COMPILER ERROR - Expected 5 arguments, but got 2 or more.(2556)

Expected behavior: given every one of these lines works in js (see mdn), one could expect them to work. Especially given the first two lines worked

Actual behavior: The following compilation error

Expected 5 arguments, but got 2 or more.(2556)
input.ts(1, 36): An argument for 'z' was not provided.

Playground Link: here

Related Issues: I actually posted it as a comment here but thought it might deserve an independent bug report

[dragomirtitian]

This actually works on 4.0 Playground Link

This is probably due to #39094

[avshyz]

Oh shame, you're right!
I thought 3.9.2 is the latest version, as it's the latest one shown in the playground.

Thanks for the quick reply

[MartinJohns]

I thought 3.9.2 is the latest version, as it's the latest one shown in the playground.

@avshyz 3.9.2 is currently the latest version. TypeScript 4.0 has not yet been released (currently scheduled for August 2020), but it's available in the playground as a "nightly" version.