Impose named argument for a variadic function

[GromNaN]

When you use variadic arguments with named arguments, the argument value can be a list or an associative array (a map).

Thanks to the @no-named-argument annotation, I can express that a list is expected: https://psalm.dev/r/0bcbce94a6

The question is to do the opposite: How can I specify that the named arguments must be used?

Exhaustive examples of calling a variadic function

function variadic(... $values) {
    var_dump($values);
}

List

variadic(1);
variadic(...[1]);
// array(1) { [0] => int(1) }

Map

variadic(a: 2);
variadic(...['a' => 2]);
// array(1) { ["a"] => int(2) }

Mix list and map

variadic(3, b:4);
variadic(...[3, 'b' => 4]);
// array(2) { [0] => int(3), ["b"] => int(4) }

named argument before positional argument not supported

variadic(b:4, 3);
variadic(...['b' => 4, '0' => 3]);
// Cannot use positional argument after named argument

Array unpacking allows to use invalid names

variadic(...['complex.string' => 5], c: 6);
// array(2) { ["complex.string"] => int(5), ["c"] => int(6) }

But order have to be respected

variadic(c: 6, ...['complex.string' => 5]);
// Cannot use argument unpacking after named arguments

Numeric name cannot be used with named arguments

variadic(7:8); 
// syntax error, unexpected token ":", expecting ")"

[GromNaN]

The @no-named-argument annotation was identified and fixed in #5420.

A @require-named-argument may be useful.