Description:
------------
In the proposal of short closures (https://wiki.php.net/rfc/arrow_functions_v2) the following is stated:

"When a variable used in the expression is defined in the parent scope it will be implicitly captured by-value."

With this example:


$y = 1;

$fn1 = fn($x) => $x + $y;

$fn2 = function ($x) use ($y) {
    return $x + $y;
};

These two behave exactly the same, as expected.
However compact doesn't behave that way, as it doesn't recognize a variable from outer scope until it is explicitly called.

Test script:
---------------
$name = 'foo';
$array = ['bar'];

$failing = fn($value) => compact('name', 'value');
$working = fn($value) => compact('name', 'value') + [$name];

var_dump(array_map($failing, $array));
var_dump(array_map($working, $array));

Expected result:
----------------
Short closures using compact should resolve outer scoped variables and behave like "long" closures using an use statement.

fn($value) => compact('name', 'value')

should work just like

function($value) use ($name) {
    return compact('name', 'value');
}

And return the following

array(1) {
  [0]=>
  array(3) {
    ["name"]=>
    string(3) "foo"
    ["value"]=>
    string(3) "bar"
  }
}

Actual result:
--------------
// Notice: compact(): Undefined variable: name

array(1) {
  [0]=>
  array(1) {
    ["value"]=>
    string(3) "bar"
  }
}