Description:
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@ in argument passed into function prevents 'Fatal error: Only variables can be passed by reference' error.

Reproduce code:
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function test(& $a) {
echo $a;
}
	
$b = "hello";
test($b); // hello
test($b[0]); // 'Fatal error: Only variables can be passed by reference'
test(@ $b[0]); // h

Expected result:
----------------
'Fatal error: Only variables can be passed by reference'

Actual result:
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test(@ $b[0]); // h