pipe operator (`|>`) fails to correctly handle returning by reference

[azjezz]

Description

There appears to be a bug in how the new pipe operator (|>) handles functions that return by reference. An expression using the pipe operator is not behaving identically to its equivalent standard function call, specifically when a reference is expected to be returned.

The expression "foo" |> get_ref(...) should, in theory, be functionally equivalent to $c = get_ref(...); $c("foo");. However, the two produce different results when the function is declared to return a reference.

This code correctly returns a reference to the static variable within get_ref without any errors ( https://3v4l.org/Ojaah ):

<?php

function &get_ref($_): string {
    static $a = "f";
    return $a;
}


function &get_ref2(): string {
    $c = get_ref(...);    
    return  $c("foo");
}

echo get_ref2();

This version, which should be equivalent, incorrectly throws a notice ( https://3v4l.org/po5A6 ):

<?php

function &get_ref($_): string {
    static $a = "f";
    return $a;
}


function &get_ref2(): string {
    return "foo" |> get_ref(...);
}

echo get_ref2();

PHP Version

master

Operating System

N/A