Add test for evaluation order

Zend/tests/list_keyed_evaluation_order.phpt

@@ -0,0 +1,85 @@
+--TEST--
+list() with keys, evaluation order
+--FILE--
+<?php
+
+// list($a => $b, $c => $d) = $e;
+// Should be evaluated in the order:
+// 1. Evaluate $e
+// 2. Evaluate $a
+// 3. Evaluate $e[$a]
+// 4. Assign $b from $e[$a]
+// 5. Evaluate $c
+// 6. Evaluate $e[$c]
+// 7. Assign $c from $e[$a]
+
+// In order to observe this evaluation order, let's use some observer objects!
+
+class Stringable
+{
+    private $name;
+    public function __construct(string $name) {
+        $this->name = $name;
+    }
+
+    public function __toString(): string {
+        echo "$this->name evaluated.", PHP_EOL;
+        return $this->name;
+    }
+}
+
+class Indexable implements ArrayAccess
+{
+    public function offsetExists($offset): bool {
+        echo "Existence of offset $offset checked for.", PHP_EOL;
+        return true;
+    }
+
+    public function offsetUnset($offset): void {
+        echo "Offset $offset removed.", PHP_EOL;
+    }
+
+    public function offsetGet($offset) {
+        echo "Offset $offset retrieved.", PHP_EOL;
+        return "value for offset $offset";
+    }
+
+    public function offsetSet($offset, $value): void {
+        echo "Offset $offset set to $value.", PHP_EOL;
+    }
+}
+
+class IndexableRetrievable
+{
+    private $label;
+    private $indexable;
+    
+    public function __construct(string $label, Indexable $indexable) {
+        $this->label = $label;
+        $this->indexable = $indexable;
+    }
+
+    public function getIndexable(): Indexable {
+        echo "Indexable $this->label retrieved.", PHP_EOL;
+        return $this->indexable;
+    }
+}
+
+$a = new Stringable("A");
+$c = new Stringable("C");
+
+$e = new IndexableRetrievable("E", new Indexable(["A" => "value for A", "C" => "value for C"]));
+
+$store = new Indexable;
+
+list((string)$a => $store["B"], (string)$c => $store["D"]) = $e->getIndexable();
+
+?>
+--EXPECT--
+Indexable E retrieved.
+A evaluated.
+Offset A retrieved.
+Offset B set to value for offset A.
+C evaluated.
+Offset C retrieved.
+Offset D set to value for offset C.