Merge branch 'PHP-8.1'

* PHP-8.1:
  Fixed type inference

Author: dstogov

Zend/Optimizer/zend_inference.c

@@ -2813,6 +2813,9 @@ static zend_always_inline zend_result _zend_update_type_info(
 				if (t1 & ((MAY_BE_ANY|MAY_BE_UNDEF) - MAY_BE_STRING)) {
 					tmp |= (OP1_DATA_INFO() & (MAY_BE_ANY | MAY_BE_ARRAY_KEY_ANY | MAY_BE_ARRAY_OF_ANY | MAY_BE_ARRAY_OF_REF));
 
+					if (OP1_DATA_INFO() & MAY_BE_UNDEF) {
+						tmp |= MAY_BE_NULL;
+					}
 					if (opline->op2_type == IS_UNUSED) {
 						/* When appending to an array and the LONG_MAX key is already used
 						 * null will be returned. */

ext/opcache/tests/jit/assign_dim_003.phpt

@@ -0,0 +1,20 @@
+--TEST--
+JIT ASSIGN_DIM: 003
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.file_update_protection=0
+opcache.jit_buffer_size=1M
+opcache.jit=tracing
+--EXTENSIONS--
+opcache
+--FILE--
+<?php
+function test() {
+    var_dump($a[0] = $v);
+}
+test();
+?>
+--EXPECTF--
+Warning: Undefined variable $v in %sassign_dim_003.php on line 3
+NULL