Do not emit ZEND_VERIFY_RETURN_TYPE if we return $this and return value is static

Author: Girgias

Zend/zend_compile.c

@@ -2696,6 +2696,17 @@ static void zend_emit_return_type_check(
 			/* we don't need run-time check */
 			return;
 		}
+		
+		/* If return type contains static and we are returning $this
+		 * (determined by checking if the previous opcode is ZEND_FETCH_THIS)
+		 * then we don't need to check the return type */
+		if (expr && ZEND_TYPE_CONTAINS_CODE(type, IS_STATIC)) {
+			const zend_op_array *op_array = CG(active_op_array);
+			zend_op previous = op_array->opcodes[op_array->last-1];
+			if (previous.opcode == ZEND_FETCH_THIS) {
+				return;
+			}
+		}
 
 		opline = zend_emit_op(NULL, ZEND_VERIFY_RETURN_TYPE, expr, NULL);
 		if (expr && expr->op_type == IS_CONST) {

ext/opcache/tests/opt/elide_static_verify_return_type_for_this.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Return type check elision
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.optimization_level=-1
+opcache.opt_debug_level=0x20000
+opcache.preload=
+--EXTENSIONS--
+opcache
+--FILE--
+<?php
+
+class C {
+    public function returnStatic(): static {
+        return $this;
+    }
+}
+
+?>
+--EXPECTF--
+$_main:
+     ; (lines=1, args=0, vars=0, tmps=0)
+     ; (after optimizer)
+     ; %s:1-10
+0000 RETURN int(1)
+
+C::returnStatic:
+     ; (lines=2, args=0, vars=0, tmps=1)
+     ; (after optimizer)
+     ; %s:4-6
+0000 T0 = FETCH_THIS
+0001 RETURN T0