Allow unlinked classes when performing in_compilation variance check

As preloading runs in in_compilation mode, we also need to allow
use of unlinked classes in lookup_class().

Author: nikic

Zend/zend_inheritance.c

@@ -239,10 +239,9 @@ static zend_bool class_visible(zend_class_entry *ce) {
 
 static zend_class_entry *lookup_class(
 		zend_class_entry *scope, zend_string *name, zend_bool register_unresolved) {
-	zend_class_entry *ce;
+	uint32_t flags = ZEND_FETCH_CLASS_ALLOW_UNLINKED | ZEND_FETCH_CLASS_NO_AUTOLOAD;
+	zend_class_entry *ce = zend_lookup_class_ex(name, NULL, flags);
 	if (!CG(in_compilation)) {
-		uint32_t flags = ZEND_FETCH_CLASS_ALLOW_UNLINKED | ZEND_FETCH_CLASS_NO_AUTOLOAD;
-		ce = zend_lookup_class_ex(name, NULL, flags);
 		if (ce) {
 			return ce;
 		}
@@ -256,7 +255,6 @@ static zend_class_entry *lookup_class(
 			zend_hash_add_empty_element(CG(delayed_autoloads), name);
 		}
 	} else {
-		ce = zend_lookup_class_ex(name, NULL, ZEND_FETCH_CLASS_NO_AUTOLOAD);
 		if (ce && class_visible(ce)) {
 			return ce;
 		}

ext/opcache/tests/preload_variance.inc

@@ -14,11 +14,13 @@ class C extends Z {
     public function method($a): self {}
     public function method2($a): C {}
     public function method3($a): object {}
+    public function method4(D $a) {}
 }
 class D extends C {
     public function method($a): self {}
     public function method2($a): D {}
     public function method3($a): stdClass {}
+    public function method4(C $a) {}
 }
 
 // Works.