Add AST export support for nullsafe operator

Fixes oss-fuzz #24403 and variants.

Author: nikic

Zend/tests/assert/expect_015.phpt

@@ -58,6 +58,8 @@ assert(0 && ($a = function &(array &$a, ?X $b = null) use ($c,&$d) : ?X {
             $x = C::$z;
             $x = ${$a . "_1"}::$z;
             $x = C::${$z . "_1"};
+            $x?->y;
+            $x?->y();
         }
     }
 }));
@@ -198,6 +200,8 @@ Warning: assert(): assert(0 && ($a = function &(array &$a, ?X $b = null) use($c,
             $x = C::$z;
             $x = ${$a . '_1'}::$z;
             $x = C::${$z . '_1'};
+            $x?->y;
+            $x?->y();
         }
 
     }

Zend/zend_ast.c

@@ -1792,8 +1792,9 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 			smart_str_appendc(str, ']');
 			break;
 		case ZEND_AST_PROP:
+		case ZEND_AST_NULLSAFE_PROP:
 			zend_ast_export_ex(str, ast->child[0], 0, indent);
-			smart_str_appends(str, "->");
+			smart_str_appends(str, ast->kind == ZEND_AST_NULLSAFE_PROP ? "?->" : "->");
 			zend_ast_export_var(str, ast->child[1], 0, indent);
 			break;
 		case ZEND_AST_STATIC_PROP:
@@ -2066,8 +2067,9 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 
 		/* 3 child nodes */
 		case ZEND_AST_METHOD_CALL:
+		case ZEND_AST_NULLSAFE_METHOD_CALL:
 			zend_ast_export_ex(str, ast->child[0], 0, indent);
-			smart_str_appends(str, "->");
+			smart_str_appends(str, ast->kind == ZEND_AST_NULLSAFE_METHOD_CALL ? "?->" : "->");
 			zend_ast_export_var(str, ast->child[1], 0, indent);
 			smart_str_appendc(str, '(');
 			zend_ast_export_ex(str, ast->child[2], 0, indent);