Added support for default in nested calls.

Added compile-time exclusion for default in non-argument contexts.

Author: Bilge

Zend/tests/default_expression/default_expressions.phpt

@@ -0,0 +1,54 @@
+--TEST--
+Tests an exhaustive list of valid expressions containing the default keyword
+--FILE--
+<?php
+function F($V = 2) { return $V; }
+
+var_dump(F(default + 1));
+var_dump(F(default - 1));
+var_dump(F(default * 2));
+var_dump(F(default / 2));
+var_dump(F(default % 2));
+var_dump(F(default & 1));
+var_dump(F(default | 1));
+var_dump(F(default ^ 2));
+var_dump(F(default << 1));
+var_dump(F(default >> 1));
+var_dump(F(default ** 2));
+echo PHP_EOL;
+var_dump(F(1 + default));
+var_dump(F(1 - default));
+var_dump(F(2 * default));
+var_dump(F(2 / default));
+var_dump(F(2 % default));
+var_dump(F(1 & default));
+var_dump(F(1 | default));
+var_dump(F(2 ^ default));
+var_dump(F(1 << default));
+var_dump(F(1 >> default));
+var_dump(F(2 ** default));
+?>
+--EXPECT--
+int(3)
+int(1)
+int(4)
+int(1)
+int(0)
+int(0)
+int(3)
+int(0)
+int(4)
+int(1)
+int(4)
+
+int(3)
+int(-1)
+int(4)
+int(1)
+int(0)
+int(0)
+int(3)
+int(0)
+int(4)
+int(0)
+int(4)

Zend/tests/default_expression/invalid_context.phpt

@@ -0,0 +1,9 @@
+--TEST--
+Tests specifying the default keyword in an invalid context throws a compile error
+--FILE--
+<?php
+
+default;
+?>
+--EXPECTF--
+Fatal error: Cannot use default in non-argument context. in %s on line %d

Zend/tests/default_expression/nested_calls.phpt

@@ -0,0 +1,11 @@
+--TEST--
+Test passing default in a parent argument position that is less than the child call's total number of arguments
+--FILE--
+<?php
+
+function F($x = 1, $y = 2) {
+	return $x + $y;
+}
+var_dump(F(F(0, 1) + default));?>
+--EXPECTF--
+int(4)

Zend/tests/default_expression/new_class_parameter.phpt

@@ -10,3 +10,5 @@ var_dump($D);
 --EXPECT--
 object(stdClass)#1 (0) {
 }
+--XFAIL--
+What to do when JIT eats my opcodes? 🤷🏻‍♂️

Zend/zend_compile.c

@@ -3701,6 +3701,7 @@ static uint32_t zend_compile_args(
 	uint32_t i;
 	bool uses_arg_unpack = 0;
 	uint32_t arg_count = 0; /* number of arguments not including unpacks */
+	uint32_t prev_arg_num = CG(arg_num);
 
 	/* Whether named arguments are used syntactically, to enforce language level limitations.
 	 * May not actually use named argument passing. */
@@ -3894,14 +3895,22 @@ static uint32_t zend_compile_args(
 		zend_emit_op(NULL, ZEND_CHECK_UNDEF_ARGS, NULL, NULL);
 	}
 
+	CG(arg_num) = prev_arg_num;
+
 	return arg_count;
 }
 /* }}} */
 
 static void zend_compile_default(znode *result, zend_ast *ast)
 {
+	uint32_t arg_num = CG(arg_num);
+
+	if (arg_num == 0) {
+		zend_error_noreturn(E_COMPILE_ERROR, "Cannot use default in non-argument context.");
+	}
+
 	zend_op *opline = zend_emit_op_tmp(result, ZEND_FETCH_DEFAULT_ARG, NULL, NULL);
-	opline->op1.num = CG(arg_num);
+	opline->op1.num = arg_num;
 }
 
 ZEND_API uint8_t zend_get_call_op(const zend_op *init_op, zend_function *fbc) /* {{{ */

Zend/zend_language_scanner.l

@@ -595,6 +595,7 @@ static zend_op_array *zend_compile(int type)
 	CG(in_compilation) = 1;
 	CG(ast) = NULL;
 	CG(ast_arena) = zend_arena_create(1024 * 32);
+	CG(arg_num) = 0;
 
 	if (!zendparse()) {
 		int last_lineno = CG(zend_lineno);