Add explicit ARRAY_ELEM_REF flag

Instead of using magic value "1". Add a test for by-ref destructing
functionality in PHP 7.3. It also worked previously, this is just
improving the dumping functionality.

Author: nikic

README.md

@@ -373,6 +373,9 @@ ast\flags\EXEC_REQUIRE_ONCE
 ast\flags\ARRAY_SYNTAX_SHORT
 ast\flags\ARRAY_SYNTAX_LONG
 ast\flags\ARRAY_SYNTAX_LIST
+
+// Used by ast\AST_ARRAY_ELEM (exclusive)
+ast\flags\ARRAY_ELEM_REF
 ```
 
 AST node kinds

ast.c

@@ -191,6 +191,11 @@ static const char *array_flags[] = {
 	NULL
 };
 
+static const char *array_elem_flags[] = {
+	AST_FLAG(ARRAY_ELEM_REF),
+	NULL
+};
+
 static const char *closure_use_flags[] = {
 	AST_FLAG(CLOSURE_USE_REF),
 	NULL
@@ -239,6 +244,7 @@ static const ast_flag_info flag_info[] = {
 	{ ZEND_AST_USE_ELEM, 0, use_flags },
 	{ ZEND_AST_INCLUDE_OR_EVAL, 0, include_flags },
 	{ ZEND_AST_ARRAY, 0, array_flags },
+	{ ZEND_AST_ARRAY_ELEM, 0, array_elem_flags },
 	{ AST_CLOSURE_VAR, 0, closure_use_flags },
 	{ ZEND_AST_METHOD, 1, func_flags },
 	{ ZEND_AST_FUNC_DECL, 1, func_flags },
@@ -1152,7 +1158,8 @@ PHP_MINIT_FUNCTION(ast) {
 	ast_register_flag_constant("FUNC_RETURNS_REF", ZEND_ACC_RETURN_REFERENCE);
 	ast_register_flag_constant("FUNC_GENERATOR", ZEND_ACC_GENERATOR);
 
-	ast_register_flag_constant("CLOSURE_USE_REF", 1);
+	ast_register_flag_constant("ARRAY_ELEM_REF", 1);
+	ast_register_flag_constant("CLOSURE_USE_REF", ZEND_BIND_REF);
 
 	ast_register_flag_constant("CLASS_ABSTRACT", ZEND_ACC_EXPLICIT_ABSTRACT_CLASS);
 	ast_register_flag_constant("CLASS_FINAL", ZEND_ACC_FINAL);

tests/by_ref_destructuring.phpt

@@ -0,0 +1,65 @@
+--TEST--
+By-reference array destructuring (PHP 7.3)
+--SKIPIF--
+<?php if (PHP_VERSION_ID < 70300) die('skip PHP >= 7.3 only'); ?>
+--FILE--
+<?php
+
+require __DIR__ . '/../util.php';
+
+$code = <<<'PHP'
+<?php
+list($a, &$b) = $c;
+[$a, &$b] = $c;
+$c = [$a, &$b];
+PHP;
+echo ast_dump(ast\parse_code($code, $version=50)), "\n";
+
+?>
+--EXPECT--
+AST_STMT_LIST
+    0: AST_ASSIGN
+        var: AST_ARRAY
+            flags: ARRAY_SYNTAX_LIST (1)
+            0: AST_ARRAY_ELEM
+                flags: 0
+                value: AST_VAR
+                    name: "a"
+                key: null
+            1: AST_ARRAY_ELEM
+                flags: ARRAY_ELEM_REF (1)
+                value: AST_VAR
+                    name: "b"
+                key: null
+        expr: AST_VAR
+            name: "c"
+    1: AST_ASSIGN
+        var: AST_ARRAY
+            flags: ARRAY_SYNTAX_SHORT (3)
+            0: AST_ARRAY_ELEM
+                flags: 0
+                value: AST_VAR
+                    name: "a"
+                key: null
+            1: AST_ARRAY_ELEM
+                flags: ARRAY_ELEM_REF (1)
+                value: AST_VAR
+                    name: "b"
+                key: null
+        expr: AST_VAR
+            name: "c"
+    2: AST_ASSIGN
+        var: AST_VAR
+            name: "c"
+        expr: AST_ARRAY
+            flags: ARRAY_SYNTAX_SHORT (3)
+            0: AST_ARRAY_ELEM
+                flags: 0
+                value: AST_VAR
+                    name: "a"
+                key: null
+            1: AST_ARRAY_ELEM
+                flags: ARRAY_ELEM_REF (1)
+                value: AST_VAR
+                    name: "b"
+                key: null

tests/metadata.phpt

@@ -88,7 +88,7 @@ AST_GREATER: []
 AST_GREATER_EQUAL: []
 AST_AND: []
 AST_OR: []
-AST_ARRAY_ELEM: []
+AST_ARRAY_ELEM: [ARRAY_ELEM_REF]
 AST_NEW: []
 AST_INSTANCEOF: []
 AST_YIELD: []