allow null coalescing (??) on constant expressions

Author: marcioAlmada

Zend/tests/constant_expressions_coalesce.phpt

@@ -0,0 +1,45 @@
+--TEST--
+Constant expressions with null coalescing operator ??
+--FILE--
+<?php
+
+const A = [1 => [[]]];
+
+const T_1 = null ?? A[1]['undefined']['index'] ?? 1;
+const T_2 = null ?? A['undefined']['index'] ?? 2;
+const T_3 = null ?? A[1][0][2] ?? 3;
+const T_4 = A[1][0][2] ?? 4;
+
+var_dump(T_1);
+var_dump(T_2);
+var_dump(T_3);
+var_dump(T_4);
+
+var_dump((function(){ static $var = null ?? A[1]['undefined']['index'] ?? 1; return $var; })());
+var_dump((function(){ static $var = null ?? A['undefined']['index'] ?? 2; return $var; })());
+var_dump((function(){ static $var = null ?? A[1][0][2] ?? 3; return $var; })());
+var_dump((function(){ static $var = A[1][0][2] ?? 4; return $var; })());
+
+var_dump((new class { public $var = null ?? A[1]['undefined']['index'] ?? 1; })->var);
+var_dump((new class { public $var = null ?? A['undefined']['index'] ?? 2; })->var);
+var_dump((new class { public $var = null ?? A[1][0][2] ?? 3; })->var);
+var_dump((new class { public $var = A[1][0][2] ?? 4; })->var);
+
+const D = [][] ?? 1;
+
+?>
+--EXPECTF--
+int(1)
+int(2)
+int(3)
+int(4)
+int(1)
+int(2)
+int(3)
+int(4)
+int(1)
+int(2)
+int(3)
+int(4)
+
+Fatal error: Cannot use [] for reading in %s.php on line 25

Zend/zend_ast.c

@@ -337,6 +337,30 @@ ZEND_API int zend_ast_evaluate(zval *result, zend_ast *ast, zend_class_entry *sc
 				zval_dtor(&op1);
 			}
 			break;
+		case ZEND_AST_COALESCE:
+			if (ast->child[0]->kind == ZEND_AST_DIM) {
+				ast->child[0]->attr = ZEND_DIM_IS;
+			}
+
+			if (UNEXPECTED(zend_ast_evaluate(&op1, ast->child[0], scope) != SUCCESS)) {
+				ret = FAILURE;
+				break;
+			}
+			if (Z_TYPE(op1) > IS_NULL) {
+				*result = op1;
+			} else {
+				if (ast->child[1]->kind == ZEND_AST_DIM) {
+					ast->child[1]->attr = ZEND_DIM_IS;
+				}
+
+				if (UNEXPECTED(zend_ast_evaluate(result, ast->child[1], scope) != SUCCESS)) {
+					zval_dtor(&op1);
+					ret = FAILURE;
+					break;
+				}
+				zval_dtor(&op1);
+			}
+			break;
 		case ZEND_AST_UNARY_PLUS:
 			if (UNEXPECTED(zend_ast_evaluate(&op2, ast->child[0], scope) != SUCCESS)) {
 				ret = FAILURE;
@@ -385,6 +409,14 @@ ZEND_API int zend_ast_evaluate(zval *result, zend_ast *ast, zend_class_entry *sc
 			}
 			break;
 		case ZEND_AST_DIM:
+			if (ast->child[1] == NULL) {
+				zend_error_noreturn(E_COMPILE_ERROR, "Cannot use [] for reading");
+			}
+
+			if (ast->attr == ZEND_DIM_IS && ast->child[0]->kind == ZEND_AST_DIM) {
+				ast->child[0]->attr = ZEND_DIM_IS;
+			}
+
 			if (UNEXPECTED(zend_ast_evaluate(&op1, ast->child[0], scope) != SUCCESS)) {
 				ret = FAILURE;
 			} else if (UNEXPECTED(zend_ast_evaluate(&op2, ast->child[1], scope) != SUCCESS)) {
@@ -393,7 +425,12 @@ ZEND_API int zend_ast_evaluate(zval *result, zend_ast *ast, zend_class_entry *sc
 			} else {
 				zval tmp;
 
-				zend_fetch_dimension_by_zval(&tmp, &op1, &op2);
+				if (ast->attr == ZEND_DIM_IS) {
+					zend_fetch_dimension_by_zval_is(&tmp, &op1, &op2, IS_CONST);
+				} else {
+					zend_fetch_dimension_by_zval(&tmp, &op1, &op2);
+				}
+
 				if (UNEXPECTED(Z_ISREF(tmp))) {
 					ZVAL_DUP(result, Z_REFVAL(tmp));
 				} else {

Zend/zend_compile.c

@@ -6833,7 +6833,7 @@ zend_bool zend_is_allowed_in_const_expr(zend_ast_kind kind) /* {{{ */
 		|| kind == ZEND_AST_CONDITIONAL || kind == ZEND_AST_DIM
 		|| kind == ZEND_AST_ARRAY || kind == ZEND_AST_ARRAY_ELEM
 		|| kind == ZEND_AST_CONST || kind == ZEND_AST_CLASS_CONST
-		|| kind == ZEND_AST_MAGIC_CONST;
+		|| kind == ZEND_AST_MAGIC_CONST || kind == ZEND_AST_COALESCE;
 }
 /* }}} */
 

Zend/zend_compile.h

@@ -889,6 +889,8 @@ ZEND_API void zend_assert_valid_class_name(const zend_string *const_name);
 #define ZEND_SEND_BY_REF     1
 #define ZEND_SEND_PREFER_REF 2
 
+#define ZEND_DIM_IS 1
+
 static zend_always_inline int zend_check_arg_send_type(const zend_function *zf, uint32_t arg_num, uint32_t mask)
 {
 	arg_num--;

Zend/zend_execute.c

@@ -1912,6 +1912,12 @@ ZEND_API void zend_fetch_dimension_by_zval(zval *result, zval *container, zval *
 	zend_fetch_dimension_address_read_R(result, container, dim, IS_TMP_VAR);
 }
 
+ZEND_API void zend_fetch_dimension_by_zval_is(zval *result, zval *container, zval *dim, int dim_type)
+{
+	zend_fetch_dimension_address_read(result, container, dim, dim_type, BP_VAR_IS, 1);
+}
+
+
 static zend_always_inline void zend_fetch_property_address(zval *result, zval *container, uint32_t container_op_type, zval *prop_ptr, uint32_t prop_op_type, void **cache_slot, int type)
 {
     if (container_op_type != IS_UNUSED && UNEXPECTED(Z_TYPE_P(container) != IS_OBJECT)) {

Zend/zend_execute.h

@@ -296,6 +296,7 @@ ZEND_API zend_class_entry *zend_fetch_class_by_name(zend_string *class_name, con
 void zend_verify_abstract_class(zend_class_entry *ce);
 
 ZEND_API void zend_fetch_dimension_by_zval(zval *result, zval *container, zval *dim);
+ZEND_API void zend_fetch_dimension_by_zval_is(zval *result, zval *container, zval *dim, int dim_type);
 
 ZEND_API zval* zend_get_compiled_variable_value(const zend_execute_data *execute_data_ptr, uint32_t var);