Add (void) cast

Zend/Optimizer/block_pass.c

@@ -274,7 +274,9 @@ static void zend_optimize_block(zend_basic_block *block, zend_op_array *op_array
 				 * If it's not local, then the other blocks successors must also eventually either FREE or consume the temporary,
 				 * hence removing the temporary is not safe in the general case, especially when other consumers are not FREE.
 				 * A FREE may not be removed without also removing the source's result, because otherwise that would cause a memory leak. */
-				if (opline->op1_type == IS_TMP_VAR) {
+				if (opline->extended_value == ZEND_FREE_VOID_CAST) {
+					/* Keep the ZEND_FREE opcode alive. */
+				} else if (opline->op1_type == IS_TMP_VAR) {
 					src = VAR_SOURCE(opline->op1);
 					if (src) {
 						switch (src->opcode) {

Zend/Optimizer/dce.c

@@ -80,7 +80,6 @@ static inline bool may_have_side_effects(
 		case ZEND_IS_IDENTICAL:
 		case ZEND_IS_NOT_IDENTICAL:
 		case ZEND_QM_ASSIGN:
-		case ZEND_FREE:
 		case ZEND_FE_FREE:
 		case ZEND_TYPE_CHECK:
 		case ZEND_DEFINED:
@@ -127,6 +126,8 @@ static inline bool may_have_side_effects(
 		case ZEND_ARRAY_KEY_EXISTS:
 			/* No side effects */
 			return 0;
+		case ZEND_FREE:
+			return opline->extended_value == ZEND_FREE_VOID_CAST;
 		case ZEND_ADD_ARRAY_ELEMENT:
 			/* TODO: We can't free two vars. Keep instruction alive. <?php [0, "$a" => "$b"]; */
 			if ((opline->op1_type & (IS_VAR|IS_TMP_VAR)) && (opline->op2_type & (IS_VAR|IS_TMP_VAR))) {

Zend/tests/attributes/nodiscard/suppress_cast.phpt

@@ -1,5 +1,5 @@
 --TEST--
-#[\NoDiscard]: Casting to (bool) suppresses.
+#[\NoDiscard]: Casting to (void) suppresses.
 --FILE--
 <?php
 
@@ -43,22 +43,22 @@ $closure2 = #[\NoDiscard] function(): int {
 	return 0;
 };
 
-(bool)test();
-(bool)test2();
-(bool)test3(1, 2, named: 3);
-(bool)call_user_func("test");
+(void)test();
+(void)test2();
+(void)test3(1, 2, named: 3);
+(void)call_user_func("test");
 $fcc = test(...);
-(bool)$fcc();
+(void)$fcc();
 
 $cls = new Clazz();
-(bool)$cls->test();
-(bool)$cls->test2();
-(bool)call_user_func([$cls, "test"]);
-(bool)Clazz::test3();
+(void)$cls->test();
+(void)$cls->test2();
+(void)call_user_func([$cls, "test"]);
+(void)Clazz::test3();
 
-(bool)$closure();
+(void)$closure();
 
-(bool)$closure2();
+(void)$closure2();
 
 ?>
 DONE

Zend/tests/attributes/nodiscard/suppress_cast_destructor.phpt

@@ -0,0 +1,31 @@
+--TEST--
+#[\NoDiscard]: Casting to (void) destroys the value.
+--FILE--
+<?php
+
+class WithDestructor {
+	public function __destruct() {
+		echo __METHOD__, PHP_EOL;
+	}
+}
+
+#[\NoDiscard]
+function test(): WithDestructor {
+	return new WithDestructor();
+}
+
+function do_it(): void {
+	echo "Before", PHP_EOL;
+
+	(void)test();
+
+	echo "After", PHP_EOL;
+}
+
+do_it();
+
+?>
+--EXPECT--
+Before
+WithDestructor::__destruct
+After

Zend/zend_compile.c

@@ -10247,6 +10247,9 @@ static void zend_compile_cast(znode *result, zend_ast *ast) /* {{{ */
 		opline = zend_emit_op_tmp(result, ZEND_BOOL, &expr_node, NULL);
 	} else if (ast->attr == IS_NULL) {
 		zend_error(E_COMPILE_ERROR, "The (unset) cast is no longer supported");
+	} else if (ast->attr == IS_UNDEF) {
+		opline = zend_emit_op_tmp(NULL, ZEND_FREE, &expr_node, NULL);
+		opline->extended_value = ZEND_FREE_VOID_CAST;
 	} else {
 		opline = zend_emit_op_tmp(result, ZEND_CAST, &expr_node, NULL);
 		opline->extended_value = ast->attr;

Zend/zend_compile.h

@@ -1095,6 +1095,7 @@ ZEND_API zend_string *zend_type_to_string(zend_type type);
 
 #define ZEND_FREE_ON_RETURN     (1<<0)
 #define ZEND_FREE_SWITCH        (1<<1)
+#define ZEND_FREE_VOID_CAST     (1<<2)
 
 #define ZEND_SEND_BY_VAL     0u
 #define ZEND_SEND_BY_REF     1u

Zend/zend_language_parser.y

@@ -217,6 +217,7 @@ static YYSIZE_T zend_yytnamerr(char*, const char*);
 %token T_OBJECT_CAST "'(object)'"
 %token T_BOOL_CAST   "'(bool)'"
 %token T_UNSET_CAST  "'(unset)'"
+%token T_VOID_CAST  "'(void)'"
 %token T_OBJECT_OPERATOR "'->'"
 %token T_NULLSAFE_OBJECT_OPERATOR "'?->'"
 %token T_DOUBLE_ARROW    "'=>'"
@@ -534,6 +535,7 @@ statement:
 			{ $$ = zend_ast_create(ZEND_AST_TRY, $3, $5, $6); }
 	|	T_GOTO T_STRING ';' { $$ = zend_ast_create(ZEND_AST_GOTO, $2); }
 	|	T_STRING ':' { $$ = zend_ast_create(ZEND_AST_LABEL, $1); }
+	|	T_VOID_CAST expr ';' { $$ = zend_ast_create_cast(IS_UNDEF, $2); }
 ;
 
 catch_list:

Zend/zend_language_scanner.l

@@ -1657,6 +1657,10 @@ OPTIONAL_WHITESPACE_OR_COMMENTS ({WHITESPACE}|{MULTI_LINE_COMMENT}|{SINGLE_LINE_
 	RETURN_TOKEN(T_UNSET_CAST);
 }
 
+<ST_IN_SCRIPTING>"("{TABS_AND_SPACES}("void"){TABS_AND_SPACES}")" {
+	RETURN_TOKEN(T_VOID_CAST);
+}
+
 <ST_IN_SCRIPTING>"eval" {
 	RETURN_TOKEN_WITH_IDENT(T_EVAL);
 }

ext/tokenizer/tokenizer_data.stub.php

@@ -642,6 +642,11 @@
  * @cvalue T_UNSET_CAST
  */
 const T_UNSET_CAST = UNKNOWN;
+/**
+ * @var int
+ * @cvalue T_VOID_CAST
+ */
+const T_VOID_CAST = UNKNOWN;
 /**
  * @var int
  * @cvalue T_OBJECT_OPERATOR