Add #[\NoDiscard] attribute definition

Author: TimWolla

Zend/tests/attributes/nodiscard/property_readonly_001.phpt

@@ -0,0 +1,14 @@
+--TEST--
+#[\NoDiscard]: NoDiscard::$message is readonly.
+--FILE--
+<?php
+
+$d = new \NoDiscard("foo");
+$d->message = 'bar';
+
+?>
+--EXPECTF--
+Fatal error: Uncaught Error: Cannot modify readonly property NoDiscard::$message in %s:%d
+Stack trace:
+#0 {main}
+  thrown in %s on line %d

Zend/tests/attributes/nodiscard/property_readonly_002.phpt

@@ -0,0 +1,15 @@
+--TEST--
+#[\NoDiscard]: __construct() respects that properties are readonly.
+--FILE--
+<?php
+
+$d = new \NoDiscard("foo");
+$d->__construct("bar");
+
+?>
+--EXPECTF--
+Fatal error: Uncaught Error: Cannot modify readonly property NoDiscard::$message in %s:%d
+Stack trace:
+#0 %s(%d): NoDiscard->__construct('bar')
+#1 {main}
+  thrown in %s on line %d

Zend/zend_attributes.c

@@ -31,6 +31,7 @@ ZEND_API zend_class_entry *zend_ce_sensitive_parameter;
 ZEND_API zend_class_entry *zend_ce_sensitive_parameter_value;
 ZEND_API zend_class_entry *zend_ce_override;
 ZEND_API zend_class_entry *zend_ce_deprecated;
+ZEND_API zend_class_entry *zend_ce_nodiscard;
 
 static zend_object_handlers attributes_object_handlers_sensitive_parameter_value;
 
@@ -193,6 +194,29 @@ ZEND_METHOD(Deprecated, __construct)
 	}
 }
 
+ZEND_METHOD(NoDiscard, __construct)
+{
+	zend_string *message = NULL;
+	zval value;
+
+	ZEND_PARSE_PARAMETERS_START(0, 1)
+		Z_PARAM_OPTIONAL
+		Z_PARAM_STR_OR_NULL(message)
+	ZEND_PARSE_PARAMETERS_END();
+
+	if (message) {
+		ZVAL_STR(&value, message);
+	} else {
+		ZVAL_NULL(&value);
+	}
+	zend_update_property_ex(zend_ce_nodiscard, Z_OBJ_P(ZEND_THIS), ZSTR_KNOWN(ZEND_STR_MESSAGE), &value);
+
+	/* The assignment might fail due to 'readonly'. */
+	if (UNEXPECTED(EG(exception))) {
+		RETURN_THROWS();
+	}
+}
+
 static zend_attribute *get_attribute(HashTable *attributes, zend_string *lcname, uint32_t offset)
 {
 	if (attributes) {
@@ -520,6 +544,9 @@ void zend_register_attribute_ce(void)
 
 	zend_ce_deprecated = register_class_Deprecated();
 	attr = zend_mark_internal_attribute(zend_ce_deprecated);
+
+	zend_ce_nodiscard = register_class_NoDiscard();
+	attr = zend_mark_internal_attribute(zend_ce_nodiscard);
 }
 
 void zend_attributes_shutdown(void)

Zend/zend_attributes.h

@@ -47,6 +47,7 @@ extern ZEND_API zend_class_entry *zend_ce_sensitive_parameter;
 extern ZEND_API zend_class_entry *zend_ce_sensitive_parameter_value;
 extern ZEND_API zend_class_entry *zend_ce_override;
 extern ZEND_API zend_class_entry *zend_ce_deprecated;
+extern ZEND_API zend_class_entry *zend_ce_nodiscard;
 
 typedef struct {
 	zend_string *name;

Zend/zend_attributes.stub.php

@@ -84,3 +84,14 @@ final class Deprecated
 
     public function __construct(?string $message = null, ?string $since = null) {}
 }
+
+/**
+ * @strict-properties
+ */
+#[Attribute(Attribute::TARGET_METHOD|Attribute::TARGET_FUNCTION)]
+final class NoDiscard
+{
+    public readonly ?string $message;
+
+    public function __construct(?string $message = null) {}
+}