Reflection: show the type of object constants used as default properties

When a property default is based on a global constant, show the type of the
default. Previously, `format_default_value()` assumed that non-scalar and
non-array defaults were always going to be `IS_CONSTANT_AST` pointers, and when
the AST expression had been evaluated and produced an object, depending on when
the `ReflectionClass` or `ReflectionProperty` instance had been created, the
default was shown as one of `callable`, `__CLASS__`, or `...`.

Instead, if the default value is an object (`IS_OBJECT`), show the type of that
object.

Add test cases for each of the `callable`, `__CLASS__`, and `...` cases to
confirm that they all now properly show the type of the constant.

Closes gh-15902

NEWS

@@ -57,6 +57,10 @@ PHP                                                                        NEWS
 - PHPDBG:
   . Fixed bug GH-16174 (Empty string is an invalid expression for ev). (cmb)
 
+- Reflection:
+  . Fixed bug GH-15902 (Core dumped in ext/reflection/php_reflection.c).
+    (DanielEScherzer)
+
 - Session:
   . Fixed bug GH-16385 (Unexpected null returned by session_set_cookie_params).
     (nielsdos)

ext/reflection/php_reflection.c

@@ -639,13 +639,19 @@ static int format_default_value(smart_str *str, zval *value) {
 		} ZEND_HASH_FOREACH_END();
 		smart_str_appendc(str, ']');
 	} else if (Z_TYPE_P(value) == IS_OBJECT) {
-		/* This branch may only be reached for default properties, which don't support arbitrary objects. */
+		/* This branch may only be reached for default properties; show enum names,
+			or the type of non-enums (GH-15902) */
 		zend_object *obj = Z_OBJ_P(value);
 		zend_class_entry *class = obj->ce;
-		ZEND_ASSERT(class->ce_flags & ZEND_ACC_ENUM);
-		smart_str_append(str, class->name);
-		smart_str_appends(str, "::");
-		smart_str_append(str, Z_STR_P(zend_enum_fetch_case_name(obj)));
+		if (class->ce_flags & ZEND_ACC_ENUM) {
+			smart_str_append(str, class->name);
+			smart_str_appends(str, "::");
+			smart_str_append(str, Z_STR_P(zend_enum_fetch_case_name(obj)));
+		} else {
+			smart_str_appends(str, "object(");
+			smart_str_append(str, class->name);
+			smart_str_appends(str, ")");
+		}
 	} else {
 		ZEND_ASSERT(Z_TYPE_P(value) == IS_CONSTANT_AST);
 		zend_string *ast_str = zend_ast_export("", Z_ASTVAL_P(value), "");

ext/reflection/tests/gh15902/ReflectionClass-callable.phpt

@@ -0,0 +1,36 @@
+--TEST--
+ReflectionClass object default property - used to say "callable"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+define('FOO', new stdClass);
+
+new C;
+
+$reflector = new ReflectionClass(C::class);
+var_dump( (string)$reflector );
+?>
+--EXPECTF--
+string(%d) "Class [ <user> class C ] {
+  @@ %sReflectionClass-callable.php %d-%d
+
+  - Constants [0] {
+  }
+
+  - Static properties [0] {
+  }
+
+  - Static methods [0] {
+  }
+
+  - Properties [1] {
+    Property [ public stdClass $a = object(stdClass) ]
+  }
+
+  - Methods [0] {
+  }
+}
+"

ext/reflection/tests/gh15902/ReflectionClass-class.phpt

@@ -0,0 +1,37 @@
+--TEST--
+ReflectionClass object default property - used to say "__CLASS__"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+$reflector = new ReflectionClass(C::class);
+
+define('FOO', new stdClass);
+new C;
+
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Class [ <user> class C ] {
+  @@ %sReflectionClass-class.php %d-%d
+
+  - Constants [0] {
+  }
+
+  - Static properties [0] {
+  }
+
+  - Static methods [0] {
+  }
+
+  - Properties [1] {
+    Property [ public stdClass $a = object(stdClass) ]
+  }
+
+  - Methods [0] {
+  }
+}
+"

ext/reflection/tests/gh15902/ReflectionProperty-callable.phpt

@@ -0,0 +1,19 @@
+--TEST--
+ReflectionProperty object default - used to say "callable"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+define('FOO', new stdClass);
+
+new C;
+
+$reflector = new ReflectionProperty(C::class, 'a');
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Property [ public stdClass $a = object(stdClass) ]
+"

ext/reflection/tests/gh15902/ReflectionProperty-class.phpt

@@ -0,0 +1,19 @@
+--TEST--
+ReflectionProperty object default - used to say "__CLASS__"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+$reflector = new ReflectionProperty(C::class, 'a');
+
+define('FOO', new stdClass);
+new C;
+
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Property [ public stdClass $a = object(stdClass) ]
+"