Add test for getClass() error conditions

Inspired by phpGH-7372, to show that these are not dead code.

Author: nikic

ext/reflection/tests/ReflectionParameter_getClass_self_parent_closure.phpt

@@ -0,0 +1,37 @@
+--TEST--
+Using invalid self/parent types in closure
+--FILE--
+<?php
+
+$fn1 = function(self $x) {};
+try {
+    (new ReflectionFunction($fn1))->getParameters()[0]->getClass();
+} catch (ReflectionException $e) {
+    echo $e->getMessage(), "\n";
+}
+
+$fn2 = function(parent $x) {};
+try {
+    (new ReflectionFunction($fn2))->getParameters()[0]->getClass();
+} catch (ReflectionException $e) {
+    echo $e->getMessage(), "\n";
+}
+
+class Test {}
+$fn3 = (function(parent $x) {})->bindTo(new Test, Test::class);
+try {
+    (new ReflectionFunction($fn3))->getParameters()[0]->getClass();
+} catch (ReflectionException $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECTF--
+Deprecated: Method ReflectionParameter::getClass() is deprecated in %s on line %d
+Parameter uses "self" as type but function is not a class member
+
+Deprecated: Method ReflectionParameter::getClass() is deprecated in %s on line %d
+Parameter uses "parent" as type but function is not a class member
+
+Deprecated: Method ReflectionParameter::getClass() is deprecated in %s on line %d
+Parameter uses "parent" as type although class does not have a parent