py/vm: Fix case of throwing GeneratorExit type into yield-from.

mp_make_raise_obj must be used to convert a possible exception type to an
instance object, otherwise the VM may raise a non-exception object.

An existing test is adjusted to test this case, with the original test
already moved to generator_throw.py.

py/vm.c

@@ -1152,7 +1152,7 @@ yield:
                     MARK_EXC_IP_SELECTIVE();
 //#define EXC_MATCH(exc, type) MP_OBJ_IS_TYPE(exc, type)
 #define EXC_MATCH(exc, type) mp_obj_exception_match(exc, type)
-#define GENERATOR_EXIT_IF_NEEDED(t) if (t != MP_OBJ_NULL && EXC_MATCH(t, MP_OBJ_FROM_PTR(&mp_type_GeneratorExit))) { RAISE(t); }
+#define GENERATOR_EXIT_IF_NEEDED(t) if (t != MP_OBJ_NULL && EXC_MATCH(t, MP_OBJ_FROM_PTR(&mp_type_GeneratorExit))) { mp_obj_t raise_t = mp_make_raise_obj(t); RAISE(raise_t); }
                     mp_vm_return_kind_t ret_kind;
                     mp_obj_t send_value = POP();
                     mp_obj_t t_exc = MP_OBJ_NULL;

tests/basics/gen_yield_from_throw2.py

@@ -1,18 +1,24 @@
-# generator ignores a thrown GeneratorExit (this is allowed)
+# outer generator ignores a thrown GeneratorExit (this is allowed)
 
 def gen():
     try:
         yield 123
     except GeneratorExit:
         print('GeneratorExit')
-    yield 456
+
+def gen2():
+    try:
+        yield from gen()
+    except GeneratorExit:
+        print('GeneratorExit outer')
+    yield 789
 
 # thrown a class
-g = gen()
+g = gen2()
 print(next(g))
 print(g.throw(GeneratorExit))
 
 # thrown an instance
-g = gen()
+g = gen2()
 print(next(g))
 print(g.throw(GeneratorExit()))