Raise TypeError for bad IO::Buffer.map argument (#8728)

* Raise TypeError when IO::Buffer.map argument is neither IO nor implements #fileno

* Use UNREACHABLE_CODE

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

* Use macro for undef check

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

---------

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/io.c b/io.c
index f4698a2cd5..28b5abb1c5 100644
--- a/io.c
+++ b/io.c
@@ -2870,8 +2870,15 @@ rb_io_descriptor(VALUE io)
         return fptr->fd;
     }
     else {
-        return RB_NUM2INT(rb_funcall(io, id_fileno, 0));
+        VALUE fileno = rb_check_funcall(io, id_fileno, 0, NULL);
+        if (!UNDEF_P(fileno)) {
+            return RB_NUM2INT(fileno);
+        }
     }
+
+    rb_raise(rb_eTypeError, "expected IO or #fileno, %"PRIsVALUE" given", rb_obj_class(io));
+
+    UNREACHABLE_RETURN(-1);
 }
 
 int