Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

When using ttf fonts such as Bitstream Vera Sans Mono, face
inheritance does not seem to work correctly.  The included file
demonstrates what I believe to be a bug:

Defining a face with an attribute that inherits from the
`default' face does not use the same fontset.  Equally,
inheriting from no face at all produces an unexpected result.  If
the defined face inherits from `fixed-pitch', the fontset is
correct.

The following command may be used to demonstrate the bug using
the attached file:

emacs -Q -fn "Bitstream Vera Sans Mono" --load face-inherit-bug.el

Using a standard X font does not show the same bug, that is, the
following works and all faces display as expected:

emacs -Q -fn 7x14 --load face-inherit-bug.el