This is regarding https://gitlab.com/embeddable-common-lisp/ecl/issues/469 .I don't think that the behaviour mentioned in there is a bug. (defstruct foo a b c) is top level inside file /tmp/foo.lisp and CLHS says

If a defstruct form appears as a top level form, the compiler must make the structure type name recognized as a valid type name in subsequent declarations (as for deftype) and make the structure slot readers known to setf.

So after (compile-file "/tmp/foo.lisp") it makes sense that FIND-CLASS would know about foo . SBCL behaves the same way.