CL-USER> (defun foo (a b)
           (declare (type number a b))
           (+ a b))
WARNING: redefining COMMON-LISP-USER::FOO in DEFUN
FOO
CL-USER> (describe 'foo)
COMMON-LISP-USER::FOO
  [symbol]

FOO names a compiled function:
  Lambda-list: (A B)
  Derived type: (FUNCTION (NUMBER NUMBER) (VALUES NUMBER &OPTIONAL))
  Source form:
    (LAMBDA (A B) (DECLARE (TYPE NUMBER A B)) (BLOCK FOO (+ A B)))
; No value