This library is another attempt at compiler-macro:form-type, due to reasons of personal taste. It does use introspect-environment by the same author though.

• Returns two values: the second value indicates whether the form-type was obtained using the declarations in the environment, or due to the absence of declarations in the environment.
• Avoids an additional (albeit minimal) layer of complexity by using defmethod instead of define-inferrer

• trivial-types:function-name

(asdf:test-system "trivial-form-type")