Here's the relevant paragraph from the Standard. It pretty much speaks for itself.
8.3.5/10
A typedef of function type may be used to declare a function but shall not be used to define a function (8.4).
Example:
typedef void F(); F fv; // OK: equivalent to void fv(); F fv { } // ill-formed void fv() { } // OK: definition of fv
A typedef of a function type whose declarator includes a cv-qualifier-seq shall be used only to declare the function type for a non-static member function, to declare the function type to which a pointer to member refers, or to declare the top-level function type of another function typedef declaration.
Example:
typedef int FIC(int) const; FIC f; // ill-formed: does not declare a member function struct S { FIC f; // OK }; FIC S::*pm = &S::f; // OK