Instantiating a type with fresh, flexi type variables

[Dr. ERDI Gergo]

For my pattern-synonyms branch (see prev. email) I had to write the 
following function, incl. making TcValidity.fvTypes public:

tcInstTypes :: [TcType] -> TcM [TcType]
tcInstTypes tys
   = do { let tvs = fvTypes tys
        ; (_, _, subst) <- tcInstTyVars tvs
        ; return $ map (substTy subst) tys }

I'm surprised I had to write this myself, and this made me wonder if 
there's a much better way to handle cases where I have some kind of 
definition which has some inferred type, and then various use sites 
of that definition must all have types that can be unified with this 
original inferred type.
Is there?

Thanks,
 	Gergo