A while ago I removed substTags and substType, thinking to streamline things by letting subst do everything. But it seems to complicate #81 if subst is able to substitute so many different kinds of variables. This puts the two functions back. However, note
substType never attempted to check for variable capture, so in a way this is a step backwards. Hopefully, whatever fixes #74 will fix this.
freeVars still considers datatype names (TpData) to be free variables, so subst is also still able to substitute them (but the latter is never used).
A while ago I removed
substTagsandsubstType, thinking to streamline things by lettingsubstdo everything. But it seems to complicate #81 ifsubstis able to substitute so many different kinds of variables. This puts the two functions back. However, notesubstTypenever attempted to check for variable capture, so in a way this is a step backwards. Hopefully, whatever fixes #74 will fix this.freeVarsstill considers datatype names (TpData) to be free variables, sosubstis also still able to substitute them (but the latter is never used).