Hi All,
I've had a bit of time to work on External Core again, and I've come
across a potential simplification. I'd like to hear what the more
seasoned developers think of it.
The current situation is that ExternalCore.lhs defines datatypes for
both expressions and types (Exp and Ty, respectively), and the
External Core parser uses IfaceType to represent type declarations,
and IfaceBndr to represent term declarations.
A while back, Simon PJ suggested extending HsBind with an alternative
for External Core bindings, and using that instead of IfaceBndr for
term declarations. Unfortunately, the parser sometimes needs to parse
types that appear as components of terms (such as abstractions, and
case expressions), and sometimes needs to parse them as part of type
declarations. Thus, the parser either needs separate productions for
parsing types that appear in terms and in type declarations, or code
to convert between IfaceType and Ty.
One way to simplify this situation would be to remove the Ty data
type altogether, and use IfaceType in ExternalCore. Code already
exists to parse External Core into an IfaceType representation, and
pretty-printing IfaceTypes shouldn't be any harder than pretty-
printing Tys. However, doing this would require ExternalCore, which
currently imports nothing at all, to import IfaceType. IfaceType, in
turn, imports a number of other modules. So ExternalCore would no
longer be so appealingly self-contained.
Does anyone have a preference? Should I scrap Ty in favor of
IfaceType, or should I make the External Core parser slightly more
complex?
Aaron
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