Data.Typeable does not use qualified names

[guest]

The TyCon in Data.Typeable does not provide the qualified type name. This can be very annoying if you try to use a TypeRep as a stored representation of a type (within a run it's OK with the equality on TypeRep).

I suggest that the TyCon be enhanced to contain a qualified name, but that the current API be maintained, except for adding some new functions to access qualified name.

If prodded I could provide the Data.Typeable implementation and the fix to ghc.

[simonpj]

Your suggestion sounds plausible to me.

There is some design to do first. Currently Data.Typeable.TyCon is really just a string (plus a key for comparison). Maybe you want three strings?

• The package name
• The module name
• The TyCon name

plus accessor functions.

Another possibility (unavailable when Data.Typeable was designed I think) would be to use a Template Haskell name: Language.Haskell.TH.Syntax.Name. After all, Data.Typeable is just another form of reflection, like TH. I'm not sure what the tradeoffs are though. For example, TH names don't have a key for fast comparison. (But the keys are quite a nuisance in some ways because they may differ from run to run.)

I suggest you progress this via the library process: make proposals, encourage discussion. Actually implementing it will not be hard.

Simon

[simonmar]

See also #1841