Why are there no Show instances for internal types

[Tom Sydney Kerckhove]

Dear GHC Devs,

I am trying to use GHC as a library but I'm having a lot of trouble with
understanding what everything means.
Up to now, I have been able to figure out what to do by reading the
sources, but it ocured to me that much of my struggles could have been
mitigated if the relevant types had Show instances.

I am specifically talking about the types concerning type checking.
TypecheckedModule and everything below that.
I am aware that most of the types have an Outputable instance, but
there are two problems with that:

- 'Outputting' a value requires DynFlags. (yes, I know about pprTrace)
- These instances are not intended to show the internal structure of a
  value, but rather a 'human readable' representation of a value.

My questions for you:

- Is there a reason that there are no derived 'Show' instances for most
  types?
- Would you accept a diff that adds these?

Thank you for your time.

-- 
Tom Sydney Kerckhove
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