Show-like output of GHC data types

Johan Tibell johan.tibell at
Sat Mar 9 00:49:45 CET 2013

On Fri, Mar 8, 2013 at 3:01 PM, Thomas Schilling <nominolo at>wrote:

> Last time I checked GHC's AST types had some fields which you weren't
> supposed to look at.  Depending on what stage you're in those may be
> different fields.  They are initialised to error thunks, hence
> automatically derived Show instances wouldn't work out of the box as
> they would force those error thunks.
> As I said, it's been a while since I looked at that closely, so maybe
> it was removed when the Typeable instances were moved into the GHC
> codebase?

I noticed that some of those are still around. I'm mainly looking at the
AST post type-checking.
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