Why can't we re-install the template-haskell package?

[Moritz Angermann]

Dear friends,

as I'm working on making lib:ghc re-installable [1][2].

Ideally I'd prefer we only had to freeze rts + ghc-prim
and maybe base (which would implicate the integer library).

However, we apparently can't re-install Template Haskell
I'm told.  Not just not upgrade it, but not even re-install
it (same version). I've attached some rough dependency graph
(which I hope is correct for ghc 8.8). Fixing template-haskell
implies ghc-boot-th, pretty, deepseq and array.

Can someone shed some light onto the details here? What
are the fundamental issues we can't reinstall template-haskell?

Cheers,
 Moritz

--
[1]: https://gitlab.haskell.org/ghc/ghc/merge_requests/490
[2]: https://gitlab.haskell.org/ghc/ghc/merge_requests/506
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