Remove unused DerivInst constructor for DerivStuff
authorRyan Scott <ryan.gl.scott@gmail.com>
Mon, 29 Aug 2016 19:26:53 +0000 (15:26 -0400)
committerRyan Scott <ryan.gl.scott@gmail.com>
Mon, 29 Aug 2016 19:26:53 +0000 (15:26 -0400)
commitf4384ef5b42bb64b55d6c930ed9850a021796f36
treeb1bbbc0742f92e2cb1340e0e6b572ab07ee4d2cf
parent822af416882a865ce57daf6938b969f072cb7e0b
Remove unused DerivInst constructor for DerivStuff

Summary:
Back when derived `Generic` instances used to generate auxiliary datatypes,
they would also generate instances for those datatypes. Nowadays, GHC generics
uses a `DataKinds`-based encoding that requires neither auxiliary datatypes
(corresponding to the `DerivTyCon` constructor of `DerivStuff`) nor instances
for them (the `DerivInst` constructor of `DerivStuff`). It appears that
`DerivTyCon` constructor was removed at some point, but `DerivInst` never was.

No `DerivInst` values are ever constructed, so we can safely remove it.

Test Plan: It builds

Reviewers: austin, hvr, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2481
compiler/typecheck/TcDeriv.hs
compiler/typecheck/TcGenDeriv.hs