RE: Motivation for refineDefaultAlt

Because if e contains …(case x of Foo p q -> e2)… as a sub-expression, we’d like to simplify it. Sorry that is not documented; please do add that to the comments in the source code. Simon From: ghc-devs On Behalf Of Matthew Pickering Sent: 11 May 2018 15:54 To: GHC developers Subject: Motivation for refineDefaultAlt Hi all, Does anyone know the motivation for refineDefaultAlt? The comment states - -- | Refine the default alternative to a 'DataAlt', if there is a unique way to do so. OK - so the code transforms something like case x of { DEFAULT -> e } ===> case x of { Foo a1 a2 a3 -> e } but why is this necessary or desirable? Perhaps you know Simon (Jakobi)? Cheers, Matt