match :: [MatchId]Variables rep'ing the exprs we're matching with ^ See Note [Match Ids]
^ Note that the Match Ids carry not only a name, but ^ also the multiplicity at which each column has been ^ type checked.
-> TypeType of the case expression
-> [EquationInfo]Info about patterns, etc. (type synonym below)
-> DsM (MatchResult CoreExpr)Desugared result!