@@ -124,6 +124,9 @@ reorder lexpr@(L s expr) =
124124 toDefs (pattern, expr, Nothing) = [ Def pattern expr ]
125125 toDefs (PVar name, expr, Just tipe) =
126126 [ TypeAnnotation name tipe, Def (PVar name) expr ]
127+ -- This case really shouldn't happen since we've
128+ -- removed everything but Def's and PVars above.
129+ toDefs (_,_,_) = error "The impossible occurred. Please report an issue at https://github.com/evancz/Elm/issues describing what led to this error message."
127130
128131 L _ let' = foldr addDefs body' defss
129132