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| -rw-r--r-- | compiler/typecheck/TcFlatten.hs | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/compiler/typecheck/TcFlatten.hs b/compiler/typecheck/TcFlatten.hs index 4c74ba9cb1..09ed3402b8 100644 --- a/compiler/typecheck/TcFlatten.hs +++ b/compiler/typecheck/TcFlatten.hs @@ -1576,6 +1576,11 @@ Consider f1 = (Given, ReprEq) f2 = (Derived, NomEq) f = (Derived, ReprEq) +I thought maybe we could never get Derived ReprEq constraints, but +we can; straight from the Wanteds during improvment. And from a Derived +ReprEq we could conceivably get a Derived NomEq improvment (by decomposing +a type constructor with Nomninal role), and hence unify. + Note [canRewriteOrSame] ~~~~~~~~~~~~~~~~~~~~~~~ canRewriteOrSame is similar but |