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| author | sheaf <sam.derbyshire@gmail.com> | 2022-04-07 16:40:27 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-04-09 13:04:14 -0400 |
| commit | 5f8d6e65f3d8268c70d6a8434ba9df03087a22eb (patch) | |
| tree | 758958a0b09670a22ca81ba007ed4164fee7a1d0 | |
| parent | 47d18b0b387fbfe07e1b4fbda578a81a74ab0eeb (diff) | |
| download | haskell-5f8d6e65f3d8268c70d6a8434ba9df03087a22eb.tar.gz | |
Fix missing SymCo in pushCoercionIntoLambda
There was a missing SymCo in pushCoercionIntoLambda. Currently
this codepath is only used with rewrite rules, so this bug managed
to slip by, but trying to use pushCoercionIntoLambda in other contexts
revealed the bug.
| -rw-r--r-- | compiler/GHC/Core/Opt/Arity.hs | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/compiler/GHC/Core/Opt/Arity.hs b/compiler/GHC/Core/Opt/Arity.hs index ab38be413c..6c0729ec5b 100644 --- a/compiler/GHC/Core/Opt/Arity.hs +++ b/compiler/GHC/Core/Opt/Arity.hs @@ -1784,7 +1784,11 @@ pushCoercionIntoLambda in_scope x e co in_scope' = in_scope `extendInScopeSet` x' subst = extendIdSubst (mkEmptySubst in_scope') x - (mkCast (Var x') co1) + (mkCast (Var x') (mkSymCo co1)) + -- We substitute x' for x, except we need to preserve types. + -- The types are as follows: + -- x :: s1, x' :: t1, co1 :: s1 ~# t1, + -- so we extend the substitution with x |-> (x' |> sym co1). in Just (x', substExpr subst e `mkCast` co2) | otherwise = pprTrace "exprIsLambda_maybe: Unexpected lambda in case" (ppr (Lam x e)) |