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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2022-05-16 13:33:12 +0100 |
|---|---|---|
| committer | Matthew Pickering <matthewtpickering@gmail.com> | 2022-06-15 17:06:44 +0100 |
| commit | 1eba76f5f5511b63fb7585fde001506f9aaf24f6 (patch) | |
| tree | f4b327019ac370bffb95ae317edd0cc03c2a26a3 /compiler/GHC/Core/Coercion.hs | |
| parent | 486f43202c8be8eaea8b54c6bac7e9238aaf9b39 (diff) | |
| download | haskell-1eba76f5f5511b63fb7585fde001506f9aaf24f6.tar.gz | |
Fix bad interaction between withDict and the Specialiser
This MR fixes a bad bug, where the withDict was inlined too
vigorously, which in turn made the type-class Specialiser generate
a bogus specialisation, because it saw the same overloaded function
applied to two /different/ dictionaries.
Solution: inline `withDict` later. See (WD8) of Note [withDict]
in GHC.HsToCore.Expr
See #21575, which is fixed by this change.
(cherry picked from commit d2284c4c9dd484a4b459366956c4aedc72336b04)
Diffstat (limited to 'compiler/GHC/Core/Coercion.hs')
| -rw-r--r-- | compiler/GHC/Core/Coercion.hs | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/compiler/GHC/Core/Coercion.hs b/compiler/GHC/Core/Coercion.hs index 4cfdc3ee82..f631932671 100644 --- a/compiler/GHC/Core/Coercion.hs +++ b/compiler/GHC/Core/Coercion.hs @@ -1707,9 +1707,8 @@ has to do in its full generality. See #18413. %************************************************************************ -} --- | If @co :: T ts ~ rep_ty@ then: --- --- > instNewTyCon_maybe T ts = Just (rep_ty, co) +-- | If `instNewTyCon_maybe T ts = Just (rep_ty, co)` +-- then `co :: T ts ~R# rep_ty` -- -- Checks for a newtype, and for being saturated instNewTyCon_maybe :: TyCon -> [Type] -> Maybe (Type, Coercion) |