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Diffstat (limited to 'compiler/GHC/Utils/Monad.hs')
| -rw-r--r-- | compiler/GHC/Utils/Monad.hs | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/compiler/GHC/Utils/Monad.hs b/compiler/GHC/Utils/Monad.hs index da415ba44c..a65947e59e 100644 --- a/compiler/GHC/Utils/Monad.hs +++ b/compiler/GHC/Utils/Monad.hs @@ -344,6 +344,17 @@ it is more elaborate. The pattern synonym approach is due to Sebastian Graaf (#18238) +Do note that for monads for multiple arguments more than one oneShot +function might be required. For example in FCode we use: + + newtype FCode a = FCode' { doFCode :: CgInfoDownwards -> CgState -> (a, CgState) } + + pattern FCode :: (CgInfoDownwards -> CgState -> (a, CgState)) + -> FCode a + pattern FCode m <- FCode' m + where + FCode m = FCode' $ oneShot (\cgInfoDown -> oneShot (\state ->m cgInfoDown state)) + Derived instances ~~~~~~~~~~~~~~~~~ One caveat of both approaches is that derived instances don't use the smart |