diff options
| -rw-r--r-- | compiler/basicTypes/MkId.hs | 4 | ||||
| -rw-r--r-- | libraries/ghc-prim/GHC/Magic.hs | 7 | ||||
| -rw-r--r-- | testsuite/tests/typecheck/should_compile/T10744.hs | 17 | ||||
| -rw-r--r-- | testsuite/tests/typecheck/should_compile/all.T | 1 |
4 files changed, 27 insertions, 2 deletions
diff --git a/compiler/basicTypes/MkId.hs b/compiler/basicTypes/MkId.hs index 11f8f788cd..29e0e64c9b 100644 --- a/compiler/basicTypes/MkId.hs +++ b/compiler/basicTypes/MkId.hs @@ -1142,11 +1142,11 @@ oneShotId = pcMiscPrelId oneShotName ty info where info = noCafIdInfo `setInlinePragInfo` alwaysInlinePragma `setUnfoldingInfo` mkCompulsoryUnfolding rhs - ty = mkForAllTys [alphaTyVar, betaTyVar] (mkFunTy fun_ty fun_ty) + ty = mkForAllTys [openAlphaTyVar, openBetaTyVar] (mkFunTy fun_ty fun_ty) fun_ty = mkFunTy alphaTy betaTy [body, x] = mkTemplateLocals [fun_ty, alphaTy] x' = setOneShotLambda x - rhs = mkLams [alphaTyVar, betaTyVar, body, x'] $ Var body `App` Var x + rhs = mkLams [openAlphaTyVar, openBetaTyVar, body, x'] $ Var body `App` Var x -------------------------------------------------------------------------------- diff --git a/libraries/ghc-prim/GHC/Magic.hs b/libraries/ghc-prim/GHC/Magic.hs index 1a6af9237d..22db69f2ae 100644 --- a/libraries/ghc-prim/GHC/Magic.hs +++ b/libraries/ghc-prim/GHC/Magic.hs @@ -69,6 +69,13 @@ lazy x = x -- argument will be called at most once, which may (or may not) enable certain -- optimizations. It can be useful to improve the performance of code in continuation -- passing style. +-- +-- If 'oneShot' is used wrongly, then it may be that computations whose result +-- that would otherwise be shared are re-evaluated every time they are used. Otherwise, +-- the use of `oneShot` is safe. +-- +-- 'oneShot' is open kinded, i.e. the type variables can refer to unlifted +-- types as well. oneShot :: (a -> b) -> (a -> b) oneShot f = f -- Implementation note: This is wired in in MkId.lhs, so the code here is diff --git a/testsuite/tests/typecheck/should_compile/T10744.hs b/testsuite/tests/typecheck/should_compile/T10744.hs new file mode 100644 index 0000000000..64219ad696 --- /dev/null +++ b/testsuite/tests/typecheck/should_compile/T10744.hs @@ -0,0 +1,17 @@ +{-# LANGUAGE MagicHash #-} +module T10744 where + +import GHC.Exts +import GHC.Magic + +-- Checks if oneShot is open-kinded + +f0 :: Int -> Int +f0 = oneShot $ \n -> n + +f1 :: Int# -> Int +f1 = oneShot $ \n# -> I# n# + +f2 :: Int -> Int# +f2 = oneShot $ \(I# n#) -> n# + diff --git a/testsuite/tests/typecheck/should_compile/all.T b/testsuite/tests/typecheck/should_compile/all.T index 47a154a849..d9f2bd8160 100644 --- a/testsuite/tests/typecheck/should_compile/all.T +++ b/testsuite/tests/typecheck/should_compile/all.T @@ -468,3 +468,4 @@ test('T10562', normal, compile, ['']) test('T10564', normal, compile, ['']) test('T10632', normal, compile, ['']) test('T10642', normal, compile, ['']) +test('T10744', normal, compile, ['']) |