[Git][ghc/ghc][wip/buggymcbugfix/15185-enum-int] Add inline pragmas to Enum methods

[Vilem-Benjamin Liepelt]

Vilem-Benjamin Liepelt pushed to branch wip/buggymcbugfix/15185-enum-int at Glasgow Haskell Compiler / GHC


Commits:
fc47ad26 by buggymcbugfix at 2020-05-13T13:31:17+03:00
Add inline pragmas to Enum methods

Fixes t15185

- - - - -


1 changed file:

- libraries/base/GHC/Enum.hs


Changes:

=====================================
libraries/base/GHC/Enum.hs
=====================================
@@ -139,13 +139,36 @@ class  Enum a   where
     --     * @enumFromThenTo 6 8 2 :: [Int] = []@
     enumFromThenTo      :: a -> a -> a -> [a]
 
-    succ                   = toEnum . (+ 1)  . fromEnum
-    pred                   = toEnum . (subtract 1) . fromEnum
-    enumFrom x             = map toEnum [fromEnum x ..]
-    enumFromThen x y       = map toEnum [fromEnum x, fromEnum y ..]
-    enumFromTo x y         = map toEnum [fromEnum x .. fromEnum y]
+    succ = toEnum . (+ 1) . fromEnum
+
+    pred = toEnum . (subtract 1) . fromEnum
+
+    -- See Note [Stable Unfolding for Enum methods]
+    {-# INLINABLE enumFrom #-}
+    enumFrom x = map toEnum [fromEnum x ..]
+
+    -- See Note [Stable Unfolding for Enum methods]
+    {-# INLINABLE enumFromThen #-}
+    enumFromThen x y = map toEnum [fromEnum x, fromEnum y ..]
+
+    -- See Note [Stable Unfolding for Enum methods]
+    {-# INLINABLE enumFromTo #-}
+    enumFromTo x y = map toEnum [fromEnum x .. fromEnum y]
+
+    -- See Note [Stable Unfolding for Enum methods]
+    {-# INLINABLE enumFromThenTo #-}
     enumFromThenTo x1 x2 y = map toEnum [fromEnum x1, fromEnum x2 .. fromEnum y]
 
+{-
+Note [Stable Unfolding for Enum methods]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The INLINABLE pragmas ensure that we export stable (unoptimised) unfoldings in
+the interface file so we can do list fusion at usage sites outside this module.
+
+Fixes https://gitlab.haskell.org/ghc/ghc/issues/15185
+-}
+
 -- Default methods for bounded enumerations
 boundedEnumFrom :: (Enum a, Bounded a) => a -> [a]
 boundedEnumFrom n = map toEnum [fromEnum n .. fromEnum (maxBound `asTypeOf` n)]



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/fc47ad267b81673626e07731530a6cb90734d725

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/fc47ad267b81673626e07731530a6cb90734d725
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