[Git][ghc/ghc][wip/T22739] compiler: Small optimisation of assertM

[Ben Gamari (@bgamari)]

Ben Gamari pushed to branch wip/T22739 at Glasgow Haskell Compiler / GHC


Commits:
4e17ebb1 by Ben Gamari at 2023-01-16T12:01:29-05:00
compiler: Small optimisation of assertM

In #22739 @AndreasK noticed that assertM performed the action to compute
the asserted predicate regardless of whether DEBUG is enabled. This is
inconsistent with the other assertion operations and general convention.
Fix this.

Closes #22739.

- - - - -


1 changed file:

- compiler/GHC/Utils/Panic/Plain.hs


Changes:

=====================================
compiler/GHC/Utils/Panic/Plain.hs
=====================================
@@ -29,6 +29,8 @@ import GHC.Utils.Constants
 import GHC.Utils.Exception as Exception
 import GHC.Stack
 import GHC.Prelude.Basic
+
+import Control.Monad (when)
 import System.IO.Unsafe
 
 -- | This type is very similar to 'GHC.Utils.Panic.GhcException', but it omits
@@ -150,4 +152,8 @@ massert cond = withFrozenCallStack (assert cond (pure ()))
 
 assertM :: (HasCallStack, Monad m) => m Bool -> m ()
 {-# INLINE assertM #-}
-assertM mcond = withFrozenCallStack (mcond >>= massert)
+assertM mcond
+  | debugIsOn = withFrozenCallStack $ do
+      res <- mcond
+      when (not res) assertPanic'
+  | otherwise = return ()



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/4e17ebb1872f1b0ec7868abe0e92c11b9effd910

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/4e17ebb1872f1b0ec7868abe0e92c11b9effd910
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