Simon Hengel pushed to branch wip/sol/MultiWayIf-docs at Glasgow Haskell Compiler / GHC Commits: c8f80cf2 by Simon Hengel at 2026-01-31T19:21:39+05:30 Update the documentation for MultiWayIf (fixes #25376) (so that it matches the implementation) - - - - - 1 changed file: - docs/users_guide/exts/multiway_if.rst Changes: ===================================== docs/users_guide/exts/multiway_if.rst ===================================== @@ -10,7 +10,7 @@ Multi-way if-expressions Allow the use of multi-way-``if`` syntax. -With :extension:`MultiWayIf` extension GHC accepts conditional expressions with +With the :extension:`MultiWayIf` extension GHC accepts conditional expressions with multiple branches: :: if | guard1 -> expr1 @@ -24,12 +24,12 @@ which is roughly equivalent to :: ... _ | guardN -> exprN -Multi-way if expressions introduce a new layout context. So the example +Multi-way if expressions introduce a new kind of layout context that does not generate semicolons. The example above is equivalent to: :: if { | guard1 -> expr1 - ; | ... - ; | guardN -> exprN + | ... + | guardN -> exprN } The following behaves as expected: :: @@ -41,14 +41,14 @@ The following behaves as expected: :: because layout translates it as :: if { | guard1 -> if { | guard2 -> expr2 - ; | guard3 -> expr3 + | guard3 -> expr3 } - ; | guard4 -> expr4 + | guard4 -> expr4 } Layout with multi-way if works in the same way as other layout contexts, -except that the semi-colons between guards in a multi-way if are -optional. So it is not necessary to line up all the guards at the same +except that desugaring does not insert semicolons. +So it is not necessary to line up all the guards at the same column; this is consistent with the way guards work in function definitions and case expressions. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/c8f80cf228374fa3f469887b5550ffde... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/c8f80cf228374fa3f469887b5550ffde... You're receiving this email because of your account on gitlab.haskell.org.