Driver: make MonadComprehensions imply ParallelListComp

This commit changes GHC.Driver.Flags.impliedXFlags to make the
MonadComprehensions extension enable the ParallelListComp extension.

Fixes #25645

compiler/GHC/Driver/Flags.hs

@@ -330,7 +330,7 @@ impliedXFlags
     , (LangExt.RecordWildCards,     On LangExt.DisambiguateRecordFields)
 
     , (LangExt.ParallelArrays, On LangExt.ParallelListComp)
-
+    , (LangExt.MonadComprehensions, On LangExt.ParallelListComp)
     , (LangExt.JavaScriptFFI, On LangExt.InterruptibleFFI)
 
     , (LangExt.DeriveTraversable, On LangExt.DeriveFunctor)

docs/users_guide/9.14.1-notes.rst

@@ -78,6 +78,8 @@ Language
 
   This causes the constructor to have type ``Rec :: Int %'Many -> Char %1 -> Record``.
 
+* The :extension:`MonadComprehensions` extension now implies :extension:`ParallelListComp` as was originally intended (see `Monad Comprehensions <https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/monad_comprehensions.html>`_).
+
 Compiler
 ~~~~~~~~
 

docs/users_guide/exts/monad_comprehensions.rst

@@ -9,6 +9,8 @@ Monad comprehensions
 .. extension:: MonadComprehensions
     :shortdesc: Allow list comprehension syntax to be used at monads other than ``List``.
 
+    :implies: :extension:`ParallelListComp`
+
     :since: 7.2.1
 
     Enable list comprehension syntax for arbitrary monads.

docs/users_guide/exts/parallel_list_comprehensions.rst

@@ -10,6 +10,8 @@ Parallel List Comprehensions
 .. extension:: ParallelListComp
     :shortdesc: Allow parallel list comprehension syntax.
 
+    :implied by: :extension:`MonadComprehensions`
+
     :since: 6.8.1
 
     Allow parallel list comprehension syntax.

testsuite/tests/parser/should_fail/readFail038.stderr

@@ -2,4 +2,4 @@
 readFail038.hs:5:9: error: [GHC-42026]
     Unexpected parallel statement in a list comprehension
     Suggested fix:
-      Perhaps you intended to use the ‘ParallelListComp’ extension (implied by ‘ParallelArrays’)
+      Perhaps you intended to use the ‘ParallelListComp’ extension (implied by ‘ParallelArrays’ and ‘MonadComprehensions’)