Align the behaviour of `dopt` and `log_dopt`

Before the behaviour of `dopt` and `logHasDumpFlag` (and the underlying
function `log_dopt`) were different as the latter did not take the
verbosity level into account. This led to problems during the
refactoring as we cannot simply replace calls to `dopt` with calls to
`logHasDumpFlag`.

In addition to that a subtle bug in the GHC module was fixed:
`setSessionDynFlags` did not update the logger and as a consequence the
verbosity value of the logger was not set appropriately.

Fixes #21861

4 files changed, 45 insertions, 32 deletions

diff --git a/compiler/GHC.hs b/compiler/GHC.hs
index 9689bd828f..750c17c141 100644
--- a/compiler/GHC.hs
+++ b/compiler/GHC.hs
@@ -597,7 +597,7 @@ setSessionDynFlags dflags0 = do
   case S.toList all_uids of
     [uid] -> do
       setUnitDynFlagsNoCheck uid dflags
-      modifySession (hscSetActiveUnitId (homeUnitId_ dflags))
+      modifySession (hscUpdateLoggerFlags . hscSetActiveUnitId (homeUnitId_ dflags))
       dflags' <- getDynFlags
       setTopSessionDynFlags dflags'
     [] -> panic "nohue"
diff --git a/compiler/GHC/Driver/Flags.hs b/compiler/GHC/Driver/Flags.hs
index bac257670c..f158e6a42b 100644
--- a/compiler/GHC/Driver/Flags.hs
+++ b/compiler/GHC/Driver/Flags.hs
@@ -1,5 +1,7 @@
 module GHC.Driver.Flags
    ( DumpFlag(..)
+   , getDumpFlagFrom
+   , enabledIfVerbose
    , GeneralFlag(..)
    , Language(..)
    , optimisationFlags
@@ -142,6 +144,46 @@ data DumpFlag
    | Opt_D_faststring_stats
    deriving (Eq, Show, Enum)
 
+-- | Helper function to query whether a given `DumpFlag` is enabled or not.
+getDumpFlagFrom
+  :: (a -> Int) -- ^ Getter for verbosity setting
+  -> (a -> EnumSet DumpFlag) -- ^ Getter for the set of enabled dump flags
+  -> DumpFlag -> a -> Bool
+getDumpFlagFrom getVerbosity getFlags f x
+  =  (f `EnumSet.member` getFlags x)
+  || (getVerbosity x >= 4 && enabledIfVerbose f)
+
+-- | Is the flag implicitly enabled when the verbosity is high enough?
+enabledIfVerbose :: DumpFlag -> Bool
+enabledIfVerbose Opt_D_dump_tc_trace               = False
+enabledIfVerbose Opt_D_dump_rn_trace               = False
+enabledIfVerbose Opt_D_dump_cs_trace               = False
+enabledIfVerbose Opt_D_dump_if_trace               = False
+enabledIfVerbose Opt_D_dump_tc                     = False
+enabledIfVerbose Opt_D_dump_rn                     = False
+enabledIfVerbose Opt_D_dump_rn_stats               = False
+enabledIfVerbose Opt_D_dump_hi_diffs               = False
+enabledIfVerbose Opt_D_verbose_core2core           = False
+enabledIfVerbose Opt_D_verbose_stg2stg             = False
+enabledIfVerbose Opt_D_dump_splices                = False
+enabledIfVerbose Opt_D_th_dec_file                 = False
+enabledIfVerbose Opt_D_dump_rule_firings           = False
+enabledIfVerbose Opt_D_dump_rule_rewrites          = False
+enabledIfVerbose Opt_D_dump_simpl_trace            = False
+enabledIfVerbose Opt_D_dump_rtti                   = False
+enabledIfVerbose Opt_D_dump_inlinings              = False
+enabledIfVerbose Opt_D_dump_verbose_inlinings      = False
+enabledIfVerbose Opt_D_dump_core_stats             = False
+enabledIfVerbose Opt_D_dump_asm_stats              = False
+enabledIfVerbose Opt_D_dump_types                  = False
+enabledIfVerbose Opt_D_dump_simpl_iterations       = False
+enabledIfVerbose Opt_D_dump_ticked                 = False
+enabledIfVerbose Opt_D_dump_view_pattern_commoning = False
+enabledIfVerbose Opt_D_dump_mod_cycles             = False
+enabledIfVerbose Opt_D_dump_mod_map                = False
+enabledIfVerbose Opt_D_dump_ec_trace               = False
+enabledIfVerbose _                                 = True
+
 -- | Enumerates the simple on-or-off dynamic flags
 data GeneralFlag
 -- See Note [Updating flag description in the User's Guide]
diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs
index 67c6ff6938..ef7a7bdd08 100644
--- a/compiler/GHC/Driver/Session.hs
+++ b/compiler/GHC/Driver/Session.hs
@@ -1427,36 +1427,7 @@ hasNoOptCoercion = gopt Opt_G_NoOptCoercion
 
 -- | Test whether a 'DumpFlag' is set
 dopt :: DumpFlag -> DynFlags -> Bool
-dopt f dflags = (f `EnumSet.member` dumpFlags dflags)
-             || (verbosity dflags >= 4 && enableIfVerbose f)
-    where enableIfVerbose Opt_D_dump_tc_trace               = False
-          enableIfVerbose Opt_D_dump_rn_trace               = False
-          enableIfVerbose Opt_D_dump_cs_trace               = False
-          enableIfVerbose Opt_D_dump_if_trace               = False
-          enableIfVerbose Opt_D_dump_tc                     = False
-          enableIfVerbose Opt_D_dump_rn                     = False
-          enableIfVerbose Opt_D_dump_rn_stats               = False
-          enableIfVerbose Opt_D_dump_hi_diffs               = False
-          enableIfVerbose Opt_D_verbose_core2core           = False
-          enableIfVerbose Opt_D_verbose_stg2stg             = False
-          enableIfVerbose Opt_D_dump_splices                = False
-          enableIfVerbose Opt_D_th_dec_file                 = False
-          enableIfVerbose Opt_D_dump_rule_firings           = False
-          enableIfVerbose Opt_D_dump_rule_rewrites          = False
-          enableIfVerbose Opt_D_dump_simpl_trace            = False
-          enableIfVerbose Opt_D_dump_rtti                   = False
-          enableIfVerbose Opt_D_dump_inlinings              = False
-          enableIfVerbose Opt_D_dump_verbose_inlinings      = False
-          enableIfVerbose Opt_D_dump_core_stats             = False
-          enableIfVerbose Opt_D_dump_asm_stats              = False
-          enableIfVerbose Opt_D_dump_types                  = False
-          enableIfVerbose Opt_D_dump_simpl_iterations       = False
-          enableIfVerbose Opt_D_dump_ticked                 = False
-          enableIfVerbose Opt_D_dump_view_pattern_commoning = False
-          enableIfVerbose Opt_D_dump_mod_cycles             = False
-          enableIfVerbose Opt_D_dump_mod_map                = False
-          enableIfVerbose Opt_D_dump_ec_trace               = False
-          enableIfVerbose _                                 = True
+dopt = getDumpFlagFrom verbosity dumpFlags
 
 -- | Set a 'DumpFlag'
 dopt_set :: DynFlags -> DumpFlag -> DynFlags
diff --git a/compiler/GHC/Utils/Logger.hs b/compiler/GHC/Utils/Logger.hs
index 878e6d52f4..83b2600439 100644
--- a/compiler/GHC/Utils/Logger.hs
+++ b/compiler/GHC/Utils/Logger.hs
@@ -146,7 +146,7 @@ defaultLogFlags = LogFlags
 
 -- | Test if a DumpFlag is enabled
 log_dopt :: DumpFlag -> LogFlags -> Bool
-log_dopt f logflags = f `EnumSet.member` log_dump_flags logflags
+log_dopt = getDumpFlagFrom log_verbosity log_dump_flags
 
 -- | Enable a DumpFlag
 log_set_dopt :: DumpFlag -> LogFlags -> LogFlags