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Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC

Commits:

db9c95ac

by Wolfgang Jeltsch at 2026-09-24T15:51:34-04:00

Correct the documentation of `explicitUnits`

Resolves #27787.

a6b642b6

by Simon Jakobi at 2026-09-24T15:51:35-04:00

Remove stale specHeader bullet from Note [Don't make fillers for constraint types]

The Note said that Specialise.specHeader also calls mkAbsentFiller.
abfc224a27c removed that call: the specialiser no longer drops dead
arguments at all, see Note [Do not drop dead args from specialisations]
in GHC.Core.Opt.Specialise.

Assisted-by: Claude Fable 5.1

2 changed files:

compiler/GHC/Core/Opt/WorkWrap/Utils.hs
compiler/GHC/Unit/State.hs

Changes:

compiler/GHC/Core/Opt/WorkWrap/Utils.hs

@@ -1367,13 +1367,8 @@ It's surprisingly subtle.
    application; see test `T27627f`.
  TL;DR: we play safe: we never make an absent filler for any /constraint-kinded/ type,
 -using `isPredTy` to decide.
+-
 -  * `mkAbsentFiller` returns `Nothing` for any constraint type, so worker/wrapper
 -    keeps the real argument.
+-
 -  * `Specialise.specHeader` calls `mkAbsentFiller` too, so it likewise keeps the
 -    dead dictionary argument rather than dropping it for a filler.
 +using `isPredTy` to decide: `mkAbsentFiller` returns `Nothing` for any constraint
 +type, so worker/wrapper keeps the real argument.
  Prior failed approaches

compiler/GHC/Unit/State.hs

@@ -369,10 +369,15 @@ data UnitState = UnitState {
    -- is always mentioned before the units it depends on.
    preloadUnits      :: [UnitId],
 -  -- | Units which we explicitly depend on (from a command line flag).
 -  -- We'll use this to generate version macros and the unused packages warning. The
 -  -- original flag which was used to bring the unit into scope is recorded for the
 -  -- -Wunused-packages warning.
 +  -- | The units that can be used by the respective home unit. Despite the
 +  -- identifier, this does not just cover units that are enabled explicitly
 +  -- using flags but also units from the package database that are enabled
 +  -- implicitly in case @-hide-all-packages@ is absent. The former are paired
 +  -- with 'Just' applied to the respective flags, the latter are paired with
 +  -- 'Nothing'.
 +  --
 +  -- This field is used for generating version macros and “unused packages”
 +  -- warnings.
    explicitUnits :: [(Unit, Maybe PackageArg)],
    homeUnitDepends    :: Set UnitId,
@@ -907,7 +912,7 @@ mkUnitState logger unit_index cfg = do
    let pkgname_map = listToUFM [ (unitPackageName p, unitInstanceOf p)
                                | p <- pkgs2
+                               ]
 -  -- The explicitUnits accurately reflects the set of units we have turned
 +  -- The explicitUnits accurately reflects the set of units that are turned
    -- on; as such, it also is the only way one can come up with requirements.
    -- The requirement context is directly based off of this: we simply
    -- look for nested unit IDs that are directly fed holes: the requirements