Require GHC 8.10 as the minimum compiler for bootstrapping

Now that GHC 9.0.1 is released, it is time to drop support for bootstrapping
with GHC 8.8, as we only support building with the previous two major GHC
releases. As an added bonus, this allows us to remove several bits of CPP that
are either always true or no longer reachable.

4 files changed, 6 insertions, 33 deletions

diff --git a/libraries/base/GHC/Windows.hs b/libraries/base/GHC/Windows.hs
index d8f8bef804..be0c3837a9 100644
--- a/libraries/base/GHC/Windows.hs
+++ b/libraries/base/GHC/Windows.hs
@@ -74,7 +74,7 @@ module GHC.Windows (
         nullHANDLE,
     ) where
 
-import Data.Bits (shiftL, shiftR, (.|.), (.&.))
+import Data.Bits (finiteBitSize, shiftL, shiftR, (.|.), (.&.))
 import Data.Char
 import Data.OldList
 import Data.Maybe
@@ -93,15 +93,6 @@ import System.IO.Error
 
 import qualified Numeric
 
-#if MIN_VERSION_base(4,7,0)
-import Data.Bits (finiteBitSize)
-#else
-import Data.Bits (Bits, bitSize)
-
-finiteBitSize :: (Bits a) => a -> Int
-finiteBitSize = bitSize
-#endif
-
 #include "windows_cconv.h"
 
 type BOOL     = Bool
diff --git a/libraries/ghc-heap/GHC/Exts/Heap.hs b/libraries/ghc-heap/GHC/Exts/Heap.hs
index 1e429ca054..2906cf6926 100644
--- a/libraries/ghc-heap/GHC/Exts/Heap.hs
+++ b/libraries/ghc-heap/GHC/Exts/Heap.hs
@@ -153,14 +153,7 @@ getClosureDataFromHeapObject
     -- ^ Heap representation of the closure.
 getClosureDataFromHeapObject x = do
     case unpackClosure# x of
-#if MIN_VERSION_ghc_prim(0,5,3)
         (# infoTableAddr, heapRep, pointersArray #) -> do
-#else
-        -- This is a hack to cover the bootstrap compiler using the old version
-        -- of 'unpackClosure'. The new 'unpackClosure' return values are not
-        -- merely a reordering, so using the old version would not work.
-        (# infoTableAddr, pointersArray, heapRep #) -> do
-#endif
             let infoTablePtr = Ptr infoTableAddr
                 ptrList = [case indexArray# pointersArray i of
                                 (# ptr #) -> Box ptr
diff --git a/libraries/ghc-heap/GHC/Exts/Heap/Closures.hs b/libraries/ghc-heap/GHC/Exts/Heap/Closures.hs
index 1a6a9371d4..3b51b22ceb 100644
--- a/libraries/ghc-heap/GHC/Exts/Heap/Closures.hs
+++ b/libraries/ghc-heap/GHC/Exts/Heap/Closures.hs
@@ -16,12 +16,7 @@ module GHC.Exts.Heap.Closures (
     , WhyBlocked(..)
     , TsoFlags(..)
     , allClosures
-#if __GLASGOW_HASKELL__ >= 809
-    -- The closureSize# primop is unsupported on earlier GHC releases but we
-    -- build ghc-heap as a boot library so it must be buildable. Drop this once
-    -- we are guaranteed to bootstsrap with GHC >= 8.9.
     , closureSize
-#endif
 
     -- * Boxes
     , Box(..)
@@ -430,11 +425,9 @@ allClosures (WeakClosure {..}) = [cfinalizers, key, value, finalizer, link]
 allClosures (OtherClosure {..}) = hvalues
 allClosures _ = []
 
-#if __GLASGOW_HASKELL__ >= 809
 -- | Get the size of the top-level closure in words.
 -- Includes header and payload. Does not follow pointers.
 --
 -- @since 8.10.1
 closureSize :: Box -> Int
 closureSize (Box x) = I# (closureSize# x)
-#endif
diff --git a/libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs b/libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs
index 67017d4926..a41d0a47b3 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
 {-# LANGUAGE Trustworthy #-}
 
 -- |
@@ -29,17 +30,12 @@ import Prelude
 -- * Type synonyms
 ----------------------------------------------------------
 
--- Since GHC 8.8 is currently the minimum boot compiler version that we must
--- support, we must use inline kind signatures to make TExpQ and CodeQ
--- levity polymorphic. When we drop support for GHC 8.8, we can instead use
--- standalone kind signatures, which are provided as comments.
-
 -- | Levity-polymorphic since /template-haskell-2.17.0.0/.
--- type TExpQ :: TYPE r -> Kind.Type
-type TExpQ (a :: TYPE r) = Q (TExp a)
+type TExpQ :: TYPE r -> Kind.Type
+type TExpQ a = Q (TExp a)
 
--- type CodeQ :: TYPE r -> Kind.Type
-type CodeQ = Code Q :: (TYPE r -> Kind.Type)
+type CodeQ :: TYPE r -> Kind.Type
+type CodeQ = Code Q
 
 type InfoQ               = Q Info
 type PatQ                = Q Pat