Fix doctests for GHC9.4

I don't know what am I doing really. But doctests now work

vector/src/Data/Vector/Storable.hs

@@ -1029,7 +1029,8 @@ izipWith6 = G.izipWith6
 -- | Checks whether two values are the same vector: they have same length
 -- and share the same buffer.
 --
--- >>> let xs = fromList [0/0::Double] in isSameVector xs xs
+-- >>> import qualified Data.Vector.Storable as VS
+-- >>> let xs = VS.fromList [0/0::Double] in VS.isSameVector xs xs
 -- True
 isSameVector :: (Storable a) => Vector a -> Vector a -> Bool
 {-# INLINE isSameVector #-}

vector/src/Data/Vector/Unboxed/Base.hs

@@ -304,6 +304,7 @@ idU = id
 -- >>> :set -XTypeFamilies -XStandaloneDeriving -XDerivingVia
 -- >>> :set -XMultiParamTypeClasses -XTypeOperators -XFlexibleInstances
 -- >>> import qualified Data.Vector.Unboxed         as VU
+-- >>> import qualified Data.Vector.Unboxed.Mutable as MVU
 -- >>> import qualified Data.Vector.Generic         as VG
 -- >>> import qualified Data.Vector.Generic.Mutable as VGM
 -- >>> :{
@@ -316,17 +317,17 @@ idU = id
 --   {-# INLINE fromURepr #-}
 -- newtype instance VU.MVector s (Foo a) = MV_Foo (VU.MVector s (Int, a))
 -- newtype instance VU.Vector    (Foo a) = V_Foo  (VU.Vector    (Int, a))
--- deriving via (Foo a `VU.As` (Int, a)) instance VU.Unbox a => VGM.MVector MVector (Foo a)
--- deriving via (Foo a `VU.As` (Int, a)) instance VU.Unbox a => VG.Vector  Vector  (Foo a)
+-- deriving via (Foo a `VU.As` (Int, a)) instance VU.Unbox a => VGM.MVector MVU.MVector (Foo a)
+-- deriving via (Foo a `VU.As` (Int, a)) instance VU.Unbox a => VG.Vector   VU.Vector   (Foo a)
 -- instance VU.Unbox a => VU.Unbox (Foo a)
 -- :}
 --
 --
 -- It's also possible to use generic-based instance for 'IsoUnbox'
 -- which should work for all product types.
 --
--- >>> :set -XTypeFamilies -XStandaloneDeriving -XDerivingVia -XDeriveGeneric
--- >>> :set -XMultiParamTypeClasses -XTypeOperators -XFlexibleInstances
+-- >>> :set -XMultiParamTypeClasses -XTypeOperators -XFlexibleInstances -XDeriveGeneric
+-- >>> :set -XDerivingVia
 -- >>> import qualified Data.Vector.Unboxed         as VU
 -- >>> import qualified Data.Vector.Generic         as VG
 -- >>> import qualified Data.Vector.Generic.Mutable as VGM

vector/tests/doctests.hs

@@ -1,4 +1,38 @@
 import Test.DocTest (doctest)
 
+-- Doctests are weirdly fragile. For example running tests for module
+-- A (D.V.Unboxed.Base) could cause tests in unrelated woudle B
+-- (D.V.Storable) to start failing with weird errors.
+--
+-- In order to avoid this one would want to run doctests with
+-- per-module granularity but this cause another sort of problems!
+-- When we load only single module and use import doctests then some
+-- data types may come from built library and some from ghci session.
+--
+-- This could be remedied by running doctests for groups of modules.
+-- This _is_ convoluted setup but doctests now works for GHC9.4
 main :: IO ()
-main = doctest [ "-Iinclude" , "-Iinternal" , "-XHaskell2010" , "src/Data" ]
+main = mapM_ run modGroups
+  where
+    run mods = do
+      mapM_ putStrLn mods
+      doctest $ ["-Iinclude", "-Iinternal", "-XHaskell2010"] ++ mods
+    --
+    modGroups =
+      [ [ "src/Data/Vector/Storable/Mutable.hs"
+        , "src/Data/Vector/Storable.hs"
+        ]
+      , [ "src/Data/Vector.hs"
+        , "src/Data/Vector/Mutable.hs"
+        ]
+      , [ "src/Data/Vector/Generic.hs"
+        , "src/Data/Vector/Generic/Mutable.hs"
+        ]
+      , [ "src/Data/Vector/Primitive.hs"
+        , "src/Data/Vector/Primitive/Mutable.hs"
+        ]
+      , [ "src/Data/Vector/Unboxed.hs"
+        , "src/Data/Vector/Unboxed/Mutable.hs"
+        , "src/Data/Vector/Unboxed/Base.hs"
+        ]
+      ]