Improve readability of numbers in traces and errors

Use stock derived show for newtypes RunNumber, TableId and CursorId,
rather than newtype derived. This means they get rendered as
"RunNumber 3" rather than 3. This makes traces easier to read. It also
means when things are shown in errors or ghci output, the result can be
pasted back in again as valid syntax.

Carefully checked that show was not being used for anything other than
derived show for other types, so we don't change the rendering of
anything important. Did this by temporarily removing the show instance
entirely and looking for build errors. Fixed two such cases in file path
rendering.

Author: dcoutts

src/Database/LSMTree/Internal/Paths.hs

@@ -209,7 +209,7 @@ runChecksumsPath :: RunFsPaths -> FsPath
 runChecksumsPath = flip runFilePathWithExt "checksums"
 
 runFilePathWithExt :: RunFsPaths -> String -> FsPath
-runFilePathWithExt (RunFsPaths dir n) ext =
+runFilePathWithExt (RunFsPaths dir (RunNumber n)) ext =
     dir </> mkFsPath [show n] <.> ext
 
 runFileExts :: ForRunFiles String
@@ -311,7 +311,7 @@ writeBufferChecksumsPath :: WriteBufferFsPaths -> FsPath
 writeBufferChecksumsPath = flip writeBufferFilePathWithExt "checksums"
 
 writeBufferFilePathWithExt :: WriteBufferFsPaths -> String -> FsPath
-writeBufferFilePathWithExt (WriteBufferFsPaths dir n) ext =
+writeBufferFilePathWithExt (WriteBufferFsPaths dir (RunNumber n)) ext =
     dir </> mkFsPath [show n] <.> ext
 
 

src/Database/LSMTree/Internal/RunNumber.hs

@@ -7,10 +7,13 @@ module Database.LSMTree.Internal.RunNumber (
 import           Control.DeepSeq (NFData)
 
 newtype RunNumber = RunNumber Int
-  deriving newtype (Eq, Ord, Show, NFData)
+  deriving stock (Eq, Ord, Show)
+  deriving newtype (NFData)
 
 newtype TableId = TableId Int
-  deriving newtype (Eq, Ord, Show, NFData)
+  deriving stock (Eq, Ord, Show)
+  deriving newtype (NFData)
 
 newtype CursorId = CursorId Int
-  deriving newtype (Eq, Ord, Show, NFData)
+  deriving stock (Eq, Ord, Show)
+  deriving newtype (NFData)