Replace Default instance for Diagnostic with Monoid

README.md

@@ -39,7 +39,8 @@ You don't even need to `import Prettyprinter`, as it is already provided to you
 A diagnostic can be viewed as a collection of reports, spanning on files.
 This is what the `Diagnostic` type embodies.
 
-It has a `Default` instance, which can be used to construct an empty diagnostic (contains no reports, and has no files).
+It is an instance of `Monoid`, which can be used to construct an empty
+diagnostic (contains no reports, and has no files).
 
 The second step is to add some reports.
 There are two kinds of reports:
@@ -99,7 +100,7 @@ let beautifulExample =
         -- ^^^^ This is a 'Note' not a 'Hint', as specified by its 'IsString' instance
 
 -- Create the diagnostic
-let diagnostic  = addFile def "somefile.zc" "let id<a>(x : a) : a := x\n  + 1"
+let diagnostic  = addFile mempty "somefile.zc" "let id<a>(x : a) : a := x\n  + 1"
 let diagnostic' = addReport diagnostic beautifulExample
 
 -- Print with unicode characters, and the default (colorful) style

src/Error/Diagnose/Diagnostic.hs

@@ -20,7 +20,6 @@ import Error.Diagnose.Diagnostic.Internal as Export
 #endif
     addFile,
     addReport,
-    def,
     errorsToWarnings,
     hasReports,
     reportsOf,

src/Error/Diagnose/Diagnostic/Internal.hs

@@ -14,7 +14,7 @@
 --            It is also highly undocumented.
 --
 --            Please limit yourself to the "Error.Diagnose.Diagnostic" module, which exports some of the useful functions defined here.
-module Error.Diagnose.Diagnostic.Internal (module Error.Diagnose.Diagnostic.Internal, def, WithUnicode(..), TabSize(..)) where
+module Error.Diagnose.Diagnostic.Internal (module Error.Diagnose.Diagnostic.Internal, WithUnicode(..), TabSize(..)) where
 
 import Control.Monad.IO.Class (MonadIO, liftIO)
 #ifdef USE_AESON
@@ -25,7 +25,6 @@ import Data.ByteString.Lazy (ByteString)
 import Data.Array (listArray)
 import Data.DList (DList)
 import qualified Data.DList as DL
-import Data.Default (Default, def)
 import Data.Foldable (fold, toList)
 import qualified Data.HashMap.Lazy as HashMap
 import Data.List (intersperse)
@@ -38,8 +37,8 @@ import System.IO (Handle)
 
 -- | The data type for diagnostic containing messages of an abstract type.
 --
---   The constructors are private, but users can use 'def' from the 'Default' typeclass
---   to create a new empty diagnostic, and 'addFile' and 'addReport' to alter its internal state.
+--   Users can use 'mempty' to create a new empty diagnostic, and 'addFile' and
+--   'addReport' to alter its internal state.
 data Diagnostic msg
   = Diagnostic
       (DList (Report msg))
@@ -50,11 +49,11 @@ data Diagnostic msg
       -- ^ A map associating files with their content as lists of lines.
   deriving (Functor, Foldable, Traversable)
 
-instance Default (Diagnostic msg) where
-  def = Diagnostic mempty mempty
+instance Monoid (Diagnostic msg) where
+  mempty = Diagnostic mempty mempty
 
 instance Semigroup (Diagnostic msg) where
-  Diagnostic rs1 file <> Diagnostic rs2 _ = Diagnostic (rs1 <> rs2) file
+  Diagnostic rs1 files1 <> Diagnostic rs2 files2 = Diagnostic (rs1 <> rs2) (files1 <> files2)
 
 #ifdef USE_AESON
 instance ToJSON msg => ToJSON (Diagnostic msg) where

test/rendering/Spec.hs

@@ -16,7 +16,6 @@ import Error.Diagnose
     Report(..),
     addFile,
     addReport,
-    def,
     defaultStyle,
     printDiagnostic,
     printDiagnostic',
@@ -90,8 +89,8 @@ main = do
           nestingReport
         ]
 
-  let diag = HashMap.foldlWithKey' addFile (foldl addReport def reports) files
-      customDiag = HashMap.foldlWithKey' addFile (foldl addReport def customAnnReports) files
+  let diag = HashMap.foldlWithKey' addFile (foldl addReport mempty reports) files
+      customDiag = HashMap.foldlWithKey' addFile (foldl addReport mempty customAnnReports) files
 
   hPutStrLn stdout "\n\nWith unicode: ─────────────────────────\n"
   printDiagnostic stdout WithUnicode (TabSize 4) defaultStyle diag