Merge #802 NixString: rm hacky funs, convert principled funs into regular ones

This nearly finishes the work people did on the NixString & StringContext handling.

HNix had hacky* implementations used for a long time, and now type and implementation systems arrived into great shape that all of the functions become principled.

* Closes: #383 #384 #385.

* Removed hacky functions/.

* Reduced prefixes from functions.

* NixString now is a Monoid, project code now leverages that.

* Clean-up & restructure in the Nix.String module.

Author: Anton-Latukha

benchmarks/ParserBench.hs

@@ -2,20 +2,20 @@ module ParserBench (benchmarks) where
 
 import           Nix.Parser
 
-import           Control.Applicative
 import           Criterion
 
 benchFile :: FilePath -> Benchmark
-benchFile = bench <*> whnfIO . parseNixFile . ("data/" ++)
+benchFile = bench <*> whnfIO . parseNixFile . ("data/" <>)
 
 benchmarks :: Benchmark
 benchmarks = bgroup
-  "Parser"
-  [ benchFile "nixpkgs-all-packages.nix"
-  , benchFile "nixpkgs-all-packages-pretty.nix"
-  , benchFile "let-comments.nix"
-  , benchFile "let-comments-multiline.nix"
-  , benchFile "let.nix"
-  , benchFile "simple.nix"
-  , benchFile "simple-pretty.nix"
-  ]
+  "Parser" $
+    fmap benchFile
+      [ "nixpkgs-all-packages.nix"
+      , "nixpkgs-all-packages-pretty.nix"
+      , "let-comments.nix"
+      , "let-comments-multiline.nix"
+      , "let.nix"
+      , "simple.nix"
+      , "simple-pretty.nix"
+      ]

main/Main.hs

@@ -143,13 +143,13 @@ main = do
       = liftIO
         .   putStrLn
         .   Text.unpack
-        .   principledStringIgnoreContext
+        .   stringIgnoreContext
         .   toXML
         <=< normalForm
       | json opts
       = liftIO
         .   Text.putStrLn
-        .   principledStringIgnoreContext
+        .   stringIgnoreContext
         <=< nvalueToJSONNixString
       | strict opts
       = liftIO . print . prettyNValue <=< normalForm