Refactor ModuleName to L.H.S.Module.Name

ModuleName used to live in GHC.Unit.Module.Name. In this commit, the
definition of ModuleName and its associated functions are moved to
Language.Haskell.Syntax.Module.Name according to the current plan
towards making the AST GHC-independent.

The instances for ModuleName for Outputable, Uniquable and Binary were
moved to the module in which the class is defined because these instances
depend on GHC.

The instance of Eq for ModuleName is slightly changed to no longer
depend on unique explicitly and instead uses FastString's instance of
Eq.

4 files changed, 63 insertions, 10 deletions

diff --git a/compiler/Language/Haskell/Syntax.hs b/compiler/Language/Haskell/Syntax.hs
index d5129cbb13..82e9f5558d 100644
--- a/compiler/Language/Haskell/Syntax.hs
+++ b/compiler/Language/Haskell/Syntax.hs
@@ -22,6 +22,7 @@ module Language.Haskell.Syntax (
         module Language.Haskell.Syntax.Expr,
         module Language.Haskell.Syntax.ImpExp,
         module Language.Haskell.Syntax.Lit,
+        module Language.Haskell.Syntax.Module.Name,
         module Language.Haskell.Syntax.Pat,
         module Language.Haskell.Syntax.Type,
         module Language.Haskell.Syntax.Extension,
@@ -32,6 +33,7 @@ import Language.Haskell.Syntax.Decls
 import Language.Haskell.Syntax.Binds
 import Language.Haskell.Syntax.Expr
 import Language.Haskell.Syntax.ImpExp
+import Language.Haskell.Syntax.Module.Name
 import Language.Haskell.Syntax.Lit
 import Language.Haskell.Syntax.Extension
 import Language.Haskell.Syntax.Pat
diff --git a/compiler/Language/Haskell/Syntax/ImpExp.hs b/compiler/Language/Haskell/Syntax/ImpExp.hs
index 7e529701c4..b31c417936 100644
--- a/compiler/Language/Haskell/Syntax/ImpExp.hs
+++ b/compiler/Language/Haskell/Syntax/ImpExp.hs
@@ -3,6 +3,7 @@
 module Language.Haskell.Syntax.ImpExp where
 
 import Language.Haskell.Syntax.Extension
+import Language.Haskell.Syntax.Module.Name
 
 import Data.Eq (Eq)
 import Data.Ord (Ord)
@@ -14,7 +15,6 @@ import Data.String (String)
 import Data.Int (Int)
 
 import GHC.Hs.Doc -- ROMES:TODO Discuss in #21592 whether this is parsed AST or base AST
-import GHC.Data.FastString
 
 {-
 ************************************************************************
@@ -26,9 +26,6 @@ Import and export declaration lists
 One per import declaration in a module.
 -}
 
--- | A ModuleName is essentially a simple string, e.g. @Data.List@.
-newtype ModuleName = ModuleName FastString deriving Show
-
 -- | Located Import Declaration
 type LImportDecl pass = XRec pass (ImportDecl pass)
         -- ^ When in a list this may have
diff --git a/compiler/Language/Haskell/Syntax/ImpExp.hs-boot b/compiler/Language/Haskell/Syntax/ImpExp.hs-boot
index 9cc78600b8..68bd7fdc53 100644
--- a/compiler/Language/Haskell/Syntax/ImpExp.hs-boot
+++ b/compiler/Language/Haskell/Syntax/ImpExp.hs-boot
@@ -1,7 +1,5 @@
 module Language.Haskell.Syntax.ImpExp where
 
-import GHC.Data.FastString
-
 import Data.Eq
 import Data.Ord
 import Text.Show
@@ -16,7 +14,3 @@ instance Eq IsBootInterface
 instance Ord IsBootInterface
 instance Show IsBootInterface
 instance Data IsBootInterface
-
-newtype ModuleName = ModuleName FastString
-
-instance Show ModuleName
diff --git a/compiler/Language/Haskell/Syntax/Module/Name.hs b/compiler/Language/Haskell/Syntax/Module/Name.hs
new file mode 100644
index 0000000000..65e64d8700
--- /dev/null
+++ b/compiler/Language/Haskell/Syntax/Module/Name.hs
@@ -0,0 +1,60 @@
+module Language.Haskell.Syntax.Module.Name where
+
+import Prelude
+
+import Data.Data
+import Data.Char (isAlphaNum)
+import Control.DeepSeq
+import qualified Text.ParserCombinators.ReadP as Parse
+import System.FilePath
+
+import GHC.Utils.Misc (abstractConstr)
+import GHC.Data.FastString
+
+-- | A ModuleName is essentially a simple string, e.g. @Data.List@.
+newtype ModuleName = ModuleName FastString deriving (Show, Eq)
+
+instance Ord ModuleName where
+  nm1 `compare` nm2 = stableModuleNameCmp nm1 nm2
+
+instance Data ModuleName where
+  -- don't traverse?
+  toConstr _   = abstractConstr "ModuleName"
+  gunfold _ _  = error "gunfold"
+  dataTypeOf _ = mkNoRepType "ModuleName"
+
+instance NFData ModuleName where
+  rnf x = x `seq` ()
+
+stableModuleNameCmp :: ModuleName -> ModuleName -> Ordering
+-- ^ Compares module names lexically, rather than by their 'Unique's
+stableModuleNameCmp n1 n2 = moduleNameFS n1 `lexicalCompareFS` moduleNameFS n2
+
+moduleNameFS :: ModuleName -> FastString
+moduleNameFS (ModuleName mod) = mod
+
+moduleNameString :: ModuleName -> String
+moduleNameString (ModuleName mod) = unpackFS mod
+
+mkModuleName :: String -> ModuleName
+mkModuleName s = ModuleName (mkFastString s)
+
+mkModuleNameFS :: FastString -> ModuleName
+mkModuleNameFS s = ModuleName s
+
+-- |Returns the string version of the module name, with dots replaced by slashes.
+--
+moduleNameSlashes :: ModuleName -> String
+moduleNameSlashes = dots_to_slashes . moduleNameString
+  where dots_to_slashes = map (\c -> if c == '.' then pathSeparator else c)
+
+-- |Returns the string version of the module name, with dots replaced by colons.
+--
+moduleNameColons :: ModuleName -> String
+moduleNameColons = dots_to_colons . moduleNameString
+  where dots_to_colons = map (\c -> if c == '.' then ':' else c)
+
+parseModuleName :: Parse.ReadP ModuleName
+parseModuleName = fmap mkModuleName
+                $ Parse.munch1 (\c -> isAlphaNum c || c `elem` "_.")
+