switch from symbol to intern as the former seems dormant

`intern` seems to serve the same purpose but is actively maintained by
Ryan G. Scott and a part of kmettoverse

this hopefully unlocks support for GHC 9.10

gibbon-compiler/gibbon.cabal

@@ -115,7 +115,7 @@ library
                      , hse-cpp                  >= 0.1       &&  < 1
                      , s-cargot                 >= 0.1.3     &&  < 1
                      , srcloc                   >= 0.6       &&  < 1
-                     , symbol                   >= 0.2.4     &&  < 1
+                     , intern                   ^>= 0.9
                      -- Pretty printers:
                      , pretty                   >= 1.1.1.3   &&  < 1.2
                      , GenericPretty            >= 1.2.1     &&  < 2

gibbon-compiler/src/Gibbon/Common.hs

@@ -10,6 +10,7 @@ module Gibbon.Common
          -- * Variables
          Var(..), LocVar, RegVar, fromVar, toVar, varAppend, toEndV, toSeqV, cleanFunName
        , TyVar(..), isUserTv
+       , Symbol, intern, unintern
 
          -- * Gensym monad
        , SyM, gensym, gensym_tag, genLetter, newUniq, runSyM
@@ -49,7 +50,8 @@ import Data.Char
 import qualified Data.List as L
 import Data.Map as M
 import Data.String
-import Data.Symbol
+import qualified Data.Interned as DI
+import Data.Interned.String
 import Data.Word
 import GHC.Generics
 import GHC.Stack (HasCallStack)
@@ -67,6 +69,21 @@ import Gibbon.DynFlags
 
 --------------------------------------------------------------------------------
 
+newtype Symbol = Symbol InternedString
+  deriving (Eq, Ord, Show)
+
+instance Read Symbol where
+  readsPrec _ s = [(Symbol $ DI.intern s, "")]
+
+instance IsString Symbol where
+  fromString = intern
+
+intern :: String -> Symbol
+intern = Symbol . DI.intern
+
+unintern :: Symbol -> String
+unintern (Symbol is) = DI.unintern is
+
 -- type CursorVar = Var
 newtype Var = Var Symbol
   deriving (Eq, Ord, Read, Show)

gibbon-compiler/src/Gibbon/L0/ElimNewtype.hs

@@ -6,7 +6,6 @@ import Gibbon.Common
 import Control.Arrow
 import qualified Data.Map as M
 import qualified Data.Set as S
-import Data.Symbol ( unintern )
 
 elimNewtypes :: Monad m => Prog0 -> m Prog0
 elimNewtypes = pure . elimProgram

gibbon-compiler/src/Gibbon/L1/GenSML.hs

@@ -9,7 +9,6 @@ import Control.Monad
 import Data.Map hiding (foldr, fold, null, empty)
 import qualified Data.Map as Map
 import qualified Data.Set as Set
-import Data.Symbol
 
 import Data.Foldable hiding ( toList )
 import Data.Graph

gibbon-compiler/src/Gibbon/Passes/Fusion2.hs

@@ -11,7 +11,6 @@ import qualified Data.Map as M
 import qualified Data.List as L
 import qualified Data.Set as S
 import qualified Data.Vector as V
-import           Data.Symbol
 import           Data.Char ( toLower )
 import           Debug.Trace
 import           Control.DeepSeq