[parser] allow '-' as the first character of an identifier. Use try for literals

src/MiniJuvix/Syntax/Concrete/Lexer.hs

@@ -86,7 +86,6 @@ bareIdentifier = interval $ do
       isAlphaNum c || validFirstChar c
     validFirstChar :: Char -> Bool
     validFirstChar c =
-      c /= '-' &&
       or
         [ isLetter c,
           cat == MathSymbol,

src/MiniJuvix/Syntax/Concrete/Parser.hs

@@ -123,7 +123,7 @@ import_ = do
 expressionAtom :: MonadParsec e Text m => m (ExpressionAtom 'Parsed)
 expressionAtom =
   do
-     AtomLiteral <$> literal
+     AtomLiteral <$> P.try literal
     <|> AtomIdentifier <$> name
     <|> (AtomUniverse <$> universe)
     <|> (AtomLambda <$> lambda)