Allow Natural and Integer literals in binary notation (#2540)

Author: kukimik

dhall/src/Dhall/Parser/Token.hs

@@ -299,11 +299,14 @@ integerLiteral = (do
 -}
 naturalLiteral :: Parser Natural
 naturalLiteral = (do
-    a <-    try (char '0' >> char 'x' >> Text.Megaparsec.Char.Lexer.hexadecimal)
+    a <-    binary
+        <|> hexadecimal
         <|> decimal
         <|> (char '0' $> 0)
     return a ) <?> "literal"
   where
+    binary = try (char '0' >> char 'b' >> Text.Megaparsec.Char.Lexer.binary)
+    hexadecimal = try (char '0' >> char 'x' >> Text.Megaparsec.Char.Lexer.hexadecimal)
     decimal = do
         n <- headDigit
         ns <- many tailDigit

dhall/tests/format/numericLiteralsA.dhall

@@ -1 +1 @@
-{ example0 = 0x42, example1 = +0x42, example2 = 1.2e20 }
+{ example0 = 0x42, example1 = +0x42, example2 = 1.2e20, example3 = -0b0111 }

dhall/tests/format/numericLiteralsB.dhall

@@ -1 +1 @@
-{ example0 = 0x42, example1 = +0x42, example2 = 1.2e20 }
+{ example0 = 0x42, example1 = +0x42, example2 = 1.2e20, example3 = -0b0111 }