Add set pretty printer

src/test.nim

@@ -70,6 +70,23 @@ proc `$`*(x: Parser): string =
   tokens: {indentKey($x.tokens, 2)},
 )"""
 
+proc prettyExpectedSet(x: set[char]): string =
+  case x:
+    of AllChars:
+      "AllChars {'\x00'..'\xFF'}"
+    of Digits:
+      "Digits {'0'..'9'}"
+    of HexDigits:
+      "HexDigits {'0'..'9', 'A'..'F', 'a'..'f'}"
+    of Letters:
+      "Letters {'A'..'Z', 'a'..'z'}"
+    of Newlines:
+      "Newlines {'\r', '\n'}"
+    of Whitespace:
+      "Whitespace {' ', '\t', '\v', '\r', '\n', '\f'}"
+    else:
+      $x
+
 proc `$`*(x: ParserError): string =
   case x:
     of charMismatchErr(expected: @expected, parser: @parser, index: @index, unexpected: @unexpected):