Use string as error for ease of use

src/test.nim

@@ -28,8 +28,8 @@ type
     endOfStringErr
   ParserError = ref object
     kind: ParseErrorKind
-    unexpected: char
-    expected: char
+    unexpected: string
+    expected: string
     index: int
     parser: Parser
   ParserResult* = Result[Parser, ParserError]
@@ -92,7 +92,7 @@ proc initParser(str: string): ParserResult =
     tokens: newSeq[Token](),
   ).ok()
 
-func ch(c1: char): (Parser -> ParserResult) {.inline.} =
+func ch(expectedChar: char): (Parser -> ParserResult) {.inline.} =
   return func(parser: Parser): ParserResult =
     let state = parser.state
     let newIndex = state.position + 1
@@ -100,26 +100,26 @@ func ch(c1: char): (Parser -> ParserResult) {.inline.} =
     if newIndex > (state.stream.len - 1):
       return err(ParserError(
         kind: endOfStringErr,
-        expected: c1,
+        expected: &"{expectedChar}",
         index: newIndex,
         parser: parser,
       ))
     else:
-      let c2 = state.stream[newIndex]
-      if c1 == c2:
+      let foundChar = state.stream[newIndex]
+      if expectedChar == foundChar:
         return Parser(
           state: ParserState(
             stream: state.stream,
             position: newIndex,
             lastPosition: parser.state.position,
           ),
-          tokens: parser.tokens & Token(value: c2)
+          tokens: parser.tokens & Token(value: foundChar)
         ).ok()
       else:
         return err(ParserError(
           kind: charMismatchErr,
-          unexpected: c2,
-          expected: c1,
+          unexpected: &"{foundChar}",
+          expected: &"{expectedChar}",
           index: newIndex,
           parser: parser,
         ))
@@ -165,11 +165,11 @@ proc foldTokens[T](
     onError(err)
 
 when isMainModule:
-  let fooParser = initParser("FOO_BAR")
+  let fooParser = initParser("FOO___BAR")
   .parseSeq(@[
     str("FOO"),
-    ignore(ch('_')),
-    ch('B'),
+    ignore(str("___")),
+    ignore(str("_")),
     ch('B'),
     ch('A'),
     ch('R'),