improve parser error messages

fire/firestorm/lexer/debug.go

@@ -0,0 +1,47 @@
+package lexer
+
+import "strconv"
+
+var debug = map[TokenType]string{
+	ID:          "identifier",
+	LPAREN:      "(",
+	RPAREN:      ")",
+	LBRACE:      "{",
+	RBRACE:      "}",
+	LBRACKET:    "[",
+	RBRACKET:    "]",
+	DIVIDE:      "/",
+	COMMA:       ",",
+	ARROW:       "->",
+	STRING:      "string",
+	ASSIGN:      "=",
+	PLUS:        "+",
+	MINUS:       "-",
+	MULTIPLY:    "*",
+	NUMBER:      "number",
+	MODULO:      "%",
+	XOR:         "^",
+	AND:         "&",
+	OR:          "|",
+	SHIFT_LEFT:  "<<",
+	SHIFT_RIGHT: ">>",
+	BIT_NOT:     "~",
+	END_OF_LINE: ";",
+	EQUALS:      "==",
+	NOT_EQUALS:  "!=",
+	LESS:        "<",
+	LESS_EQUALS: "<=",
+	MORE:        ">",
+	MORE_EQUALS: ">=",
+	NOT:         "!",
+	INCREASE:    "++",
+	DECREASE:    "--",
+}
+
+func ToString(token TokenType) string {
+	if str, ok := debug[token]; ok {
+		return str
+	} else {
+		return strconv.Itoa(int(token))
+	}
+}

fire/firestorm/parser.go

@@ -57,7 +57,7 @@ func (p *Parser) error(message string, pos int) {
 
 func (p *Parser) expect(tokenType lexer.TokenType) {
 	if p.current.Type != tokenType {
-		p.error("Expected "+strconv.Itoa(int(tokenType))+" but was "+strconv.Itoa(int(p.current.Type)), p.current.Pos)
+		p.error("Expected "+lexer.ToString(tokenType)+" but was "+lexer.ToString(p.current.Type), p.current.Pos)
 	}
 }
 
@@ -74,7 +74,7 @@ func (p *Parser) commaOrRparen() bool {
 		p.advance()
 		return true
 	} else {
-		p.error("Unexpected "+strconv.Itoa(int(p.current.Type)), p.current.Pos)
+		p.error("Unexpected "+lexer.ToString(p.current.Type), p.current.Pos)
 	}
 	panic("?")
 }