Add support for comments

Author: antonmedv

checker/checker_test.go

@@ -477,6 +477,11 @@ MapOfAny[0]
 cannot use int to get an element from map[string]interface {} (1:10)
  | MapOfAny[0]
  | .........^
+
+1 /* one */ + "2"
+invalid operation: + (mismatched types int and string) (1:13)
+ | 1 /* one */ + "2"
+ | ............^
 `
 
 func TestCheck_error(t *testing.T) {

expr_test.go

@@ -1032,6 +1032,10 @@ func TestExpr(t *testing.T) {
 			`lowercase`,
 			"lowercase",
 		},
+		{
+			`1 /* one*/ + 2 /* two */`,
+			3,
+		},
 	}
 
 	for _, tt := range tests {

parser/lexer/lexer_test.go

@@ -163,6 +163,23 @@ var lexTests = []lexTest{
 			{Kind: EOF},
 		},
 	},
+	{
+		`foo // comment
+		bar // comment`,
+		[]Token{
+			{Kind: Identifier, Value: "foo"},
+			{Kind: Identifier, Value: "bar"},
+			{Kind: EOF},
+		},
+	},
+	{
+		`foo /* comment */ bar`,
+		[]Token{
+			{Kind: Identifier, Value: "foo"},
+			{Kind: Identifier, Value: "bar"},
+			{Kind: EOF},
+		},
+	},
 }
 
 func compareTokens(i1, i2 []Token) bool {

parser/lexer/state.go

@@ -26,11 +26,13 @@ func root(l *lexer) stateFn {
 		return number
 	case r == '?':
 		return questionMark
+	case r == '/':
+		return slash
 	case strings.ContainsRune("([{", r):
 		l.emit(Bracket)
 	case strings.ContainsRune(")]}", r):
 		l.emit(Bracket)
-	case strings.ContainsRune("#,?:%+-/^", r): // single rune operator
+	case strings.ContainsRune("#,?:%+-^", r): // single rune operator
 		l.emit(Operator)
 	case strings.ContainsRune("&|!=*<>", r): // possible double rune operator
 		l.accept("&|=*")
@@ -158,3 +160,39 @@ func questionMark(l *lexer) stateFn {
 	l.emit(Operator)
 	return root
 }
+
+func slash(l *lexer) stateFn {
+	if l.accept("/") {
+		return singleLineComment
+	}
+	if l.accept("*") {
+		return multiLineComment
+	}
+	l.emit(Operator)
+	return root
+}
+
+func singleLineComment(l *lexer) stateFn {
+	for {
+		r := l.next()
+		if r == eof || r == '\n' {
+			break
+		}
+	}
+	l.ignore()
+	return root
+}
+
+func multiLineComment(l *lexer) stateFn {
+	for {
+		r := l.next()
+		if r == eof {
+			return l.error("unclosed comment")
+		}
+		if r == '*' && l.accept("/") {
+			break
+		}
+	}
+	l.ignore()
+	return root
+}