scanner.go: Strings can be enclosed between two single-quotes too

scanner.go

@@ -178,13 +178,18 @@ func (self *scanner) fetchNextToken() (tk *Token) {
 				tk = self.makeToken(SymDot, ch)
 			}
 		case '\'':
-			tk = self.makeToken(SymQuote, ch)
+			if escape {
+				tk = self.makeToken(SymQuote, ch)
+				escape = false
+			} else {
+				tk = self.fetchString(ch)
+			}
 		case '"':
 			if escape {
 				tk = self.makeToken(SymDoubleQuote, ch)
 				escape = false
 			} else {
-				tk = self.fetchString()
+				tk = self.fetchString(ch)
 			}
 		case '`':
 			tk = self.makeToken(SymBackTick, ch)
@@ -533,7 +538,7 @@ func (self *scanner) fetchUntil(sym Symbol, allowEos bool, endings ...byte) (tk
 	return
 }
 
-func (self *scanner) fetchString() (tk *Token) {
+func (self *scanner) fetchString(termCh byte) (tk *Token) {
 	var err error
 	var ch, prev byte
 	var sb strings.Builder
@@ -554,7 +559,7 @@ func (self *scanner) fetchString() (tk *Token) {
 				sb.WriteByte(ch)
 			}
 			prev = 0
-		} else if ch == '"' {
+		} else if ch == termCh {
 			break
 		} else {
 			prev = ch