empty expressions no more return error, now they return nil

operator-selector.go

@@ -74,18 +74,21 @@ func newSelectorTerm(tk *Token) (inst *term) {
 	}
 }
 
-func isSelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (selectedValue any, err error) {
+func isSelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (match bool, selectedValue any, err error) {
 	caseData, _ := caseSel.(*selectorCase)
 	if caseData.filterList == nil {
 		selectedValue, err = caseData.caseExpr.eval(ctx, false)
+		match = true
 	} else if filterList, ok := caseData.filterList.value().([]*term); ok {
 		if len(filterList) == 0 && exprValue == int64(caseIndex) {
 			selectedValue, err = caseData.caseExpr.eval(ctx, false)
+			match = true
 		} else {
 			var caseValue any
 			for _, caseTerm := range filterList {
 				if caseValue, err = caseTerm.compute(ctx); err != nil || caseValue == exprValue {
 					selectedValue, err = caseData.caseExpr.eval(ctx, false)
+					match = true
 					break
 				}
 			}
@@ -96,7 +99,7 @@ func isSelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (sel
 
 func evalSelector(ctx ExprContext, self *term) (v any, err error) {
 	var exprValue any
-	// var caseList []*term
+	var match bool
 
 	if err = self.checkOperands(); err != nil {
 		return
@@ -110,11 +113,11 @@ func evalSelector(ctx ExprContext, self *term) (v any, err error) {
 	caseList, _ := caseListTerm.value().([]*term)
 	for i, caseTerm := range caseList {
 		caseSel := caseTerm.value()
-		if v, err = isSelectorCase(ctx, exprValue, caseSel, i); err != nil || v != nil {
+		if match, v, err = isSelectorCase(ctx, exprValue, caseSel, i); err != nil || match {
 			break
 		}
 	}
-	if err == nil && v == nil {
+	if err == nil && !match {
 		err = exprTerm.tk.Errorf("no case catches the value (%v) of the selection expression", exprValue)
 	}
 	return