ast.go, pasrse.go: fixed the recover routine

ast.go

@@ -111,11 +111,10 @@ func (ast *ast) Eval(ctx kern.ExprContext) (result any, err error) {
 		if r := recover(); r != nil {
 			if errVal, ok := r.(error); ok {
 				err = errVal
+			} else {
+				err = errors.New("unexpected error while evaluating the expression")
 			}
 		}
-		if err == nil {
-			err = errors.New("unexpected error while evaluating the expression")
-		}
 	}()
 
 	ast.Finish()
@@ -123,8 +122,8 @@ func (ast *ast) Eval(ctx kern.ExprContext) (result any, err error) {
 	if ast.root != nil {
 		// initDefaultVars(ctx)
 		if ast.forest != nil {
-			for _, root := range ast.forest {
+			for _, tree := range ast.forest {
-				if result, err = root.Compute(ctx); err == nil {
+				if result, err = tree.Compute(ctx); err == nil {
 					ctx.UnsafeSetVar(kern.ControlLastResult, result)
 				} else {
 					//err = fmt.Errorf("error in expression nr %d: %v", i+1, err)

parser.go

@@ -386,11 +386,10 @@ func (parser *parser) Parse(scanner *scanner, termSymbols ...Symbol) (tree *ast,
 		if r := recover(); r != nil {
 			if errVal, ok := r.(error); ok {
 				err = errVal
+			} else {
+				err = errors.New("unexpected error while parsing the expression")
 			}
 		}
-		if err == nil {
-			err = errors.New("unexpected error while parsing the expression")
-		}
 	}()
 	termSymbols = append(termSymbols, SymEos)
 	return parser.parseGeneral(scanner, allowMultiExpr, termSymbols...)