Simplify variadic function support and add a test for it

expr_test.go

@@ -172,6 +172,16 @@ func TestMethodCall(t *testing.T) {
 	}
 }
 
+func TestVariadic(t *testing.T) {
+	res := execStr(t, `#(sprintf("%s %d", x, y))`, map[string]any{
+		"x": "test",
+		"y": 4,
+	})
+	if res != "test 4" {
+		t.Errorf("Expected %q, got %q", "test 4", res)
+	}
+}
+
 func execStr(t *testing.T, tmplStr string, vars map[string]any) string {
 	t.Helper()
 	tmpl, err := New().ParseString("test", tmplStr)

salix.go

@@ -496,18 +496,18 @@ func (t *Template) execFunc(fn reflect.Value, node ast.Node, args []ast.Node, lo
 			return nil, err
 		}
 		params = append(params, reflect.ValueOf(paramVal))
+
+		var paramType reflect.Type
 		if isVariadic && i >= lastIndex {
-			if params[i].CanConvert(fnType.In(lastIndex).Elem()) {
-				params[i] = params[i].Convert(fnType.In(lastIndex).Elem())
+			paramType = fnType.In(lastIndex).Elem()
 		} else {
-				return nil, ast.PosError(node, "%s: invalid parameter type: %T (expected %s)", valueToString(node), paramVal, fnType.In(i))
+			paramType = fnType.In(i)
 		}
+
+		if params[i].CanConvert(paramType) {
+			params[i] = params[i].Convert(paramType)
 		} else {
-			if params[i].CanConvert(fnType.In(i)) {
-				params[i] = params[i].Convert(fnType.In(i))
-			} else {
-				return nil, ast.PosError(node, "%s: invalid parameter type: %T (expected %s)", valueToString(node), paramVal, fnType.In(i))
-			}
+			return nil, ast.PosError(node, "%s: invalid parameter type: %T (expected %s)", valueToString(node), paramVal, paramType)
 		}
 	}