attribute: fix slice related function bug (#3252)

* attribute: fix slice related function bug

Signed-off-by: Ziqi Zhao <zhaoziqi9146@gmail.com>
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>
Co-authored-by: Chester Cheung <cheung.zhy.csu@gmail.com>

internal/attribute/attribute.go

@@ -0,0 +1,45 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/*
+Package attribute provide several helper functions for some commonly used
+logic of processing attributes.
+*/
+package attribute // import "go.opentelemetry.io/otel/internal/attribute"
+
+import (
+	"reflect"
+)
+
+// SliceValue convert a slice into an array with same elements as slice.
+func SliceValue[T bool | int64 | float64 | string](v []T) any {
+	var zero T
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero)))
+	copy(cp.Elem().Slice(0, len(v)).Interface().([]T), v)
+	return cp.Elem().Interface()
+}
+
+// AsSlice convert an array into a slice into with same elements as array.
+func AsSlice[T bool | int64 | float64 | string](v any) []T {
+	rv := reflect.ValueOf(v)
+	if rv.Type().Kind() != reflect.Array {
+		return nil
+	}
+	var zero T
+	correctLen := rv.Len()
+	correctType := reflect.ArrayOf(correctLen, reflect.TypeOf(zero))
+	cpy := reflect.New(correctType)
+	_ = reflect.Copy(cpy.Elem(), rv)
+	return cpy.Elem().Slice(0, correctLen).Interface().([]T)
+}