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LocalInstances.scala
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LocalInstances.scala
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/*
* Copyright 2022 Typelevel
*
* 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 org.typelevel.otel4s.instances
import cats.Applicative
import cats.Functor
import cats.effect.IOLocal
import cats.effect.LiftIO
import cats.effect.MonadCancelThrow
import cats.mtl.Local
trait LocalInstances {
// We hope this instance is moved into Cats Effect.
// See https://github.com/typelevel/cats-effect/pull/3429
implicit final def localForIOLocal[F[_]: MonadCancelThrow: LiftIO, E](implicit
ioLocal: IOLocal[E]
): Local[F, E] =
new Local[F, E] {
def applicative: Applicative[F] =
Applicative[F]
def ask[E2 >: E]: F[E2] =
Functor[F].widen[E, E2](ioLocal.get.to[F])
def local[A](fa: F[A])(f: E => E): F[A] =
MonadCancelThrow[F].bracket(ioLocal.modify(e => (f(e), e)).to[F])(_ =>
fa
)(ioLocal.set(_).to[F])
}
}