Simplify code

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/packet/login/LoginResult.kt

@@ -90,10 +90,7 @@ inline fun LoginResult.requireSuccess(lazyMessage: (LoginResult) -> String) {
  * 检查 [this] 为 [LoginResult.SUCCESS].
  * 失败则 [error]
  */
-fun LoginResult.requireSuccess() {
-    if (requireSuccessOrNull() === null)
-        error("Login failed: $this")
-}
+fun LoginResult.requireSuccess() = requireSuccess { "Login failed: $this" }
 
 /**
  * 检查 [this] 为 [LoginResult.SUCCESS].
@@ -101,10 +98,7 @@ fun LoginResult.requireSuccess() {
  *
  * @return 成功时 [Unit], 失败时 `null`
  */
-fun LoginResult.requireSuccessOrNull(): Unit? {
-    return if (this == SUCCESS) Unit else null
-}
-
+fun LoginResult.requireSuccessOrNull(): Unit? = if (this == SUCCESS) Unit else null
 
 /**
  * 检查 [this] 为 [LoginResult.SUCCESS].