*   <li>methods whose return type is a type variable but which can never return {@code null},
 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)

 *   <li>methods whose return type is a type variable but which can never return {@code null},
 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)

 *   <li>methods whose return type is a type variable but which can never return {@code null},
 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)

        HTTP_BAD_METHOD,
        HTTP_GONE,
        HTTP_REQ_TOO_LONG,
        HTTP_NOT_IMPLEMENTED,
        HTTP_PERM_REDIRECT,
        -> {
          // These codes can be cached unless headers forbid it.
        }

        HTTP_MOVED_TEMP,
        HTTP_TEMP_REDIRECT,
        -> {
          // These codes can only be cached with the right response headers.

     * Apply inbound settings and send an acknowledgement to the peer that provided them.
     *
     * We need to apply the settings and ack them atomically. This is because some HTTP/2
     * implementations (nghttp2) forbid peers from taking advantage of settings before they have
     * acknowledged! In particular, we shouldn't send frames that assume a new `initialWindowSize`
     * until we send the frame that acknowledges this new size.
     *

    write fails, leaving the connection in an inconsistent state.
 *  Fix: Make sure the default user agent is ASCII.


## Version 2.4.0

_2015-05-22_

 *  **Forbid response bodies on HTTP 204 and 205 responses.** Webservers that
    return such malformed responses will now trigger a `ProtocolException` in
    the client.

      apply {
        // Create a private copy of the list.
        val protocolsCopy = protocols.toMutableList()

        // Validate that the list has everything we require and nothing we forbid.
        require(Protocol.H2_PRIOR_KNOWLEDGE in protocolsCopy || HTTP_1_1 in protocolsCopy) {
          "protocols must contain h2_prior_knowledge or http/1.1: $protocolsCopy"
        }

    HTTP/2 server, close all but the first connection.
 *  Fix: Fail the HTTP/2 connection if first frame isn't `SETTINGS`.
 *  Fix: Forbid spaces in header names.
 *  Fix: Don't offer to do gzip if the request is partial.
 *  Fix: MockWebServer is now usable with JUnit 5. That update [broke the rules][junit_5_rules].

    )
    executeSynchronously(Request(server.url("/")))
    assertThat(server.takeRequest().exchangeIndex).isEqualTo(0)
    assertThat(server.takeRequest().exchangeIndex).isEqualTo(1)
  }

  /** We forbid non-ASCII characters in outgoing request headers, but accept UTF-8.  */
  @Test
  fun responseHeaderParsingIsLenient() {
    val headersBuilder = Headers.Builder()
    headersBuilder.add("Content-Length", "0")

        builder.addHeader("WWW-Authenticate: Basic realm=\"protected area\"")
      }

      HttpURLConnection.HTTP_NO_CONTENT, HttpURLConnection.HTTP_RESET -> {
        builder.body("") // We forbid bodies for 204 and 205.
      }
    }
    server.enqueue(builder.build())
    if (responseCode == HttpURLConnection.HTTP_CLIENT_TIMEOUT) {