title: Xcode build error for Flutter with Firebase-auth plugin on beta 0.3.2 : incompatible block pointer
body: <p>This concerns <code>firebase-auth</code> plugin for <code>flutter</code>.
  I have the same code running on two mac computers.
  I just did a fresh install on the latter, and get a build error on <code>FirebaseAuthPlugin.m</code> : Incompatible block pointer</p>
  
  <pre><code>/Users/sergebesnard/Development/flutter/.pub-cache/hosted/pub.dartlang.org/
  firebase_auth-0.5.9/ios/Classes/FirebaseAuthPlugin.m:69:53:
  Incompatible block pointer types sending 'void (^)(FIRUser *__strong, NSError *__strong)' to parameter of type 'FIRAuthDataResultCallback _Nullable' (aka 'void (^)(FIRAuthDataResult * _Nullable __strong, NSError * _Nullable __strong)')
  </code></pre>
  
  <p>On my laptop, the code builds smoothly, the only difference being the beta version, which is <code>0.3.1</code> and that the android toolchain is installed.</p>
  
  <p>On the iMac (failing) :</p>
  
  <pre><code>flutter doctor -v
  [✓] Flutter (Channel beta, v0.3.2, on Mac OS X 10.13.4 17E202, locale fr-BE)
      • Flutter version 0.3.2 at /Users/sergebesnard/Development/flutter
      • Framework revision 44b7e7d3f4 (3 weeks ago), 2018-04-20 01:02:44 -0700
      • Engine revision 09d05a3891
      • Dart version 2.0.0-dev.48.0.flutter-fe606f890b
  
  [✗] Android toolchain - develop for Android devices
      ✗ Unable to locate Android SDK.
        Install Android Studio from: https://developer.android.com/studio/index.html
        On first launch it will assist you in installing the Android SDK components.
        (or visit https://flutter.io/setup/#android-setup for detailed instructions).
        If Android SDK has been installed to a custom location, set $ANDROID_HOME to that location.
  
  [✓] iOS toolchain - develop for iOS devices (Xcode 9.3)
      • Xcode at /Applications/Xcode.app/Contents/Developer
      • Xcode 9.3, Build version 9E145
      • ios-deploy 1.9.2
      • CocoaPods version 1.5.0
  
  [✗] Android Studio (not installed)
      • Android Studio not found; download from https://developer.android.com/studio/index.html
        (or visit https://flutter.io/setup/#android-setup for detailed instructions).
  
  [✓] VS Code (version 1.23.0)
      • VS Code at /Applications/Visual Studio Code.app/Contents
      • Dart Code extension version 2.12.1
  
  [✓] Connected devices (1 available)
      • iPhone X • 780C4B10-21A6-41E0-9A05-A6175FC20FA0 • ios • iOS 11.3 (simulator)
  
  ! Doctor found issues in 2 categories.
  </code></pre>
  
  <p>on the macbook (working):</p>
  
  <pre><code>[✓] Flutter (Channel beta, v0.3.1, on Mac OS X 10.13.4 17E199, locale fr-BE)
      • Flutter version 0.3.1 at /Users/sergebesnard/flutter
      • Framework revision 12bbaba9ae (3 weeks ago), 2018-04-19 23:36:15 -0700
      • Engine revision 09d05a3891
      • Dart version 2.0.0-dev.48.0.flutter-fe606f890b
  
  [✓] Android toolchain - develop for Android devices (Android SDK 27.0.2)
      • Android SDK at /Users/sergebesnard/Library/Android/sdk
      • Android NDK location not configured (optional; useful for native profiling support)
      • Platform android-27, build-tools 27.0.2
      • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
      • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08)
      • All Android licenses accepted.
  
  [✓] iOS toolchain - develop for iOS devices (Xcode 9.3)
      • Xcode at /Applications/Xcode.app/Contents/Developer
      • Xcode 9.3, Build version 9E145
      • ios-deploy 1.9.2
      • CocoaPods version 1.5.0
  
  [✓] Android Studio (version 3.0)
      • Android Studio at /Applications/Android Studio.app/Contents
      • Flutter plugin version 20.0.1
      • Dart plugin version 171.4424
      • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08)
  
  [✓] IntelliJ IDEA Community Edition (version 2017.3.4)
      • IntelliJ at /Applications/IntelliJ IDEA CE.app
      • Flutter plugin version 23.2.2
      • Dart plugin version 173.4700
  
  [✓] VS Code (version 1.23.0)
      • VS Code at /Applications/Visual Studio Code.app/Contents
      • Dart Code extension version 2.12.0
  
  [✓] Connected devices (1 available)
      • iPhone X • 03F5FA6E-7332-46A2-9BF8-A1CACE723CC8 • ios • iOS 11.3 (simulator)
  
  • No issues found!
  </code></pre>
  
  <p>the Podfile is the same : </p>
  
  <pre><code># Uncomment this line to define a global platform for your project
  # platform :ios, '9.0'
  
  # CocoaPods analytics sends network stats synchronously affecting flutter build latency.
  ENV['COCOAPODS_DISABLE_STATS'] = 'true'
  
  def parse_KV_file(file, separator='=')
    file_abs_path = File.expand_path(file)
    if !File.exists? file_abs_path
      return [];
    end
    pods_ary = []
    skip_line_start_symbols = ["#", "/"]
    File.foreach(file_abs_path) { |line|
        next if skip_line_start_symbols.any? { |symbol| line =~ /^\s*#{symbol}/ }
        plugin = line.split(pattern=separator)
        if plugin.length == 2
          podname = plugin[0].strip()
          path = plugin[1].strip()
          podpath = File.expand_path("#{path}", file_abs_path)
          pods_ary.push({:name =&gt; podname, :path =&gt; podpath});
        else
          puts "Invalid plugin specification: #{line}"
        end
    }
    return pods_ary
  end
  
  target 'Runner' do
    use_frameworks!
    # Prepare symlinks folder. We use symlinks to avoid having Podfile.lock
    # referring to absolute paths on developers' machines.
    system('rm -rf Pods/.symlinks')
    system('mkdir -p Pods/.symlinks/plugins')
  
    # Flutter Pods
    generated_xcode_build_settings = parse_KV_file('./Flutter/Generated.xcconfig')
    if generated_xcode_build_settings.empty?
      puts "Generated.xcconfig must exist. If you're running pod install manually, make sure flutter packages get is executed first."
    end
    generated_xcode_build_settings.map { |p|
      if p[:name] == 'FLUTTER_FRAMEWORK_DIR'
        symlink = File.join('Pods', '.symlinks', 'flutter')
        File.symlink(File.dirname(p[:path]), symlink)
        pod 'Flutter', :path =&gt; File.join(symlink, File.basename(p[:path]))
      end
    }
  
    # Plugin Pods
    plugin_pods = parse_KV_file('../.flutter-plugins')
    plugin_pods.map { |p|
      symlink = File.join('Pods', '.symlinks', 'plugins', p[:name])
      File.symlink(p[:path], symlink)
      pod p[:name], :path =&gt; File.join(symlink, 'ios')
    }
  end
  
  post_install do |installer|
    installer.pods_project.targets.each do |target|
      target.build_configurations.each do |config|
        config.build_settings['ENABLE_BITCODE'] = 'NO'
      end
    end
  end
  </code></pre>
  
  <p>The pod version is 1.5.0 in both cases.</p>
  
  <p>Pubspec.yaml :</p>
  
  <pre><code>dependencies:
    flutter:
      sdk: flutter
    google_sign_in: "^3.0.2"
    firebase_analytics: "^0.3.3"
    firebase_auth: "^0.5.5"
    firebase_database: "^0.4.6"
    firebase_storage: "^0.2.6"
    cloud_firestore: "^0.6.3"
    #firebase_messaging: "^0.2.4"  removed due to bug in android
  
    simple_permissions: "^0.1.2"
  
    diff_match_patch : 0.2.1
    path_provider: "^0.4.0"
    intl: "^0.15.6"
    #timeago: 1.2.0
    #side_header_list_view: "^0.0.2"
    uuid: "^1.0.0"
    #location: "^1.2.0" causes a problem in android
  
    robyn_nlp:
      path: ../robyn-nlp
  
    async_message_queue_controller:
      path: ../AsyncMessageQueueProcessor
  
    oscillo_wave_painter:
      path: ../oscillo-wave-painter
  
    #medcorder_audio:
    #  path: ../flutter_audio # super important, because the original doesn't work
  
    voice_recorder:
      path: ../voice_recorder
  
    # The following adds the Cupertino Icons font to your application.
    # Use with the CupertinoIcons class for iOS style icons.
    cupertino_icons: ^0.1.0
  
  dev_dependencies:
    flutter_test:
      sdk: flutter
  
  
  # For information on the generic Dart part of this file, see the
  # following page: https://www.dartlang.org/tools/pub/pubspec
  
  # The following section is specific to Flutter.
  flutter:
  
    # The following line ensures that the Material Icons font is
    # included with your application, so that you can use the icons in
    # the material Icons class.
    uses-material-design: true
  
    # To add assets to your application, add an assets section, like this:
    assets:
    - assets/logo-solo.png
    - assets/banner.png
  </code></pre>
  
  <p>I frankly would prefer not to test upgrading the flutter sdk on my working setup, I still need to work on that stuff...</p>
  
  <p>I don't know if this is helpful, but during setup, I ran into a problem on the installation of flutter on XCODE, because XCODE was not fully setup when at the time.
  flutter doctor did ask me to install the package six, and had problem because of a conflict in python@2 versions, so I force uninstalled via brew python@2 and reinstalled it, then could install via `pip install six``</p>
  
  <p>If this is the cause, I will have to reinstall XCODE &amp; Flutter. Hopefully not the case.</p>
  
  <p>Thanks
  Serge</p>