title: Proguard - Can't find common super class of [com/google/android/gms/d/kl]
body: <p>I am failing to create a release build. Suddenly Android Studio started throwing below error.</p>
  
  <pre><code>Unexpected error while performing partial evaluation:
    Class       = [com/google/android/gms/d/lc]
    Method      = [a(Lcom/google/android/gms/d/kk;Landroid/content/Context;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Lcom/google/android/gms/d/lh;Lcom/google/android/gms/d/en;Lcom/google/android/gms/d/lb;)Lcom/google/android/gms/d/kn;]
    Exception   = [java.lang.IllegalArgumentException] (Can't find common super class of [com/google/android/gms/d/kn] (with 1 known super classes) and [java/lang/String] (with 2 known super classes))
  Unexpected error while preverifying:
    Class       = [com/google/android/gms/d/lc]
    Method      = [a(Lcom/google/android/gms/d/kk;Landroid/content/Context;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Lcom/google/android/gms/d/lh;Lcom/google/android/gms/d/en;Lcom/google/android/gms/d/lb;)Lcom/google/android/gms/d/kn;]
    Exception   = [java.lang.IllegalArgumentException] (Can't find common super class of [com/google/android/gms/d/kn] (with 1 known super classes) and [java/lang/String] (with 2 known super classes))
  Warning: Exception while processing task java.io.IOException: java.lang.IllegalArgumentException: Can't find common super class of [com/google/android/gms/d/kn] (with 1 known super classes) and [java/lang/String] (with 2 known super classes)
  </code></pre>
  
  <p>Here is my Proguard Configurations</p>
  
  <pre><code>-keep public class com.google.android.gms.* { public *; }
  -dontwarn com.google.android.gms.**
  
  -keep class com.facebook.ads.** { *; }
  </code></pre>
  
  <p>Here is the list of gradle dependencies of my project</p>
  
  <pre><code>dependencies {
      implementation fileTree(include: ['*.jar'], dir: 'libs')
      androidTestImplementation('com.android.support.test.espresso:espresso-core:2.2.2', {
          exclude group: 'com.android.support', module: 'support-annotations'
      })
      implementation 'com.android.support.constraint:constraint-layout:1.1.0'
      implementation 'com.android.support:design:27.1.1'
      implementation 'com.android.support:appcompat-v7:27.1.1'
      implementation 'com.android.support:cardview-v7:27.1.1'
      implementation 'com.google.firebase:firebase-perf:16.0.0'
      implementation 'com.google.firebase:firebase-config:16.0.0'
      implementation 'com.google.firebase:firebase-core:16.0.0'
      implementation 'com.google.firebase:firebase-messaging:17.0.0'
      implementation 'com.google.android.gms:play-services-analytics:16.0.0'
      implementation 'com.google.android.gms:play-services-drive:15.0.1'
      implementation 'com.google.android.gms:play-services-auth:15.0.1'
      implementation 'com.startapp:inapp-sdk:3.8.4'
      implementation 'com.facebook.android:audience-network-sdk:4.28.2'
      testImplementation 'junit:junit:4.12'
      testImplementation 'org.mockito:mockito-core:2.7.1'
      testImplementation 'org.powermock:powermock-mockito-release-full:1.4.9'   
      implementation('com.crashlytics.sdk.android:crashlytics:2.9.1@aar') {
          transitive = true
      }
  }
  </code></pre>
  
  <p><strong>Note</strong> Commenting the Facebook audience network dependency fixes the error. Unfortunately I cannot do it permanently from the project.</p>
  
  <p>Please help me identifying the cause of an issue. Thanks in advance.</p>