build failing on play-services:11.8.x with pro guard parser error

Question

So it looks like there is a bug in the latest play-services to be deployed. Does anyone know how to work around this issue?

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':myappname:transformClassesWithAndroidGradleClassShrinkerForDevelopmentDebug'.
> ProGuard configuration parser error: /Users/myusername/.gradle/caches/transforms-1/files-1.1/play-services-base-11.8.0.aar/d2ad9e16677fda9cf07a1280a66e91ca/proguard.txt line 3:88 no viable alternative at input '<fields>'

So more information. seems the problem is in the core module:

Error:Execution failed for task ':myappname:transformClassesWithAndroidGradleClassShrinkerForDevelopmentDebug'.
> ProGuard configuration parser error: /Users/myusername/.gradle/caches/transforms-1/files-1.1/play-services-base-11.8.0.aar/d2ad9e16677fda9cf07a1280a66e91ca/proguard.txt line 3:88 no viable alternative at input '<fields>'

EDIT: The contents of the file that is causing that error is:

# b/35135904 Ensure that proguard will not strip the mResultGuardian.
-keepclassmembers class com.google.android.gms.common.api.internal.BasePendingResult {
  com.google.android.gms.common.api.internal.BasePendingResult.ReleasableResultGuardian <fields>;
}

Answer 1

It seems the default shrinker has changed. Adding the configuration to turn on ProGuard seemed to work.

buildTypes {
        release {
            debuggable false
            minifyEnabled true
            useProguard true
            ...
        }
        debug {
            debuggable true
            minifyEnabled true
            useProguard true
            ...
        }
    }