Add assertion for keep rules on unboxed enums

Change-Id: Iaaaf7ed49f6c2797454adc56d5d5ee06259ad3ae

src/main/java/com/android/tools/r8/shaking/KeepInfoCollection.java

diff --git a/src/main/java/com/android/tools/r8/shaking/KeepInfoCollection.java b/src/main/java/com/android/tools/r8/shaking/KeepInfoCollection.java
index 03104f6..fda4b97 100644
--- a/src/main/java/com/android/tools/r8/shaking/KeepInfoCollection.java
+++ b/src/main/java/com/android/tools/r8/shaking/KeepInfoCollection.java
@@ -318,8 +318,7 @@
           (type, info) -> {
             DexType newType = lens.lookupType(type);
             if (newType == options.dexItemFactory().intType) {
-              // If the enum has been unboxed, then the keep info is no longer valid. This
-              // typically happens for conditional keep rules such as -keepclassmembers.
+              assert !info.isPinned(options);
               return;
             }
             assert newType == type