Can't compile - Overload resolution ambiguity

[ferinagy]

I checked out current master (7935c28f249f32786ccc53bc0098d073065b1ec5) and run ./gradlew clean assemble with result

UserSessionMatcher.kt: (86, 52): Overload resolution ambiguity: 
public open fun contains(@Nullable element: TagIdAndCategory): Boolean defined in java.util.HashSet
public open fun contains(@Nullable element: TagIdAndCategory!): Boolean defined in java.util.HashSet

Full build log is here: build.txt