import com.google.inject.spi.ProviderWithExtensionVisitor; //导入依赖的package包/类
@Override
@SuppressWarnings("unchecked") // the extension type is always consistent with the provider type
public <V> V acceptTargetVisitor(BindingTargetVisitor<? super T, V> visitor) {
  if (providerInstance instanceof ProviderWithExtensionVisitor) {
    return ((ProviderWithExtensionVisitor<? extends T>) providerInstance)
        .acceptExtensionVisitor(visitor, this);
  } else {
    return visitor.visit(this);
  }
}
 

import com.google.inject.spi.ProviderWithExtensionVisitor; //导入依赖的package包/类
@SuppressWarnings("unchecked") // the extension type is always consistent with the provider type
public <V> V acceptTargetVisitor(BindingTargetVisitor<? super T, V> visitor) {
  if(providerInstance instanceof ProviderWithExtensionVisitor) {
    return ((ProviderWithExtensionVisitor<? extends T>) providerInstance)
        .acceptExtensionVisitor(visitor, this);
  } else {
    return visitor.visit(this);
  }
}