core/src/com/google/inject/spi/ProviderLookup.java
public void initializeDelegate(Provider<T> delegate) {
    checkState(this.delegate == null, "delegate already initialized");
    this.delegate = checkNotNull(delegate, "delegate");
  }
public void initializeDelegate(Provider<T> delegate) {
    checkState(this.delegate == null, "delegate already initialized");
    this.delegate = checkNotNull(delegate, "delegate");
  }
Sets the actual provider.

@throws IllegalStateException if the delegate is already set