core/src/com/google/inject/internal/Errors.java
public Errors withSource(Object source) {
    return source == this.source || source == SourceProvider.UNKNOWN_SOURCE
        ? this
        : new Errors(this, source);
  }
public Errors withSource(Object source) {
    return source == this.source || source == SourceProvider.UNKNOWN_SOURCE
        ? this
        : new Errors(this, source);
  }
Returns an instance that uses {@code source} as a reference point for newly added errors.