docs: TypeMirror builderMethodReturnType(ExecutableElement builderMethod) {
      DeclaredType builderTypeMirror = MoreTypes.asDeclared(builderType.asType());
      TypeMirror methodMirror;
      try {
        methodMirror = typeUtils.asMemberOf(builderTypeMirror, builderMethod);
      } catch (IllegalArgumentException e) {
        // Presumably we've hit the Eclipse bug cited.
        return builderMethod.getReturnType();
      }
      return MoreTypes.asExecutable(methodMirror).getReturnType();
    }