Lifetime tracking

[Walter Bright via Digitalmars-d]

On 6/2/2016 4:05 PM, Timon Gehr wrote:
> I'd like to point out again why that design is inadequate:
>
> Whenever the type checker is using a certain piece of information to check
> validity of a program, there should be a way to pass that kind of information
> across function boundaries. Otherwise the type system is not modular. This is a
> serious defect.

I don't understand where the defect is. Please give an example.