range algorithms on container class

[Paul Backus]

On Thursday, 9 January 2020 at 10:26:07 UTC, Jonathan M Davis 
wrote:
> On Wednesday, January 8, 2020 10:56:20 PM MST rikki cattermole 
> via Digitalmars-d-learn wrote:
>> Slicing via the opSlice operator overload is a convention, not 
>> a requirement.
>
> It's not a requirement, but it's more than a convention. If you 
> use the container with foreach, the compiler will call opSlice 
> on the container to get a range. So, there's no need to 
> implement opApply to iterate over a container with foreach. You 
> could choose to implement a container with opApply and use a 
> function other than opSlice for getting a range, but the 
> compiler understands enough to try to slice the container for 
> you automatically when using it with foreach.
>
> - Jonathan M Davis

Is this documented in the language spec anywhere? I don't see 
anything about it in the section on foreach [1] or the section on 
slice operator overloading [2].

[1] https://dlang.org/spec/statement.html#foreach-statement
[2] https://dlang.org/spec/operatoroverloading.html#slice