foreach seems to work with opIndex()

[Tofu Ninja via Digitalmars-d-learn]

Foreach seems to work if there is an opIndex() with no arguments 
that returns a range interface, is this documented? I can't seem 
to find anything that say this is supposed to happen. I am not 
really complaining, its nice, but I just didnt really expect it 
because I feel like I remember this being an error some time ago.