Why is this allowed

[JN via Digitalmars-d-learn]

Spent some time debugging because I didn't notice it at first, 
essentially something like this:

int[3] foo = [1, 2, 3];
foo = 5;
writeln(foo);   // 5, 5, 5
Why does such code compile? I don't think this should be 
permitted, because it's easy to make a mistake (when you wanted 
foo[index] but forgot the []). If someone wants to assign a value 
to every element they could do foo[] = 5; instead which is 
explicit.