Should slice[]=slice be disallowed?

[Ali Çehreli]

Ali Çehreli wrote:
 > (This must have been discussed before, but I couldn't come up with a way
 > to search in the archives.)
 >
 > There is a hidden danger with two uses of slices:
 >
 >     double[] slice1 = [ 1, 1, 1];
 >     double[] slice2 = [ 2, 2, 2];
 >     double[] slice3 = [ 3, 3, 3];
 >
 >     slice2 = slice1;              // (1)
 >     slice3[] = slice1;            // (2)
 >
 > The last two lines mean very different things:
 >
 >   (1) start sharing elements with slice1
 >
 >   (2) copy slice1's elements
 >
 > If either gets used by accident, the difference may not be noticed until
 > the elements are modified in the future.
 >
 > Could we limit the syntax to reduce the chances of such a risk? e.g.
 > "When two slices are involved, both sides must use the array-wise
 > syntax".

Oy! :( I meant the above only in the array-wise semantics. Both of these 
should be valid with their different meanings:

     slice2 = slice1;
     slice3[] = slice1[];

This is still ok:

     slice2 = slice1[];   // a slice to "all of" slice1

This should be illegal:

     slice3[] = slice1;

Should it be?

Ali