[Bug]: creating a negative length tuple results in compiler hang

[jabraham17]

The following code results in the compiler hanging forever

var x: (-1)*int;

This should be a better error, saying negative length tuples are not allowed.

This can also occur in more subtle ways. The following program also hangs on compilation and should have a similar error

proc foo(param x): x*int where x == -1 {
  var tup: x*int;
  return tup;
}
foo(-1);

[bradcray]

:o

I wonder if it's really "forever" or just "looping through all of the negative integers, treating them as large positive ones, until we recurse down to 0"? (effectively the same thing, particularly given how expensive our compiler's tuple implementation is).