On Tuesday, 30 August 2016 at 14:58:16 UTC, Chris Wright wrote:
On Tue, 30 Aug 2016 13:24:04 +0000, tsbockman wrote:
Ranges don't always grow. Some operations will also cause them
to shrink, if they're really being tracked correctly:
We can only track types, not values, and that strongly hampers
our ability to reduce ranges. We can still do it sometimes, but
no operation always reduces ranges (and every operation
sometimes extends ranges).
Then don't try to propagate the ranges at all.
Use regular `CheckedInt` as the return type for all of
`BoundInt`'s non-assignment binary operations. Make the user
explicitly label which variables should be checked against what
ranges, instead of automatically inserting the usually-wrong
guess that every intermediate value belongs in the same narrow
range as the inputs. Otherwise, `BoundInt` will generate tons of
spurious exceptions, particularly for multiplication.
Expressions that are complicated enough that custom range-based
sanity checks need to be done inside of it, on rvalues, should
probably be broken up into smaller pieces, anyway.
