Fix non-terminating shrink streams. #278
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This was reported as typelevel#244. The root cause was that shrinking certain values would produce an infinite stream. There were several ways this could happen -- in the reported case, the fact that Char was unsigned meant that the strategy of including inverses was able to produce loops. The fix was to detect when Integral[T] cannot support negative values, and disabling negation. While working on this, I noticed that shrinking floating point sentinels (i.e. infinities and NaN) would cause a similar issue. I added code to detect those cases as well. Fixes typelevel#244.
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(This issue was first introduced with the introduction of the generic shrinker in 1.13.0.) |
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Thanks! |
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Thanks, great to get some insight into what was causing this. |
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This was reported as #244. The root cause was that shrinking certain
values would produce an infinite stream. There were several ways this
could happen -- in the reported case, the fact that Char was unsigned
meant that the strategy of including inverses was able to produce
loops.
The fix was to detect when Integral[T] cannot support negative values,
and disabling negation.
While working on this, I noticed that shrinking floating point
sentinels (i.e. infinities and NaN) would cause a similar issue. I
added code to detect those cases as well.
Fixes #244.