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Consistent shift behavior in generic math

  • Artikkel

Shift operations in generic math now have consistent behavior across all built-in integer types.

Previous behavior

The behavior when utilizing generic math to perform a shift on a T could differ based on the type. In some cases, it appropriately masked the shift amount by sizeof(T) - 1. And in other cases, there was no masking. This meant that "overshifting" (such as shifting a byte by 8) could result in different answers than expected.

New behavior

The implementations were updated to mask the shift amount, as appropriate, to ensure consistent behavior across all built-in integer types and with the behavior documented by the System.Numerics.IShiftOperators<TSelf,TOther,TResult> interface.

Version introduced

.NET 10 Preview 1

Type of breaking change

This change is a behavioral change.

Reason for change

The behavior differed from the designed behavior due to a difference in how masking works for small integer types in C#.

Update any code that relies on the previous inconsistent behavior to ensure it works with the new consistent behavior.

Affected APIs

  • operator <<
  • operator >>
  • operator >>> for byte, char, sbyte, short, and ushort when used via generic math, which requires a T constrained to where T : IShiftOperators<T, int, T> or a similar interface.