Commits on Aug 18, 2022

1. Fix nullable annotations on generic math interfaces …

   - All `where TSelf : ...` constraints become `where TSelf : ...?`.  Without this, trying to define a type like `Matrix<T> where T : INumber<T>?` in order to support nullable T types warns because `INumber<T>` constrains its `T` (`TSelf`) to be non-nullable.
   - All `where TOther : ...` constraints are changed to be oblivious. They can't be correctly annotated as there's no way to express the nullability relationship with the nullability of TSelf.
   - Use `[MaybeNullWhen(false)] out T` instead of `[NotNullWhen(true)] out T?`, as we do with other generics, since if the instantiation of `T` is nullable, we can't guarantee `NotNullWhen(true)`.
   - Make `IEqualityOperators` `==` and `!=` accept `TSelf?`. This keeps it consistent with `IEquatable<T>.Equals(T?)`, `IEqualityComparer<in T>.Equals(T?, T?)`, `IEqualityComparer.Equals(object?, object?)`, `IStructuralEquatable.Equals(object?, IEqualityComparer)`, and `object.Equals(object?)` which all allow null even if generic and the generic is non-null. It in turn enables checks like `T.Zero == default` without nullability warnings.

   

   stephentoub authored and github-actions committed Aug 18, 2022
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2. Address PR feedback

   

   stephentoub authored and github-actions committed Aug 18, 2022
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