Added: LDM notes for April 3rd, 2019

[agocke]

https://github.com/dotnet/csharplang/blob/master/meetings/2019/LDM-2019-04-03.md

[YairHalberstadt]

@agocke @gafter

3. No new syntax, do matching in two passes. First, look if the old form (where T : struct) is present and use it if present. Second, expand to look for both forms if no match was found.

...
Conclusion
We like option 3. This would maintain backwards compatibility and is a simple explanation for what T? means in OHI.

This seems at odds with #2378 (comment)

We discussed this 2019-04-03 at the LDM. What we came away with are the following resolutions:

1. In an override or implementation (that lacks constraints), T? would always mean Nullable. This "fix" will be implemented ASAP to fix the product compatibility bug. The other steps below would be done separately.
2. If you want to use a nullable reference type annotation on a type parameter (e.g. T?) in an override or implementation, you would be required to write the constraint where T: class in the override or implementation. The ability to write that constraint is a new feature.
3. We would also allow where T: struct in an override or implementation for symmetry.

Could you please clarify this?
Thanks

[agocke]

Thanks that should read option 2, that was a typo. Fixed.