Fix DateOnly and TimeOnly Formatting using interpolated strings

[tarekgh]

Fixes #64292

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[ghost]

Tagging subscribers to this area: @dotnet/area-system-runtime
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes #64292

Author:	tarekgh
Assignees:	tarekgh
Labels:	area-System.Runtime
Milestone:	-

[stephentoub]

Thanks! It's interesting this doesn't cause any tests to fail. Are we missing direct tests of TryFormat?

[tarekgh]

It's interesting this doesn't cause any tests to fail. Are we missing direct tests of TryFormat?

We were testing the positive cases only. I added the interpolated string tests which should catch the negative cases. If you think we should add specific negative tests for TryFormat, I can do that. We already testing the not enough destination buffer space here

runtime/src/libraries/System.Runtime/tests/System/DateOnlyTests.cs

Line 513 in d016569

Assert.False(dateOnly.TryFormat(buffer.Slice(0, 3), out charsWritten));

. and here

runtime/src/libraries/System.Runtime/tests/System/TimeOnlyTests.cs

Line 483 in d016569

Assert.False(timeOnly.TryFormat(buffer.Slice(0, 3), out charsWritten));

[stephentoub]

Thanks. Yes, I think we should have those tests for TryFormat. It'd be fine to do those instead of the interpolation ones.

[tarekgh]

The failures in the CI are tracked by the issue #64389.

[tarekgh]

/backport to release/6.0

[github-actions]

Started backporting to release/6.0: https://github.com/dotnet/runtime/actions/runs/1762869247