[Pre-release] Productize System.Span and ReadOnlySpan

[ahsonkhan]

Pri 0 - Must complete for release

• Finalize API shape of SpanExtensionsLab and merge with SpanExtensions - Finalize API shape of SpanExtensionsLab and merge with SpanExtensions #1292
• Add tests to increase code coverage - https://github.com/dotnet/corefx/issues/17078
• Add stress tests - Add stress tests for Span<T> APIs #1313 / https://github.com/dotnet/corefx/issues/28227
• Remove System.Slices - Remove System.Slices #1295
• Consider changing CopyTo methods to copy as much as possible and return int - https://github.com/dotnet/corefx/issues/16888
• Should we rename Span to Memory and Memory to something else - https://github.com/dotnet/corefx/issues/16997
• Improve Span.StartsWith(ReadOnlySpan|ReadOnlySpan) performance + investigate API that takes index - Span.StartsWith(ReadOnlySpan<T>|ReadOnlySpan<byte>) #1294
• Span/ReadonlySpan TryCopy/CopyTo are very slow (slow span) - https://github.com/dotnet/corefx/issues/16840
• System.Memory.Tests crashing on Windows outer loop runs - https://github.com/dotnet/corefx/issues/16492
• Fix array variance checks in slow Span - https://github.com/dotnet/corefx/issues/14533
• Remove System.Buffers.Experimental dependency from Pipelines.

Pri 1 - Nice to have

• Debugger proxies don't work on Spans - https://github.com/dotnet/corefx/issues/14376
• Test: System.SpanTests.ReadOnlySpanTests/IndexOverflow failed with "System.OutOfMemoryException" - https://github.com/dotnet/corefx/issues/16593
• Span: DangerousCreate should avoid argument validation - https://github.com/dotnet/corefx/issues/14486

Pri 2 - Nice to have

• Fix Spanbench benchmark tests for fast span to be more reliable - https://github.com/dotnet/coreclr/issues/10099
• Add slow span benchmarks to benchview - https://github.com/dotnet/coreclr/issues/10098
• Add IndexOfAny overload - Add Span.IndexOfAny overload #1293

---

Future - Not part of this release
- [ ] Add a way to efficiently compare memory - https://github.com/dotnet/corefx/issues/16878
- [ ] Span == null throws ArgumentNullException - https://github.com/dotnet/corefx/issues/16730
- [ ] Span: Add BinarySearch(...) extension methods for ReadOnlySpan (and Span) - https://github.com/dotnet/corefx/issues/15818
- [ ] Proposal: Add Sort(...) extension methods for Span - https://github.com/dotnet/corefx/issues/15329
- [ ] Slicing pattern (range) - #1306

- [ ] Finish design for Memory and friends - #1296 This issue tracks System.Memory.dll APIs only
- [ ] Design BytesReader - #1297 This issue tracks System.Memory.dll APIs only
- [ ] Implement Memory final design - #1298 This issue tracks System.Memory.dll APIs only

[ahsonkhan]

Issue tracking the work items for Span
Feel free to add/tweak work items or adjust priorities.

cc @KrzysztofCwalina, @shiftylogic, @jkotas, @davidfowl, @joshfree

[jkotas]

dotnet/corefx#14533 should be P0. It is a real bug, not just a test issue.

[KrzysztofCwalina]

dotnet/corefx#14376 should be pri 1. I would do it rather than dotnet/corefx#14486. Debugging span code is so painful without this fix. I moved it.

[KrzysztofCwalina]

Also, some of the Future items are probably not actually future, e.g. #1298.

But, I would just move the Memory (and friends) issues to a separate location. This issue should track System.Memory.dll APIs only.

[joshfree]

Thanks for organizing this @ahsonkhan.

[ahsonkhan]

But, I would just move the Memory (and friends) issues to a separate location. This issue should track System.Memory.dll APIs only.

Updated.

[benaadams]

Should Span Fill & Clear be moved to extension methods in corefx from operations on Span in coreclr?

They don't particularly need access to anything only internal to the struct and then could be specialized with Vectors if that was better.