Expose {ReadOnly}Memory from System.Runtime

[ahsonkhan]

Part of dotnet/corefxlab#1711

Adding the following types:

• Memory<T>
• ReadOnlyMemory<T>
• OwnedMemory<T>
• MemoryHandle
• IRetainable

Order of changes:

1. Add to mscorlib (Adding {ReadOnly}Memory, OwnedMemory, MemoryHandle, and IRetainable coreclr#13583).
2. After the type has been added to mscorlib, add impl (for portable) and type forwarders to System.Memory (Adding Memory, OwnedMemory, MemoryHandle, and IRetainable & Tests #23701) and System.Runtime (this PR) here in corefx.
3. Remove impl from corefxlab and update uses/references in Pipelines/Buffers.Experimental.
4. Other changes/additions like review/add APIs from MemoryExtensions

cc @shiftylogic, @KrzysztofCwalina, @davidfowl, @jkotas, @stephentoub, @atsushikan, @ericstj

[ahsonkhan]

I am not sure how to resolve this error:
System.Runtime.cs(3815,108): error CS0234: The type or namespace name 'GCHandle' does not exist in the namespace 'System.Runtime.InteropServices' (are you missing an assembly reference?) [D:\GitHub\Fork\corefx\src\System.Runtime\ref\System.Runtime.csproj]

GCHandle was not in .NET Standard 1.0 (it was added in .NET Standard 1.1).
https://github.com/dotnet/standard/blob/master/docs/versions/netstandard1.1_diff.md
Any ideas?

[stephentoub]

Any ideas?

GCHandle is currently defined in System.Runtime.InteropServices:

corefx/src/System.Runtime.InteropServices/ref/System.Runtime.InteropServices.cs

Line 259 in bffef76

public partial struct GCHandle

Presumably it'll need to be forwarded down to System.Runtime.
cc: @weshaggard

[weshaggard]

Presumably it'll need to be forwarded down to System.Runtime.

Yes it would need to be moved down to resolve this dependency.

@ahsonkhan have these APIs been reviewed and approved yet? If so can you point me to the issue for that if not can you please file an issue to track the review of these APIs?

[ahsonkhan]

have these APIs been reviewed and approved yet? If so can you point me to the issue for that

Yes, we had the API review iterations offline back in June and it was approved. I don't have an API specific issue (this is the issue for moving the types to corefx - dotnet/corefxlab#1711).

cc @terrajobst

if not can you please file an issue to track the review of these APIs?

Should I file an issue regardless?
Edit: https://github.com/dotnet/corefx/issues/23862

[mmitche]

@dotnet-bot test this please (accidentlaly deleted VMs while in use)

[ahsonkhan]

Is the PR good to go?
@stephentoub, @wes

[stephentoub]

Thanks, @ahsonkhan. LGTM.