If the indexing service fails to determine the commmand line arguments (for example because the
targeting pack is not installed), it passes us an empty string for the TargetPath.  Our code wasn't
prepared to handle an empty string, so convert it to null instead, which we are prepared to handle.

Fixes internal bugs 269571 and 274711.

This PR fixes speculative-T completion for the return type of local
functions. However, it doesn't include completion for generic arguments
to async local functions, which will require a significant change in the
parsing strategy and tree produced.

Fixes #13480.

Create an ExecutableCodeBinder when speculatively binding an expression or attribute.
Fixes #14384

porting 3 PR to dev15-rc - sharing checksum and enabling oop by default

the way we added cancellation support to StreamJsonRpc can cause ObjectDisposedException from happening.

Propagate InvolvesNarrowingFromNumericConstant flag for tuple conversions.

enable remost host by default

separated checksum creation from ISolutionSynchronizationService

Fix issue where we overly aggressively removed xml doc comment trivia.

Fixes #13436

Related to #14255.
Fixes #14473.

Use Guid constructor instead of Guid.Parse...

Validate our bootstrap build phase

Fix finding of event-parameters after the recent compiler API change.

Deal with a cancellation exception being thrown through a sync-path in navigate-to.

Fixes #12550.

...for dynamic analysis instrumentation.  Guid.Parse is not available when
targeting .NET 2.0/3.5.

Be resilient to being called while the text view is being initialized.

Add support for AB testing in Roslyn.

This is to work around a bug in MSBuild 15.0 which prevents bootstrapping of the compiler.

Our bootstrap phase relies on loading Microsoft.Build.Tasks.CodeAnalysis from a specific place on disk.  There is no way in MSBuild to guarantee that suceeds.  It's possible for instance for MSBuild to have already loaded a DLL of the same name from a new location.  Or even if our DLL is loaded, it's possible that some of the downstream depenedencies fell prey to the same problem.

This adds a validation layer to our bootstrap phase to guard against that.  It verifies that our build task and dependencies are loading from the location that we expect them to load from.

Note: there is actually a bug in MSBuild right now that prevents us from correctly doing this in MSBuild 15.0.  This check will help us validate that bug was fixed properly. https://github.com/Microsoft/msbuild/issues/1183

Treat ref assignments and ref returns as potential writes.