This adds a null check to Workspace.SetCurrentSolution;
the method would have thrown but not in a clean way.

Ensure we have stack spilling support for the recently-added expression node `BoundReadOnlySpanFromArray` (#37057)

Fixes #36856

Add cache to target-typed completion

Fix Solution.WithDocumentFilePath not updating the file path of the tree

 Make NullableWalker aware of calls to Interlocked.CompareExchange

Avoid generating or emitting NullablePublicOnlyAttribute when no other nullable attributes are emitted (#37019)

Move refactorings to new set of helpers 

Small amounts of cleanup

Optimize flow analysis assembly

Turn on nullable semantic analysis by default

Merge release/dev16.3-preview1 to master

Address minor PR comments.

Merge remote-tracking branch 'dotnet/release/dev16.3-preview1' into merges/release/dev16.3-preview1-to-master

Make Field Readonly - Keep leading trivia

DocumentState.UpdateFilePath was still passing in the old attributes
when producing a new tree source -- oops!

Merge pull request #36903 from jasonmalinowski/fix-diagnostic-options-not-flowing-through-recoverable-trees

Don't lose tree DiganosticOptions when we recover or replace a tree

made error and todo list initialization lazy

Require System.Index/Range to be present to offer to use the new language features.