Possible race conditions in WeakReference<T>.SetTarget

[sharwell]

The following two cases may suffer from race conditions in the use of WeakReference<T>, similar to the one described in #25839.

roslyn/src/Workspaces/Core/Portable/SemanticModelWorkspaceService/SemanticModelWorkspaceServiceFactory.cs

Lines 229 to 239 in 4f3739a

	var weakReference = new WeakReference<SemanticModel>(speculativeSemanticModel);
	var cached = nodeMap.GetValue(newMember, _ => weakReference);
	if (cached.TryGetTarget(out var cachedModel))
	{
	return cachedModel;
	}
	// oops. somebody has beaten me, but the model has gone.
	// set me as new target
	cached.SetTarget(speculativeSemanticModel);
	return speculativeSemanticModel;

roslyn/src/VisualStudio/Core/Def/Implementation/ProjectSystem/MetadataReferences/VisualStudioMetadataReferenceManager.RecoverableMetadataValueSource.cs

Line 58 in 878ffad

_weakValue.SetTarget(metadata);

[CyrusNajmabadi]

Closing out as this has been rewritten and does not use weakrefs anymore.