Repro steps

1. Invoke Edit.CompleteWord (Ctrl+Space)

Expected behavior

It asynchronously computes completion.

Actual behavior

It synchonously blocks

Known workarounds

Using Edit.ListMembers (Ctrl+J) instead should start an asynchronous computation, but not block until commit happens.

Related information

We can/should tweak the command handler to just do the ListMembers behavior.

A further concern however is that Roslyn doesn't have any cancellation support in completion once an operation has triggered a commit - it will block until it knows what to commit. Given the existence of type providers, we may need to change Roslyn to accommodate that.

Tagging @CyrusNajmabadi and @rchande for thoughts.