cmd/compile: import empty closure function correctly
On import, make sure that an empty closure is represented as a single
empty block statement. Otherwise, the closure is dropped. Block
statements are not exported explicitly, so must recreate on import.
Fixes #44330
Change-Id: I061598f0f859dd71d2d0cbd10c77cdd81525d1f2
Reviewed-on: https://go-review.googlesource.com/c/go/+/297569
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Trust: Dan Scales <danscales@google.com>