compiler: no nil check needed for closure var dereferences

Add the "no nil check needed" annotation to the dereference operations
created in Parse::enclosing_var_reference (this is safe since the
closure object is under control of the compiler, and pointer fields in
it will always be non-nil).

Change-Id: I218f9e2226582792c7cbd5a26fe7a3d1cc2236f6
Reviewed-on: https://go-review.googlesource.com/81795
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
1 file changed