always use the closure to resolve variable names (#27515)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27515
Resoving variable names using the local activation frames does not work
when using recursive scripting, but our current code tries to do it
(incorrectly) anyway. The reason it works is only because the script
call is in the same local frame as the definition. This will not be
true in practice and makes it seem like the API works in more cases
than it really does. This forces us to always use closure-based annotations,
documents it, and it fixes the tests so that they still pass.
Test Plan: Imported from OSS
Differential Revision: D17803403
Pulled By: zdevito
fbshipit-source-id: e172559c655b05f0acf96c34f5bdc849f4e09ce2
