Fix long line splitting issue in python_print (#37088)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37088
For an inlined expression tree like `(e_0, (e_1, e_long))` the previous
algoritm only scanned the same statement as `e_long`, splitting the
inlined expressions across lines. Because it did not scan `e_0`, `e_0`
would still get emitted inline, causing it to reverse order with `e_1` and
`e_long`. The new algorithm scans starting at `e_long` and going all
the way back up the expression until it reaches the end of the inlined
statement. Caching of what has already been scanned has been added so that
if there was a second long long `e_long2` after `e_long`, it would not
rescan and re-inline the statements that were already split.
Test Plan: Imported from OSS
Differential Revision: D21180394
Pulled By: zdevito
fbshipit-source-id: 4d142c83a04c89a47d04282f67a513f82cf153c0
