Here’s a diff when I added this feature to Frozenset literals and comprehensions :
https://github.com/nineteendo/cpython/compare/bf83dffab33c4c070bd3e0e4cd12a12e3942252c..0cc9de93a7ca5772afafcb525015f753ae5116b0
Sidenote: I didn’t think it was worth the churn to replace the 160 occurences of set() with {/} across the standard library.