[CP] Adjust nullability computations in the upper bound algorithm in the CFE #53999
Labels
area-front-end
Use area-front-end for front end / CFE / kernel format related issues.
cherry-pick-approved
Label for approved cherrypick request
merge-to-stable
Commit(s) to merge
ad298bf
Target
stable
Prepared changelist for beta/stable
https://dart-review.googlesource.com/c/sdk/+/333825
Issue Description
Currently the CFE emits some types with incorrect nullability in some cases. According to user reports, it prevents using package
typings
. The issue is reported for the DDC, but other platforms may be affected as well, because the fix is in the core of the CFE code used by all backends.What is the fix
The fix adjusts the computations of the nullability in the algorithm for the upper bound between two types in the CFE. The fix is small and self-contained.
Why cherry-pick
The user who reported an issue asked for a fix to land sooner. It seems that they are blocked in their work by being unable to use package
typings
and don't have a work-around.Risk
low
Issue link(s)
#52726
Extra Info
My evaluation of the risk as low is based on the assumption that the fix corrects some malformed programs emitted by the CFE, but leaves the well-formed programs intact.
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