tree 03d15fd793f008844920c6df0f15ff4d72e06dd8
parent 145a9230de377dc1564ea563c55afbfa1912f102
author Paul Berry <paulberry@google.com> 1658155884 +0000
committer Commit Bot <commit-bot@chromium.org> 1658155884 +0000

Flow analysis: clarify behavior of ifNullExpression_rightBegin.

Previously, it was unclear what information was stored in
_IfNullExpressionContext._previous.  It turned out that it was the
"shortcut state", i.e. the flow state if the LHS of the `??` was
non-`null`.  I've renamed variables and added comments to clarify
this.  Also, based on the implementation of
`ifNullExpression_rightBegin`, it looked like it might update
`_current`, but in fact it did not (because `tryMarkNonNullable`
always returns an `ExpressionInfo` whose `ifFalse` is unchanged); I've
refactored the code so that this is clearer, and added a comment
explaining why it is the right thing to do.

Bug: https://github.com/dart-lang/language/issues/2020
Change-Id: Ib8a5235f9b9482f4b290ad90686385514660a95d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/251142
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>