Adds a replacement visitor for Constant types using null as a
sentinel value for whether a subnode has changed or not (except
in the case of TreeNodes in order to match existing Visitor
semantics).
Change-Id: Iaaab1b1c608af07f36ece08071b3d703884cd91b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/248944
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Srujan Gaddam <srujzs@google.com>
Srujan Gaddam
0036dc7c57