tree f0b0d96d927a129385440ba7d451759bf29ccc5f
parent 0b5e37a4298886711e6cb54109c5904d7510d868
author Paul Berry <paulberry@google.com> 1560370224 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> 1560370224 +0000

Migration: add the ability to "union" nullability nodes.

This will simplify some situations where nullability migration would
otherwise have to visit the source code in a very careful order.  For
example, when analyzing top level fields undergoing type inference, we
can simply create a node for the nullability of each top level field,
and then later use the "union" operation to hook up those nodes to the
nodes resulting from analyzing their initializers.  Without the union
operation, we would have to be careful to visit the top level fields
in dependency order.

Change-Id: I3b07e1abccc5b1c9f1c7c9fa7b13fb6af60c07d6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/105800
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>