commit 7d7d85ffa2618de166861fbd0c91d2e850ede5fc
author Paul Berry <paulberry@google.com> Sat Feb 16 13:35:48 2019 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> Sat Feb 16 13:35:48 2019 +0000
tree 4de6af47099b6d2f06ecd82c606d6a9a4d015cba
parent fa8c552fd9b9bcb752f7fccf511d58669911b148

Change the default assumption for named parameters to "assume nullable".

If a named parameter has no default value, the default behavior is now
to assume that the parameter is meant to be nullable, even if no code
path can be found that passes null.

This was inspired by discussion with Matan and Ferhat--they were
concerned that users would see the migration tool changing parameters
to required that shouldn't actually be required, and react by adding
special sentinel default values.  This is not what we want to
encourage users to do; if the parameter is truly meant to be optional,
it is sensible for it to be nullable.

I will soon add logic that allows non-null intent to override this
behavior; this means that if the user asserts that the parameter is
non-null, or uses the parameter in such a way that a null value would
guaranteed to cause an exception, we'll take that as an indication
that they really mean for it to be required.

Change-Id: Iff388d0316b922d2bacae330d94bec65478d8ee0
Reviewed-on: https://dart-review.googlesource.com/c/93366
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>