commit fc387f0f7be6d83ba2349b9986c553ef63f9cffb
author Paul Berry <paulberry@google.com> Thu Jul 20 20:14:39 2023 +0000
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> Thu Jul 20 20:14:39 2023 +0000
tree 0435bb86b73e6f87dbaf3a2cfb4de1a84ba1e2d6
parent 6fd249d3793b71dff435803ead85bbafe781dd46

Update SDK to prepare for enabling `interface-update-2`.

Several locations in the core SDK contain `!` or `?.` operations that
will become unnecessary once the language feature `inference-update-2`
(which provides field promotion) is enabled.  For example, in this
method from the class `_IOOverridesScope`, `_previous` refers to a
private final field, so after field promotion is enabled, the test `if
(_previous != null)` will promote it, and the `!` in
`_previous!.createDirectory` will become unnecessary:

    Directory createDirectory(String path) {
      if (_createDirectory != null) return _createDirectory!(path);
      if (_previous != null) return _previous!.createDirectory(path);
      return super.createDirectory(path);
    }

Since the SDK is built in a mode where warnings like this result in
build failures, we need to temporarily change the logic into a form
where the same promotion effect is achieved through local variable
type promotion:

    Directory createDirectory(String path) {
      if (_createDirectory != null) return _createDirectory!(path);
      var previous = _previous;
      if (previous != null) return previous.createDirectory(path);
      return super.createDirectory(path);
    }

(Note that `_createDirectory` doesn't need to change, because it is a
non-final field, so it won't undergo promotion).

After `interface-update-2` has been enabled, I will make a follow-up
CL that removes the local variables and simply takes advantage of
field promotion, e.g.:

    Directory createDirectory(String path) {
      if (_createDirectory != null) return _createDirectory!(path);
      if (_previous != null) return _previous.createDirectory(path);
      return super.createDirectory(path);
    }

Note: in theory it would be possible to do all this in a single step,
by atomically enabling field promotion and changing the SDK in the
same CL. However, I prefer breaking it up into stages like this,
because the act of flipping a langauge flag on tends to have
wide-ranging consequences, so I want the CL that does the flip to be
as small as possible.

Change-Id: I421c7661348bf407093ee64ef7f9dbfc0c04a353
Bug: https://github.com/dart-lang/language/issues/2020
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/314500
Reviewed-by: Siva Annamalai <asiva@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Reviewed-by: Bob Nystrom <rnystrom@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Lasse Nielsen <lrn@google.com>
Reviewed-by: Joshua Litt <joshualitt@google.com>
Reviewed-by: Stephen Adams <sra@google.com>