commit ca3e67a3b654c492b85b546354619137d1f2f95d
author Mayank Patke <fishythefish@google.com> Wed Jun 12 21:28:23 2024 +0000
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> Wed Jun 12 21:28:23 2024 +0000
tree 08fac432a92dbdc43df8d230fbf038994f258309
parent bb66bd92c81905b4a610130c7be3f4e0dc99cfdb

[dart2js] Add --interop-null-assertions.

This CL adds a new --interop-null-assertions flag (cf.
--native-null-assertions) with the goal of validating that JS interop
APIs with non-nullable static return types do not return null values.
This flag is currently disabled by default but is intended to assist in
sound null safety migrations.

In general, we don't guarantee type soundness of package:js interop
since users can write incorrect static types which are not backed by
any runtime checks. However, it is likely that during the null safety
migration, some interop APIs which should have been made nullable
weren't. Therefore, we want to offer some additional (but limited)
checking for this case.

For static invocations of functions with non-nullable return types, we
can simply perform a null check on the result of the call.
For instance methods (which could be invoked virtually/dynamically), we
want to perform a null check on the return value in the callee (the
interceptor method) itself when possible.

It's possible for multiple interop bindings to share the same
interceptor method. We produce a null check in the interceptor method
body if all the methods have non-nullable return types. Otherwise, we
insert checks at callsites when appropriate.

Change-Id: Ifd155d7f8326152b6d57d61199e0b7973c4a1211
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/369784
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Mayank Patke <fishythefish@google.com>