language/nnbd/late/covariant_instance_field_test fails with inlining disabled

[eseidel]

I suspect the answer may be "we don't support turning off inlining", but we were experimenting with such this week as part of attempting to fix other issues with Shorebird's linker. Turning off inlining causes only a few tests to fail.

This one is about language/nnbd/late/covariant_instance_field_test. I'll file others if needed/useful.

import 'package:expect/expect.dart';

class Foo {
  covariant late num a;
}

class Bar extends Foo {
  @override
  late int a;
}

void main() {
  Foo bar = Bar();
  bar.a = 2;
  Expect.equals(2, bar.a);
  Expect.throws(() {
    bar.a = 3.14 as dynamic;
    print('bar.a is now ${bar.a}');
  });
  print("success!");
}

Running in stock jit works fine:

dart test.dart
success!

But running in aot with inlining disabled fails:

DART_CONFIGURATION=DebugARM64 pkg/vm/tool/precompiler2 --deterministic --dedup_instructions --compiler-passes=-Inlining test.dart test.aot
xcodebuild/DebugARM64/dart_precompiled_runtime test.aot
bar.a is now -4609118966639786721
Unhandled exception:
Expect.throws fails: Did not throw
#0      Expect._fail (package:expect/expect.dart:881)
#1      Expect.throws (package:expect/expect.dart:766)
#2      main (file:///Users/eseidel/Documents/GitHub/unmodified-dart-sdk/sdk/test.dart:16)
#3      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:297)
#4      _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184)

My guess is that some part of the compiler's logic for control flow is now dependent on inlining optimizations for correctness.

[dart-github-bot]

Labels: area-vm, type-bug
Summary: The covariant_instance_field_test fails when inlining is disabled, causing a runtime error where a late covariant field is assigned a value of the wrong type. This issue may be related to the experimental linker changes made to Shorebird.

[mraleph]

@alexmarkov could you take a look if you have a moment? This is unexpected and might indicate a bug.

[alexmarkov]

https://dart-review.googlesource.com/c/sdk/+/372721

[eseidel]

We paused our efforts to disable inlining, but if we choose to look at disabling inlining again I will file any remaining issues we see. Thank you for the amazingly fast turn-around.