co19/Language/Variables/Evaluation_of_Implicit_Variable_Getters/definition_A01_t02 fails on dart2wasm

[sgrekhov]

/====================================================================================================================================\
| co19/Language/Variables/Evaluation_of_Implicit_Variable_Getters/definition_A01_t02 is new and failed (RuntimeError, expected Pass) |
\====================================================================================================================================/

--- Command "dart2wasm" (took 01.000029s):
DART_CONFIGURATION=ReleaseX64 CHROME_PATH=/b/s/w/ir/third_party/browsers/chrome/chrome/google-chrome pkg/dart2wasm/tool/compile_benchmark -O0 --compiler-asserts --enable-asserts -Dtest_runner.configuration=dart2wasm-asserts-linux-chrome /b/s/w/ir/tests/co19/src/Language/Variables/Evaluation_of_Implicit_Variable_Getters/definition_A01_t02.dart /b/s/w/ir/out/ReleaseX64/generated_tests/dart2wasm-asserts-linux-chrome/tests_co19_src_Language_Variables_Evaluation_of_Implicit_Variable_Getters_definition_A01_t02/definition_A01_t02.wasm

exit code:
0

--- Command "chrome" (took 45ms):
/b/s/w/ir/tools/sdks/dart-sdk/bin/dart pkg/test_runner/bin/launch_browser.dart chrome http://127.0.0.1:39719/root_build/generated_tests/dart2wasm-asserts-linux-chrome/tests_co19_src_Language_Variables_Evaluation_of_Implicit_Variable_Getters_definition_A01_t02/test.html?crossOriginPort=43695

Runtime error:
[object WebAssembly.Exception]
<undefined stack>

exit code:
0

--- To debug locally, run:
/b/s/w/ir/tools/sdks/dart-sdk/bin/dart /b/s/w/ir/pkg/test_runner/bin/http_server.dart -p 39719 -c 43695 --network 127.0.0.1 --build-directory=/b/s/w/ir/out/ReleaseX64/ --runtime=chrome --packages=/b/s/w/ir/.dart_tool/package_config.json

--- Re-run this test:
python3 tools/test.py -n dart2wasm-asserts-linux-chrome co19/Language/Variables/Evaluation_of_Implicit_Variable_Getters/definition_A01_t02

[osa1]

I reduced the repro to this:

int count = 0;

f(func) {
  count++;
  if (count < 5) func();
}

final int? finalVariable = f(() => finalVariable);

main() {
  print(finalVariable);
}

The use of finalVariable in the function expression calls the initializer for finalVariable recursively, which causes this exception in the VM. After 5 calls f implicitly returns null which initializes finalVariable, and when the parent function returns and initializes finalVariable again. VM throws this exception in the second initialization:

Unhandled exception:
LateInitializationError: Field 'finalVariable' has been assigned during initialization.
#0      finalVariable (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart)
#1      finalVariable.<anonymous closure> (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:8:36)
#2      f (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:5:22)
#3      finalVariable (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:8:28)
#4      finalVariable (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart)
#5      finalVariable.<anonymous closure> (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:8:36)
#6      f (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:5:22)
#7      finalVariable (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:8:28)
#8      finalVariable (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart)
#9      finalVariable.<anonymous closure> (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:8:36)
#10     f (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:5:22)
#11     finalVariable (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:8:28)
#12     finalVariable (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart)
#13     main (file:///usr/local/google/home/omersa/dart/sdk/test/test.dart:11:9)
#14     _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:297:19)
#15     _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

In dart2wasm we don't check for this so we don't throw an exception.

I don't understand how VM can tell that this happens during initialization though. Is there no other way to initialize a late final variable multiple times?