Failures on Add record-related `wait` extensions on `Future` tuples.

[lrhn]

There are new test failures on Add record-related wait extensions on Future tuples..

The tests

lib/async/future_record_extension_test RuntimeError (expected Pass)

are failing on configurations

dart2js-hostasserts-linux-chrome-unsound

The error message is

Type '(JSInt, JSBool)' is not a subtype of type 'FutureOr<(int, bool)>?'

which suggests an error related to record types, internal types and FutureOr.
Possibly related to: #51731

The full error report is:

/========================================================================================\
| lib/async/future_record_extension_test is new and failed (RuntimeError, expected Pass) |
\========================================================================================/

--- Command "dart2js" (took 07.000290s):
DART_CONFIGURATION=ReleaseX64 sdk/bin/dart2js_developer -Dtest_runner.configuration=dart2js-hostasserts-linux-d8 --sound-null-safety --test-mode --packages=/b/s/w/ir/.dart_tool/package_config.json /b/s/w/ir/tests/lib/async/future_record_extension_test.dart --sound-null-safety --out=/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js

exit code:
0

stdout:
Hint: When run on the command-line, the compiled output might require a preamble file located in:
  <sdk>/lib/_internal/js_runtime/lib/preambles.
Compiled 9,775,330 characters Dart to 243,576 characters JavaScript in 7.22 seconds using 486.145 MB of memory
Dart file tests/lib/async/future_record_extension_test.dart compiled to JavaScript: out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js

--- Command "d8" (took 74ms):
DART_CONFIGURATION=ReleaseX64 /b/s/w/ir/third_party/d8/linux/d8 /b/s/w/ir/sdk/lib/_internal/js_runtime/lib/preambles/d8.js /b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js

exit code:
1

stdout:
unittest-suite-wait-for-done
/b/s/w/ir/sdk/lib/_internal/js_runtime/lib/preambles/d8.js:263: TypeError: Record (2, true): type '(JSInt, JSBool)' is not a subtype of type 'FutureOr<(int, bool)>?'
          throw e;
          ^
TypeError: Record (2, true): type '(JSInt, JSBool)' is not a subtype of type 'FutureOr<(int, bool)>?'
    at Object.wrapException (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:329:17)
    at Object._failedAsCheck (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:1269:15)
    at Rti._generalNullableAsCheckImplementation [as _as] (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:1266:9)
    at Rti._installSpecializedAsCheck (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:1194:22)
    at _SyncCompleter.complete$1 (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:5171:25)
    at FutureRecord2_get_wait_closure.call$1 (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:4993:12)
    at _FutureResult__waitAll_onReady.call$1 (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:5150:24)
    at _FutureResult._onValue$1 (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:5132:20)
    at tear_off.<anonymous> (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:622:45)
    at _RootZone.runUnary$2$2 (/b/s/w/ir/out/ReleaseX64/generated_compilations/dart2js-hostasserts-linux-d8/tests_lib_async_future_record_extension_test/future_record_extension_test.js:5567:18)

Deobfuscated error and stack:
TypeError: Record (2, true): type '(JSInt, JSBool)' is not a subtype of type 'FutureOr<(int, bool)>?'
    at wrapException                             org-dartlang-sdk:///lib/_internal/js_runtime/lib/js_helper.dart 1194:37
    at _failedAsCheck                            org-dartlang-sdk:///lib/_internal/js_shared/lib/rti.dart 1164:3
    at _generalNullableAsCheckImplementation     org-dartlang-sdk:///lib/_internal/js_shared/lib/rti.dart 1159:3
    at _installSpecializedAsCheck                org-dartlang-sdk:///lib/_internal/js_shared/lib/rti.dart 1052:3
    at _SyncCompleter.complete                   org-dartlang-sdk:///lib/async/future_impl.dart 47:22
    at FutureRecord2|get#wait.<anonymous>        org-dartlang-sdk:///lib/async/future_extensions.dart 79:9
    at _FutureResult._waitAll.onReady            org-dartlang-sdk:///lib/async/future_extensions.dart 527:9
    at _FutureResult._onValue                    org-dartlang-sdk:///lib/async/future_extensions.dart 508:12
    at Closure.fromTearOff                       org-dartlang-sdk:///lib/_internal/js_runtime/lib/js_helper.dart 2181:9
    at _RootZone.runUnary                        org-dartlang-sdk:///lib/async/zone.dart 1661:46

[fishythefish]

Repro:

import 'dart:async';

@pragma('dart2js:noInline')
T cast<T>(dynamic x) => x as T;

void main() {
  print(cast<FutureOr<(int, bool)>>((2, true)));
}

The issue seems to be that the Rti for (2, true) is _Record_2 rather than +(int, bool), so rather than doing recursive subtype checks on the record fields, we immediately fail the subtype check after recursing into the FutureOr argument type.

The constant pool contains: B.Record2_2_true = new A._Record_2(2, true);

Note that cast<(int, bool)>((2, true)) succeeds (I assume via a different mechanism than the full isSubtype check), which may have hidden the issue.