CFE doesn't specify place of an error

[sgrekhov]

We have problems with the test https://github.com/dart-lang/co19/blob/master/Language/Mixins/declaration_t01.dart on CFE. The test looks like

// SharedOptions=--enable-experiment=nonfunction-type-aliases
class C {}
typedef CAlias = C;

mixin CM on C, CAlias {}
//             ^^^^^^
// [analyzer] unspecified
// [cfe] unspecified

main() {
}

It fails on CFE (tested on the edge version of SDK) with the following error

sgrekhov@SGREKHOV-HP:~/Google/dart-sdk/sdk$ out/ReleaseX64/dart-sdk/bin/dart --version
Dart SDK version: 2.13.0-edge.d6824468f90b8e0ec04abde6978a8a04acaa335a (be) (Thu Apr 8 03:27:54 2021 +0000) on "linux_x64"

sgrekhov@SGREKHOV-HP:~/Google/dart-sdk/sdk$ tools/test.py -n cfe-strong-linux co19/Language/Mixins/declaration_t01
Test configuration:
    cfe-strong-linux(architecture: x64, compiler: fasta, mode: release, runtime: none, system: linux, nnbd: strong)
Suites tested: co19

FAILED: fasta-none release_x64 co19/Language/Mixins/declaration_t01
Expected: Pass
Actual: MissingCompileTimeError
Missing expected compile error.

--- Command "fasta" (took 04.000476s):
(cd /home/sgrekhov/Google/dart-sdk/sdk/ ; DART_CONFIGURATION=ReleaseX64 ./out/ReleaseX64/dart ./pkg/front_end/tool/_fasta/compile.dart --verify --skip-platform-verification -o ./out/ReleaseX64/generated_compilations/cfe-strong-linux/tests_co19_src_Language_Mixins_declaration_t01/out.dill --platform ./out/ReleaseX64/vm_platform_strong.dill --enable-experiment=nonfunction-type-aliases --nnbd-strong --packages=./.packages ./tests/co19/src/Language/Mixins/declaration_t01.dart )

static error failures:
- Missing expected unspecified error at line 19, column 16, length 6.

--- Re-run this test:
python tools/test.py -n cfe-strong-linux co19/Language/Mixins/declaration_t01
[00:04 | 100% | +    0 | -    1]

=== 0 tests passed, 1 failed ===

But if to run it, it does produce a compile error

sgrekhov@SGREKHOV-HP:~/Google/dart-sdk/sdk$ out/ReleaseX64/dart-sdk/bin/dart --enable-experiment=nonfunction-type-aliases tests/co19/src/Language/Mixins/declaration_t01.dart
tests/co19/src/Language/Mixins/declaration_t01.dart: Error: 'C' can only be implemented once.
Try removing 1 of the occurrences.

Why CFE doesn't specify the place of an error here? I'm unable to check if test fails because we expect a CFE error in a wrong place. Usually it generates errors as

declaring_constructor_t10.dart:22:7: Error: Can't use 'M' as a mixin because it has constructors.
class C = A with M;
      ^

But not in this case. It looks like a bug in a CFE

[leafpetersen]

I believe this is the same issue as #45558 - not sure if it's a test runner issue (cc @munificent ) or a front end issue.