flag_fuzzer managed to produce unexpected output

[derekxu16]

https://logs.chromium.org/logs/dart/buildbucket/cr-buildbucket/8728425132939576785/+/u/collect_shards/dartfuzz_-_flags_shard_45/task_stdout_stderr:_dartfuzz_-_flags_shard_45

=== FAILURE ===
command: out/ReleaseX64C/dart --profiler --max_profile_depth=252 --runtime_allocate_spill_tlab --force_clone_compiler_objects --inlining_depth_threshold=6 --inlining_callee_call_sites_threshold=2 pkg/compiler/lib/src/dart2js.dart --invoker=test --platform-binaries=out/ReleaseX64 --out=out/dartfuzz/4.js --no-source-maps pkg/compiler/lib/src/util/memory_compiler.dart
command: diff out/dartfuzz/expected.js out/dartfuzz/4.js
exitCode: 1
stdout:
319807c319807
<       var t1, t2, variable, matchedType, t3, expression, expressionType, equalsTargetReference, typeArgument, patterns, requiredType, matchedValueType, flags, lookupType, lengthTargetReference, lengthType, lengthCheckTargetReference, sublistTargetReference, sublistType, minusTargetReference, minusType, indexGetTargetReference, indexGetType, keyType, valueType, entries, containsKeyTargetReference, $name, pattern, fieldName, accessKind, targetReference, resultType, recordFieldIndex, typeArguments, t4, type, fields, objectType, recordType, kind, _this = this, _null = null,
---
>       var t1, t2, variable, matchedType, t3, expression, expressionType, equalsTargetReference, typeArgument, patterns, requiredType, matchedValueType, flags, lookupType, lengthTargetReference, lengthType, lengthCheckTargetReference, sublistTargetReference, sublistType, minusTargetReference, minusType, indexGetTargetReference, indexGetType, keyType, valueType, entries, containsKeyTargetReference, type, fields, objectType, t4, recordType, kind, accessKind, $name, targetReference, typeArguments, _this = this, _null = null,
319913,319943c319913
<           t1 = _this.readUInt30$0();
<           t2 = _this._stringTable;
<           t3 = _this.readUInt30$0();
<           if (!(t3 < t2.length))
<             return A.ioore(t2, t3);
<           $name = t2[t3];
<           pattern = _this._readPattern$0();
<           fieldName = _this.readName$0();
<           t3 = _this.readByte$0();
<           if (!(t3 < 12))
<             return A.ioore(B.List_DET, t3);
<           accessKind = B.List_DET[t3];
<           targetReference = _this.readNullableMemberReference$0();
<           resultType = _this.readAndCheckOptionTag$0() ? _this.readDartType$0() : _null;
<           t2 = _this.readAndCheckOptionTag$0() ? _this.readDartType$0() : _null;
<           type$.nullable_RecordType._as(t2);
<           recordFieldIndex = _this.readUInt30$0();
<           t3 = _this.readAndCheckOptionTag$0() ? _this.readDartType$0() : _null;
<           type$.nullable_FunctionType_2._as(t3);
<           typeArguments = _this.readAndCheckOptionTag$0() ? _this.readDartTypeList$0() : _null;
<           t4 = A.NamedPattern$($name, pattern);
<           t4.fieldName = fieldName;
<           t4.accessKind = accessKind;
<           t4.targetReference = targetReference;
<           t4.resultType = resultType;
<           t4.recordType = t2;
<           t4.recordFieldIndex = recordFieldIndex;
<           t4.functionType = t3;
<           t4.set$typeArguments(typeArguments);
<           t4.fileOffset = t1 - 1;
<           return t4;
---
>           return _this._readNamedPattern$0();
320065a320036,320069
>     },
>     _readNamedPattern$0() {
>       var $name, pattern, fieldName, accessKind, targetReference, resultType, recordFieldIndex, typeArguments, t4, _this = this, _null = null,
>         t1 = _this.readUInt30$0(),
>         t2 = _this._stringTable,
>         t3 = _this.readUInt30$0();
>       if (!(t3 < t2.length))
>         return A.ioore(t2, t3);
>       $name = t2[t3];
>       pattern = _this._readPattern$0();
>       fieldName = _this.readName$0();
>       t3 = _this.readByte$0();
>       if (!(t3 < 12))
>         return A.ioore(B.List_DET, t3);
>       accessKind = B.List_DET[t3];
>       targetReference = _this.readNullableMemberReference$0();
>       resultType = _this.readAndCheckOptionTag$0() ? _this.readDartType$0() : _null;
>       t2 = _this.readAndCheckOptionTag$0() ? _this.readDartType$0() : _null;
>       type$.nullable_RecordType._as(t2);
>       recordFieldIndex = _this.readUInt30$0();
>       t3 = _this.readAndCheckOptionTag$0() ? _this.readDartType$0() : _null;
>       type$.nullable_FunctionType_2._as(t3);
>       typeArguments = _this.readAndCheckOptionTag$0() ? _this.readDartTypeList$0() : _null;
>       t4 = A.NamedPattern$($name, pattern);
>       t4.fieldName = fieldName;
>       t4.accessKind = accessKind;
>       t4.targetReference = targetReference;
>       t4.resultType = resultType;
>       t4.recordType = t2;
>       t4.recordFieldIndex = recordFieldIndex;
>       t4.functionType = t3;
>       t4.set$typeArguments(typeArguments);
>       t4.fileOffset = t1 - 1;
>       return t4;

[a-siva]

This does not reproduce when tried on the latest main build, closing issue.