"dart analyze" output gives wrong file for context message

[davidmorgan]

Forked from #54661

this command

DART_CONFIGURATION=ReleaseX64 out/ReleaseX64/dart-sdk/bin/dart out/ReleaseX64/gen/dartanalyzer.dart.snapshot -Dtest_runner.configuration=analyzer-asserts-linux --ignore-unrecognized-flags --packages=/usr/local/google/home/davidmorgan/git/dart-sdk/sdk/.dart_tool/package_config.json --format=json /usr/local/google/home/davidmorgan/git/dart-sdk/sdk/tests/co19/src/Language/Libraries_and_Scripts/Parts/compilation_t01.dart

results in correct JSON output, pointing to the duplicate in compilation_t04.dart:

"contextMessages":[{"message":"The first definition of this name.","location":{"file":"/usr/local/google/home/davidmorgan/git/dart-sdk/sdk/tests/co19/src/Language/Libraries_and_Scripts/Parts/compilation_t04.dart","offset":856,"length":3,"startLine":17,"startColumn":483,"endLine":17,"endColumn":486}}]

but the corresponding run of "dart analyze"

dart analyze tests/co19/src/Language/Libraries_and_Scripts/Parts/part_0.dart

reports the context message against the wrong file, against the part file:

  error • part_0.dart:16:5 • The name 'bar' is already defined. Try renaming one of the declarations. • duplicate_definition
           - The first definition of this name at part_0.dart:17:483.