I just ran migrate-call-by-name on a WIP backend. Then mypy complained about one of my rules returning

Any

, even though it has a return type hint.

23:01:20.36 [ERROR] Completed: Typecheck using MyPy - mypy - mypy failed (exit code 1).
src/python/pants/backend/nfpm/rules.py: note: In function "package_nfpm_rpm_package":
src/python/pants/backend/nfpm/rules.py:160:5: error: Returning Any from function declared to return "BuiltPackage"  [no-any-return]
        return await package_nfpm_package(NfpmPackageRequest(field_set), **implicitly())
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Found 1 error in 1 file (checked 1 source file)

So, I had to change from this:

@rule
async def package_nfpm_rpm_package(field_set: NfpmRpmPackageFieldSet) -> BuiltPackage:
    return await package_nfpm_package(NfpmPackageRequest(field_set), **implicitly())

to this, with an explicit type hint:

@rule
async def package_nfpm_rpm_package(field_set: NfpmRpmPackageFieldSet) -> BuiltPackage:
    built_package: BuiltPackage = await package_nfpm_package(
        NfpmPackageRequest(field_set), **implicitly()
    )
    return built_package

where the

package_nfpm_package

rule is type hinted:

@rule(level=LogLevel.INFO)
async def package_nfpm_package(
    request: NfpmPackageRequest,
    nfpm_subsystem: NfpmSubsystem,
    platform: Platform,
) -> BuiltPackage:

Any idea why mypy couldn't tell that

package_nfpm_package

returns

BuiltPackage

?