interface A extends B fails if B is exported from a private file

[rix0rrr]

The following succeeds:

export interface A extends B { /* ... */ }

interface B { /* ... */ }

It will "hide" the interface B entirely from jsii.

But the following fails:

import { B } from './private/b';

export interface A extends B { /* ... */ }

With the error "can't find B, make sure it's exported".

Even though it's the exact same situation.

aws-cloudwatch/lib/alarm.ts:33:1 - error JSII9002: Unable to resolve type "aws-cdk-lib.CreateAlarmOptionsBase". It may be @internal or not exported from the module's entry point (as configured in "package.json" as "main").

Adding @internal to B does appease jsii, but this still shouldn't happen this way.

Probable reason

I'm guessing that the code that checks whether or not the B type should be hidden or should be visible looks at the export keyword and nothing else, but it B must have export if it comes from a different file, even if that file is itself not exported on purpose.