@ts-ignore on an import that gets redefined strips the import from output

TypeScript Version: 3.7.5 and 3.8.0

Search Terms:

• ts-ignore remove import
• ts-ignore strip import

Code

// @ts-ignore: Local Foo override
import Foo from "foo";

declare const Foo: {
    bar(): number;
}

Foo.bar();

Expected behavior:

JS output should probably be:

import Foo from "foo";

Foo.bar();

Actual behavior:

JS output is:

Foo.bar();

Playground Link: https://www.typescriptlang.org/play/index.html?ts=3.8-Beta&ssl=9&ssc=1&pln=1&pc=1#code/PTAEAEBcGcFoEsDmA7A9gJwKYC5QBlUBjAQwBtQAxVVUVAN03XXgBNMAoeAWwAcNJK1UADN0qLqABEw6pIDc7dm0KliWUIVTJoAqqlwBvdqBOgARmoAUASlzIArlzOMFAX0V6AdBfQ2FQA

Related Issues: None so far

Additional remarks: We are aware of other ways to type the foo module but in this particular case the foo override needs to be done in the file using it. As far as we tried, adding a ts-ignore is the only way to make ts understand that we want to redefine the module.
Now, this seems to move the declaration site from the import to the the declare statement and that has the effect to mark the import site as unused, since the import is unused, ts strips it.

提供された TypeScript 3.7.5/3.8.0 のコードと Playground リンクから動作を再現し、その後、import に続いて再宣言がある場合の import 消去に関するコンパイラーの判断を追跡します。期待される出力に示されているとおり、出力された JavaScript に import が保持され、このケースのテストカバレッジがある状態を完了とします。