Feature request: Cleaner handling of TypeScript type-only import elision on externally imported registrations

[cmidgley]

I commonly encounter a situation where I get errors because TypeScript has removed the value-import because it thinks it is a type-only import. For example, a fairly typical index.ts for a module might be:

import { MyImplementation } from './MyCode.js';
export type { MyInterface } from './types.js';

container.registerSingleton<MyInterface, MyImplementation>();

This commonly will fail because TypeScript removes what it believes is a type-only import (I think before passing to the transformer), so when the generated code then tries to reference MyImplementation as a value, it gets an error that it doesn't exist.

The work-around is to reference MyImplementation somewhere in the file, for which I've added a global namespace function retainValue:

import { MyImplementation } from './MyCode.js';
export type { MyInterface } from './types.js';

retainValue(MyImplementation);
container.registerSingleton<MyInterface, MyImplementation>();

My proposal is to extend the interface and the compiler to support this syntax:

container.registerSingleton<MyInterface>(MyImplementation);

This seems straightforward in the DI types and has little change there. The heavier lifting would be in DI-compiler as it would need to know the implementation is a class and generate the same registerSingleton(undefined, { identifier: "MyImplementation", implementation: MyImplementation }) that the other usage does. This would be superior to using registerSingleton<MyInterface>(() => new MyImplementation()); as it would use injected properties for the new class instance.

I'm not proposing to eliminate the current syntax, but instead extend the definition of "implementation" to be a function OR a class.

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P.S. The test script no longer works on Windows due to switching DI and DI-compiler to Node's built-in testing feature. The tests run fine, but Node / the Windows shell does not provide glob expansion, so the test names don't match. Not your bug, but FYI.