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Without the type assertion, compiler resulting npm package type definition for provideClass looks like:

providesClass: <Token extends TokenType, Service, Tokens extends readonly ValidTokens<Services>[]>(token: Token, cls: InjectableClass<Services, Service, Tokens>) => Container<AddService<Services, Token, import("./Injectable").ConstructorReturnType<InjectableClass<Services, Service, Tokens>>>>;

The last bit (ConstructorReturnType<InjectableClass<Services, Service, Tokens>>>>) is somehow problematic. Resolving types for services provided using the function breaks, e.g. container.providesClass('serivice', Service) returns a container of type Container<{ service: any }>.

The fix addresses the issue by asserting the function's return type, so the generated function signature looks like:

providesClass: <Token extends TokenType, Service, Tokens extends readonly ValidTokens<Services>[]>(token: Token, cls: InjectableClass<Services, Service, Tokens>) => Container<AddService<Services, Token, Service>>;

With that container.providesClass('serivice', Service) correctly returns a container of type Container<{ service: Service }>.

src/Container.ts Outdated
token: Token,
cls: InjectableClass<Services, Service, Tokens>
) => this.providesService(ClassInjectable(token, cls));
) => this.providesService(ClassInjectable(token, cls)) as Container<AddService<Services, Token, Service>>;
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I would prefer if we have return type explicitly declared on this method. There is a eslint rule for this, I'm thinking to enable it. That will not solve our problem, but that will prevent similar issues to happen in future when TS infers type incorrectly.

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Done! 93365db

@kburov-sc kburov-sc merged commit 5b2c728 into main Nov 28, 2024
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@kburov-sc kburov-sc deleted the kb-fix-constructor-return-type branch November 28, 2024 06:39
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3 participants