Fix Signature handling for unions and generics #391
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chriskrycho
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test/types/component-test.ts
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| // Intentionally checking the shape of the exports *and* the export itself. | ||
| import * as gc from '@glimmer/component'; | ||
| // eslint-disable-next-line no-duplicate-imports | ||
| import Component from '@glimmer/component'; |
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Linting doesn't seem to like this
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Ahhh, the problem is that it's tslint instead of eslint. Ugh.
(cherry picked from commit 9c9f023)
When using a `keyof` type to check whether the type parameter for Glimmer Component is a `Signature` or the classic `Args`-only type, if we do not force TS to distribute over union types, it resolves the `keyof` check for union types with no shared members as `never`, and `never extends <anything>` is always true. This in turn meant that for all such unions, as well as for cases where users were providing generic types which could then be further extended in their own subclasses. Accordingly, introduce the standard technique TypeScript provides for opting into distributivity: conditional types are documented to support exactly this. (cherry picked from commit ad429d5)
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Cherry-picks this fix to
masterfrom #390 (which targetsv1.x).Ultimately, we should be able to drop these shenanigans entirely before cutting v2.0, but we’ll want to give folks currently using the v2 betas a heads-up about it.