Add never helper function
#18287
Merged
Add never helper function
#18287
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ghost
requested review from
weswigham
reviewed
Sep 6, 2017
src/compiler/core.ts
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| @@ -2628,4 +2628,8 @@ namespace ts { | |||
| export function and<T>(f: (arg: T) => boolean, g: (arg: T) => boolean) { | |||
| return (arg: T) => f(arg) && g(arg); | |||
| } | |||
|
|
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| export function never(never: never): never { | |||
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I think this should be in Debug and should be an assert, like assertNever. I also think that retaining the custom error messages which were at these sites prior to this is valuable; so it should have an (optional?) argument for the message. It should likely also defer to Debug.fail for throwing the error so it can pass the never asserting function as the stackCrawlMark so that there are not extra irrelevant stack frames in the error.
ghost
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Moved out of #18154.
This would add a
neverfunction which both:never.#18154 uses a function
assertTypeIsNeverbut handles the value regardless.I think @weswigham was going to add a similar function in one of his PRs.