Microsoft/TypeScript
Vedi su GitHub?? and ??= behave differently when they shouldn't
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#40.359 aperta il 2 set 2020
BugDomain: check: Control FlowEffort: ModerateHelp Wanted
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Descrizione
TypeScript Version: 4.0.2, Nightly (2020-9-2)
Search Terms: Nullish coalescing operator Nullish never Coalescing never Nullish coalescing assignment
Code
According to this post usage of ?? and ??= should be equivalent in the sample code below:
const values: { a?: string[] } = { };
delete values.a;
(values.a ?? (values.a = [])).push("hello"); // error
values.a = undefined;
(values.a ?? (values.a = [])).push("hello"); // error
delete values.a;
(values.a ??= []).push("hello");
values.a = undefined;
(values.a ??= []).push("hello");
Expected behavior:
Examples with ?? and ??= should compile and behave similarly.
Actual behavior:
Examples with ?? do not compile (Argument of type 'string' is not assignable to parameter of type 'never'.(2345))
Playground Link: link
Related Issues: Didn't find anything similar