Microsoft/TypeScript
Auf GitHub ansehen?? and ??= behave differently when they shouldn't
Open
#40.359 geöffnet am 2. Sept. 2020
BugDomain: check: Control FlowEffort: ModerateHelp Wanted
Repository-Metriken
- Stars
- (48.455 Stars)
- PR-Merge-Metriken
- (Durchschn. Merge 6T 17h) (9 gemergte PRs in 30 T)
Beschreibung
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