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TypeScript Version: 2.0.3 AND nightly (2.1.0-dev.20161102)
Code
interfaceFoo{kind: 'foo';a: number;}interfaceBar{kind: 'bar';b: string;}functiontest(x: Bar|Foo){if(x.kind==='foo'){console.log(x.a);// Valid, as expected}}interfaceQux{c: boolean;}functiontest2(x: (Bar|Foo)&Qux){if(x.kind==='foo'){// Type of x should be Foo&Qux now, but is still (Bar|Foo)&Quxconsole.log(x.a);// Error}}
Expected behavior:
In test2(), the discriminated union check should narrow the type down to (Foo)&Qux, letting you access property a, since a is guaranteed to be there if x.type === 'foo'.
Actual behavior:
No type narrowing is done whatsoever. The type of x remains (Foo|Bar)&Qux.
The text was updated successfully, but these errors were encountered:
This looks like a duplicate of #9919, which was fixed in #11717. I can compile your example with no error in the nightly build and x is narrowed to Foo & Qux as expected. Can you reconfirm that there's an issue in the nightly?
@ahejlsberg Ah I stand corrected. tsc on the command line does indeed work, it's just that it's still be reported as an error in VS Code. Not sure whether to report that as a different issue or not.
Also I do have another, different but related bug that is reproduceable on the command line on the nightly build :)
TypeScript Version: 2.0.3 AND nightly (2.1.0-dev.20161102)
Code
Expected behavior:
In
test2()
, the discriminated union check should narrow the type down to(Foo)&Qux
, letting you access propertya
, sincea
is guaranteed to be there ifx.type === 'foo'
.Actual behavior:
No type narrowing is done whatsoever. The type of x remains
(Foo|Bar)&Qux
.The text was updated successfully, but these errors were encountered: