Protected field with same name in two classes messing up type constraint when narrowing array. #49517
Description
Bug Report
(I'm not even sure how to properly name that issue 🙃 )
🔎 Search Terms
typescript inheritance protected intersection
🕗 Version & Regression Information
Seen it recently in 4.6.2. Update to 4.7.3 without changing the behaviour (and 4.8.0 nightly in the playground). I don't know if it was here before.
- I was unable to test this on prior versions because this triggered with unrelated change elsewhere in my code
⏯ Playground Link
Playground link with relevant code
💻 Code
class Foo {
protected foo = 0;
}
class Bar {
protected foo = 0;
}
type Nothing<V extends Foo> = void;
type Broken<V extends Array<Foo | Bar>> = {
readonly [P in keyof V]: V[P] extends Foo ? Nothing<V[P]> : never;
};🙁 Actual behavior
(error located at the V[P] in Nothing<V[P]>)
Type 'Foo & V[P]' does not satisfy the constraint 'Foo'.
Property 'foo' is missing in type 'Foo & V[P]' but required in type 'Foo'.
Changing foo from protected to public in either Foo or Bar makes the error disappear.
Removing (or renaming) protected foo = 0 from either Foo or Bar makes the error disappear.
Replacing the Array<Foo | Bar> in Broken by Array<Foo> makes the error disappear.
🙂 Expected behavior
Since V[P] is already in a type guard that is the same as the constraint for Nothing, this should not generate any typing error.