Microsoft/TypeScript
Auf GitHub ansehenSubclass of a (non-abstract class that uses declaration merging to implement parent abstract member) also has to implement same abstract member
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#57.263 geöffnet am 1. Feb. 2024
BugDomain: classesHelp Wanted
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Beschreibung
🔎 Search Terms
subclass inherit abstract concrete method property member complains parent declaration merge merging satisfy implement
🕗 Version & Regression Information
- This is the behavior in every version I tried, and I reviewed all the FAQ entries
⏯ Playground Link
💻 Code
interface ParentI {
foo(): void
}
abstract class Parent {
abstract foo(): void
}
// Middle implements Parent via declaration merge
class Middle extends Parent {}
interface Middle extends ParentI {}
class Child extends Middle {} // doesn't work
// Middle implements Parent directly
class Middle2 extends Parent {
foo() {}
}
class Child2 extends Middle2 {} // works
🙁 Actual behavior
Typescript complains that Child must implement an foo, even though Middle has already implemented foo via declaration merging.
🙂 Expected behavior
I would expect Child to pass type-checking, just as Child2 does. Seeing as how Middle (a concrete class) is type-safe and Child extends Middle with no further modification, this feels very surprising.
Additional information about the issue
No response