swiftlang/swift
Bad diagnostic when inheriting from class in extension
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#64,903 opened on 2023/04/04
bugcompilerdiagnostics qualityextensiongood first issueinheritanceswift 6.0type checker
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説明
The following errors are misleading and could use a rewording as clear language rules, depending on the kinds of extended and inherited types.
protocol P {}
struct S {}
class C1 {}
class C2 {}
extension C2: S {} // error: inheritance from non-protocol type 'S'
extension C2: C1 {} // error: inheritance from non-protocol type 'C1'
extension C2: C1 & P {} // error: inheritance from class-constrained protocol composition type 'C1 & P'
Environment
- Swift version 5.9-dev (LLVM 6a04c4848990c70, Swift c1d5118c21d)
NB: How to improve on these is left as an exercise to whoever takes the issue.