Generic typed errors cannot be used without appearing outside the "throws argument".

[JessyCatterwaul]

Description / Reproduction

If a generic error is "used in the function signature", the code compiles:

func ƒ<Error: Swift.Error>(_: Error) throws(Error) { }

But otherwise, no.

func ƒ<Error: Swift.Error>() throws(Error) { } // ❌ Generic parameter 'Error' is not used in function signature
func ƒ() throws(some Error) { } // ❌ 'some' types are only permitted in properties, subscripts, and functions

Expected behavior

SE-0413 says it should work.

Environment

swift-driver version: 1.109.2 Apple Swift version 6.0 (swiftlang-6.0.0.3.300 clang-1600.0.20.10)
Target: arm64-apple-macosx14.0