Wrong warning on extension with specialized variadic type

[dehesa]

Description

After extending a variadic type with a conditional conformance, the compiler generates an incorrect warning when executing the code below. The warning refers to line:

self.characteristics = () as! (repeat each C)

and the warning states:

Cast from '()' to unrelated type '(repeat each C)' always fails

This is incorrect because the cast can succeed when C is the empty pack.

Reproduction

public struct Person<each C> {
  public var name: String
  public var characteristics: (repeat each C)
}

extension Person< >: ExpressibleByStringLiteral {
  public init(stringLiteral value: String) {
    self.name = value
    self.characteristics = () as! (repeat each C)
  }
}

let x: Person< > = "Tom Bombadil"

Expected behavior

No warning is displayed.

Environment

swift-driver version: 1.87.3 Apple Swift version 5.9.2 (swiftlang-5.9.2.2.56 clang-1500.1.0.2.5)
Target: arm64-apple-macosx14.0

Additional information

This has been discussed with @slavapestov in the forums.