Conditional cast from 'any Error' to 'any Equatable' always succeeds... but doesn't

[jasonbobier]

Description

The compiler tells me that the cast from 'any Error' to 'any Equatable' always succeeds, but then tells me that it doesn't.

Reproduction

enum SomeError: Error {
	case error
}

let t: any Error = SomeError.error

func needsEquatable<E: Equatable>(e: E) {
}

if let t = t as? (any Equatable) { // Warning: Conditional cast from 'any Error' to 'any Equatable' always succeeds
	needsEquatable(e: t)
}

needsEquatable(e: t) // Error: Global function 'needsEquatable(e:)' requires that 'E' conform to 'Equatable'

Expected behavior

I don't think that Error is Equatable, so the warning is probably wrong.

Environment

swift-driver version: 1.87.1 Apple Swift version 5.9 (swiftlang-5.9.0.128.108 clang-1500.0.40.1) Target: arm64-apple-macosx14.0

Additional information

No response

[jasonbobier]

@AnthonyLatsis this one seems to have been overlooked. This is still an issue in Xcode Version 16.0 beta 4 (16A5211f).

[nonameplum]

+1

[fzy-github]

seeing similar issue here but when trying to cast any Error to CustomDebugStringConvertible

[tbkka]

CC: @xedin

[jasonbobier]

This is still an issue as of Xcode Version 26.0.1 (17A400)