Getting wrong type in conformingTo protocols in ExtensionMacro

[soumyamahunt]

Description

When declaring an extension macro that provides extensions for multiple protocols, i.e. Codable macro providing extension for Decodable and Encodable, by default protocol names are joined together and provided as a single type in the protocols array.

For each protocol conformance is provided, protocols array should have a separate type syntax item.

Steps to Reproduce

Xcode: Version 15.0 beta 6 (15A5219j)
Swift syntax version: 509.0.0-swift-DEVELOPMENT-SNAPSHOT-2023-08-07-a

Create an extension macro implementation that should print the protocols array in build log:

public struct CodableMacro: ExtensionMacro {
    public static func expansion(
        of node: AttributeSyntax,
        attachedTo declaration: some DeclGroupSyntax,
        providingExtensionsOf type: some TypeSyntaxProtocol,
        conformingTo protocols: [TypeSyntax],
        in context: some MacroExpansionContext
    ) throws -> [ExtensionDeclSyntax] {
        precondition(protocols.count == 0, "\(protocols)")
        return []
    }
}

@attached(extension, conformances: Decodable, Encodable)
public macro Codable() = #externalMacro(module: "ExtensionMacroMacros", type: "CodableMacro")

And attach this macro to a type:

@Codable
struct SomeCodable {
    let val: String
}

Inspect the protocols array in build log:

[IdentifierTypeSyntax
╰─name: identifier("DecodableEncodable")]

[ahoppen]

Tracked in Apple’s issue tracker as rdar://113668922

[ahoppen]

Thanks for reporting the issue @soumyamahunt. @hborla is fixing it in swiftlang/swift#67889.

[soumyamahunt]

Thanks @ahoppen and @hborla for the quick fix, let me know once fix is available in latest snapshots. This is a major blocker for MetaCodable migrating to extension macros.

[ahoppen]

The August 12 main development snapshot should contain the fix.

[soumyamahunt]

The August 12 main development snapshot should contain the fix.

Thanks @ahoppen, with latest main snapshot this issue is fixed, MetaCodable is buildable now (although tests are failing due to #2031). Closing this issue.

[soumyamahunt]

@ahoppen @hborla getting this issue again with latest Xcode release and swift-syntax version:

Xcode: Version 15.0 (15A240d)
Swift syntax version: 509.0.0

IdentifierTypeSyntax
╰─name: identifier("DecodableEncodable")

[ahoppen]

The fix hasn’t made it into Xcode 15.0, unfortunately. As this is fixed in the GitHub repo, the fix should be included in a future Xcode version.