1

When trying to generate an enum with associated values, the generated enum is missing comma separating it's values.

This is the my expansion function (I'm using a PeermMacro)

public enum MyMacro: PeerMacro {

    public static func expansion(
        of _: AttributeSyntax,
        providingPeersOf _: some DeclSyntaxProtocol,
        in _: some MacroExpansionContext
    ) throws -> [DeclSyntax] {
        [
            DeclSyntax(
                EnumDeclSyntax(name: "MyEnum") {
                    EnumCaseDeclSyntax {
                        EnumCaseElementSyntax(
                            name: "myCase",
                            parameterClause: EnumCaseParameterClauseSyntax(
                                parameters: EnumCaseParameterListSyntax(
                                    [
                                        EnumCaseParameterSyntax(type: TypeSyntax("Int")),
                                        EnumCaseParameterSyntax(type: TypeSyntax("String"))
                                    ]
                                )
                            )
                        )
                    }
                }
            )
        ]
    }
}

The code above generates the following code, which doesn't compile because there's a comma missing between the associated values:

enum MyEnum {
    case myCase(Int String)
}

How can I update my expansion code so that the generated code contains comma between my associated values?

2

You just need to add a trailingComma argument to EnumCaseParameterSyntax initializer like so:

- EnumCaseParameterSyntax(type: TypeSyntax("Int"))
+ EnumCaseParameterSyntax(type: TypeSyntax("Int"), trailingComma: .commaToken())
3

Alternatively you can import SwiftSyntaxBuilder and use the result builder initializer that automatically adds commas.

EnumCaseParameterListSyntax {
  EnumCaseParameterSyntax(type: TypeSyntax("Int")),
  EnumCaseParameterSyntax(type: TypeSyntax("String"))
}