How to get the return type of a macro from FreestandingMacroExpansionSyntax

Development Macros
1

I declared the expression Macro and I have retrieved the parameters from FreestandingMacroExpansionSyntax as below.

Macro declaration

public macro sfImage<T>(_ value: String) -> T

Retrieve parameters

public struct sfImage: ExpressionMacro {
    public static func expansion(
        of node: some FreestandingMacroExpansionSyntax,
        in context: some MacroExpansionContext
    ) -> ExprSyntax {
        guard let argument = node.argumentList.first?.expression else {
            fatalError("compiler bug: the macro does not have any arguments")
        }

       // Return Image or UIImage based on return type.
        return ""
    }
}

I would like to get the return type of Macro by parsing FreestandingMacroExpansionSyntax. Please suggest how can we retrieve the return type of macro. Thanks in advance.

2

I believe there is no way to do this.

FreestandingMacroExpansionSyntax is the macro body, which does not specify the return type. Like, if I wrote this:

let image = #sfImage("foo_bar.png") as Image

The macro would receive this.

#sfImage("foo_bar.png")

You need to either define two separate macros

#sfUIImage("foo_bar.png")
#sfSwiftUIImage("foo_bar.png")

or put the type as a parameter.

#sfImage("foo_bar.png", as: Image.self)
1 Like
3

Thanks Aggie33 for the valuable Information.