Body macros on properties

Evolution Discussion
2

There is also an open question in the implementation that may have public API impacts: Add support for body macros on variables and accessors by calda · Pull Request #3298 · swiftlang/swift-syntax · GitHub

The existing signature of BodyMacro.expansion is:

static func expansion(
  of node: AttributeSyntax,
  providingBodyFor declaration: some DeclSyntaxProtocol & WithOptionalCodeBlockSyntax,
  in context: some MacroExpansionContext
) throws -> [CodeBlockItemSyntax]

This works for get / set accessors (AccessorDeclSyntax, conforms to WithOptionalCodeBlockSyntax) but doesn’t work out of the box for properties without explicit accessors (VariableDeclSyntax doesn’t conform to WithOptionalCodeBlockSyntax).

Should we introduce a new expansion signature for computed properties without accessors?

static func expansion(
  of node: AttributeSyntax,
  providingBodyFor declaration: VariableDeclSyntax, // new
  in context: some MacroExpansionContext
) throws -> [CodeBlockItemSyntax]

Or, should we make this work through the existing WithOptionalCodeBlockSyntax signature (implementation options discussion here)?

If we prefer a new signature, this seems like it would need to be ran as an amendment to SE-0415. Would love a suggestion from the LSG on the direction here.