assertMacroExpansion should emit an error if member macro is applied to declaration that can’t have members #2206

func testMemberMacroOnVar() {
  struct TestMacro: MemberMacro {
    static func expansion(
      of node: AttributeSyntax,
      providingMembersOf declaration: some DeclGroupSyntax,
      conformingTo protocols: [TypeSyntax],
      in context: some MacroExpansionContext
    ) throws -> [DeclSyntax] {
      return []
    }
  }

  assertMacroExpansion(
    """
    @Test var x: Int
    """,
    expandedSource: """
      var x: Int
      """,
    macros: [
      "Test": TestMacro.self
    ]
  )
}