[Macros] Don't apply member attribute macros to expanded members.

Author: hborla

lib/Sema/TypeCheckMacros.cpp

@@ -496,6 +496,10 @@ ArrayRef<unsigned> ExpandMemberAttributeMacros::evaluate(Evaluator &evaluator,
   if (decl->isImplicit())
     return { };
 
+  // Member attribute macros do not apply to macro-expanded members.
+  if (decl->isInMacroExpansionInContext())
+    return { };
+
   auto *parentDecl = decl->getDeclContext()->getAsDecl();
   if (!parentDecl || !isa<IterableDeclContext>(parentDecl))
     return { };

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -1488,3 +1488,20 @@ public struct VarValueMacro: DeclarationMacro, PeerMacro {
     ]
   }
 }
+
+public struct SingleMemberMacro: MemberMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    providingMembersOf decl: some DeclGroupSyntax,
+    in context: some MacroExpansionContext
+  ) throws -> [DeclSyntax] {
+    let member: DeclSyntax =
+      """
+      var expandedMember: Int = 10
+      """
+
+    return [
+      member,
+    ]
+  }
+}

test/Macros/macro_expand_attributes.swift

@@ -123,3 +123,20 @@ class C2: P {
 
   var blah: Int { squareOfLength }
 }
+
+@attached(member, names: named(expandedMember))
+macro AddMember() = #externalMacro(module: "MacroDefinition", type: "SingleMemberMacro")
+
+@AddMember
+@wrapAllProperties
+struct TestExpansionOrder {
+  var originalMember: Int = 10
+}
+
+var expansionOrder = TestExpansionOrder()
+
+// CHECK-NOT: setting 27
+expansionOrder.expandedMember = 27
+
+// CHECK: setting 28
+expansionOrder.originalMember = 28