[Macros] Ignore the @TaskLocal macro attached to vars with projected value vars.

lib/Sema/TypeCheckMacros.cpp

@@ -1369,6 +1369,22 @@ static SourceFile *evaluateAttachedMacro(MacroDecl *macro, Decl *attachedTo,
     dc = attachedTo->getInnermostDeclContext();
   }
 
+  // FIXME: compatibility hack for the transition from property wrapper
+  // to macro for TaskLocal.
+  //
+  // VarDecls with `@_projectedValueProperty` have already had the property
+  // wrapper transform applied. This only impacts swiftinterfaces, and if
+  // a swiftinterface was produced against a Concurrency library that does
+  // not declare TaskLocal as a macro, we need to ignore the macro to avoid
+  // producing duplicate declarations. This is only needed temporarily until
+  // all swiftinterfaces have been built against the Concurrency library
+  // containing the new macro declaration.
+  if (auto *var = dyn_cast<VarDecl>(attachedTo)) {
+    if (var->getAttrs().getAttribute<ProjectedValuePropertyAttr>()) {
+      return nullptr;
+    }
+  }
+
   ASTContext &ctx = dc->getASTContext();
 
   auto moduleDecl = dc->getParentModule();

test/ModuleInterface/task_local_attr.swiftinterface

@@ -0,0 +1,20 @@
+// swift-interface-format-version: 1.0
+// swift-compiler-version: Swift version 6.0
+// swift-module-flags: -swift-version 5 -disable-availability-checking
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-typecheck-module-from-interface(%s)
+
+import Swift
+import _Concurrency
+
+@_hasMissingDesignatedInitializers final public class C {
+  @_Concurrency.TaskLocal @_projectedValueProperty($x) public static var x: Swift.Int? {
+    get
+  }
+  public static var $x: _Concurrency.TaskLocal<Swift.Int?> {
+    get
+    @available(*, unavailable, message: "use '$myTaskLocal.withValue(_:do:)' instead")
+    set
+  }
+}