From 0a1fbe7f3060a6412b1897279d9dffeab510117c Mon Sep 17 00:00:00 2001
From: Doug Gregor <dgregor@apple.com>
Date: Wed, 2 Aug 2023 22:58:11 -0700
Subject: [PATCH 1/2] [Macros] Emit deprecation warnings for uses of
 freestanding macros.

Fixes rdar://113138432.
---
 lib/Sema/TypeCheckAvailability.cpp |  5 +++++
 test/Macros/macro_expand.swift     | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/lib/Sema/TypeCheckAvailability.cpp b/lib/Sema/TypeCheckAvailability.cpp
index 5c35966d5caa2..07a9579331577 100644
--- a/lib/Sema/TypeCheckAvailability.cpp
+++ b/lib/Sema/TypeCheckAvailability.cpp
@@ -3285,6 +3285,11 @@ class ExprAvailabilityWalker : public ASTWalker {
       }
     }
 
+    if (auto ME = dyn_cast<MacroExpansionExpr>(E)) {
+      diagnoseDeclRefAvailability(
+          ME->getMacroRef(), ME->getMacroNameLoc().getSourceRange());
+    }
+
     return Action::Continue(E);
   }
 
diff --git a/test/Macros/macro_expand.swift b/test/Macros/macro_expand.swift
index cd74d5ebd4304..7141e8a5bb81a 100644
--- a/test/Macros/macro_expand.swift
+++ b/test/Macros/macro_expand.swift
@@ -547,3 +547,23 @@ func testExpressionAsDeclarationMacro() {
   // expected-error@-1{{macro implementation type 'StringifyMacro' doesn't conform to required protocol 'DeclarationMacro' (from macro 'stringifyAsDeclMacro')}}
 #endif
 }
+
+// Deprecated macro
+@available(*, deprecated, message: "This macro is deprecated.")
+@freestanding(expression) macro deprecatedStringify<T>(_ value: T) -> (T, String) = #externalMacro(module: "MacroDefinition", type: "StringifyMacro")
+
+@available(*, deprecated, message: "This macro is deprecated.")
+@freestanding(declaration) macro deprecatedStringifyAsDeclMacro<T>(_ value: T) = #externalMacro(module: "MacroDefinition", type: "StringifyMacro")
+
+func testDeprecated() {
+  // expected-warning@+1{{'deprecatedStringify' is deprecated: This macro is deprecated.}}
+  _ = #deprecatedStringify(1 + 1)
+}
+
+#if TEST_DIAGNOSTICS
+struct DeprecatedStructWrapper {
+  // expected-error@+2{{macro implementation type 'StringifyMacro' doesn't conform to required protocol 'DeclarationMacro' (from macro 'deprecatedStringifyAsDeclMacro')}}
+  // expected-warning@+1{{'deprecatedStringifyAsDeclMacro' is deprecated: This macro is deprecated.}}
+  #deprecatedStringifyAsDeclMacro(1 + 1)
+}
+#endif

From c3af8cbe42d98678006ae70d13f9ad94519aaf6a Mon Sep 17 00:00:00 2001
From: Doug Gregor <dgregor@apple.com>
Date: Wed, 2 Aug 2023 23:23:38 -0700
Subject: [PATCH 2/2] [Macros] Diagnose availability of attached macros

---
 lib/Sema/TypeCheckAccess.cpp         | 13 +++++++++++++
 test/Macros/macro_expand_peers.swift | 15 +++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/lib/Sema/TypeCheckAccess.cpp b/lib/Sema/TypeCheckAccess.cpp
index 3996bf09beaf5..5d90d6ff95989 100644
--- a/lib/Sema/TypeCheckAccess.cpp
+++ b/lib/Sema/TypeCheckAccess.cpp
@@ -528,6 +528,7 @@ class AccessControlChecker : public AccessControlCheckerBase,
 
     DeclVisitor<AccessControlChecker>::visit(D);
     checkGlobalActorAccess(D);
+    checkAttachedMacrosAccess(D);
   }
 
   // Force all kinds to be handled at a lower level.
@@ -1260,6 +1261,18 @@ class AccessControlChecker : public AccessControlCheckerBase,
       noteLimitingImport(MD->getASTContext(), minImportLimit, complainRepr);
     }
   }
+
+  void checkAttachedMacrosAccess(const Decl *D) {
+    for (auto customAttrC : D->getSemanticAttrs().getAttributes<CustomAttr>()) {
+      auto customAttr = const_cast<CustomAttr *>(customAttrC);
+      auto *macroDecl = D->getResolvedMacro(customAttr);
+      if (macroDecl) {
+        diagnoseDeclAvailability(
+          macroDecl, customAttr->getTypeRepr()->getSourceRange(), nullptr,
+          ExportContext::forDeclSignature(const_cast<Decl *>(D)), llvm::None);
+      }
+    }
+  }
 };
 
 class UsableFromInlineChecker : public AccessControlCheckerBase,
diff --git a/test/Macros/macro_expand_peers.swift b/test/Macros/macro_expand_peers.swift
index 83e3474859e33..b7eca3b3325fb 100644
--- a/test/Macros/macro_expand_peers.swift
+++ b/test/Macros/macro_expand_peers.swift
@@ -235,3 +235,18 @@ func testStructWithPeers() {
   let x = SomeStructWithPeerProperties()
   print(x)
 }
+
+
+#if TEST_DIAGNOSTICS
+@available(*, deprecated, message: "This macro is deprecated.")
+@attached(peer, names: overloaded)
+macro deprecatedAddCompletionHandler() = #externalMacro(module: "MacroDefinition", type: "AddCompletionHandler")
+
+
+// expected-warning@+1{{'deprecatedAddCompletionHandler()' is deprecated: This macro is deprecated.}}
+@deprecatedAddCompletionHandler
+func fDeprecated(a: Int, for b: String, _ value: Double) async -> String {
+  return b
+}
+
+#endif