Account for out-of-line declarations in members_of.

clang/include/clang/AST/Decl.h

@@ -559,6 +559,11 @@ class NamespaceDecl : public NamedDecl,
   /// The unnamed namespace that inhabits this namespace, if any.
   NamespaceDecl *AnonymousNamespace = nullptr;
 
+  /// The most recent Decl whose target scope is this namespace, but whose
+  /// lexical scope is another DeclContext. Used to traverse namespace members
+  /// (i.e., for reflection).
+  Decl *LastMultDCSemaDecl = nullptr;
+
 protected:
   NamespaceDecl(Kind K, ASTContext &C, DeclContext *DC, bool Inline,
                 SourceLocation StartLoc, SourceLocation IdLoc,
@@ -645,6 +650,9 @@ public:
   NamespaceDecl *getCanonicalDecl() override { return getFirstDecl(); }
   const NamespaceDecl *getCanonicalDecl() const { return getFirstDecl(); }
 
+  Decl *getLastMultDCSemaDecl() { return LastMultDCSemaDecl; }
+  void setLastMultDCSemaDecl(Decl *D) { LastMultDCSemaDecl = D; }
+
   SourceRange getSourceRange() const override LLVM_READONLY {
     return SourceRange(LocStart, RBraceLoc);
   }

clang/include/clang/AST/DeclBase.h

@@ -254,6 +254,8 @@ private:
   struct MultipleDC {
     DeclContext *SemanticDC;
     DeclContext *LexicalDC;
+
+    Decl *PrevMultDCSemaDecl;
   };
 
   /// DeclCtx - Holds either a DeclContext* or a MultipleDC*.
@@ -448,6 +450,11 @@ public:
   Decl *getNextDeclInContext() { return NextInContextAndBits.getPointer(); }
   const Decl *getNextDeclInContext() const {return NextInContextAndBits.getPointer();}
 
+  Decl *getPrevMultDCDeclInSemaContext();
+  const Decl *getPrevMultDCDeclInSemaContext() const {
+    return const_cast<Decl*>(this)->getPrevMultDCDeclInSemaContext();
+  }
+
   DeclContext *getDeclContext() {
     if (isInSemaDC())
       return getSemanticDC();

clang/lib/AST/DeclBase.cpp

@@ -403,6 +403,7 @@ void Decl::setDeclContextsImpl(DeclContext *SemaDC, DeclContext *LexicalDC,
     auto *MDC = new (Ctx) Decl::MultipleDC();
     MDC->SemanticDC = SemaDC;
     MDC->LexicalDC = LexicalDC;
+    MDC->PrevMultDCSemaDecl = nullptr;
     DeclCtx = MDC;
   }
 }
@@ -1237,6 +1238,11 @@ bool Decl::isFunctionPointerType() const {
   return Ty.getCanonicalType()->isFunctionPointerType();
 }
 
+Decl *Decl::getPrevMultDCDeclInSemaContext() {
+  assert(!isInSemaDC());
+  return getMultipleDC()->PrevMultDCSemaDecl;
+}
+
 DeclContext *Decl::getNonTransparentDeclContext() {
   assert(getDeclContext());
   return getDeclContext()->getNonTransparentContext();
@@ -1782,6 +1788,14 @@ void DeclContext::addHiddenDecl(Decl *D) {
     FirstDecl = LastDecl = D;
   }
 
+  if (auto *NS = dyn_cast<NamespaceDecl>(D->getDeclContext());
+      NS && !D->isInSemaDC()) {
+    NS = NS->getCanonicalDecl();
+
+    D->getMultipleDC()->PrevMultDCSemaDecl = NS->getLastMultDCSemaDecl();
+    NS->setLastMultDCSemaDecl(D);
+  }
+
   // Notify a C++ record declaration that we've added a member, so it can
   // update its class-specific state.
   if (auto *Record = dyn_cast<CXXRecordDecl>(this))

clang/lib/AST/ExprConstantMeta.cpp

@@ -1334,7 +1334,16 @@ static bool ensureDeclared(ASTContext &C, QualType QT, SourceLocation SpecLoc) {
 static bool isReflectableDecl(MetaActions &Meta, ASTContext &C, Decl *D) {
   assert(D && "null declaration");
 
-  if (D != D->getCanonicalDecl())
+  if (D != D->getCanonicalDecl()) {
+    Decl *First = nullptr;
+    for (Decl *I = D->getMostRecentDecl(); I; I = I->getPreviousDecl())
+      if (I->getLexicalDeclContext() == D->getLexicalDeclContext())
+        First = I;
+    if (D != First)
+      return false;
+  }
+
+  if (D->isLocalExternDecl())
     return false;
 
   if (isa<NamespaceAliasDecl>(D))
@@ -1355,7 +1364,6 @@ static bool isReflectableDecl(MetaActions &Meta, ASTContext &C, Decl *D) {
   if (auto *FD = dyn_cast<FunctionDecl>(D)) {
     for (auto *R = FD->getMostRecentDecl(); R; R = R->getPreviousDecl()) {
       if (!R->getDeclaredReturnType()->isUndeducedType() &&
-          R->getDeclContext() == R->getLexicalDeclContext() &&
           Meta.HasSatisfiedConstraints(R))
         return true;
     }
@@ -1386,26 +1394,35 @@ static Decl *findIterableMember(MetaActions &Meta, ASTContext &C, Decl *D,
   }
 
   do {
-    DeclContext *DC = D->getDeclContext();
+    DeclContext *DC = D->getDeclContext();  // note: SemanticDC
 
-    // Get the next declaration in the DeclContext.
-    //
-    // Explicit specializations of templates are created with the DeclContext of
-    // the template from which they're instantiated, but they end up in the
-    // DeclContext within which they're declared. We therefore skip over any
-    // declarations whose DeclContext is different from the previous Decl;
-    // otherwise, we may inadvertently break the chain of redeclarations in
-    // difficult to predit ways.
-    do {
-      D = D->getNextDeclInContext();
-    } while (D && D->getDeclContext() != DC);
+    if (D->getLexicalDeclContext() == DC) {
+      // Get the next declaration in the DeclContext.
+      //
+      // Explicit specializations of templates are created with the DeclContext
+      // of the template from which they're instantiated, but they end up in the
+      // DeclContext within which they're declared. We therefore skip over any
+      // declarations whose DeclContext is different from the previous Decl;
+      // otherwise, we may inadvertently break the chain of redeclarations in
+      // difficult to predit ways.
+      do {
+        D = D->getNextDeclInContext();
+      } while (D && D->getDeclContext() != DC);
 
-    // In the case of namespaces, walk the redeclaration chain.
-    if (auto *NSDecl = dyn_cast<NamespaceDecl>(DC)) {
-      while (!D && NSDecl) {
-        NSDecl = NSDecl->getPreviousDecl();
-        D = NSDecl ? *NSDecl->decls_begin() : nullptr;
+      // In the case of namespaces, walk the redeclaration chain.
+      if (auto *NSDecl = dyn_cast<NamespaceDecl>(DC)) {
+        while (!D && NSDecl) {
+          NSDecl = NSDecl->getPreviousDecl();
+          D = NSDecl ? *NSDecl->decls_begin() : nullptr;
+        }
+
+        if (!D) {
+          auto *Canonical = cast<NamespaceDecl>(DC->getPrimaryContext());
+          D = Canonical->getLastMultDCSemaDecl();
+        }
       }
+    } else {
+      D = D->getPrevMultDCDeclInSemaContext();
     }
 
     // We need to recursively descend into LinkageSpecDecls to iterate over the

libcxx/test/std/experimental/reflection/members-and-subobjects.pass.cpp

@@ -435,6 +435,46 @@ static_assert(members_of(^^NS,
 
 }  // namespace deduced_return_type
 
+                          // ========================
+                          // out_of_line_declarations
+                          // ========================
+
+namespace out_of_line_declarations {
+constexpr auto ctx = std::meta::access_context::current();
+
+namespace NS1 {
+struct A;
+
+}  // namespace NS1
+
+struct NS1::A {
+static void f(class C *);
+static auto g();
+};
+void NS1::A::f(NS1::C *) {}
+void gq(NS1::C *) {}
+
+static_assert(
+    *std::ranges::find(
+        [](const auto &r) -> const auto & { return r; }(
+            members_of(^^NS1, ctx)),
+        ^^NS1::C) ==
+    ^^NS1::C);
+
+namespace NS2 {
+namespace Inner {
+struct S {
+  friend void f();
+};
+} // namespace Inner
+void Inner::f() {}
+
+} // namespace NS2
+
+static_assert(1 == members_of(^^NS2, ctx).size());
+static_assert(2 == members_of(^^NS2::Inner, ctx).size());
+}  // namespace out_of_line_declarations
+
 int main() {
   class_members::usage_example();
 }