Provide fresh DetachedCaptures for each nested fragment

clang/include/clang/Sema/Sema.h

@@ -12497,16 +12497,20 @@ class Sema final {
   class CXXFragmentScopeRAII {
     Sema &S;
     bool PreviouslyInFragment;
+    SmallVector<CXXFragmentCaptureExpr *, 10> OriginalDetachedCaptures;
 
   public:
     CXXFragmentScopeRAII(Sema &S)
-        : S(S), PreviouslyInFragment(S.FragmentScope) {
+        : S(S), PreviouslyInFragment(S.FragmentScope),
+          OriginalDetachedCaptures() {
       S.FragmentScope = true;
+      OriginalDetachedCaptures.swap(S.DetachedCaptures);
     }
 
     ~CXXFragmentScopeRAII() {
       S.FragmentScope = PreviouslyInFragment;
       assert(S.DetachedCaptures.empty() && "captures left unattached");
+      OriginalDetachedCaptures.swap(S.DetachedCaptures);
     }
   };
 

clang/test/CXX/meta/nested_fragment_with_captures.cpp

@@ -0,0 +1,42 @@
+// RUN: %clang_cc1 -freflection -std=c++2a %s
+
+#define assert(E) if (!(E)) __builtin_abort();
+
+namespace meta {
+  using info = decltype(^void);
+}
+
+struct Member {
+  const char* name;
+  meta::info type;
+};
+
+constexpr Member members[]{
+  Member{"a", ^int},
+  Member{"b", ^int}
+};
+
+consteval void generate_struct(const char* name) {
+  -> fragment namespace {
+    struct [# %{name} #] {
+      consteval {
+        for (auto member : %{members}) {
+          -> fragment struct {
+            typename [: %{member.type} :] [# %{member.name} #];
+          };
+        }
+      }
+    };
+  };
+}
+
+consteval {
+  generate_struct("S");
+}
+
+int main() {
+  S s{1, 2};
+  assert(s.a == 1);
+  assert(s.b == 2);
+  return 0;
+}