Fix some crashes.

- members_of(^int), bases_of(^int), etc.
- Tree transform that leaves a value-dependent splice in place.

Also replace 'member_of' with 'enumerators_of' in P2996 example.

Tested:
    Ran 'check-all' on MacOS.

clang/lib/Sema/Metafunctions.cpp

@@ -950,7 +950,7 @@ bool get_begin_enumerator_decl_of(APValue &Result, Sema &S, EvalFn Evaluator,
   case ReflectionValue::RK_type: {
     Decl *D = findTypeDecl(R.getReflectedType());
 
-    if (auto enumDecl = dyn_cast<EnumDecl>(D)) {
+    if (auto enumDecl = dyn_cast_or_null<EnumDecl>(D)) {
       if (auto itr = enumDecl->enumerator_begin();
           itr != enumDecl->enumerator_end()) {
         return SetAndSucceed(Result, makeReflection(*itr));
@@ -1030,9 +1030,9 @@ bool get_ith_base_of(APValue &Result, Sema &S, EvalFn Evaluator,
   case ReflectionValue::RK_type: {
     Decl *typeDecl = findTypeDecl(R.getReflectedType());
 
-    ensureInstantiated(S, typeDecl, Range);
+    if (auto cxxRecordDecl = dyn_cast_or_null<CXXRecordDecl>(typeDecl)) {
+      ensureInstantiated(S, typeDecl, Range);
 
-    if (auto cxxRecordDecl = dyn_cast<CXXRecordDecl>(typeDecl)) {
       auto numBases = cxxRecordDecl->getNumBases();
       if (idx >= numBases)
         return SetAndSucceed(Result, Sentinel);
@@ -1131,6 +1131,8 @@ bool get_begin_member_decl_of(APValue &Result, Sema &S, EvalFn Evaluator,
 
     ensureDeclared(S, QT, Range.getBegin());
     Decl *typeDecl = findTypeDecl(QT);
+    if (!typeDecl)
+      return true;
 
     DeclContext *declContext = dyn_cast<DeclContext>(typeDecl);
     assert(declContext && "no DeclContext?");
@@ -1962,8 +1964,10 @@ bool is_accessible(APValue &Result, Sema &S, EvalFn Evaluator,
 
   switch (R.getReflection().getKind()) {
   case ReflectionValue::RK_type: {
-    bool Accessible = isAccessible(S, AccessDC,
-                                   findTypeDecl(R.getReflectedType()));
+    NamedDecl *D = findTypeDecl(R.getReflectedType());
+    if (!D)
+      return true;
+    bool Accessible = isAccessible(S, AccessDC, D);
     return SetAndSucceed(Result, makeBool(S.Context, Accessible));
   }
   case ReflectionValue::RK_declaration: {
@@ -1978,6 +1982,8 @@ bool is_accessible(APValue &Result, Sema &S, EvalFn Evaluator,
   case ReflectionValue::RK_base_specifier: {
     // TODO(P2996): Need an edge back to derived class.
     NamedDecl *ND = findTypeDecl(R.getReflectedBaseSpecifier()->getType());
+    if (!ND)
+      return true;
     bool Accessible = isAccessible(S, AccessDC, ND);
     return SetAndSucceed(Result, makeBool(S.Context, Accessible));
   }

clang/lib/Sema/TreeTransform.h

@@ -4451,6 +4451,12 @@ NestedNameSpecifierLoc TreeTransform<Derived>::TransformNestedNameSpecifierLoc(
 
       if (ER.isInvalid())
         return NestedNameSpecifierLoc();
+      else if (ER.get()->isValueDependent()) {
+        SS.MakeIndeterminateSplice(SemaRef.Context,
+                                   cast<CXXIndeterminateSpliceExpr>(ER.get()),
+                                   Q.getLocalEndLoc());
+        break;
+      }
       Expr *Operand = ER.get();
 
       // Should have a non-dependent expression now: Evaluate it.

libcxx/test/std/experimental/reflection/p2996-ex-enum-to-string.pass.cpp

@@ -51,7 +51,7 @@ template <typename E>
   requires std::is_enum_v<E>
 constexpr std::string enum_to_string(E value) {
     std::string result = "<unnamed>";
-    [:expand(members_of(^E)):] >> [&] <auto e> {
+    [:expand(enumerators_of(^E)):] >> [&] <auto e> {
         if (value == [:e:]) {
             result = std::string(name_of(e));
         }
@@ -63,7 +63,7 @@ template <typename E>
   requires std::is_enum_v<E>
 constexpr std::optional<E> string_to_enum(std::string_view name) {
   std::optional<E> result = std::nullopt;
-  [:expand(members_of(^E)):] >> [&] <auto e> {
+  [:expand(enumerators_of(^E)):] >> [&] <auto e> {
     if (name == name_of(e)) {
       result = [:e:];
     }