[CIR][NFC] Mark CXXTypeidExpr lvalue emission as NYI

More skeleton: this change adds a specific NYI marker for C++ typeid
expressions when used as lvalues, replacing the generic "not
implemented" assertion.

Author: bcardosolopes

clang/include/clang/CIR/MissingFeatures.h

@@ -438,6 +438,10 @@ struct MissingFeatures {
   // do not yet support this yet.
   static bool inallocaArgs() { return false; }
 
+  // C++ typeid expression support (returns type_info object reference)
+  // Requires RTTI support including vtable lookups for polymorphic types.
+  static bool cxxTypeid() { return false; }
+
   // Parameters may have additional attributes (e.g. [[noescape]]) that affect
   // the compiler. This is not yet supported in CIR.
   static bool extParamInfo() { return false; }

clang/lib/CIR/CodeGen/CIRGenExpr.cpp

@@ -2101,6 +2101,11 @@ LValue CIRGenFunction::emitCastLValue(const CastExpr *E) {
   llvm_unreachable("Unhandled lvalue cast kind?");
 }
 
+LValue CIRGenFunction::emitCXXTypeidLValue(const CXXTypeidExpr *E) {
+  assert(!cir::MissingFeatures::cxxTypeid() && "NYI");
+  llvm_unreachable("NYI");
+}
+
 // TODO(cir): candidate for common helper between LLVM and CIR codegen.
 static DeclRefExpr *tryToConvertMemberExprToDeclRefExpr(CIRGenFunction &CGF,
                                                         const MemberExpr *ME) {
@@ -2726,6 +2731,9 @@ LValue CIRGenFunction::emitLValue(const Expr *E) {
   case Expr::MaterializeTemporaryExprClass:
     return emitMaterializeTemporaryExpr(cast<MaterializeTemporaryExpr>(E));
 
+  case Expr::CXXTypeidExprClass:
+    return emitCXXTypeidLValue(cast<CXXTypeidExpr>(E));
+
   case Expr::ObjCPropertyRefExprClass:
     llvm_unreachable("cannot emit a property reference directly");
   case Expr::StmtExprClass:

clang/lib/CIR/CodeGen/CIRGenFunction.h

@@ -1914,6 +1914,7 @@ class CIRGenFunction : public CIRGenTypeCache {
                                              cir::CaseOpKind kind,
                                              bool buildingTopLevelCase);
   LValue emitCastLValue(const CastExpr *E);
+  LValue emitCXXTypeidLValue(const CXXTypeidExpr *E);
 
   mlir::LogicalResult emitCaseStmt(const clang::CaseStmt &S,
                                    mlir::Type condType,