[clang][bytecode] Handle UsingDirectiveDecls (#128888)

By ignoring them.

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -5107,7 +5107,7 @@ template <class Emitter>
 bool Compiler<Emitter>::visitDeclStmt(const DeclStmt *DS) {
   for (const auto *D : DS->decls()) {
     if (isa<StaticAssertDecl, TagDecl, TypedefNameDecl, BaseUsingDecl,
-            FunctionDecl, NamespaceAliasDecl>(D))
+            FunctionDecl, NamespaceAliasDecl, UsingDirectiveDecl>(D))
       continue;
 
     const auto *VD = dyn_cast<VarDecl>(D);

clang/test/AST/ByteCode/literals.cpp

@@ -1330,3 +1330,14 @@ void localConstexpr() {
   static_assert(a == 0, ""); // both-error {{not an integral constant expression}} \
                              // both-note {{initializer of 'a' is not a constant expression}}
 }
+
+namespace Foo {
+  namespace Bar {
+    constexpr int FB = 10;
+  }
+}
+constexpr int usingDirectiveDecl() {
+  using namespace Foo::Bar;
+  return FB;
+}
+static_assert(usingDirectiveDecl() == 10, "");