Add variable for dyn type (e.g. type(dyn(1)) == dyn)

PiperOrigin-RevId: 688186304

Author: jnthntatum

checker/standard_library.cc

@@ -116,6 +116,12 @@ Type TypeTimestampType() {
   return *kInstance;
 }
 
+Type TypeDynType() {
+  static absl::NoDestructor<Type> kInstance(
+      TypeType(BuiltinsArena(), DynType()));
+  return *kInstance;
+}
+
 Type TypeListType() {
   static absl::NoDestructor<Type> kInstance(
       TypeType(BuiltinsArena(), ListOfA()));
@@ -998,6 +1004,9 @@ absl::Status AddTimeFunctions(TypeCheckerBuilder& builder) {
 }
 
 absl::Status AddTypeConstantVariables(TypeCheckerBuilder& builder) {
+  CEL_RETURN_IF_ERROR(
+      builder.AddVariable(MakeVariableDecl(builtin::kDyn, TypeDynType())));
+
   CEL_RETURN_IF_ERROR(
       builder.AddVariable(MakeVariableDecl("bool", TypeBoolType())));
 

checker/standard_library_test.cc

@@ -125,13 +125,14 @@ TEST_P(StdlibTypeVarDefinitionTest, DefinesTypeConstants) {
   const auto& checked_impl = AstImpl::CastFromPublicAst(*checked_ast);
   EXPECT_THAT(checked_impl.GetReference(1),
               Pointee(Property(&Reference::name, GetParam())));
+  EXPECT_THAT(checked_impl.GetType(1), Property(&AstType::has_type, true));
 }
 
 INSTANTIATE_TEST_SUITE_P(StdlibTypeVarDefinitions, StdlibTypeVarDefinitionTest,
-                         ::testing::Values("bool", "int", "uint", "double",
-                                           "string", "bytes", "list", "map",
-                                           "duration", "timestamp", "null_type",
-                                           "type"),
+                         ::testing::Values("bool", "bytes", "double",
+                                           "duration", "dyn", "int", "list",
+                                           "map", "null_type", "string",
+                                           "timestamp", "type", "uint"),
                          [](const auto& info) -> std::string {
                            return info.param;
                          });