Introduce cel::Expr

PiperOrigin-RevId: 627733102

common/BUILD

@@ -16,6 +16,54 @@ package(default_visibility = ["//visibility:public"])
 
 licenses(["notice"])
 
+cc_library(
+    name = "ast",
+    srcs = ["ast.cc"],
+    hdrs = ["ast.h"],
+    deps = [
+        ":constant",
+        "@com_google_absl//absl/algorithm:container",
+        "@com_google_absl//absl/base:core_headers",
+        "@com_google_absl//absl/base:no_destructor",
+        "@com_google_absl//absl/strings:string_view",
+        "@com_google_absl//absl/types:optional",
+        "@com_google_absl//absl/types:span",
+        "@com_google_absl//absl/types:variant",
+    ],
+)
+
+cc_test(
+    name = "ast_test",
+    srcs = ["ast_test.cc"],
+    deps = [
+        ":ast",
+        "//internal:testing",
+    ],
+)
+
+cc_library(
+    name = "constant",
+    srcs = ["constant.cc"],
+    hdrs = ["constant.h"],
+    deps = [
+        "@com_google_absl//absl/base:core_headers",
+        "@com_google_absl//absl/base:no_destructor",
+        "@com_google_absl//absl/strings:string_view",
+        "@com_google_absl//absl/time",
+        "@com_google_absl//absl/types:variant",
+    ],
+)
+
+cc_test(
+    name = "constant_test",
+    srcs = ["constant_test.cc"],
+    deps = [
+        ":constant",
+        "//internal:testing",
+        "@com_google_absl//absl/time",
+    ],
+)
+
 cc_library(
     name = "operators",
     srcs = [

common/ast.cc

@@ -0,0 +1,66 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "common/ast.h"
+
+#include "absl/base/no_destructor.h"
+
+namespace cel {
+
+const UnspecifiedExpr& UnspecifiedExpr::default_instance() {
+  static const absl::NoDestructor<UnspecifiedExpr> instance;
+  return *instance;
+}
+
+const IdentExpr& IdentExpr::default_instance() {
+  static const absl::NoDestructor<IdentExpr> instance;
+  return *instance;
+}
+
+const SelectExpr& SelectExpr::default_instance() {
+  static const absl::NoDestructor<SelectExpr> instance;
+  return *instance;
+}
+
+const CallExpr& CallExpr::default_instance() {
+  static const absl::NoDestructor<CallExpr> instance;
+  return *instance;
+}
+
+const ListExpr& ListExpr::default_instance() {
+  static const absl::NoDestructor<ListExpr> instance;
+  return *instance;
+}
+
+const StructExpr& StructExpr::default_instance() {
+  static const absl::NoDestructor<StructExpr> instance;
+  return *instance;
+}
+
+const MapExpr& MapExpr::default_instance() {
+  static const absl::NoDestructor<MapExpr> instance;
+  return *instance;
+}
+
+const ComprehensionExpr& ComprehensionExpr::default_instance() {
+  static const absl::NoDestructor<ComprehensionExpr> instance;
+  return *instance;
+}
+
+const Expr& Expr::default_instance() {
+  static const absl::NoDestructor<Expr> instance;
+  return *instance;
+}
+
+}  // namespace cel