diff --git a/common/types/map_test.go b/common/types/map_test.go
index 19d8f8a0..6407b88d 100644
--- a/common/types/map_test.go
+++ b/common/types/map_test.go
@@ -23,15 +23,16 @@ import (
 	"github.com/google/cel-go/common/types/pb"
 	"github.com/google/cel-go/common/types/ref"
 	"github.com/google/cel-go/common/types/traits"
-	"github.com/google/cel-go/test/proto3pb"
 
 	"google.golang.org/protobuf/encoding/protojson"
 	"google.golang.org/protobuf/proto"
 
+	proto3pb "github.com/google/cel-go/test/proto3pb"
+
 	anypb "google.golang.org/protobuf/types/known/anypb"
 	structpb "google.golang.org/protobuf/types/known/structpb"
 	tpb "google.golang.org/protobuf/types/known/timestamppb"
-	"google.golang.org/protobuf/types/known/wrapperspb"
+	wrapperspb "google.golang.org/protobuf/types/known/wrapperspb"
 )
 
 type testStruct struct {
diff --git a/common/types/provider_test.go b/common/types/provider_test.go
index 95e32dc2..bd6d3de1 100644
--- a/common/types/provider_test.go
+++ b/common/types/provider_test.go
@@ -23,10 +23,11 @@ import (
 
 	"github.com/google/cel-go/common/types/ref"
 	"github.com/google/cel-go/common/types/traits"
-	"github.com/google/cel-go/test/proto3pb"
 
 	"google.golang.org/protobuf/proto"
 
+	proto3pb "github.com/google/cel-go/test/proto3pb"
+
 	exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
 	anypb "google.golang.org/protobuf/types/known/anypb"
 	structpb "google.golang.org/protobuf/types/known/structpb"
diff --git a/interpreter/prune.go b/interpreter/prune.go
index 9f7c3193..2ad522bc 100644
--- a/interpreter/prune.go
+++ b/interpreter/prune.go
@@ -22,7 +22,6 @@ import (
 
 	structpb "google.golang.org/protobuf/types/known/structpb"
 
-	expr "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
 	exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
 )
 
@@ -122,7 +121,7 @@ func (p *astPruner) maybeCreateLiteral(id int64, val ref.Val) (*exprpb.Expr, boo
 		return &exprpb.Expr{
 			Id: id,
 			ExprKind: &exprpb.Expr_ListExpr{
-				ListExpr: &expr.Expr_CreateList{
+				ListExpr: &exprpb.Expr_CreateList{
 					Elements: elemExprs,
 				},
 			},
diff --git a/parser/gen/doc.go b/parser/gen/doc.go
new file mode 100644
index 00000000..57edd443
--- /dev/null
+++ b/parser/gen/doc.go
@@ -0,0 +1,16 @@
+// Copyright 2021 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
+//
+//      http://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.
+
+// Package gen contains all of the ANTLR-generated sources used by the cel-go parser.
+package gen