Fixes for google import. (#1102)

- Go lint findings
- Use generic proto interface to simplify proto deps in conformance
  test.

common/types/err.go

@@ -62,7 +62,7 @@ func NewErr(format string, args ...any) ref.Val {
 	return &Err{error: fmt.Errorf(format, args...)}
 }
 
-// NewErr creates a new Err with the provided message.
+// NewErrFromString creates a new Err with the provided message.
 // TODO: Audit the use of this function and standardize the error messages and codes.
 func NewErrFromString(message string) ref.Val {
 	return &Err{error: errors.New(message)}

conformance/BUILD.bazel

@@ -82,6 +82,7 @@ go_test(
         "@io_bazel_rules_go//go/runfiles",
         "@org_golang_google_genproto_googleapis_api//expr/v1alpha1:go_default_library",
         "@org_golang_google_protobuf//encoding/prototext:go_default_library",
+        "@org_golang_google_protobuf//proto:go_default_library",
         "@org_golang_google_protobuf//testing/protocmp:go_default_library",
     ],
 )

conformance/conformance_test.go

@@ -20,6 +20,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 
 	"google.golang.org/protobuf/encoding/prototext"
+	"google.golang.org/protobuf/proto"
 	"google.golang.org/protobuf/testing/protocmp"
 
 	valuepb "cel.dev/expr"
@@ -168,7 +169,7 @@ func exprValueToRefValue(adapter types.Adapter, ev *valuepb.ExprValue) (ref.Val,
 	return nil, errors.New("unknown ExprValue kind")
 }
 
-func diffType(want *valuepb.Type, t *cel.Type) (string, error) {
+func diffType(want proto.Message, t *cel.Type) (string, error) {
 	got, err := types.TypeToProto(t)
 	if err != nil {
 		return "", err

parser/parser.go

@@ -167,7 +167,7 @@ func (p *parser) normalizeIdent(ctx gen.IEscapeIdentContext) (string, error) {
 		}
 		return unescapeIdent(ident.GetId().GetText())
 	}
-	return "", errors.New("Unsupported ident kind.")
+	return "", errors.New("unsupported ident kind")
 }
 
 // Parse converts a source input a parsed expression.