Update docs on IO methods (#1070)

cel/io.go

@@ -102,12 +102,14 @@ func AstToString(a *Ast) (string, error) {
 	return parser.Unparse(a.impl.Expr(), a.impl.SourceInfo())
 }
 
-// RefValueToValue converts between ref.Val and api.expr.Value.
+// RefValueToValue converts between ref.Val and google.api.expr.v1alpha1.Value.
 // The result Value is the serialized proto form. The ref.Val must not be error or unknown.
 func RefValueToValue(res ref.Val) (*exprpb.Value, error) {
 	return ValueAsAlphaProto(res)
 }
 
+// ValueAsAlphaProto converts between ref.Val and google.api.expr.v1alpha1.Value.
+// The result Value is the serialized proto form. The ref.Val must not be error or unknown.
 func ValueAsAlphaProto(res ref.Val) (*exprpb.Value, error) {
 	canonical, err := ValueAsProto(res)
 	if err != nil {
@@ -118,6 +120,8 @@ func ValueAsAlphaProto(res ref.Val) (*exprpb.Value, error) {
 	return alpha, err
 }
 
+// ValueAsProto converts between ref.Val and cel.expr.Value.
+// The result Value is the serialized proto form. The ref.Val must not be error or unknown.
 func ValueAsProto(res ref.Val) (*celpb.Value, error) {
 	switch res.Type() {
 	case types.BoolType:
@@ -205,11 +209,12 @@ var (
 	anyPbType = reflect.TypeOf(&anypb.Any{})
 )
 
-// ValueToRefValue converts between exprpb.Value and ref.Val.
+// ValueToRefValue converts between google.api.expr.v1alpha1.Value and ref.Val.
 func ValueToRefValue(adapter types.Adapter, v *exprpb.Value) (ref.Val, error) {
 	return AlphaProtoAsValue(adapter, v)
 }
 
+// AlphaProtoAsValue converts between google.api.expr.v1alpha1.Value and ref.Val.
 func AlphaProtoAsValue(adapter types.Adapter, v *exprpb.Value) (ref.Val, error) {
 	canonical := &celpb.Value{}
 	if err := convertProto(v, canonical); err != nil {
@@ -218,6 +223,7 @@ func AlphaProtoAsValue(adapter types.Adapter, v *exprpb.Value) (ref.Val, error)
 	return ProtoAsValue(adapter, canonical)
 }
 
+// ProtoAsValue converts between cel.expr.Value and ref.Val.
 func ProtoAsValue(adapter types.Adapter, v *celpb.Value) (ref.Val, error) {
 	switch v.Kind.(type) {
 	case *celpb.Value_NullValue: