Convert driver.Valuer's earlier in bind path

fixes #449

messages.go

@@ -1,6 +1,7 @@
 package pgx
 
 import (
+	"database/sql/driver"
 	"math"
 	"reflect"
 	"time"
@@ -162,6 +163,12 @@ func appendBind(
 	buf = append(buf, preparedStatement...)
 	buf = append(buf, 0)
 
+	var err error
+	arguments, err = convertDriverValuers(arguments)
+	if err != nil {
+		return nil, err
+	}
+
 	buf = pgio.AppendInt16(buf, int16(len(parameterOIDs)))
 	for i, oid := range parameterOIDs {
 		buf = pgio.AppendInt16(buf, chooseParameterFormatCode(connInfo, oid, arguments[i]))
@@ -185,6 +192,22 @@ func appendBind(
 	return buf, nil
 }
 
+func convertDriverValuers(args []interface{}) ([]interface{}, error) {
+	for i, arg := range args {
+		switch arg := arg.(type) {
+		case pgtype.BinaryEncoder:
+		case pgtype.TextEncoder:
+		case driver.Valuer:
+			v, err := callValuerValue(arg)
+			if err != nil {
+				return nil, err
+			}
+			args[i] = v
+		}
+	}
+	return args, nil
+}
+
 // appendExecute appends a PostgreSQL wire protocol execute message to buf and returns it.
 func appendExecute(buf []byte, portal string, maxRows uint32) []byte {
 	buf = append(buf, 'E')

values.go

@@ -200,14 +200,6 @@ func encodePreparedStatementArgument(ci *pgtype.ConnInfo, buf []byte, oid pgtype
 		return buf, nil
 	}
 
-	if arg, ok := arg.(driver.Valuer); ok {
-		v, err := callValuerValue(arg)
-		if err != nil {
-			return nil, err
-		}
-		return encodePreparedStatementArgument(ci, buf, oid, v)
-	}
-
 	if strippedArg, ok := stripNamedType(&refVal); ok {
 		return encodePreparedStatementArgument(ci, buf, oid, strippedArg)
 	}
@@ -227,16 +219,6 @@ func chooseParameterFormatCode(ci *pgtype.ConnInfo, oid pgtype.OID, arg interfac
 
 	if dt, ok := ci.DataTypeForOID(oid); ok {
 		if _, ok := dt.Value.(pgtype.BinaryEncoder); ok {
-			if arg, ok := arg.(driver.Valuer); ok {
-				if err := dt.Value.Set(arg); err != nil {
-					if value, err := callValuerValue(arg); err == nil {
-						if _, ok := value.(string); ok {
-							return TextFormatCode
-						}
-					}
-				}
-			}
-
 			return BinaryFormatCode
 		}
 	}