Support nil pointers to value implementing driver.Valuer

fixes #339

query_test.go

@@ -9,6 +9,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/cockroachdb/apd"
 	"github.com/jackc/pgx"
 	"github.com/jackc/pgx/pgtype"
 	satori "github.com/jackc/pgx/pgtype/ext/satori-uuid"
@@ -1001,6 +1002,27 @@ func TestConnQueryDatabaseSQLDriverValuer(t *testing.T) {
 	ensureConnValid(t, conn)
 }
 
+// https://github.com/jackc/pgx/issues/339
+func TestConnQueryDatabaseSQLDriverValuerWithAutoGeneratedPointerReceiver(t *testing.T) {
+	t.Parallel()
+
+	conn := mustConnect(t, *defaultConnConfig)
+	defer closeConn(t, conn)
+
+	mustExec(t, conn, "create temporary table t(n numeric)")
+
+	var d *apd.Decimal
+	commandTag, err := conn.Exec(`insert into t(n) values($1)`, d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if commandTag != "INSERT 0 1" {
+		t.Fatalf("want %s, got %s", "INSERT 0 1", commandTag)
+	}
+
+	ensureConnValid(t, conn)
+}
+
 func TestConnQueryDatabaseSQLDriverValuerWithBinaryPgTypeThatAcceptsSameType(t *testing.T) {
 	t.Parallel()