AlterColumn(dst interface{}, field string) error
	MigrateColumn(dst interface{}, field *schema.Field, columnType ColumnType) error
	// MigrateColumnUnique migrate column's UNIQUE constraint, it's part of MigrateColumn.
	MigrateColumnUnique(dst interface{}, field *schema.Field, columnType ColumnType) error
	HasColumn(dst interface{}, field string) bool
	RenameColumn(dst interface{}, oldName, field string) error

// Calling [Reader.UnreadByte] after ReadLine will always unread the last byte read
// (possibly a character belonging to the line end) even if that byte is not
// part of the line returned by ReadLine.
func (b *Reader) ReadLine() (line []byte, isPrefix bool, err error) {
	line, err = b.ReadSlice('\n')
	if err == ErrBufferFull {
		// Handle the case where "\r\n" straddles the buffer.

		b.WriteString("abc")
		tw.check(t, "", "")
		b.WriteString("123456789012345")      // long string, non-empty buffer
		tw.check(t, "abc12345", "6789012345") // use Write and then WriteString since the remaining part is still longer than BufSize
	}
	{
		tw := &teststringwriter{}
		b := NewWriterSize(tw, BufSize)
		b.Write([]byte("abc")) // same as above, but use Write instead of WriteString
		tw.check(t, "", "")