Either the documentation or the signature of gtk_tree_view_set_tooltip_cell() is wrong. It takes a GtkCellRenderer* but the documentation says that it must be a GtkCellRendererText*.

/**
 * gtk_tree_view_set_tooltip_cell:
 * @tree_view: a #GtkTreeView
 * @tooltip: a #GtkTooltip
 * @path: a #GtkTreePath or %NULL
 * @column: a #GtkTreeViewColumn or %NULL
 * @cell: a #GtkCellRendererText or %NULL
 *
 * Sets the tip area of @tooltip to the area @path, @column and @cell have
 * in common.  For example if @path is %NULL and @column is set, the tip
 * area will be set to the full area covered by @column.  See also
 * gtk_tooltip_set_tip_area().
 *
 * Since: 2.12
 */
void
gtk_tree_view_set_tooltip_cell (GtkTreeView       *tree_view,
				GtkTooltip        *tooltip,
				GtkTreePath       *path,
				GtkTreeViewColumn *column,
				GtkCellRenderer   *cell)