User is editing his spreadsheet, in which he enters some cells, which contain
numbers at beginning, but also another symbols inside, for example "-". You can
imagine telephone numbers or so (555-55-5555).

He sets the format of these cells to be "text".

Then he formats other cells as "number" and writes some numbers into them. If
they match initial sequence of previously entered cells, the strings are
autocompleted even using strings from text cells.

There is a question: should autocomplete function insert strings to "number"
cells even in the case, that these strings originate in "text" cells? It may
annoy and/or lead to unexpected results in target cell..

Target cell type is unaffected (stays "number") which is correct IMO, because
user has chosen it and program should respect that.