Check more carefully for cases where a rename can't be done

Attempting to rename an element of a tuple field would previously
replace the type with the new name, which doesn't make sense; now it
fails instead.

The check is done in both `prepare_rename` and `rename` so that the case
is caught before the user is prompted for a new name. Some other
existing failure cases are also now additionally checked in
`prepare_rename`.

0 files changed, 0 insertions, 0 deletions