Problem:    Vim9: error for not using string doesn't mention argument.
Solution:   Add argument number.
https://github.com/vim/vim/commit/f28f2ac425600b88da0bdcc12a82cd620f575681

vim-patch:9.0.0341: mapset() does not restore <Nop> mapping properly

Problem:    mapset() does not restore <Nop> mapping properly.
Solution:   Use an empty string for <Nop>. (closes vim/vim#11022)
https://github.com/vim/vim/commit/92a3d20682d46359bb50a452b4f831659e799155

`!did_throw` doesn't exactly imply `!current_exception`, as `did_throw = false`
is sometimes used to defer exception handling for later (without forgetting the
exception). E.g: uncaught exception handling in `do_cmdline()` may be deferred
to a different call (e.g: when `try_level > 0`).

In #7881, `current_exception = NULL` in `do_cmdline()` is used as an analogue of
`did_throw = false`, but also causes the pending exception to be lost, which
also leaks as `discard_exception()` wasn't used.

It may be possible to fix this by saving/restoring `current_exception`, but
handling all of `did_throw`'s edge cases seems messier. Maybe not worth
diverging over.

This fix also uncovers a `man_spec.lua` bug on Windows: exceptions are thrown
due to Windows missing `man`, but they're lost; skip these tests if `man` isn't
executable.

Problem:    Several errors are not tested for.
Solution:   Add tests. (Yegappan Lakshmanan, closes vim/vim#5892)
https://github.com/vim/vim/commit/ee4e0c1e9a81cb5d96e0060203a9033c2f28588e

Omit Test_range() change: reverted in patch 8.2.0615.
Cherry-pick Test_z_no_space_before_xxx() from patch 8.2.0195.
Cherry-pick Test_reverse_sort_uniq() change from patch 8.2.0183.
Make uniq() error behavior consistent with sort().
Cherry-pick Test_set_ttytype() change from patch 8.1.1826.
Cherry-pick quickfix checks from patch 8.1.2373 to test_preview.vim.
Test_viminfo_error() is applicable.
Cherry-pick E1058 from patch 8.2.0149 and port Test_deep_nest() to Lua.

Problem:    confirm() is not tested.
Solution:   Add a test. (Dominique Pelle, closes vim/vim#3868)
https://github.com/vim/vim/commit/2e0500921891e4fec57e97d3c0021aa2d2b4d7ae

Problem:    Peeking and flushing output slows down execution.
Solution:   Do not update the mode message when global_busy is set.  Do not
            flush when only peeking for a character. (Ken Takata)
https://github.com/vim/vim/commit/cb574f415486adff645ce384979bfecf27f5be8c

Omit inchar() change: it breaks too many tests.

N/A patches for version.c:

vim-patch:8.2.5170: tiny issues

Problem:    Tiny issues.
Solution:   Tiny improvements.
https://github.com/vim/vim/commit/944cc9ceba8868acd238264d4a3894803c566b37

Problem:    This doesn't give the right result: eval(string(v:true)). (Nikolay
            Pavlov)
Solution:   Make the string "v:true" instead of "true".
https://github.com/vim/vim/commit/f48aa160fdd7b8caa7678e1a2139244dd2bdc547

Test ":unlet self-referencing node in a List graph #6070" feeds many characters into typeahead, so a timeout of only 100 milliseconds sometimes fails. Change that timeout to 1000 milliseconds.

Problem:    maparg() does not provide enough information for mapset().
Solution:   Add "lhsraw" and "lhsrawalt" items.  Drop "simplified"
https://github.com/vim/vim/commit/9c65253fe702ea010afec11aa971acd542c35de2

vim-patch:9.0.0127: unused variable

Problem:    Unused variable.
Solution:   Remove the variable. (closes vim/vim#10829)
https://github.com/vim/vim/commit/e95f22f63a1871b91e5508088e5ae4905ce28cd7