Dynamic precision for `nested_formatter` does not work

[tobiasleibner]

When changing the struct Point example explaining nested_formatter-usage in the API reference to use dynamic precision, execution fails with an error

Execution build compiler returned: 0
Program returned: 139
terminate called after throwing an instance of 'fmt::v10::format_error'
  what():  precision is not integer
Program terminated with signal: SIGSEGV

Reproducer on godbolt: https://godbolt.org/z/srYqdvnEb

[vitaut]

Thanks for reporting. The problem is that the wrong format context is being used in the nested format call. We'll need to tweak the API a bit to synchronize contexts.

[IRainman]

Well, it may be related with #4734

[barry3406]

can repro — nested_formatter's inner formatter stores the precision arg_ref during parse, but when format runs the arg lookup happens against the inner format_to's context (which only has the nested_view args), so the original precision index can't be resolved. opening a pr.