How about adding a few more names from the std namespace to get appropriate hints? This patch compiles and the appropriate messages are printed. Is there a problem with just adding more or even at some point all the symbols of the standard library?
gcc/ChangeLog:
* cp/name-lookup.cc (get_std_name_hint): Add more symbols from the
<iomanip>, <ios>, <istream> and <ostream> headers.
d-g++-std-io-syms-hints
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