C++
gcc HEAD 11.0.0 20200917 (experimental)
$ g++ prog.cc -Wall -Wextra -I/opt/wandbox/boost-1.73.0/gcc-head/include -std=c++2a
prog.cc:7:11: error: taking address of rvalue [-fpermissive] 7 | C * pC = &C(); // C4238 | ^~~