fix promise& generator operator= #102

Job	Run time
posix-cmake-subdir (ubuntu-22.04, OFF)	34s
posix (gcc-11, 2a, ubuntu-22.04)	3m 34s
posix-cmake-install (ubuntu-22.04, OFF)	39s
posix-cmake-subdir (ubuntu-22.04, ON)	54s
posix-cmake-test (ubuntu-22.04, OFF)	3m 56s
posix-cmake-install (ubuntu-22.04, ON)	51s
posix (gcc-12, 20,2b, ubuntu-22.04, g++-12)	7m 32s
posix-cmake-subdir (macos-13, OFF)	1m 30s
posix-cmake-test (ubuntu-22.04, ON)	3m 18s
posix-cmake-install (macos-13, OFF)	1m 29s
posix (gcc-13, 20,2b, ubuntu-latest, ubuntu:23.04, g++-13)	7m 2s
posix-cmake-test (macos-13, OFF)	2m 12s
posix-cmake-subdir (macos-13, ON)	1m 29s
posix-cmake-install (macos-13, ON)	1m 27s
posix-cmake-test (macos-13, ON)	1m 54s
posix (clang, clang++-14, 20,2b, libc++, ubuntu-22.04, clang-14 libc++-14-dev)	6m 54s
posix (clang, 20,2b, macos-13, libc++)	5m 59s
windows (msvc-14.3, 20,latest, 32,64, windows-2022)	17m 16s
windows-cmake-install (windows-2022, OFF)	2m 42s
windows (gcc, 2a, 64, windows-2019)	1m 29s
windows-cmake-install (windows-2022, ON)	2m 26s
windows-cmake-subdir (windows-2022, OFF)	2m 3s
windows-cmake-test (windows-2022, OFF)	7m 10s
windows-cmake-test (windows-2022, ON)	7m 21s
	1h 31m 41s

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