rewriter: allow setting values regardless of the previous type #14656

Job	Run time
Arch Linux	16m 14s
CUDA (on Arch)	6m 2s
Arch / PyPy	19m 20s
Fedora	20m 34s
Ubuntu Rolling (gcc, g++)	18m 5s
OpenSUSE	14m 42s
Ubuntu Rolling (--unity=on -Ddefault_library=static, --no-unittests, gcc, g++)	10m 44s
Ubuntu Bionic	15m 39s
Ubuntu Rolling (-Ddefault_library=both, --no-unittests, gcc, g++)	10m 56s
Ubuntu Rolling (clang, clang++)	18m 31s
Ubuntu Rolling (--unity=on, --no-unittests, clang, clang++)	12m 49s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, 0, gcc, g++)	10m 53s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, --unity=on, gcc, g++)	10m 22s
	3h 4m 51s

Provide feedback