Maybe PL/S, IBM's "secret weapon," (haha) would be better if we're talking C++ replacements. I did like how the language let you describe how exactly the compiler should handle the individual function. I can see that have payoff in OS and security-critical software.
Nope. But Pascal was so simple that a listing for a working subset compiler for it (written in BASIC) was published in BYTE magazine back in the 70s.
But I (and many other compiler devs) thought back in the early 80's that Ada was so complex it was unimplementable. Today that thought seems charmingly naive.
https://en.wikipedia.org/wiki/IBM_PL/S