Infinite precision intermediate arithmetic: how much would break?

chrefr:

C has shown that promotion rules are deeply unintuitive and confusing

C has shown that C's promotion rules are confusing.

C is uniquely bad at this with footguns like mixing ints and floats causing silent truncation, vaguely defined platform-specific sizes, changing unsigned to signed with potential UB on top. These are unforced errors that C has, but aren't inherent to the problem space.

I don't support the particular proposal in this thread, but I want to push back against using C as an example, because it leads to wrong conclusions.

Similarly, C++ has shown that references are dangerous, closures are full of footguns, smart pointers have unavoidable overheads, and yet we have robust versions of these things in Rust.