This gave a weird error when you did e.g. `math Foo / 6`:
"Missing Operator" and only the "F" marked.
Adding an operator here anywhere won't help, so calling this an
"Unknown function" is closer to the truth. We also get nicer markings
because we know the extent of the identifier.
Mostly replacing std::<type>::MAX with <type>::MAX.
Surprising here is replacing
.expect(format!(...))
with
.unwrap_or_else(|_| panic!(...))
It explains that this is because the "format!" would always be called.
