These don't do short-circuit evaluation, and so I ran into some
some very subtle side-effects when converting code to DistinctNumeric.
In code like this:
MyDistinctNumeric n;
if (n && check_thing(n))
return;
There would be no short-circuit evaluation if the return type of
check_thing() was implicitly convertible to MyDistinctNumeric.
Ran into this while making Ext2FS::GroupIndex a DistinctNumeric.
Problem:
- `typedef` is a keyword which comes from C and carries with it old
syntax that is hard to read.
- Creating type aliases with the `using` keyword allows for easier
future maintenance because it supports template syntax.
- There is inconsistent use of `typedef` vs `using`.
Solution:
- Use `clang-tidy`'s checker called `modernize-use-using` to update
the syntax to use the newer syntax.
- Remove unused functions to make `clang-tidy` happy.
- This results in consistency within the codebase.
This template class allows for easy generation of incompatible numeric types.
This is useful whenever code has to handle heterogenous data (like meters and
seconds) but the underlying data types are compatible (like int and int).
The motivation comes from the Kernel's inconsistent use of pid_t for process and
thread IDs even though the ID spaces are incompatible, and translating forth/back
is nontrivial.
Other uses could be units (as described above), or incompatible index systems.
A popular use in real life is image manipulation, when there are multiple
coordinate systems.
