...book has a diagram that shows implicit conversions.

It is Figure 2.3 on page...

...has a diagram that shows implicit conversions. All implicit conversions from integral types to floating...

...real'. It is described under "Usual Arithmetic Conversions" here:

  http://dlang.org/type.html

Quoting...

...typed - adding this might cause unwanted implicit conversions.

Maybe it could be pulled off with...

...code is my life.
They are trivial conversions. It could be done on the stack...

...are mostly false positives. Though I don't remember whether if was about implicit conversions.

...am I interacting with?  Unix Time <=> SysTime conversions are purely D code.

It won't...

...and none of std.conv.to's conversions will work, then you'll get an...

There are so many implicit conversions between signed and unsigned? Are they all ok?

...with UDA).
* I am required to implement conversions I have no implementation for.

This leaves...