Allow for "forced let"

[joshop]

I'd like there to be a way to force creating a variable even if it would conflict/overwrite a previously defined unit, or even just "kill" an existing unit definition so it can be overwritten. For example, the Minecraft mod GregTech has a simplified system of electric energy distribution with units of "amps" and "volts" that use the real world symbols, but do not actually correspond to the real world units. I'm making a numbat module for working with this game's mechanics and would like to be able to redefine the existing A and V to refer to those units. Also, the game has a unit of volume called the "bucket", denoted B - this would conflict with the builtin unit of byte, but units of information are simply not relevant in the calculations this module is designed for, so overwriting it wouldn't lose any functionality. Is the only way to accomplish this by simply not including the prelude, and redefining necessary units as I see fit?

[sharkdp]

Thank you for your feedback!

I'd like there to be a way to force creating a variable even if it would conflict/overwrite a previously defined unit, or even just "kill" an existing unit definition so it can be overwritten.

We definitely want to implement something like this. Please see #293 and #86 for previous discussions.

For example, the Minecraft mod GregTech has a simplified system of electric energy distribution with units of "amps" and "volts" that use the real world symbols, but do not actually correspond to the real world units. I'm making a numbat module for working with this game's mechanics [...]

Awesome 😍. Great to see someone playing with custom unit systems. I hope we can cover your use case even better in the future.

Is the only way to accomplish this by simply not including the prelude, and redefining necessary units as I see fit?

For now, if you really want to use A, V and B, I'm afraid this is the only way. The prelude is modular, so you might be able to include some existing modules in your own prelude (like the ones in core)... but I have never really played with this and I'm afraid that this approach is a bit limited (as a lot of things depend on units::si. Even if we don't have overwritable units, we might be able to implement something like #55 — which might also help in some of these cases.