This point advocates against the use of mod with content in a file unless it is used for a testing module. A common pattern is to have the unit tests for a module inside the main module file. Tests in rust are just specially tagged functions. To avoid compilation costs in non-test builds and false unused code warnings you can put all test related code in a submodule and tag that module with #[cfg(test)]. That way the module will only be included and compiled if the crate is being compiled to run tests.

The Star wars thing refers to scrolling long text files similar to the intro of the starwars movies where a long text is scrolled for the viewer.

Formatters are off-topic for this, styles come first, formatters are developed later.

My other reply:

How about this one? it more closely mirrors the switch example:

match suffix {
'G' | 'g' => mem -= 30,
'M' | 'm' => mem -= 20,
'K' | 'k' => mem -= 10,
_ => {},
}

How about this other one? it goes as far as cloning the switch example's indentation:

match suffix {
'G' | 'g' => {
  mem -= 30;
       }
'M' | 'm' => {
  mem -= 20;
       }
'K' | 'k' => {
  mem -= 10;
       }
_ => {},
}

How about this one? it more closely mirrors the switch example:

match suffix {
'G' | 'g' => mem -= 30,
'M' | 'm' => mem -= 20,
'K' | 'k' => mem -= 10,
_ => {},
}

How about this other one? it goes as far as cloning the switch example's indentation:

match suffix {
'G' | 'g' => {
	mem -= 30;
        }
'M' | 'm' => {
	mem -= 20;
        }
'K' | 'k' => {
	mem -= 10;
        }
_ => {},
}

I just got some idea yesterday regarding impl blocks, ready to be my respondent?

I had a big impl block with 4 levels of indentation, so I cut the block, and replaced

impl InputList {
    //snip
}

with mod impl_inputlist; and moved the impl block to a new file, and did not indent anything inside that block.

The advantage this has over just not indenting the impl block in place, is that people will have difficulty distinguishing between what's in the block and what's outside, and that's why the impl was moved to its own exclusive file, impl_inputlist.rs

Maybe I am overstressing indentation. Ss there something wrong with my setup that prevents me from accepting 4-space indentation?

I use:

Editor: Neovide

Font: "FiraCode Nerd Font Mono:h16" (16px fonts are addicintg)

Monitor: 1366x768, 18.5 inch, 10+ years old, frankenstein-ly repaired Samsung monitor.

Distance: I sit at about 40-60 Cm from my monitor.

That leaves me with a 32x99 view of code excluding line numbers and such.

Oh, then you use and_then() or something similar.

There's also the possibility to use the guard clauses patern and do let <...> = <...> else {}.

And finally, you can always split into another function.

It's not straight rules. It depends on what makes it more readable for your case.