Warning for explicit norange ( uInt..0 )

[NimonSour]

The issue I'd like to address was discussed and closed ten years ago in #9555.
I wonder how many people have come across it.

I see the point, I understand the benefits of having this particular behaviour!

However, the fact that there isn't any algorithm still, stating that Rust's range is different from ranges in other languages makes me raise this matter again.

My proposition is to include a warning, for expicit norage ( uInt..0 ) so a for i in uInt..0 {} may triger:

Warning: Unused block of code
or
Note: Rust range (start..end) if and only start < end
or
Help: If you meant to iter over revers range use (0..uInt).rev()

anything but silence really!

It looks like something unimportant but silencing an explicit dead block of code it is not what's expected from an environment
which casually warns about unused variables, this is not why we love Rust so much:

[chenyukang]

worked a draft version:

warning: this range is empty, so the loop body will never run
 --> ./p/range.rs:2:15
  |
2 |     for _i in 10..0 {
  |               ^^^^^ - the iterator loop block starts here
3 |         println!("Hello, World!");
4 |     }
  |      - the iterator loop block ends here
  |
  = note: `#[warn(iter_empty_range)]` on by default
help: you may want to use `.rev()` to reverse the iterator
  |
2 |     for _i in (0..10).rev() {
  |               ++++++++++++

warning: 1 warning emitted

seems it's too limited if we only report for literals.

[compiler-errors]

@chenyukang you should probably just uplift clippy::reversed_empty_ranges instead of rewriting the lint yourself.

[chenyukang]

@chenyukang you should probably just uplift clippy::reversed_empty_ranges instead of rewriting the lint yourself.

thanks for the tip! @compiler-errors

@NimonSour I think the current reversed_empty_ranges is enough for reporting this kind of issues?
the output is:

error: this range is empty so it will yield no values
  --> src/main.rs:10:15
   |
10 |     for _i in 10..0 {
   |               ^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#reversed_empty_ranges
   = note: `#[deny(clippy::reversed_empty_ranges)]` on by default
help: consider using the following if you are attempting to iterate over this range in reverse
   |
10 |     for _i in (0..10).rev() {
   |               ~~~~~~~~~~~~~