Profoundly unhelpful compiler error message when "mod" accidentally used as "%"

[mcolinj]

error: Could not compile `leap`.
warning: build failed, waiting for other jobs to finish...
error[E0308]: mismatched types
 --> src/lib.rs:1:40
  |
1 |   pub fn is_leap_year(year: i32) -> bool {
  |  ________________________________________^
2 | |     if year mod 4 == 0 {
3 | |         true
4 | |     } else {
5 | |         false
6 | |     }
7 | | }
  | |_^ expected bool, found ()
  |
  = note: expected type `bool`
             found type `()`

error: aborting due to 2 previous errors

error: Could not compile `leap`.

[scottmcm]

Note that it also gives this as the first error:

error: expected `{`, found `mod`
 --> src/main.rs:2:13
  |
2 |     if year mod 4 == 0 {
  |             ^^^

[mcolinj]

Yes, thanks. I see that now that I've reproduced it. That first error scrolled off the screen so I did not see it! I'm a newbie at Rust Belt Rust today and my workshop instructor suggest I file this PR after seeing it. Not sure if it is reasonable to response to the "mod" command so out of place.

[scottmcm]

Thanks for filing! There's definitely opportunity for improvement here -- perhaps type errors should never be shown for methods whose bodies failed to parse, or something.

[estebank]

@fixed in #46732. The compiler now only complains about mod and won't try to type check blocks that have had parse errors:

error: expected `{`, found `mod`
 --> src/main.rs:2:13
  |
2 |     if year mod 4 == 0 {
  |             ^^^

error: aborting due to previous error