Compiler suggests using the removed placement syntax

[mickethespike]

So I'm writing a hangman app in Rust and I get this weird error message. It doesn't make sense since <- isn't even in Rust anymore.

error: expected `{`, found `in`
  --> src/main.rs:8:17
   |
8  |           if line in words {
   |  _________________-^
9  | |             println!("Success");
10 | |         } else {
   | |_________- help: try placing this code inside a block: `{ words <- { println!("Success"); }; }`

error: aborting due to previous error

error: Could not compile `hangman`.

[kennytm]

Could we just stop parsing in «expr» «block» as an ObsoleteInPlace expression? Will it break any macros or code behind #[cfg]?

[pietroalbini]

Yeah #50832.

[kennytm]

#50832 was about x <- y though

[aidanhs]

I think the same issue applies though - the parser still needs to be able to recognise the code as something. So if there are crates using that syntax, they'll break in the same way.

[estebank]

Current output:

error: expected `{`, found `in`
 --> src/main.rs:2:10
  |
2 |       if i in 0..10 {
  |       --   -^
  |  _____|____|
  | |     |
  | |     this `if` statement has a condition, but no block
3 | |         break;
4 | |     }
  | |_____- help: try placing this code inside a block: `{ (0..10) <- { break ; }; }`

Still need to remove the suggestion, but otherwise the error would seem reasonable:

error: expected `{`, found `in`
 --> src/main.rs:2:10
  |
2 |     if i in 0..10 {
  |     --   ^^ expected `{`
  |     |
  |     this `if` statement has a condition, but no block

[PramodBisht]

@estebank should this be done only for in keyword or you also have other statements in mind.

[estebank]

@PramodBisht I believe that in and type ascription (:) are the only two that regularly cause problems with this kind of errors.