unhelpful "expected item" error when putting let binding outside of function

[matthiaskrgr]

let s = String::new();

fn main()  {
    println!("Hello world");
}

   Compiling playground v0.0.1 (/playground)
error: expected item, found keyword `let`
 --> src/main.rs:1:1
  |
1 | let s = String::new();
  | ^^^ expected item

Could we have some suggestions what kind of item should be put there? :)
Also there seems to be no error code which is strange..

rustc 1.37.0-nightly (02564de47 2019-06-10)

[matthiaskrgr]

@rustbot modify labels: A-diagnostics

[estebank]

Also there seems to be no error code which is strange

This is a parser error and those rarely have codes because the surface of things that could have gone wrong is much larger.

[matthiaskrgr]

Since it works with const instead of let, maybe we could suggest this?

[merriam]

I am a newcommer to Rust and have a similar issue. In my case, the code is:

/ Why does uncommenting the below item give "error: expected item, found `[`?"
// [#should_panic]
fn test_bad_card() {
    let a = to_card(&"Ten of Spades");
}

The problem with the error message is probably the word 'item'. Is this expected 'function, struct, or enum item' or 'top level item' or is there some other term?

Also, if you spot my error, let me know ;)

[dawnofmidnight]

Since it works with const instead of let, maybe we could suggest this?

The compiler now suggests this (although only for immutable bindings):

error: expected item, found keyword `let`
 --> src/lib.rs:1:1
  |
1 | let s = String::new();
  | ^^^ consider using `const` or `static` instead of `let` for global variables