Rust: error: expected one of `{` or an operator, found `}`

[glandium]

I did a stupid typo in a program, where I typed in twice in a for statement:

fn main() {
    for i in in 1..2 {
        println!("{}", i);
    }
}

The compiler pointed the error on the closing brace, which, in the real code, with much more things happening in the loop (plus nested loops) was completely unhelpful.

error: expected one of `{` or an operator, found `}`
 --> <anon>:5:1
  |
5 | }
  | ^

error: aborting due to previous error

[TimNN]

Fixing the errors reported by the compiler reveals why this parses that far:

fn main() {
    for i in in 1..2 {
        println!("{}", i);
    }
{ } }

error: placement-in expression syntax is experimental and subject to change. (see issue #27779)
 --> <anon>:2:14
  |
2 |     for i in in 1..2 {
  |              ^

[estebank]

Current output points at the char immediately after the closing of the for scope, still needs some improvement:

error: expected one of `{` or an operator, found `}`
 --> src/main.rs:5:1
  |
4 |     }
  |      - expected one of `{` or an operator here
5 | }
  | ^ unexpected token

[estebank]

Closed by #48333:

error: expected expression, found keyword `in`
 --> src/main.rs:2:14
  |
2 |     for i in in 1..2 {
  |              ^^ expected expression

---

That PR was reverted :(

[cczufish]

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=81c748636e6aab123c5592ffc1df8436

use std::collections::HashMap;

fn main() {
    let vec:Vec<i32> = vec![2,2,1];
    single_number(vec);
}

fn single_number(nums: Vec<i32>) -> i32 {
    let mut result = HashMap::new();

    for v in vec! {
       // 类型转换
       let str_key = v.to_string();
       //插入之前先判断,当前的key对应的value有值则加1，没值初始化为1
       if result.get(&str_key) == None {
        result.insert(str_key,1);
       }else{
            let str_key1 = v.to_string();
            let _strValue = result.get(&str_key1);

            let value = _strValue.unwrap();
            result.insert(str_key,value + 1);

       }
    }


   // 遍历result

    let mut resultK = 0;
    for (k,v) in &result {
        println!("{},{}",k,v);
        let value = *v as i32;
        if value == 1
        {
          resultK = k.parse::<i32>().unwrap();;
        }
    }
    resultK
}

 Compiling playground v0.0.1 (/playground)
error: expected one of `.`, `?`, `{`, or an operator, found `let`
  --> src/main.rs:30:5
   |
25 |     }
   |      - expected one of `.`, `?`, `{`, or an operator here
...
30 |     let mut resultK = 0;
   |     ^^^ unexpected token

error: aborting due to previous error

error: Could not compile `playground`.

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