Unhelpful error message not pointing to the issue

[xNxExOx]

Code

struct MyStruct {
    foo: String
}

fn ok() -> MyStruct {
    MyStruct {
        foo: std::env::temp_dir().join("something").to_str().unwrap().to_string()
    }
}

fn bad_refactor() -> MyStruct {
    let foo: std::env::temp_dir().join("something").to_str().unwrap().to_string();
    MyStruct {
        foo
    }
}

Current output

error: expected one of `!`, `+`, `->`, `::`, `;`, or `=`, found `.`
  --> src/main.rs:14:34
   |
12 |     let foo: std::env::temp_dir().join("something").to_str().unwrap().to_string();
   |                                  ^ expected one of `!`, `+`, `->`, `::`, `;`, or `=`

Desired output

error: did you mean `=` instead of `:`?
  --> src/main.rs:14:34
   |
12 |     let foo: std::env::temp_dir().join("something").to_str().unwrap().to_string();
   |            ^ did you mean `=` instead of `:`?

OR
error: expected type, found function `expresion`
  --> src/main.rs:14:34
   |
12 |     let foo: std::env::temp_dir().join("something").to_str().unwrap().to_string();
   |            --^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a type
   |            |
   |            help: use `=` if you meant to assign

Rationale and extra context

I was just been asked about this in not too much complicated code, and we was both thinking, why join does not work, if there needs to be some use ... to bring it to the scope.

When I tried to write the simplified example I got much better error. (help: use `=` if you meant to assign)

Other cases

fn ok2() -> MyStruct {
    MyStruct {
        foo: some_fn()
    }
}

fn bad_refactor2() -> MyStruct {
    let foo: some_fn();
    MyStruct {
        foo
    }
}

fn some_fn() -> String {
    "".into()
}

// produces:
error[E0573]: expected type, found function `some_fn`
  --> src/main.rs:25:14
   |
25 |     let foo: some_fn();
   |            --^^^^^^^^^ not a type
   |            |
   |            help: use `=` if you meant to assign

Anything else?

No response

[jieyouxu]

@rustbot label +A-parser +D-newcomer-roadblock -needs-triage