Cannot infer type in test from section 12.4 of rust book v2

[ghost]

Hello everyone!
I'm learning Rust now using this book and faced strange(as for me) error on section 12.4 when running tests.

You can reproduce a bug with next snippet of code

pub fn search<'a> (q: &str, text: &'a str) -> Vec<&'a str> {
    text.lines().filter(|line| line.contains(q)).collect()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_should_compile_but_it_doesnt () {
        let q = "queryABCD";
        let t = "text with query";
        assert_eq!( vec![], search(q, t) );
    }
}

// error[E0282]: type annotations needed
//   --> src/lib.rs:13:21
//    |
// 13 |         assert_eq!( vec![], search(q, t) );
//    |                     ^^^^^^ cannot infer type for `T`
//    |
//    = note: this error originates in a macro outside of the current crate

However, it's fairly obvious that compiler knows the type annotation that must be infered from vec![] macro. Next snippet makes it clear

pub fn search<'a> (q: &str, text: &'a str) -> Vec<&'a str> {
    text.lines().filter(|line| line.contains(q)).collect()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_should_compile_but_it_doesnt () {
        let q = "queryABCD";
        let t = "text with query";
        assert_eq!( 333, search(q, t) );
    }
}

// error[E0277]: the trait bound `{integer}: std::cmp::PartialEq<std::vec::Vec<&str>>` is not satisfied
//   --> src/lib.rs:13:9
//    |
// 13 |         assert_eq!( 333, search(q, t) );
//    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't compare `{integer}` with `std::vec::Vec<&str>`
//    |
//    = help: the trait `std::cmp::PartialEq<std::vec::Vec<&str>>` is not implemented for `{integer}`
//    = note: this error originates in a macro outside of the current crate

I think it's a bug but not sure since I'm novice in rust. I tried different toolchains, specifically 1.16, 1.18, 1.20(stable) and nightly and got the same result.

[TimNN]

I think this is expected behaviour, but maybe the error could be better.

The problem is that while the compiler knows that you want to compare something to Vec<&str>, it doesn't know what exactly: You can, for example, compare both a Vec<String> and Vec<&str>.

[ghost]

Thanks for your reply, I got the idea. Should I file a bug elsewhere for documentation team to fix their code in problematic section?

[estebank]

Current output

error[E0282]: type annotations needed
  --> src/lib.rs:13:21
   |
13 |         assert_eq!( vec![], search(q, t) );
   |                     ^^^^^^ cannot infer type of the type parameter `T` declared on the struct `Vec`
   |
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0283]: type annotations needed
  --> src/lib.rs:13:21
   |
13 |         assert_eq!( vec![], search(q, t) );
   |         ------------^^^^^^----------------
   |         |           |
   |         |           cannot infer type of the type parameter `T` declared on the struct `Vec`
   |         type must be known at this point
   |
   = note: multiple `impl`s satisfying `_: PartialEq<&str>` found in the following crates: `alloc`, `core`, `std`:
           - impl<'a, 'b> PartialEq<&'a str> for String;
           - impl<'a, 'b> PartialEq<&'b str> for Cow<'a, str>;
           - impl<> PartialEq<&str> for OsString;
           - impl<A, B> PartialEq<&B> for &A
             where A: PartialEq<B>, A: ?Sized, B: ?Sized;
           - impl<A, B> PartialEq<&B> for &mut A
             where A: PartialEq<B>, A: ?Sized, B: ?Sized;
   = note: required for `Vec<_>` to implement `PartialEq<Vec<&str>>`
   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)