Suboptimal error reporting of invalid argument to generic function

[Seeker14491]

The following code produces two compilation errors.

use std::fmt::Display;

fn main() {
    let _ = Vec::with_capacity("0"); // error #1

    displayer(()); // error #2
}

fn displayer<T: Display>(t: T) {
    println!("{}", t);
}

Error 1

error[E0308]: mismatched types
 --> <anon>:4:32
  |
4 |     let _ = Vec::with_capacity("0"); // error #1
  |                                ^^^ expected usize, found reference
  |
  = note: expected type `usize`
  = note:    found type `&'static str`

The first error looks great. The compiler points at the erroneous argument.

Error 2

error[E0277]: the trait bound `(): std::fmt::Display` is not satisfied
 --> <anon>:6:5
  |
6 |     displayer(()); // error #2
  |     ^^^^^^^^^ trait `(): std::fmt::Display` not satisfied
  |
  = note: `()` cannot be formatted with the default formatter; try using `:?` instead if you are using a format string
  = note: required by `displayer`

In the second error, however, the compiler points at the function instead of the erroneous argument. This is no big problem in this case, as the function only takes one argument, and the argument has a very simple type. But in more complex functions, it might be hard to figure out which argument is problematic.

[estebank]

Current output:

error[E0308]: mismatched types
 --> src/main.rs:4:32
  |
4 |     let _ = Vec::with_capacity("0"); // error #1
  |                                ^^^ expected usize, found reference
  |
  = note: expected type `usize`
             found type `&'static str`

error[E0277]: `()` doesn't implement `std::fmt::Display`
 --> src/main.rs:6:15
  |
6 |     displayer(()); // error #2
  |               ^^ `()` cannot be formatted with the default formatter
...
9 | fn displayer<T: Display>(t: T) {
  | ------------------------------ required by `displayer`
  |
  = help: the trait `std::fmt::Display` is not implemented for `()`
  = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead

Fixed in #64498.