Confusing error message for misplaced lifetime annotation in reference

[Storyyeller]

I recently forgot where in a mutable reference the lifetime goes, and got a confusing wall of error messages. Out of the six error messages produced, only the fifth hints at the actual problem, with the rest being misleading.

I think the error messages in this case could be improved in case a newcomer runs into this issue in order to avoid leading them down a false path of trying to figure out trait objects.

Specifically, with the following code

pub struct SpanMaker<'a> {
    parent: &mut 'a SpanManager,
    source: usize,
}

I got the following compiler errors:

error: lifetime in trait object type must be followed by `+`
  --> src/spans.rs:20:18
   |
20 |     parent: &mut 'a SpanManager,
   |                  ^^

error: expected `,`, or `}`, found `SpanManager`
  --> src/spans.rs:20:20
   |
20 |     parent: &mut 'a SpanManager,
   |                    ^ help: try adding a comma: `,`

error: expected `:`, found `,`
  --> src/spans.rs:20:32
   |
20 |     parent: &mut 'a SpanManager,
   |                                ^ expected `:`

warning: trait objects without an explicit `dyn` are deprecated
  --> src/spans.rs:20:18
   |
20 |     parent: &mut 'a SpanManager,
   |                  ^^ help: use `dyn`: `dyn 'a`
   |
   = note: `#[warn(bare_trait_objects)]` on by default

error[E0106]: missing lifetime specifier
  --> src/spans.rs:20:13
   |
20 |     parent: &mut 'a SpanManager,
   |             ^ help: consider using the named lifetime: `&'a`

error[E0224]: at least one trait is required for an object type
  --> src/spans.rs:20:18
   |
20 |     parent: &mut 'a SpanManager,
   |                  ^^

error: aborting due to 5 previous errors; 1 warning emitted

I am using stable Rust.

rustc --version --verbose
rustc 1.44.1 (c7087fe00 2020-06-17)
binary: rustc
commit-hash: c7087fe00d2ba919df1d813c040a5d47e43b0fe7
commit-date: 2020-06-17
host: x86_64-unknown-linux-gnu
release: 1.44.1
LLVM version: 9.0

[SNCPlay42]

Duplicate of #73568

[JohnTitor]

Current output:

error: lifetime must precede `mut`
 --> src/lib.rs:2:13
  |
2 |     parent: &mut 'a SpanManager,
  |             ^^^^^^^ help: place the lifetime before `mut`: `&'a mut`

error[E0412]: cannot find type `SpanManager` in this scope
 --> src/lib.rs:2:21
  |
2 |     parent: &mut 'a SpanManager,
  |                     ^^^^^^^^^^^ not found in this scope

error: aborting due to 2 previous errors

Indeed #73595 improved the diagnostics and it has a regression test for this case so I'm going to just close this. Thanks!