-Z macro-backtrace doesn't provide new information

Code

Any (I think) proc macro which outputs syntactically correct but semantically invalid code. I encountered this issue here when running cargo test easy.

Current output

This is the compiler error without -Z macro-backtrace:

error[E0282]: type annotations needed
   --> pg-worm/src/query/table.rs:225:14
    |
225 |     #[derive(Model)]
    |              ^^^^^ cannot infer type
    |
    = note: this error originates in the derive macro `Model` (in Nightly builds, run with -Z macro-backtrace for more info)

And this is the ouput with the flag:

error[E0282]: type annotations needed
   --> pg-worm/src/query/table.rs:225:14
    |
225 |     #[derive(Model)]
    |              ^^^^^
    |              |
    |              cannot infer type
    |              in this derive macro expansion
    |
   ::: /home/me/code/pg-worm/pg-worm-derive/src/lib.rs:12:1
    |
12  | pub fn derive(input: OldTokenStream) -> OldTokenStream {
    | ------------------------------------------------------ in this expansion of `#[derive(Model)]`

Desired output

I would expect -Z macro-backtrace to show the error in the expanded code, so something like this (assuming this were the code produced):

error[E0282]: type annotations needed
   --> pg-wprm/src/query/table.rs:255:14
225 |     let foo = "bar".into();
    |                     ^^^^
    |                     |
    |                     cannot infer type
    |                     in this derive macro expansion
    |
    | ------------------------------------------------------ in this expansion of `#[derive(Model)]`

Rationale and extra context

As it stands, when code produced by a proc macro fails to compile for semantic reasons we only receive the error message, no span or note etc. Debugging such an error is no pleasant task and aften spending hours on separate days going through the cargo expand output I still can't figure out what is wrong with my code. I would expect the macro-backtrace flag to produce a more detailed account of what went wrong, including the span of the error in the expanded code.

Other cases

No response

Anything else?

No response

Reproduce the report with cargo test easy in the linked pg-worm project, comparing output with and without -Z macro-backtrace. Start from pg-worm-derive/src/lib.rs:12 and the derive use at pg-worm/src/query/table.rs:225, then trace the compiler's macro-backtrace handling. Done means semantic errors from proc-macro output include a useful span or location in the expanded code.