error: overflow evaluating the requirement without precise link to origin of the error

[gui1117]

When some type doesn't implement some trait, rust error message overflow evaluating the requirement (which is ok), but it fails to give a proper error message, as it doesn't show where the error comes from. It would be very more helpful if the error message points to where the failing evaluation comes from.

I tried this code:

pub struct Compact<T>(pub T);

pub trait Decode {}

pub trait WrapperTypeDecode {
	type Wrapped;
}

pub trait CompactAs {
	type As;
}

pub trait HasCompact {}


impl<T, X> Decode for X
where
	X: WrapperTypeDecode<Wrapped=T>,
	T: Decode,
{}

impl<T> HasCompact for T
where
	Compact<T>: Decode,
{}

impl<T> Decode for Compact<T>
where
	T: CompactAs,
	Compact<T::As>: Decode,
{}

fn _foo<T: HasCompact>() {}

fn bar<T>() { _foo::<T>() }

// The last line trigger the following error without span:
/*
error[E0275]: overflow evaluating the requirement `Compact<_>: Decode`
  |
  = help: consider adding a `#![recursion_limit="256"]` attribute to your crate (`playground`)
  = note: required because of the requirements on the impl of `Decode` for `Compact<_>`
  = note: 126 redundant requirements hidden
  = note: required because of the requirements on the impl of `Decode` for `Compact<_>`
*/

fn main() {}

I expected to see this happen: have a reference to what trigger the error, i.e. this call _foo::<T>()

Instead, this happened: a not very helpful error message:

error[E0275]: overflow evaluating the requirement `Compact<_>: Decode`
  |
  = help: consider adding a `#![recursion_limit="256"]` attribute to your crate (`playground`)
  = note: required because of the requirements on the impl of `Decode` for `Compact<_>`
  = note: 126 redundant requirements hidden
  = note: required because of the requirements on the impl of `Decode` for `Compact<_>`

Meta

the bug exist on stable, and nightly 2021-02-04

rustc --version --verbose:

rustc 1.49.0 (e1884a8e3 2020-12-29)
binary: rustc
commit-hash: e1884a8e3c3e813aada8254edfa120e85bf5ffca
commit-date: 2020-12-29
host: x86_64-unknown-linux-gnu
release: 1.49.0

[compiler-errors]

Output now:

error[[E0277]](https://doc.rust-lang.org/nightly/error-index.html#E0277): the trait bound `Compact<T>: Decode` is not satisfied
  --> src/main.rs:35:22
   |
35 | fn bar<T>() { _foo::<T>() }
   |                      ^ the trait `Decode` is not implemented for `Compact<T>`
   |
   = help: the trait `Decode` is implemented for `Compact<T>`
note: required for `T` to implement `HasCompact`
  --> src/main.rs:22:9
   |
22 | impl<T> HasCompact for T
   |         ^^^^^^^^^^     ^
23 | where
24 |     Compact<T>: Decode,
   |                 ------ unsatisfied trait bound introduced here
note: required by a bound in `_foo`
  --> src/main.rs:33:12
   |
33 | fn _foo<T: HasCompact>() {}
   |            ^^^^^^^^^^ required by this bound in `_foo`