Trying to iterate &Res<Assets<T>> results in a poor compiler error

[JMS55]

for mesh in &meshes {}

error[E0275]: overflow evaluating the requirement `&_: IntoIterator`
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`scene_viewer`)
  = note: required for `&bevy::prelude::Res<'_, _>` to implement `IntoIterator`
  = note: 126 redundant requirements hidden
  = note: required for `&Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, Res<'_, ...>>>>>>>>>>>>>>>>>>>>>>>>` to implement `IntoIterator`
  = note: the full name for the type has been written to '<redacted>.long-type-3364561052137337366.txt'
  = note: consider using `--verbose` to print the full type name to the console

For more information about this error, try `rustc --explain E0275`.

Increasing the recursion limit to 256 then says it overflows and suggest increasing to 512, ongoing forever.

The correct solution seems to be using meshes.iter(). I'm curious why that is.

[Victoronz]

You can treat this as a limitation of the current rust trait solver, it'll go away once -Znext-solver stabilizes (I think coherence is enough? I've run into this kind of error too, and -Znext-solver=coherence fixed it)
This has been reported a couple times, both in bevy #14799 and in rust-lang.

This error happens when there is recursion in the type bounds.
I don't know what triggers it here, but if I were to guess, the 'a lifetime?

As for why .iter() fixes it:
for loops call IntoIterator::into_iter(value)
In contrast, .iter() doesn't exist for Res so the compiler simply derefs/method resolves til something does.