error[E0275]: overflow evaluating the requirement `&_: IntoIterator` does not show a line number

[Folcon]

Location

In the compiler rustc 1.76.0-nightly (37b2813 2023-11-24).

Summary

Still learning the language so sorry if this isn't super detailed, I wrote a type and got this error message:

error[E0275]: overflow evaluating the requirement `&_: IntoIterator`
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`bevy_game`)
  = note: required for `&bevy::prelude::ResMut<'_, _>` to implement `IntoIterator`
  = note: 126 redundant requirements hidden
  = note: required for `&ResMut<'_, ResMut<'_, ResMut<'_, ResMut<'_, ResMut<'_, ResMut<'_, ResMut<'_, ResMut<'_, ResMut<'_, ResMut<'_, ...>>>>>>>>>>` to implement `IntoIterator`
  = note: the full type name has been written to '<project-folder>/target/debug/deps/bevy_game-f668298e2ba0aa7c.long-type-4538768014950909176.txt'

The problem is I'm not sure where this is broken and the error message doesn't provide a line number of any kind for the problematic code.
I recalled in a talk that we should be filing documentation issues as bugs so I thought I'd drop this here, please let me know if that was in error.

[compiler-errors]

@Folcon: Please provide any reproduction instructions here if you have them, and ideally any code that can be built. Also, I don't think this issue makes it clear that you encountered this issue (what I'm guessing) in rustdoc/cargo doc. Is this correct?

[Folcon]

@compiler-errors, I found this while running cargo run, so I'm assuming the rust compiler.

I encountered it developing a bevy project, I can't share the code.

The project uses #![feature(box_patterns)] but I'm not certain it's relevant.

The full type name that appears in the text file generated is below:

&bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, bevy::prelude::Ref<'_, _>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

In terms of a minimal repro case, after I reported the error I managed to fix it and I'm not certain how I did so unfortunately. I'm still in the process of learning rust as a I mentioned. Otherwise I'd give you a better error or have built a minimal repro case =)...

Please let me know if there's anything else I can help with.

[compiler-errors]

Ok, I was just confused why this issue was tagged "docs"

[bas-ie]

I just hit this too with 12.1. If I fix it, I'll let you know what it was! 😆

[Atreyagaurav]

I also got this recently.

error[E0275]: overflow evaluating the requirement `&_: IntoIterator`
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`nadi_core`)
  = note: required for `&joinery::join::Join<_, _>` to implement `IntoIterator`
  = note: 126 redundant requirements hidden
  = note: required for `&Join<Join<Join<Join<Join<Join<Join<Join<Join<Join<Join<Join<..., ...>, ...>, ...>, ...>, ...>, ...>, ...>, ...>, ...>, ...>, ...>, ...>` to implement `IntoIterator`
  = note: the full type name has been written to '/home/gaurav/github/nadi/target/release/deps/nadi_core.long-type-6255917270899944681.txt'

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

It doesn't have line number. It was hard to trace what was causing it. But I found it's due to the following code:

The green is the fix I did. So in this case looks like the toml::Table from toml crate being converted into "Iter" was a problem. The internal error could be due to serde and other things it uses. But without the line numbers I can only tell this fixed it.

     pub fn with_args(args: Vec<toml::Value>) -> Self {
         let mut ctx = Self::new();
-        args.iter().filter_map(|a| a.as_table()).for_each(|t| {
-            ctx.kwargs.extend(t.into());
-        });
-        ctx.args = args;
+        ctx.args = args.clone();
+        args.into_iter()
+            .filter_map(|a| a.as_table().cloned())
+            .for_each(|t| {
+                ctx.kwargs.extend(t);
+            });
         ctx
     }

EDIT:

I want to add that Self here is:

pub struct FunctionCtx {
    args: Vec<toml::Value>,
    kwargs: toml::Table,
    result: anyhow::Result<()>,
}

So converting toml::Table which can contain other toml::Table could be the reason.

[Atreyagaurav]

I tried to recreate the example in playground, and it doesn't allow me to compile unless I add the type for the expand. Maybe in my complete code, it was trying to guess the hint for .into() and got into a loop.

https://play.rust-lang.org/?version=stable&mode=release&edition=2021&gist=ab4332b2a303f490f6518572cb83d7ab

[hecrj]

Here is a simpler example with no external dependencies that reproduces the issue in stable:

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=ec772634936a120b6c935475d6c831be

This is an annoying issue because if some library changes the argument of a function from a Vec to impl IntoIterator (a common change) and ANY of your dependencies has an IntoIterator implementation like the one in the example (like palette does), then you may hit this error which renders you completely blind; since there is no context nor mention of the code causing it.