Bad error message for infinite type recursion

[pacak]

Code

#![recursion_limit = "5"]
#![allow(unconditional_recursion)]

fn quicksort<It, I>(i: I) -> Vec<i32>
where
    It: Iterator<Item = i32>,
    I: IntoIterator<IntoIter = It>,
{
    quicksort(i.into_iter().filter(|_| true))
}

pub fn bar(xs: Vec<i32>) -> Vec<i32> {
    quicksort(xs)
}

Current output

relevant error:

error[E0275]: overflow evaluating the requirement `Filter<Filter<Filter<Filter<Filter<std::vec::IntoIter<i32>, ...>, ...>, ...>, ...>, ...>: Iterator`
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "10"]` attribute to your crate (`qsort`)
  = note: required for `Filter<Filter<Filter<Filter<Filter<std::vec::IntoIter<i32>, {closure@src/lib.rs:8:36: 8:39}>, {closure@src/lib.rs:8:36: 8:39}>, {closure@src/lib.rs:8:36: 8:39}>, {closure@src/lib.rs:8:36: 8:39}>, {closure@src/lib.rs:8:36: 8:39}>` to implement `IntoIterator`

Desired output

something-something infinite recursion

Rationale and extra context

Suggestion to increase recursion limit is wrong

Other cases

No response

Rust Version

rustc 1.76.0 (07dca489a 2024-02-04)
binary: rustc
commit-hash: 07dca489ac2d933c78d3c5158e3f43beefeb02ce
commit-date: 2024-02-04
host: x86_64-unknown-linux-gnu
release: 1.76.0
LLVM version: 17.0.6

Anything else?

No response

[pacak]

New error message is as following:

Compiling playground v0.0.1 (/playground)
error[[E0275]](https://doc.rust-lang.org/nightly/error_codes/E0275.html): overflow evaluating the requirement `{closure@src/main.rs:6:41: 6:44}: Sized`
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`playground`)
  = note: required for `Filter<std::array::IntoIter<i32, 11>, {closure@src/main.rs:6:41: 6:44}>` to implement `Iterator`
  = note: 127 redundant requirements hidden
  = note: required for `Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<..., ...>, ...>, ...>, ...>, ...>, ...>, ...>, ...>` to implement `Iterator`
  = note: required for `Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<..., ...>, ...>, ...>, ...>, ...>, ...>, ...>, ...>` to implement `IntoIterator`
  = note: the full name for the type has been written to '/playground/target/debug/deps/playground-22e77209e34c162a.long-type-15773489000561340382.txt'
  = note: consider using `--verbose` to print the full type name to the console
  = note: the full name for the type has been written to '/playground/target/debug/deps/playground-22e77209e34c162a.long-type-15773489000561340382.txt'
  = note: consider using `--verbose` to print the full type name to the console

For more information about this error, try `rustc --explain E0275`.
error: could not compile `playground` (bin "playground") due to 1 previous error

Suggestion to increase recursion limit is wrong.

[oli-obk]

Under the new solver this gives the following output:

error[E0283]: type annotations needed
 --> <source>:9:5
  |
9 |     quicksort(i.into_iter().filter(|_| true))
  |     ^^^^^^^^^ cannot infer type of the type parameter `It` declared on the function `quicksort`
  |
  = note: cannot satisfy `_: Iterator`
note: required by a bound in `quicksort`
 --> <source>:6:9
  |
4 | fn quicksort<It, I>(i: I) -> Vec<i32>
  |    --------- required by a bound in this function
5 | where
6 |     It: Iterator<Item = i32>,
  |         ^^^^^^^^^^^^^^^^^^^^ required by this bound in `quicksort`
help: consider specifying the generic arguments
  |
9 |     quicksort::<It, _>(i.into_iter().filter(|_| true))
  |              +++++++++

error[E0275]: overflow evaluating the requirement `Filter<It, {closure@<source>:9:36: 9:39}>: IntoIterator`
 --> <source>:9:15
  |
9 |     quicksort(i.into_iter().filter(|_| true))
  |     --------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |     |
  |     required by a bound introduced by this call
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "10"]` attribute to your crate (`example`)
note: required by a bound in `quicksort`
 --> <source>:7:8
  |
4 | fn quicksort<It, I>(i: I) -> Vec<i32>
  |    --------- required by a bound in this function
...
7 |     I: IntoIterator<IntoIter = It>,
  |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `quicksort`
help: consider removing this method call, as the receiver has type `<I as IntoIterator>::IntoIter` and `<I as IntoIterator>::IntoIter: IntoIterator` trivially holds
  |
9 -     quicksort(i.into_iter().filter(|_| true))
9 +     quicksort(i.into_iter())
  |

error[E0275]: overflow evaluating the requirement `<Filter<It, {closure@<source>:9:36: 9:39}> as IntoIterator>::IntoIter == It`
 --> <source>:9:15
  |
9 |     quicksort(i.into_iter().filter(|_| true))
  |     --------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |     |
  |     required by a bound introduced by this call
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "10"]` attribute to your crate (`example`)
note: required by a bound in `quicksort`
 --> <source>:7:21
  |
4 | fn quicksort<It, I>(i: I) -> Vec<i32>
  |    --------- required by a bound in this function
...
7 |     I: IntoIterator<IntoIter = It>,
  |                     ^^^^^^^^^^^^^ required by this bound in `quicksort`