clippy hangs

[matthiaskrgr]

Summary

clippy seems to hang with this code:

// run-pass
// Example taken from RFC 1238 text

// https://github.com/rust-lang/rfcs/blob/master/text/1238-nonparametric-dropck.md
//     #examples-of-code-that-must-continue-to-work

use std::cell::Cell;

struct Concrete<'a>(#[allow(unused_tuple_struct_fields)] u32, Cell<Option<&'a Concrete<'a>>>);

fn main() {
    let mut data = Vec::new();
    data.push(Concrete(0, Cell::new(None)));
    data.push(Concrete(0, Cell::new(None)));

    data[0].1.set(Some(&data[1]));
    data[1].1.set(Some(&data[0]));
}

Version

clippy 0.1.65 (c07a8b4 2022-08-26)

Error output

No response

[matthiaskrgr]

  38,57%  librustc_driver-924e5f35a0df5cca.so  [.] <rustc_middle::hir::map::ParentHirIterator as core::iter::traits::iterator::Iterator>::next
   7,73%  librustc_driver-924e5f35a0df5cca.so  [.] <rustc_middle::dep_graph::dep_node::DepKind as rustc_query_system::dep_graph::DepKind>::read_deps::<<rustc
   5,10%  clippy-driver                        [.] clippy_utils::get_parent_expr
   2,40%  clippy-driver                        [.] <clippy_utils::visitors::for_each_local_use_after_expr::V<<clippy_lints::vec_init_then_push::VecPushSearch
   1,06%  [kernel]                             [k] mangle_path

[matthiaskrgr]

reduced a bit:

use std::cell::Cell;

struct Concrete<'a>(Cell<Option<&'a Concrete<'a>>>);

fn main() {
    let mut data = Vec::new();
    data.push(Concrete(Cell::new(None)));
    data[0].0.set(None);
}

when I inline the vec.push() via let data = vec![..], the hang goes away 🤔