error reporting loop

// build-pass
// revisions: all strong basic
// compile-flags: --target nvptx64-nvidia-cuda
// needs-llvm-components: nvptx
// [all] compile-flags: -Z stack-protector[no_std]
#[lang = "sized"]

#![crate_type = "lib"]
fn T(){trait Copy {}

#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]

#![crate_type = "lib"]
fn T<'a, main>(){trait Copy {}

#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]

#![crate_type = "lib"]
pub fn T(){trait Copy {}

#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]

#![crate_type = "lib"]
async fn T<'a, main>(){"sized"

#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]

#![crate_type = "lib"]
fn T(){trait Copy {}

#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]

#![crate_type = "lib"]
fn T<'a, main>(){trait Copy {}

#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]

#![crate_type = "lib"]
pub fn T(){trait Copy {}

#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]

#![crate_type = "lib"]
async fn T<'a, main>(){"sized"

#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]

#![crate_type = "lib"]
trait Copy{ {}}
#[lang = ]
fn main(){}

 fn main()fn main(){}

#[lang = ]
fn main(){}

 fn main()fn main(){}
(0)
#[lang = ]
fn main(){}

 fn main()fn main(){}

#[lang = ]
fn main(){}

 fn main()fn main(){}
(0)          

if I run rustfmt on this, it looks like it just prints errors in a loop

Reproduce the report by running rustfmt on the Rust snippet in the issue and confirm whether diagnostics repeat indefinitely. Trace the error-reporting path involved in the repeated output; done means malformed input produces a finite diagnostic result rather than an error-reporting loop.