OOM during type collection

[matthiaskrgr]

I tried this code:
This is modification of tests/ui/traits/cycle-cache-err-60010.rs with the difference being

@@ -41,7 +41,7 @@
 {
     type Data = RootDatabase;
 }
-impl<T> SourceDatabase for T
+impl<T> Database for T
 where
     T: RefUnwindSafe,
     T: HasQueryGroup,

Rust OOM'd here after eating at least 20 gb of memory 😅

// Test that we properly detect the cycle amongst the traits
// here and report an error.

use std::panic::RefUnwindSafe;

trait Database {
    type Storage;
}
trait HasQueryGroup {}
trait Query<DB> {
    type Data;
}
trait SourceDatabase {
    fn parse(&self) {
        loop {}
    }
}

struct ParseQuery;
struct RootDatabase {
    _runtime: Runtime<RootDatabase>,
}
struct Runtime<DB: Database> {
    _storage: Box<DB::Storage>,
}
struct SalsaStorage {
    _parse: <ParseQuery as Query<RootDatabase>>::Data,
    //~^ ERROR overflow
}

impl Database for RootDatabase {
    // This would also be an error if we didn't abort compilation on the error
    // above.
    type Storage = SalsaStorage;
}
impl HasQueryGroup for RootDatabase {}
impl<DB> Query<DB> for ParseQuery
where
    DB: SourceDatabase,
    DB: Database,
{
    type Data = RootDatabase;
}
impl<T> Database for T
where
    T: RefUnwindSafe,
    T: HasQueryGroup,
{
}

pub(crate) fn goto_implementation(db: &RootDatabase) -> u32 {
    // This is not satisfied:
    //
    // - `RootDatabase: SourceDatabase`
    //   - requires `RootDatabase: RefUnwindSafe` + `RootDatabase: HasQueryGroup`
    // - `RootDatabase: RefUnwindSafe`
    //   - requires `Runtime<RootDatabase>: RefUnwindSafe`
    // - `Runtime<RootDatabase>: RefUnwindSafe`
    //   - requires `DB::Storage: RefUnwindSafe` (`SalsaStorage: RefUnwindSafe`)
    // - `SalsaStorage: RefUnwindSafe`
    //    - requires `<ParseQuery as Query<RootDatabase>>::Data: RefUnwindSafe`,
    //      which means `ParseQuery: Query<RootDatabase>`
    // - `ParseQuery: Query<RootDatabase>`
    //    - requires `RootDatabase: SourceDatabase`,
    // - `RootDatabase: SourceDatabase` is already on the stack, so we have a
    //   cycle with non-coinductive participants
    //
    // we used to fail to report an error here because we got the
    // caching wrong.
    SourceDatabase::parse(db);
    22
}

fn main() {}

I expected to see this happen: explanation
NO OOM, maybe an error

Instead, this happened: explanation
OOM

Meta

rustc --version --verbose:

rustc 1.71.0-nightly (e9e1bbc7a 2023-05-17)
binary: rustc
commit-hash: e9e1bbc7a820c472b39d3de54b3049bf14050655
commit-date: 2023-05-17
host: x86_64-unknown-linux-gnu
release: 1.71.0-nightly
LLVM version: 16.0.2

[apiraino]

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-medium