Commit b4aa629

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Ignore coroutine witness type region args in auto trait confirmation

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+29

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Lines changed: 15 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -2333,10 +2333,23 @@ impl<'tcx> SelectionContext<'_, 'tcx> {`
`2333`	`2333`
`2334`	`2334`	`ty::Coroutine(def_id, args) => {`
`2335`	`2335`	`let ty = self.infcx.shallow_resolve(args.as_coroutine().tupled_upvars_ty());`
	`2336`	`+ let tcx = self.tcx();`
`2336`	`2337`	`let witness = Ty::new_coroutine_witness(`
`2337`		`- self.tcx(),`
	`2338`	`+ tcx,`
`2338`	`2339`	`def_id,`
`2339`		`- self.tcx().mk_args(args.as_coroutine().parent_args()),`
	`2340`	`+ ty::GenericArgs::for_item(tcx, def_id, \|def, _\| match def.kind {`
	`2341`	`+ // HACK: Coroutine witnesse types are lifetime erased, so they`
	`2342`	`+ // never reference any lifetime args from the coroutine. We erase`
	`2343`	`+ // the regions here since we may get into situations where a`
	`2344`	`+ // coroutine is recursively contained within itself, leading to`
	`2345`	`+ // witness types that differ by region args. This means that`
	`2346`	`+ // cycle detection in fulfillment will not kick in, which leads`
	`2347`	`+ // to unnecessary overflows in async code. See the issue:`
	`2348`	`+ // <https://github.com/rust-lang/rust/issues/145151>.`
	`2349`	`+ ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),`
	`2350`	`+ ty::GenericParamDefKind::Type { .. }`
	`2351`	`+ \| ty::GenericParamDefKind::Const { .. } => args[def.index as usize],`
	`2352`	`+ }),`
`2340`	`2353`	`);`
`2341`	`2354`	`ty::Binder::dummy(AutoImplConstituents {`
`2342`	`2355`	`types: [ty].into_iter().chain(iter::once(witness)).collect(),`

Lines changed: 14 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,14 @@`
	`1`	`+// Regression test for <https://github.com/rust-lang/rust/issues/145151>.`
	`2`	`+`
	`3`	`+//@ edition: 2024`
	`4`	`+//@ check-pass`
	`5`	`+`
	`6`	`+async fn process<'a>() {`
	`7`	`+ Box::pin(process()).await;`
	`8`	`+}`
	`9`	`+`
	`10`	`+fn require_send(_: impl Send) {}`
	`11`	`+`
	`12`	`+fn main() {`
	`13`	`+ require_send(process());`
	`14`	`+}`

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