diff options
| -rw-r--r-- | compiler/rustc_hir_typeck/src/upvar.rs | 66 | ||||
| -rw-r--r-- | tests/ui/async-await/async-closures/non-copy-arg-does-not-force-inner-move.rs | 17 |
2 files changed, 70 insertions, 13 deletions
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs index e64f4ebf45d..55f002291f0 100644 --- a/compiler/rustc_hir_typeck/src/upvar.rs +++ b/compiler/rustc_hir_typeck/src/upvar.rs @@ -219,7 +219,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { // `async-await/async-closures/force-move-due-to-inferred-kind.rs`. // // 2. If the coroutine-closure is forced to be `FnOnce` due to the way it - // uses its upvars, but not *all* upvars would force the closure to `FnOnce`. + // uses its upvars (e.g. it consumes a non-copy value), but not *all* upvars + // would force the closure to `FnOnce`. // See the test: `async-await/async-closures/force-move-due-to-actually-fnonce.rs`. // // This would lead to an impossible to satisfy situation, since `AsyncFnOnce` @@ -227,11 +228,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { // we force the inner coroutine to also be `move`. This only matters for // coroutine-closures that are `move` since otherwise they themselves will // be borrowing from the outer environment, so there's no self-borrows occuring. - // - // One *important* note is that we do a call to `process_collected_capture_information` - // to eagerly test whether the coroutine would end up `FnOnce`, but we do this - // *before* capturing all the closure args by-value below, since that would always - // cause the analysis to return `FnOnce`. if let UpvarArgs::Coroutine(..) = args && let hir::CoroutineKind::Desugared(_, hir::CoroutineSource::Closure) = self.tcx.coroutine_kind(closure_def_id).expect("coroutine should have kind") @@ -246,19 +242,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { capture_clause = hir::CaptureBy::Value { move_kw }; } // (2.) The way that the closure uses its upvars means it's `FnOnce`. - else if let (_, ty::ClosureKind::FnOnce, _) = self - .process_collected_capture_information( - capture_clause, - &delegate.capture_information, - ) - { + else if self.coroutine_body_consumes_upvars(closure_def_id, body) { capture_clause = hir::CaptureBy::Value { move_kw }; } } // As noted in `lower_coroutine_body_with_moved_arguments`, we default the capture mode // to `ByRef` for the `async {}` block internal to async fns/closure. This means - // that we would *not* be moving all of the parameters into the async block by default. + // that we would *not* be moving all of the parameters into the async block in all cases. + // For example, when one of the arguments is `Copy`, we turn a consuming use into a copy of + // a reference, so for `async fn x(t: i32) {}`, we'd only take a reference to `t`. // // We force all of these arguments to be captured by move before we do expr use analysis. // @@ -535,6 +528,53 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } } + /// Determines whether the body of the coroutine uses its upvars in a way that + /// consumes (i.e. moves) the value, which would force the coroutine to `FnOnce`. + /// In a more detailed comment above, we care whether this happens, since if + /// this happens, we want to force the coroutine to move all of the upvars it + /// would've borrowed from the parent coroutine-closure. + /// + /// This only really makes sense to be called on the child coroutine of a + /// coroutine-closure. + fn coroutine_body_consumes_upvars( + &self, + coroutine_def_id: LocalDefId, + body: &'tcx hir::Body<'tcx>, + ) -> bool { + // This block contains argument capturing details. Since arguments + // aren't upvars, we do not care about them for determining if the + // coroutine body actually consumes its upvars. + let hir::ExprKind::Block(&hir::Block { expr: Some(body), .. }, None) = body.value.kind + else { + bug!(); + }; + // Specifically, we only care about the *real* body of the coroutine. + // We skip out into the drop-temps within the block of the body in order + // to skip over the args of the desugaring. + let hir::ExprKind::DropTemps(body) = body.kind else { + bug!(); + }; + + let mut delegate = InferBorrowKind { + closure_def_id: coroutine_def_id, + capture_information: Default::default(), + fake_reads: Default::default(), + }; + + let _ = euv::ExprUseVisitor::new( + &FnCtxt::new(self, self.tcx.param_env(coroutine_def_id), coroutine_def_id), + &mut delegate, + ) + .consume_expr(body); + + let (_, kind, _) = self.process_collected_capture_information( + hir::CaptureBy::Ref, + &delegate.capture_information, + ); + + matches!(kind, ty::ClosureKind::FnOnce) + } + // Returns a list of `Ty`s for each upvar. fn final_upvar_tys(&self, closure_id: LocalDefId) -> Vec<Ty<'tcx>> { self.typeck_results diff --git a/tests/ui/async-await/async-closures/non-copy-arg-does-not-force-inner-move.rs b/tests/ui/async-await/async-closures/non-copy-arg-does-not-force-inner-move.rs new file mode 100644 index 00000000000..cd9d98d0799 --- /dev/null +++ b/tests/ui/async-await/async-closures/non-copy-arg-does-not-force-inner-move.rs @@ -0,0 +1,17 @@ +//@ aux-build:block-on.rs +//@ edition:2021 +//@ build-pass + +#![feature(async_closure)] + +extern crate block_on; + +fn wrapper(f: impl Fn(String)) -> impl async Fn(String) { + async move |s| f(s) +} + +fn main() { + block_on::block_on(async { + wrapper(|who| println!("Hello, {who}!"))(String::from("world")).await; + }); +} |