diff --git a/compiler/rustc_typeck/src/check/upvar.rs b/compiler/rustc_typeck/src/check/upvar.rs index d097f863ad2..79c60ab3cfe 100644 --- a/compiler/rustc_typeck/src/check/upvar.rs +++ b/compiler/rustc_typeck/src/check/upvar.rs @@ -180,7 +180,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { debug!("seed place {:?}", place); let upvar_id = ty::UpvarId::new(*var_hir_id, local_def_id); - let capture_kind = self.init_capture_kind(capture_clause, upvar_id, span); + let capture_kind = + self.init_capture_kind_for_place(&place, capture_clause, upvar_id, span); let fake_info = ty::CaptureInfo { capture_kind_expr_id: None, path_expr_id: None, @@ -449,7 +450,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { base => bug!("Expected upvar, found={:?}", base), }; - let place = restrict_capture_precision(place, capture_info.capture_kind); + let place = restrict_capture_precision(place); let min_cap_list = match root_var_min_capture_list.get_mut(&var_hir_id) { None => { @@ -897,15 +898,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } } - fn init_capture_kind( + fn init_capture_kind_for_place( &self, + place: &Place<'tcx>, capture_clause: hir::CaptureBy, upvar_id: ty::UpvarId, closure_span: Span, ) -> ty::UpvarCapture<'tcx> { match capture_clause { - hir::CaptureBy::Value => ty::UpvarCapture::ByValue(None), - hir::CaptureBy::Ref => { + // In case of a move closure if the data is accessed through a reference we + // want to capture by ref to allow precise capture using reborrows. + // + // If the data will be moved out of this place, then the place will be truncated + // at the first Deref in `adjust_upvar_borrow_kind_for_consume` and then moved into + // the closure. + hir::CaptureBy::Value if !place.deref_tys().any(ty::TyS::is_ref) => { + ty::UpvarCapture::ByValue(None) + } + hir::CaptureBy::Value | hir::CaptureBy::Ref => { let origin = UpvarRegion(upvar_id, closure_span); let upvar_region = self.next_region_var(origin); let upvar_borrow = ty::UpvarBorrow { kind: ty::ImmBorrow, region: upvar_region }; @@ -1109,12 +1119,18 @@ impl<'a, 'tcx> InferBorrowKind<'a, 'tcx> { place_with_id, diag_expr_id, mode ); - // we only care about moves - match mode { - euv::Copy => { - return; - } - euv::Move => {} + let place = truncate_capture_for_move(place_with_id.place.clone()); + match (self.capture_clause, mode) { + // In non-move closures, we only care about moves + (hir::CaptureBy::Ref, euv::Copy) => return, + + (hir::CaptureBy::Ref, euv::Move) | (hir::CaptureBy::Value, euv::Move | euv::Copy) => {} + }; + + let place_with_id = PlaceWithHirId { place: place.clone(), hir_id: place_with_id.hir_id }; + + if !self.capture_information.contains_key(&place) { + self.init_capture_info_for_place(&place_with_id, diag_expr_id); } let tcx = self.fcx.tcx; @@ -1128,13 +1144,15 @@ impl<'a, 'tcx> InferBorrowKind<'a, 'tcx> { let usage_span = tcx.hir().span(diag_expr_id); - // To move out of an upvar, this must be a FnOnce closure - self.adjust_closure_kind( - upvar_id.closure_expr_id, - ty::ClosureKind::FnOnce, - usage_span, - place_with_id.place.clone(), - ); + if matches!(mode, euv::Move) { + // To move out of an upvar, this must be a FnOnce closure + self.adjust_closure_kind( + upvar_id.closure_expr_id, + ty::ClosureKind::FnOnce, + usage_span, + place.clone(), + ); + } let capture_info = ty::CaptureInfo { capture_kind_expr_id: Some(diag_expr_id), @@ -1317,8 +1335,12 @@ impl<'a, 'tcx> InferBorrowKind<'a, 'tcx> { if let PlaceBase::Upvar(upvar_id) = place_with_id.place.base { assert_eq!(self.closure_def_id.expect_local(), upvar_id.closure_expr_id); - let capture_kind = - self.fcx.init_capture_kind(self.capture_clause, upvar_id, self.closure_span); + let capture_kind = self.fcx.init_capture_kind_for_place( + &place_with_id.place, + self.capture_clause, + upvar_id, + self.closure_span, + ); let expr_id = Some(diag_expr_id); let capture_info = ty::CaptureInfo { @@ -1392,15 +1414,10 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for InferBorrowKind<'a, 'tcx> { } /// Truncate projections so that following rules are obeyed by the captured `place`: -/// -/// - No Derefs in move closure, this will result in value behind a reference getting moved. /// - No projections are applied to raw pointers, since these require unsafe blocks. We capture /// them completely. /// - No Index projections are captured, since arrays are captured completely. -fn restrict_capture_precision<'tcx>( - mut place: Place<'tcx>, - capture_kind: ty::UpvarCapture<'tcx>, -) -> Place<'tcx> { +fn restrict_capture_precision<'tcx>(mut place: Place<'tcx>) -> Place<'tcx> { if place.projections.is_empty() { // Nothing to do here return place; @@ -1412,7 +1429,6 @@ fn restrict_capture_precision<'tcx>( } let mut truncated_length = usize::MAX; - let mut first_deref_projection = usize::MAX; for (i, proj) in place.projections.iter().enumerate() { if proj.ty.is_unsafe_ptr() { @@ -1426,31 +1442,36 @@ fn restrict_capture_precision<'tcx>( truncated_length = truncated_length.min(i); break; } - ProjectionKind::Deref => { - // We only drop Derefs in case of move closures - // There might be an index projection or raw ptr ahead, so we don't stop here. - first_deref_projection = first_deref_projection.min(i); - } + ProjectionKind::Deref => {} ProjectionKind::Field(..) => {} // ignore ProjectionKind::Subslice => {} // We never capture this } } - let length = place - .projections - .len() - .min(truncated_length) - // In case of capture `ByValue` we want to not capture derefs - .min(match capture_kind { - ty::UpvarCapture::ByValue(..) => first_deref_projection, - ty::UpvarCapture::ByRef(..) => usize::MAX, - }); + let length = place.projections.len().min(truncated_length); place.projections.truncate(length); place } +/// Truncates a place so that the resultant capture doesn't move data out of a reference +fn truncate_capture_for_move(mut place: Place<'tcx>) -> Place<'tcx> { + for (i, proj) in place.projections.iter().enumerate() { + match proj.kind { + ProjectionKind::Deref => { + // We only drop Derefs in case of move closures + // There might be an index projection or raw ptr ahead, so we don't stop here. + place.projections.truncate(i); + return place; + } + _ => {} + } + } + + place +} + fn construct_place_string(tcx: TyCtxt<'_>, place: &Place<'tcx>) -> String { let variable_name = match place.base { PlaceBase::Upvar(upvar_id) => var_name(tcx, upvar_id.var_path.hir_id).to_string(), diff --git a/src/test/ui/closures/2229_closure_analysis/by_value.rs b/src/test/ui/closures/2229_closure_analysis/by_value.rs index 1007fb582e5..27c8fb1363f 100644 --- a/src/test/ui/closures/2229_closure_analysis/by_value.rs +++ b/src/test/ui/closures/2229_closure_analysis/by_value.rs @@ -26,7 +26,8 @@ fn big_box() { //~^ First Pass analysis includes: //~| Min Capture analysis includes: let p = t.0.0; - //~^ NOTE: Capturing t[(0, 0),Deref,(0, 0)] -> ByValue + //~^ NOTE: Capturing t[(0, 0),Deref,(0, 0)] -> ImmBorrow + //~| NOTE: Capturing t[(0, 0)] -> ByValue //~| NOTE: Min Capture t[(0, 0)] -> ByValue println!("{} {:?}", t.1, p); //~^ NOTE: Capturing t[(1, 0)] -> ImmBorrow diff --git a/src/test/ui/closures/2229_closure_analysis/by_value.stderr b/src/test/ui/closures/2229_closure_analysis/by_value.stderr index fe04dbef6d8..944e4c40a78 100644 --- a/src/test/ui/closures/2229_closure_analysis/by_value.stderr +++ b/src/test/ui/closures/2229_closure_analysis/by_value.stderr @@ -28,13 +28,18 @@ LL | | LL | | }; | |_____^ | -note: Capturing t[(0, 0),Deref,(0, 0)] -> ByValue +note: Capturing t[(0, 0),Deref,(0, 0)] -> ImmBorrow + --> $DIR/by_value.rs:28:17 + | +LL | let p = t.0.0; + | ^^^^^ +note: Capturing t[(0, 0)] -> ByValue --> $DIR/by_value.rs:28:17 | LL | let p = t.0.0; | ^^^^^ note: Capturing t[(1, 0)] -> ImmBorrow - --> $DIR/by_value.rs:31:29 + --> $DIR/by_value.rs:32:29 | LL | println!("{} {:?}", t.1, p); | ^^^ @@ -57,7 +62,7 @@ note: Min Capture t[(0, 0)] -> ByValue LL | let p = t.0.0; | ^^^^^ note: Min Capture t[(1, 0)] -> ImmBorrow - --> $DIR/by_value.rs:31:29 + --> $DIR/by_value.rs:32:29 | LL | println!("{} {:?}", t.1, p); | ^^^ diff --git a/src/test/ui/closures/2229_closure_analysis/move_closure.rs b/src/test/ui/closures/2229_closure_analysis/move_closure.rs index 8bdc999ca3c..d57c2280438 100644 --- a/src/test/ui/closures/2229_closure_analysis/move_closure.rs +++ b/src/test/ui/closures/2229_closure_analysis/move_closure.rs @@ -18,8 +18,8 @@ fn simple_ref() { //~^ ERROR: First Pass analysis includes: //~| ERROR: Min Capture analysis includes: *ref_s += 10; - //~^ NOTE: Capturing ref_s[Deref] -> ByValue - //~| NOTE: Min Capture ref_s[] -> ByValue + //~^ NOTE: Capturing ref_s[Deref] -> UniqueImmBorrow + //~| NOTE: Min Capture ref_s[Deref] -> UniqueImmBorrow }; c(); } @@ -39,8 +39,8 @@ fn struct_contains_ref_to_another_struct() { //~^ ERROR: First Pass analysis includes: //~| ERROR: Min Capture analysis includes: t.0.0 = "new s".into(); - //~^ NOTE: Capturing t[(0, 0),Deref,(0, 0)] -> ByValue - //~| NOTE: Min Capture t[(0, 0)] -> ByValue + //~^ NOTE: Capturing t[(0, 0),Deref,(0, 0)] -> UniqueImmBorrow + //~| NOTE: Min Capture t[(0, 0),Deref,(0, 0)] -> UniqueImmBorrow }; c(); diff --git a/src/test/ui/closures/2229_closure_analysis/move_closure.stderr b/src/test/ui/closures/2229_closure_analysis/move_closure.stderr index a745f14598e..554dc11f6ba 100644 --- a/src/test/ui/closures/2229_closure_analysis/move_closure.stderr +++ b/src/test/ui/closures/2229_closure_analysis/move_closure.stderr @@ -46,7 +46,7 @@ LL | | LL | | }; | |_____^ | -note: Capturing ref_s[Deref] -> ByValue +note: Capturing ref_s[Deref] -> UniqueImmBorrow --> $DIR/move_closure.rs:20:9 | LL | *ref_s += 10; @@ -64,7 +64,7 @@ LL | | LL | | }; | |_____^ | -note: Min Capture ref_s[] -> ByValue +note: Min Capture ref_s[Deref] -> UniqueImmBorrow --> $DIR/move_closure.rs:20:9 | LL | *ref_s += 10; @@ -82,7 +82,7 @@ LL | | LL | | }; | |_____^ | -note: Capturing t[(0, 0),Deref,(0, 0)] -> ByValue +note: Capturing t[(0, 0),Deref,(0, 0)] -> UniqueImmBorrow --> $DIR/move_closure.rs:41:9 | LL | t.0.0 = "new s".into(); @@ -100,7 +100,7 @@ LL | | LL | | }; | |_____^ | -note: Min Capture t[(0, 0)] -> ByValue +note: Min Capture t[(0, 0),Deref,(0, 0)] -> UniqueImmBorrow --> $DIR/move_closure.rs:41:9 | LL | t.0.0 = "new s".into(); diff --git a/src/test/ui/closures/2229_closure_analysis/run_pass/move_closure.rs b/src/test/ui/closures/2229_closure_analysis/run_pass/move_closure.rs index 4007a5a48aa..afaafbda018 100644 --- a/src/test/ui/closures/2229_closure_analysis/run_pass/move_closure.rs +++ b/src/test/ui/closures/2229_closure_analysis/run_pass/move_closure.rs @@ -56,9 +56,50 @@ fn no_ref_nested() { c(); } +struct A<'a>(&'a mut String, &'a mut String); +// Test that reborrowing works as expected for move closures +// by attempting a disjoint capture through a reference. +fn disjoint_via_ref() { + let mut x = String::new(); + let mut y = String::new(); + + let mut a = A(&mut x, &mut y); + let a = &mut a; + + let mut c1 = move || { + a.0.truncate(0); + }; + + let mut c2 = move || { + a.1.truncate(0); + }; + + c1(); + c2(); +} + +// Test that even if a path is moved into the closure, the closure is not FnOnce +// if the path is not moved by the closure call. +fn data_moved_but_not_fn_once() { + let x = Box::new(10i32); + + let c = move || { + // *x has type i32 which is Copy. So even though the box `x` will be moved + // into the closure, `x` is never moved when the closure is called, i.e. the + // ownership stays with the closure and therefore we can call the function multiple times. + let _x = *x; + }; + + c(); + c(); +} + fn main() { simple_ref(); struct_contains_ref_to_another_struct(); no_ref(); no_ref_nested(); + + disjoint_via_ref(); + data_moved_but_not_fn_once(); }