diff --git a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs index cfefe0a3e6517..e616449ccd412 100644 --- a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs +++ b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs @@ -3,6 +3,7 @@ use rustc_data_structures::graph::WithSuccessors; use rustc_index::bit_set::{HybridBitSet, SparseBitMatrix}; use rustc_index::interval::IntervalSet; use rustc_infer::infer::canonical::QueryRegionConstraints; +use rustc_infer::infer::outlives::for_liveness; use rustc_middle::mir::{BasicBlock, Body, ConstraintCategory, Local, Location}; use rustc_middle::traits::query::DropckOutlivesResult; use rustc_middle::ty::{RegionVid, Ty, TyCtxt, TypeVisitable, TypeVisitableExt}; @@ -601,34 +602,36 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> { values::location_set_str(elements, live_at.iter()), ); - let tcx = typeck.tcx(); - let borrowck_context = &mut typeck.borrowck_context; - // When using `-Zpolonius=next`, we want to record the loans that flow into this value's // regions as being live at the given `live_at` points: this will be used to compute the // location where a loan goes out of scope. - let num_loans = borrowck_context.borrow_set.len(); - let mut value_loans = HybridBitSet::new_empty(num_loans); - - tcx.for_each_free_region(&value, |live_region| { - let live_region_vid = borrowck_context.universal_regions.to_region_vid(live_region); - - borrowck_context - .constraints - .liveness_constraints - .add_elements(live_region_vid, live_at); - - // There can only be inflowing loans for this region when we are using - // `-Zpolonius=next`. - if let Some(inflowing) = inflowing_loans.row(live_region_vid) { - value_loans.union(inflowing); - } + let num_loans = typeck.borrowck_context.borrow_set.len(); + let value_loans = &mut HybridBitSet::new_empty(num_loans); + + value.visit_with(&mut for_liveness::FreeRegionsVisitor { + tcx: typeck.tcx(), + param_env: typeck.param_env, + op: |r| { + let live_region_vid = typeck.borrowck_context.universal_regions.to_region_vid(r); + + typeck + .borrowck_context + .constraints + .liveness_constraints + .add_elements(live_region_vid, live_at); + + // There can only be inflowing loans for this region when we are using + // `-Zpolonius=next`. + if let Some(inflowing) = inflowing_loans.row(live_region_vid) { + value_loans.union(inflowing); + } + }, }); // Record the loans reaching the value. if !value_loans.is_empty() { for point in live_at.iter() { - borrowck_context.live_loans.union_row(point, &value_loans); + typeck.borrowck_context.live_loans.union_row(point, value_loans); } } } diff --git a/compiler/rustc_infer/src/infer/opaque_types.rs b/compiler/rustc_infer/src/infer/opaque_types.rs index e1a14ed0faf6c..7a5dec22fe049 100644 --- a/compiler/rustc_infer/src/infer/opaque_types.rs +++ b/compiler/rustc_infer/src/infer/opaque_types.rs @@ -362,6 +362,8 @@ impl<'tcx> InferCtxt<'tcx> { .collect(), ); + // FIXME(#42940): This should use the `FreeRegionsVisitor`, but that's + // not currently sound until we have existential regions. concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor { tcx: self.tcx, op: |r| self.member_constraint(opaque_type_key, span, concrete_ty, r, &choice_regions), diff --git a/compiler/rustc_infer/src/infer/outlives/for_liveness.rs b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs new file mode 100644 index 0000000000000..ebc51b98be53f --- /dev/null +++ b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs @@ -0,0 +1,121 @@ +use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor}; + +use std::ops::ControlFlow; + +use crate::infer::outlives::test_type_match; +use crate::infer::region_constraints::VerifyIfEq; + +/// Visits free regions in the type that are relevant for liveness computation. +/// These regions are passed to `OP`. +/// +/// Specifically, we visit all of the regions of types recursively, except if +/// the type is an alias, we look at the outlives bounds in the param-env +/// and alias's item bounds. If there is a unique outlives bound, then visit +/// that instead. If there is not a unique but there is a `'static` outlives +/// bound, then don't visit anything. Otherwise, walk through the opaque's +/// regions structurally. +pub struct FreeRegionsVisitor<'tcx, OP: FnMut(ty::Region<'tcx>)> { + pub tcx: TyCtxt<'tcx>, + pub param_env: ty::ParamEnv<'tcx>, + pub op: OP, +} + +impl<'tcx, OP> TypeVisitor> for FreeRegionsVisitor<'tcx, OP> +where + OP: FnMut(ty::Region<'tcx>), +{ + fn visit_binder>>( + &mut self, + t: &ty::Binder<'tcx, T>, + ) -> ControlFlow { + t.super_visit_with(self); + ControlFlow::Continue(()) + } + + fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow { + match *r { + // ignore bound regions, keep visiting + ty::ReLateBound(_, _) => ControlFlow::Continue(()), + _ => { + (self.op)(r); + ControlFlow::Continue(()) + } + } + } + + fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow { + // We're only interested in types involving regions + if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) { + return ControlFlow::Continue(()); + } + + match ty.kind() { + // We can prove that an alias is live two ways: + // 1. All the components are live. + // + // 2. There is a known outlives bound or where-clause, and that + // region is live. + // + // We search through the item bounds and where clauses for + // either `'static` or a unique outlives region, and if one is + // found, we just need to prove that that region is still live. + // If one is not found, then we continue to walk through the alias. + ty::Alias(kind, ty::AliasTy { def_id, args, .. }) => { + let tcx = self.tcx; + let param_env = self.param_env; + let outlives_bounds: Vec<_> = tcx + .item_bounds(def_id) + .iter_instantiated(tcx, args) + .chain(param_env.caller_bounds()) + .filter_map(|clause| { + let outlives = clause.as_type_outlives_clause()?; + if let Some(outlives) = outlives.no_bound_vars() + && outlives.0 == ty + { + Some(outlives.1) + } else { + test_type_match::extract_verify_if_eq( + tcx, + param_env, + &outlives.map_bound(|ty::OutlivesPredicate(ty, bound)| { + VerifyIfEq { ty, bound } + }), + ty, + ) + } + }) + .collect(); + // If we find `'static`, then we know the alias doesn't capture *any* regions. + // Otherwise, all of the outlives regions should be equal -- if they're not, + // we don't really know how to proceed, so we continue recursing through the + // alias. + if outlives_bounds.contains(&tcx.lifetimes.re_static) { + // no + } else if let Some(r) = outlives_bounds.first() + && outlives_bounds[1..].iter().all(|other_r| other_r == r) + { + assert!(r.type_flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS)); + r.visit_with(self)?; + } else { + // Skip lifetime parameters that are not captures. + let variances = match kind { + ty::Opaque => Some(self.tcx.variances_of(*def_id)), + _ => None, + }; + + for (idx, s) in args.iter().enumerate() { + if variances.map(|variances| variances[idx]) != Some(ty::Variance::Bivariant) { + s.visit_with(self)?; + } + } + } + } + + _ => { + ty.super_visit_with(self)?; + } + } + + ControlFlow::Continue(()) + } +} diff --git a/compiler/rustc_infer/src/infer/outlives/mod.rs b/compiler/rustc_infer/src/infer/outlives/mod.rs index cb92fc6ddb64a..0987915f4fdb3 100644 --- a/compiler/rustc_infer/src/infer/outlives/mod.rs +++ b/compiler/rustc_infer/src/infer/outlives/mod.rs @@ -9,6 +9,7 @@ use rustc_middle::ty; pub mod components; pub mod env; +pub mod for_liveness; pub mod obligations; pub mod test_type_match; pub mod verify; diff --git a/tests/ui/borrowck/alias-liveness/gat-static.rs b/tests/ui/borrowck/alias-liveness/gat-static.rs new file mode 100644 index 0000000000000..92153124af932 --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/gat-static.rs @@ -0,0 +1,29 @@ +// check-pass + +trait Foo { + type Assoc<'a> + where + Self: 'a; + + fn assoc(&mut self) -> Self::Assoc<'_>; +} + +fn overlapping_mut(mut t: T) +where + T: Foo, + for<'a> T::Assoc<'a>: 'static, +{ + let a = t.assoc(); + let b = t.assoc(); +} + +fn live_past_borrow(mut t: T) +where + T: Foo, + for<'a> T::Assoc<'a>: 'static { + let x = t.assoc(); + drop(t); + drop(x); +} + +fn main() {} diff --git a/tests/ui/borrowck/alias-liveness/higher-ranked-outlives-for-capture.rs b/tests/ui/borrowck/alias-liveness/higher-ranked-outlives-for-capture.rs new file mode 100644 index 0000000000000..1f26c7babf210 --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/higher-ranked-outlives-for-capture.rs @@ -0,0 +1,16 @@ +// known-bug: #42940 + +trait Captures<'a> {} +impl Captures<'_> for T {} + +trait Outlives<'a>: 'a {} +impl<'a, T: 'a> Outlives<'a> for T {} + +// Test that we treat `for<'a> Opaque: 'a` as `Opaque: 'static` +fn test<'o>(v: &'o Vec) -> impl Captures<'o> + for<'a> Outlives<'a> {} + +fn statik() -> impl Sized { + test(&vec![]) +} + +fn main() {} diff --git a/tests/ui/borrowck/alias-liveness/higher-ranked-outlives-for-capture.stderr b/tests/ui/borrowck/alias-liveness/higher-ranked-outlives-for-capture.stderr new file mode 100644 index 0000000000000..58a42d8afe4d7 --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/higher-ranked-outlives-for-capture.stderr @@ -0,0 +1,16 @@ +error[E0716]: temporary value dropped while borrowed + --> $DIR/higher-ranked-outlives-for-capture.rs:13:11 + | +LL | test(&vec![]) + | ------^^^^^^- + | | | + | | creates a temporary value which is freed while still in use + | argument requires that borrow lasts for `'static` +LL | } + | - temporary value is freed at the end of this statement + | + = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info) + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0716`. diff --git a/tests/ui/borrowck/alias-liveness/higher-ranked.rs b/tests/ui/borrowck/alias-liveness/higher-ranked.rs new file mode 100644 index 0000000000000..afd0d3b31e3f3 --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/higher-ranked.rs @@ -0,0 +1,16 @@ +// check-pass + +trait Captures<'a> {} +impl Captures<'_> for T {} + +trait Outlives<'a>: 'a {} +impl<'a, T: 'a> Outlives<'a> for T {} + +// Test that we treat `for<'a> Opaque: 'a` as `Opaque: 'static` +fn test<'o>(v: &'o Vec) -> impl Captures<'o> + for<'a> Outlives<'a> {} + +fn opaque_doesnt_use_temporary() { + let a = test(&vec![]); +} + +fn main() {} diff --git a/tests/ui/borrowck/alias-liveness/opaque-capture.rs b/tests/ui/borrowck/alias-liveness/opaque-capture.rs new file mode 100644 index 0000000000000..f4ca2728bdbed --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/opaque-capture.rs @@ -0,0 +1,17 @@ +// check-pass + +// Check that opaques capturing early and late-bound vars correctly mark +// regions required to be live using the item bounds. + +trait Captures<'a> {} +impl Captures<'_> for T {} + +fn captures_temp_late<'a>(x: &'a Vec) -> impl Sized + Captures<'a> + 'static {} +fn captures_temp_early<'a: 'a>(x: &'a Vec) -> impl Sized + Captures<'a> + 'static {} + +fn test() { + let x = captures_temp_early(&vec![]); + let y = captures_temp_late(&vec![]); +} + +fn main() {} diff --git a/tests/ui/borrowck/alias-liveness/opaque-type-param.rs b/tests/ui/borrowck/alias-liveness/opaque-type-param.rs new file mode 100644 index 0000000000000..a292463b2ac45 --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/opaque-type-param.rs @@ -0,0 +1,14 @@ +// known-bug: #42940 + +trait Trait {} +impl Trait for () {} + +fn foo<'a>(s: &'a str) -> impl Trait + 'static { + bar(s) +} + +fn bar>(s: P) -> impl Trait + 'static { + () +} + +fn main() {} diff --git a/tests/ui/borrowck/alias-liveness/opaque-type-param.stderr b/tests/ui/borrowck/alias-liveness/opaque-type-param.stderr new file mode 100644 index 0000000000000..e1fbbc14f44ee --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/opaque-type-param.stderr @@ -0,0 +1,13 @@ +error[E0700]: hidden type for `impl Trait + 'static` captures lifetime that does not appear in bounds + --> $DIR/opaque-type-param.rs:7:5 + | +LL | fn foo<'a>(s: &'a str) -> impl Trait + 'static { + | -- -------------------- opaque type defined here + | | + | hidden type `impl Trait + 'static` captures the lifetime `'a` as defined here +LL | bar(s) + | ^^^^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0700`. diff --git a/tests/ui/borrowck/alias-liveness/rpit-static.rs b/tests/ui/borrowck/alias-liveness/rpit-static.rs new file mode 100644 index 0000000000000..45da3edb8780b --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/rpit-static.rs @@ -0,0 +1,22 @@ +// check-pass + +trait Captures<'a> {} +impl Captures<'_> for T {} + +fn foo(x: &mut i32) -> impl Sized + Captures<'_> + 'static {} + +fn overlapping_mut() { + let i = &mut 1; + let x = foo(i); + let y = foo(i); +} + +fn live_past_borrow() { + let y; + { + let x = &mut 1; + y = foo(x); + } +} + +fn main() {} diff --git a/tests/ui/borrowck/alias-liveness/rpitit-static.rs b/tests/ui/borrowck/alias-liveness/rpitit-static.rs new file mode 100644 index 0000000000000..2cc68d2bf3d81 --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/rpitit-static.rs @@ -0,0 +1,18 @@ +// check-pass + +trait Foo { + fn rpitit(&mut self) -> impl Sized + 'static; +} + +fn live_past_borrow(mut t: T) { + let x = t.rpitit(); + drop(t); + drop(x); +} + +fn overlapping_mut(mut t: T) { + let a = t.rpitit(); + let b = t.rpitit(); +} + +fn main() {} diff --git a/tests/ui/borrowck/alias-liveness/rtn-static.rs b/tests/ui/borrowck/alias-liveness/rtn-static.rs new file mode 100644 index 0000000000000..1f136b8b998b2 --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/rtn-static.rs @@ -0,0 +1,23 @@ +// check-pass + +#![feature(return_type_notation)] +//~^ WARN the feature `return_type_notation` is incomplete + +trait Foo { + fn borrow(&mut self) -> impl Sized + '_; +} + +fn live_past_borrow>(mut t: T) { + let x = t.borrow(); + drop(t); + drop(x); +} + +// Test that the `'_` item bound in `borrow` does not cause us to +// overlook the `'static` RTN bound. +fn overlapping_mut>(mut t: T) { + let x = t.borrow(); + let x = t.borrow(); +} + +fn main() {} diff --git a/tests/ui/borrowck/alias-liveness/rtn-static.stderr b/tests/ui/borrowck/alias-liveness/rtn-static.stderr new file mode 100644 index 0000000000000..e9202db2c7902 --- /dev/null +++ b/tests/ui/borrowck/alias-liveness/rtn-static.stderr @@ -0,0 +1,11 @@ +warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes + --> $DIR/rtn-static.rs:3:12 + | +LL | #![feature(return_type_notation)] + | ^^^^^^^^^^^^^^^^^^^^ + | + = note: see issue #109417 for more information + = note: `#[warn(incomplete_features)]` on by default + +warning: 1 warning emitted + diff --git a/tests/ui/impl-trait/bivariant-lifetime-liveness.rs b/tests/ui/impl-trait/bivariant-lifetime-liveness.rs new file mode 100644 index 0000000000000..fe99fe3f34068 --- /dev/null +++ b/tests/ui/impl-trait/bivariant-lifetime-liveness.rs @@ -0,0 +1,15 @@ +// check-pass +// issue: 116794 + +// Uncaptured lifetimes should not be required to be live. + +struct Invariant(*mut T); + +fn opaque<'a: 'a>(_: &'a str) -> Invariant { + Invariant(&mut ()) +} + +fn main() { + let x = opaque(&String::new()); + drop(x); +}