check FnDef return type for WF

rust-lang · Sep 5, 2023 · c4d6215 · c4d6215
1 parent bf1e3f3
commit c4d6215
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Showing 6 changed files with 136 additions and 45 deletions.
diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs
@@ -518,6 518,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  /// Pushes all the predicates needed to validate that `ty` is WF into `out`.
  #[instrument(level = "debug", skip(self))]
  fn compute(&mut self, arg: GenericArg<'tcx>) {
  let tcx = self.tcx();
  let mut walker = arg.walk();
  let param_env = self.param_env;
  let depth = self.recursion_depth;
@@ -542,7 543,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  ));
  let cause = self.cause(traits::WellFormed(None));
  self.out.push(traits::Obligation::with_depth(
- self.tcx(),
  tcx,
  cause,
  self.recursion_depth,
  self.param_env,
@@ -554,7 555,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  let cause = self.cause(traits::WellFormed(None));
 
  self.out.push(traits::Obligation::with_depth(
- self.tcx(),
  tcx,
  cause,
  self.recursion_depth,
  self.param_env,
@@ -576,7 577,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  ));
  let cause = self.cause(traits::WellFormed(None));
  self.out.push(traits::Obligation::with_depth(
- self.tcx(),
  tcx,
  cause,
  self.recursion_depth,
  self.param_env,
@@ -661,6 662,16 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  }
 
  ty::FnDef(did, args) => {
  // HACK: Check the return type of function definitions for
  // well-formedness to mostly fix #84533. This is still not
  // perfect and there may be ways to abuse the fact that we
  // ignore requirements with escaping bound vars. That's a
  // more general issue however.
  //
  // FIXME(eddyb) add the type to `walker` instead of recursing.
  let fn_sig = tcx.fn_sig(did).instantiate(tcx, args);
  self.compute(fn_sig.output().skip_binder().into());
 
  let obligations = self.nominal_obligations(did, args);
  self.out.extend(obligations);
  }
@@ -670,7 681,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  if !r.has_escaping_bound_vars() && !rty.has_escaping_bound_vars() {
  let cause = self.cause(traits::ReferenceOutlivesReferent(ty));
  self.out.push(traits::Obligation::with_depth(
- self.tcx(),
  tcx,
  cause,
  depth,
  param_env,
@@ -745,7 756,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  // All of the requirements on type parameters
  // have already been checked for `impl Trait` in
  // return position. We do need to check type-alias-impl-trait though.
- if self.tcx().is_type_alias_impl_trait(def_id) {
  if tcx.is_type_alias_impl_trait(def_id) {
  let obligations = self.nominal_obligations(def_id, args);
  self.out.extend(obligations);
  }
@@ -767,12 778,12 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  // obligations that don't refer to Self and
  // checking those
 
- let defer_to_coercion = self.tcx().features().object_safe_for_dispatch;
  let defer_to_coercion = tcx.features().object_safe_for_dispatch;
 
  if !defer_to_coercion {
  let cause = self.cause(traits::WellFormed(None));
  let component_traits = data.auto_traits().chain(data.principal_def_id());
- let tcx = self.tcx();
  let tcx = tcx;
  self.out.extend(component_traits.map(|did| {
  traits::Obligation::with_depth(
  tcx,
@@ -800,7 811,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
  ty::Infer(_) => {
  let cause = self.cause(traits::WellFormed(None));
  self.out.push(traits::Obligation::with_depth(
- self.tcx(),
  tcx,
  cause,
  self.recursion_depth,
  param_env,

diff --git a/tests/ui/fn/fn-item-lifetime-bounds.rs b/tests/ui/fn/fn-item-lifetime-bounds.rs
diff --git a/tests/ui/wf/wf-fn-def-check-sig-1.rs b/tests/ui/wf/wf-fn-def-check-sig-1.rs
@@ -0,0 1,44 @@
 // Regression test for #84533.
 
 use std::marker::PhantomData;
 
 fn foo<'b, 'a>() -> PhantomData<&'b &'a ()> {
  PhantomData
 }
 
 fn extend_lifetime<'a, 'b, T: ?Sized>(x: &'a T) -> &'b T {
  let f = foo::<'b, 'a>;
  //~^ ERROR lifetime may not live long enough
  f.baz(x)
 }
 
 trait Foo<'a, 'b, T: ?Sized> {
  fn baz(self, s: &'a T) -> &'b T;
 }
 impl<'a, 'b, R, F, T: ?Sized> Foo<'a, 'b, T> for F
 where
  F: Fn() -> R,
  R: ProofForConversion<'a, 'b, T>,
 {
  fn baz(self, s: &'a T) -> &'b T {
  self().convert(s)
  }
 }
 
 trait ProofForConversion<'a, 'b, T: ?Sized> {
  fn convert(self, s: &'a T) -> &'b T;
 }
 impl<'a, 'b, T: ?Sized> ProofForConversion<'a, 'b, T> for PhantomData<&'b &'a ()> {
  fn convert(self, s: &'a T) -> &'b T {
  s
  }
 }
 
 fn main() {
  let d;
  {
  let x = "Hello World".to_string();
  d = extend_lifetime(&x);
  }
  println!("{}", d);
 }
diff --git a/tests/ui/wf/wf-fn-def-check-sig-1.stderr b/tests/ui/wf/wf-fn-def-check-sig-1.stderr
@@ -0,0 1,14 @@
 error: lifetime may not live long enough
  --> $DIR/wf-fn-def-check-sig-1.rs:10:13
  |
 LL | fn extend_lifetime<'a, 'b, T: ?Sized>(x: &'a T) -> &'b T {
  | -- -- lifetime `'b` defined here
  | |
  | lifetime `'a` defined here
 LL | let f = foo::<'b, 'a>;
  | ^^^^^^^^^^^^^ requires that `'a` must outlive `'b`
  |
  = help: consider adding the following bound: `'a: 'b`
 
 error: aborting due to previous error
 
diff --git a/tests/ui/wf/wf-fn-def-check-sig-2.rs b/tests/ui/wf/wf-fn-def-check-sig-2.rs
@@ -0,0 1,44 @@
 // Regression test for #84533 involving higher-ranked regions
 // in the return type.
 use std::marker::PhantomData;
 
 fn foo<'c, 'b, 'a>(_: &'c ()) -> (&'c (), PhantomData<&'b &'a ()>) {
  (&(), PhantomData)
 }
 
 fn extend_lifetime<'a, 'b, T: ?Sized>(x: &'a T) -> &'b T {
  let f = foo;
  f.baz(x)
  //~^ ERROR lifetime may not live long enough
 }
 
 trait Foo<'a, 'b, T: ?Sized> {
  fn baz(self, s: &'a T) -> &'b T;
 }
 impl<'a, 'b, R, F, T: ?Sized> Foo<'a, 'b, T> for F
 where
  F: for<'c> Fn(&'c ()) -> (&'c (), R),
  R: ProofForConversion<'a, 'b, T>,
 {
  fn baz(self, s: &'a T) -> &'b T {
  self(&()).1.convert(s)
  }
 }
 
 trait ProofForConversion<'a, 'b, T: ?Sized> {
  fn convert(self, s: &'a T) -> &'b T;
 }
 impl<'a, 'b, T: ?Sized> ProofForConversion<'a, 'b, T> for PhantomData<&'b &'a ()> {
  fn convert(self, s: &'a T) -> &'b T {
  s
  }
 }
 
 fn main() {
  let d;
  {
  let x = "Hello World".to_string();
  d = extend_lifetime(&x);
  }
  println!("{}", d);
 }
diff --git a/tests/ui/wf/wf-fn-def-check-sig-2.stderr b/tests/ui/wf/wf-fn-def-check-sig-2.stderr
@@ -0,0 1,15 @@
 error: lifetime may not live long enough
  --> $DIR/wf-fn-def-check-sig-2.rs:11:5
  |
 LL | fn extend_lifetime<'a, 'b, T: ?Sized>(x: &'a T) -> &'b T {
  | -- -- lifetime `'b` defined here
  | |
  | lifetime `'a` defined here
 LL | let f = foo;
 LL | f.baz(x)
  | ^^^^^^^^ function was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
  |
  = help: consider adding the following bound: `'a: 'b`
 
 error: aborting due to previous error