From 2b4a2b95dd1a6b85678537332045d122afda682f Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 30 Jan 2024 14:22:05 +0000
Subject: [PATCH] Check normalized call signature for WF in mir typeck
---
compiler/rustc_borrowck/src/type_check/mod.rs | 24 ++++++++--
tests/ui/nll/check-normalized-sig-for-wf.rs | 27 +++++++++++
.../ui/nll/check-normalized-sig-for-wf.stderr | 47 +++++++++++++++++++
3 files changed, 94 insertions(+), 4 deletions(-)
create mode 100644 tests/ui/nll/check-normalized-sig-for-wf.rs
create mode 100644 tests/ui/nll/check-normalized-sig-for-wf.stderr
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index cfb46f3ac8a96..ae4000f02a7d6 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -1432,7 +1432,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
return;
}
};
- let (sig, map) = tcx.instantiate_bound_regions(sig, |br| {
+ let (unnormalized_sig, map) = tcx.instantiate_bound_regions(sig, |br| {
use crate::renumber::RegionCtxt;
let region_ctxt_fn = || {
@@ -1454,7 +1454,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
region_ctxt_fn,
)
});
- debug!(?sig);
+ debug!(?unnormalized_sig);
// IMPORTANT: We have to prove well formed for the function signature before
// we normalize it, as otherwise types like `<&'a &'b () as Trait>::Assoc`
// get normalized away, causing us to ignore the `'b: 'a` bound used by the function.
@@ -1464,7 +1464,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
//
// See #91068 for an example.
self.prove_predicates(
- sig.inputs_and_output.iter().map(|ty| {
+ unnormalized_sig.inputs_and_output.iter().map(|ty| {
ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(
ty.into(),
)))
@@ -1472,7 +1472,23 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
term_location.to_locations(),
ConstraintCategory::Boring,
);
- let sig = self.normalize(sig, term_location);
+
+ let sig = self.normalize(unnormalized_sig, term_location);
+ // HACK(#114936): `WF(sig)` does not imply `WF(normalized(sig))`
+ // with built-in `Fn` implementations, since the impl may not be
+ // well-formed itself.
+ if sig != unnormalized_sig {
+ self.prove_predicates(
+ sig.inputs_and_output.iter().map(|ty| {
+ ty::Binder::dummy(ty::PredicateKind::Clause(
+ ty::ClauseKind::WellFormed(ty.into()),
+ ))
+ }),
+ term_location.to_locations(),
+ ConstraintCategory::Boring,
+ );
+ }
+
self.check_call_dest(body, term, &sig, *destination, *target, term_location);
// The ordinary liveness rules will ensure that all
diff --git a/tests/ui/nll/check-normalized-sig-for-wf.rs b/tests/ui/nll/check-normalized-sig-for-wf.rs
new file mode 100644
index 0000000000000..cb0f34ce02f7a
--- /dev/null
+++ b/tests/ui/nll/check-normalized-sig-for-wf.rs
@@ -0,0 +1,27 @@
+// <https://github.com/rust-lang/rust/issues/114936>
+fn whoops(
+ s: String,
+ f: impl for<'s> FnOnce(&'s str) -> (&'static str, [&'static &'s (); 0]),
+) -> &'static str
+{
+ f(&s).0
+ //~^ ERROR `s` does not live long enough
+}
+
+// <https://github.com/rust-lang/rust/issues/118876>
+fn extend<T>(input: &T) -> &'static T {
+ struct Bounded<'a, 'b: 'static, T>(&'a T, [&'b (); 0]);
+ let n: Box<dyn FnOnce(&T) -> Bounded<'static, '_, T>> = Box::new(|x| Bounded(x, []));
+ n(input).0
+ //~^ ERROR borrowed data escapes outside of function
+}
+
+// <https://github.com/rust-lang/rust/issues/118876>
+fn extend_mut<'a, T>(input: &'a mut T) -> &'static mut T {
+ struct Bounded<'a, 'b: 'static, T>(&'a mut T, [&'b (); 0]);
+ let mut n: Box<dyn FnMut(&mut T) -> Bounded<'static, '_, T>> = Box::new(|x| Bounded(x, []));
+ n(input).0
+ //~^ ERROR borrowed data escapes outside of function
+}
+
+fn main() {}
diff --git a/tests/ui/nll/check-normalized-sig-for-wf.stderr b/tests/ui/nll/check-normalized-sig-for-wf.stderr
new file mode 100644
index 0000000000000..5c96b0c6561a1
--- /dev/null
+++ b/tests/ui/nll/check-normalized-sig-for-wf.stderr
@@ -0,0 +1,47 @@
+error[E0597]: `s` does not live long enough
+ --> $DIR/check-normalized-sig-for-wf.rs:7:7
+ |
+LL | s: String,
+ | - binding `s` declared here
+...
+LL | f(&s).0
+ | --^^-
+ | | |
+ | | borrowed value does not live long enough
+ | argument requires that `s` is borrowed for `'static`
+LL |
+LL | }
+ | - `s` dropped here while still borrowed
+
+error[E0521]: borrowed data escapes outside of function
+ --> $DIR/check-normalized-sig-for-wf.rs:15:5
+ |
+LL | fn extend<T>(input: &T) -> &'static T {
+ | ----- - let's call the lifetime of this reference `'1`
+ | |
+ | `input` is a reference that is only valid in the function body
+...
+LL | n(input).0
+ | ^^^^^^^^
+ | |
+ | `input` escapes the function body here
+ | argument requires that `'1` must outlive `'static`
+
+error[E0521]: borrowed data escapes outside of function
+ --> $DIR/check-normalized-sig-for-wf.rs:23:5
+ |
+LL | fn extend_mut<'a, T>(input: &'a mut T) -> &'static mut T {
+ | -- ----- `input` is a reference that is only valid in the function body
+ | |
+ | lifetime `'a` defined here
+...
+LL | n(input).0
+ | ^^^^^^^^
+ | |
+ | `input` escapes the function body here
+ | argument requires that `'a` must outlive `'static`
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0521, E0597.
+For more information about an error, try `rustc --explain E0521`.