From f46eabb9e56fab132ec8171d0e0239f42c986e52 Mon Sep 17 00:00:00 2001
From: Matthew Jasper <mjjasper1@gmail.com>
Date: Fri, 5 May 2023 15:52:53 +0100
Subject: [PATCH] Report nicer lifetime errors for specialization
Add an obligation cause for these error so that the error points to the
implementations that caused the error.
---
.../src/impl_wf_check/min_specialization.rs | 19 +++++--
.../src/traits/coherence.rs | 4 +-
.../rustc_trait_selection/src/traits/mod.rs | 4 +-
.../src/traits/specialize/mod.rs | 34 +++++++++++--
.../rustc_trait_selection/src/traits/util.rs | 4 +-
.../specialize_with_generalize_lifetimes.rs | 50 +++++++++++++++++++
...pecialize_with_generalize_lifetimes.stderr | 27 ++++++++++
7 files changed, 132 insertions(+), 10 deletions(-)
create mode 100644 tests/ui/specialization/min_specialization/specialize_with_generalize_lifetimes.rs
create mode 100644 tests/ui/specialization/min_specialization/specialize_with_generalize_lifetimes.stderr
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
index 4f0df5c5677..e84da2519ae 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
@@ -80,7 +80,7 @@ use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
use rustc_span::Span;
use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
-use rustc_trait_selection::traits::{self, translate_substs, wf, ObligationCtxt};
+use rustc_trait_selection::traits::{self, translate_substs_with_cause, wf, ObligationCtxt};
pub(super) fn check_min_specialization(tcx: TyCtxt<'_>, impl_def_id: LocalDefId) {
if let Some(node) = parent_specialization_node(tcx, impl_def_id) {
@@ -180,8 +180,21 @@ fn get_impl_substs(
ocx.assumed_wf_types(param_env, tcx.def_span(impl1_def_id), impl1_def_id);
let impl1_substs = InternalSubsts::identity_for_item(tcx, impl1_def_id);
- let impl2_substs =
- translate_substs(infcx, param_env, impl1_def_id.to_def_id(), impl1_substs, impl2_node);
+ let impl1_span = tcx.def_span(impl1_def_id);
+ let impl2_substs = translate_substs_with_cause(
+ infcx,
+ param_env,
+ impl1_def_id.to_def_id(),
+ impl1_substs,
+ impl2_node,
+ |_, span| {
+ traits::ObligationCause::new(
+ impl1_span,
+ impl1_def_id,
+ traits::ObligationCauseCode::BindingObligation(impl2_node.def_id(), span),
+ )
+ },
+ );
let errors = ocx.select_all_or_error();
if !errors.is_empty() {
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index b7690f79933..9f405aaf1a8 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -322,7 +322,9 @@ fn negative_impl(tcx: TyCtxt<'_>, impl1_def_id: DefId, impl2_def_id: DefId) -> b
let selcx = &mut SelectionContext::new(&infcx);
let impl2_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl2_def_id);
let (subject2, obligations) =
- impl_subject_and_oblig(selcx, impl_env, impl2_def_id, impl2_substs);
+ impl_subject_and_oblig(selcx, impl_env, impl2_def_id, impl2_substs, |_, _| {
+ ObligationCause::dummy()
+ });
!equate(&infcx, impl_env, subject1, subject2, obligations, impl1_def_id)
}
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index 8b8c50f6b83..138b0fb7432 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -54,7 +54,9 @@ pub use self::select::{EvaluationCache, SelectionCache, SelectionContext};
pub use self::select::{EvaluationResult, IntercrateAmbiguityCause, OverflowError};
pub use self::specialize::specialization_graph::FutureCompatOverlapError;
pub use self::specialize::specialization_graph::FutureCompatOverlapErrorKind;
-pub use self::specialize::{specialization_graph, translate_substs, OverlapError};
+pub use self::specialize::{
+ specialization_graph, translate_substs, translate_substs_with_cause, OverlapError,
+};
pub use self::structural_match::{
search_for_adt_const_param_violation, search_for_structural_match_violation,
};
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index 8bbebadb22a..9a4b72013b8 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -82,6 +82,30 @@ pub fn translate_substs<'tcx>(
source_impl: DefId,
source_substs: SubstsRef<'tcx>,
target_node: specialization_graph::Node,
+) -> SubstsRef<'tcx> {
+ translate_substs_with_cause(
+ infcx,
+ param_env,
+ source_impl,
+ source_substs,
+ target_node,
+ |_, _| ObligationCause::dummy(),
+ )
+}
+
+/// Like [translate_substs], but obligations from the parent implementation
+/// are registered with the provided `ObligationCause`.
+///
+/// This is for reporting *region* errors from those bounds. Type errors should
+/// not happen because the specialization graph already checks for those, and
+/// will result in an ICE.
+pub fn translate_substs_with_cause<'tcx>(
+ infcx: &InferCtxt<'tcx>,
+ param_env: ty::ParamEnv<'tcx>,
+ source_impl: DefId,
+ source_substs: SubstsRef<'tcx>,
+ target_node: specialization_graph::Node,
+ cause: impl Fn(usize, Span) -> ObligationCause<'tcx>,
) -> SubstsRef<'tcx> {
debug!(
"translate_substs({:?}, {:?}, {:?}, {:?})",
@@ -99,7 +123,7 @@ pub fn translate_substs<'tcx>(
return source_substs;
}
- fulfill_implication(infcx, param_env, source_trait_ref, source_impl, target_impl)
+ fulfill_implication(infcx, param_env, source_trait_ref, source_impl, target_impl, cause)
.unwrap_or_else(|()| {
bug!(
"When translating substitutions from {source_impl:?} to {target_impl:?}, \
@@ -154,7 +178,10 @@ pub(super) fn specializes(tcx: TyCtxt<'_>, (impl1_def_id, impl2_def_id): (DefId,
let infcx = tcx.infer_ctxt().build();
// Attempt to prove that impl2 applies, given all of the above.
- fulfill_implication(&infcx, penv, impl1_trait_ref, impl1_def_id, impl2_def_id).is_ok()
+ fulfill_implication(&infcx, penv, impl1_trait_ref, impl1_def_id, impl2_def_id, |_, _| {
+ ObligationCause::dummy()
+ })
+ .is_ok()
}
/// Attempt to fulfill all obligations of `target_impl` after unification with
@@ -168,6 +195,7 @@ fn fulfill_implication<'tcx>(
source_trait_ref: ty::TraitRef<'tcx>,
source_impl: DefId,
target_impl: DefId,
+ error_cause: impl Fn(usize, Span) -> ObligationCause<'tcx>,
) -> Result<SubstsRef<'tcx>, ()> {
debug!(
"fulfill_implication({:?}, trait_ref={:?} |- {:?} applies)",
@@ -195,7 +223,7 @@ fn fulfill_implication<'tcx>(
let selcx = &mut SelectionContext::new(&infcx);
let target_substs = infcx.fresh_substs_for_item(DUMMY_SP, target_impl);
let (target_trait, obligations) =
- util::impl_subject_and_oblig(selcx, param_env, target_impl, target_substs);
+ util::impl_subject_and_oblig(selcx, param_env, target_impl, target_substs, error_cause);
// do the impls unify? If not, no specialization.
let Ok(InferOk { obligations: more_obligations, .. }) =
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 7b7e297c64b..82f3df40198 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -197,6 +197,7 @@ pub fn impl_subject_and_oblig<'a, 'tcx>(
param_env: ty::ParamEnv<'tcx>,
impl_def_id: DefId,
impl_substs: SubstsRef<'tcx>,
+ cause: impl Fn(usize, Span) -> ObligationCause<'tcx>,
) -> (ImplSubject<'tcx>, impl Iterator<Item = PredicateObligation<'tcx>>) {
let subject = selcx.tcx().impl_subject(impl_def_id);
let subject = subject.subst(selcx.tcx(), impl_substs);
@@ -208,8 +209,7 @@ pub fn impl_subject_and_oblig<'a, 'tcx>(
let predicates = predicates.instantiate(selcx.tcx(), impl_substs);
let InferOk { value: predicates, obligations: normalization_obligations2 } =
selcx.infcx.at(&ObligationCause::dummy(), param_env).normalize(predicates);
- let impl_obligations =
- super::predicates_for_generics(|_, _| ObligationCause::dummy(), param_env, predicates);
+ let impl_obligations = super::predicates_for_generics(cause, param_env, predicates);
let impl_obligations = impl_obligations
.chain(normalization_obligations1.into_iter())
diff --git a/tests/ui/specialization/min_specialization/specialize_with_generalize_lifetimes.rs b/tests/ui/specialization/min_specialization/specialize_with_generalize_lifetimes.rs
new file mode 100644
index 00000000000..d90b81f717a
--- /dev/null
+++ b/tests/ui/specialization/min_specialization/specialize_with_generalize_lifetimes.rs
@@ -0,0 +1,50 @@
+// Regression test for #79457.
+
+#![feature(min_specialization)]
+
+use std::any::Any;
+
+pub trait Tr {
+ fn method(self) -> Box<dyn Any + 'static>;
+ fn other(self);
+}
+
+impl<T: Any + 'static> Tr for T {
+ default fn method(self) -> Box<dyn Any + 'static> {
+ Box::new(self)
+ }
+
+ default fn other(self) {}
+}
+
+impl<'a> Tr for &'a i32 {
+ //~^ ERROR does not fulfill the required lifetime
+ fn other(self) {}
+}
+
+fn promote_to_static<'a>(i: &'a i32) -> &'static i32 {
+ *i.method().downcast().unwrap()
+}
+
+struct Wrapper<'a>(&'a i32);
+
+impl<'a> Tr for Wrapper<'a> {
+ //~^ ERROR does not fulfill the required lifetime
+ fn other(self) {}
+}
+
+fn promote_to_static_2<'a>(w: Wrapper<'a>) -> Wrapper<'static> {
+ *w.method().downcast().unwrap()
+}
+
+fn main() {
+ let i = Box::new(100_i32);
+ let static_i: &'static i32 = promote_to_static(&*i);
+ drop(i);
+ println!("{}", *static_i);
+
+ let j = Box::new(200_i32);
+ let static_w: Wrapper<'static> = promote_to_static_2(Wrapper(&*j));
+ drop(j);
+ println!("{}", *static_w.0);
+}
diff --git a/tests/ui/specialization/min_specialization/specialize_with_generalize_lifetimes.stderr b/tests/ui/specialization/min_specialization/specialize_with_generalize_lifetimes.stderr
new file mode 100644
index 00000000000..2af75876d5b
--- /dev/null
+++ b/tests/ui/specialization/min_specialization/specialize_with_generalize_lifetimes.stderr
@@ -0,0 +1,27 @@
+error[E0477]: the type `&'a i32` does not fulfill the required lifetime
+ --> $DIR/specialize_with_generalize_lifetimes.rs:20:1
+ |
+LL | impl<'a> Tr for &'a i32 {
+ | ^^^^^^^^^^^^^^^^^^^^^^^
+ |
+note: type must satisfy the static lifetime as required by this binding
+ --> $DIR/specialize_with_generalize_lifetimes.rs:12:15
+ |
+LL | impl<T: Any + 'static> Tr for T {
+ | ^^^^^^^
+
+error[E0477]: the type `Wrapper<'a>` does not fulfill the required lifetime
+ --> $DIR/specialize_with_generalize_lifetimes.rs:31:1
+ |
+LL | impl<'a> Tr for Wrapper<'a> {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+note: type must satisfy the static lifetime as required by this binding
+ --> $DIR/specialize_with_generalize_lifetimes.rs:12:15
+ |
+LL | impl<T: Any + 'static> Tr for T {
+ | ^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0477`.