provide generic_param_scope for region errors

rust-lang · bors · Jul 15, 2022 · Jul 7, 2022 · Jul 7, 2022 · Jul 7, 2022
commit 5bd8c960f5f7b07128ebdb12e7f788b1ba0a1902
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -181,11 +181,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         let generic_ty = type_test.generic_kind.to_ty(self.infcx.tcx);
                         let origin = RelateParamBound(type_test_span, generic_ty, None);
                         self.buffer_error(self.infcx.construct_generic_bound_failure(
+                            self.body.source.def_id().expect_local(),
                             type_test_span,
                             Some(origin),
                             type_test.generic_kind,
                             lower_bound_region,
-                            self.body.source.def_id().as_local(),
                         ));
                     } else {
                         // FIXME. We should handle this case better. It

diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -63,7 +63,7 @@ use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString, Mul
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::lang_items::LangItem;
-use rustc_hir::{Item, ItemKind, Node};
+use rustc_hir::Node;
 use rustc_middle::dep_graph::DepContext;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{
@@ -348,7 +348,11 @@ pub fn same_type_modulo_infer<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
 }
 
 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
-    pub fn report_region_errors(&self, errors: &[RegionResolutionError<'tcx>]) {
+    pub fn report_region_errors(
+        &self,
+        generic_param_scope: LocalDefId,
+        errors: &[RegionResolutionError<'tcx>],
+    ) {
         debug!("report_region_errors(): {} errors to start", errors.len());
 
         // try to pre-process the errors, which will group some of them
@@ -379,6 +383,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
                     RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
                         self.report_generic_bound_failure(
+                            generic_param_scope,
                             origin.span(),
                             Some(origin),
                             param_ty,
@@ -2269,56 +2274,30 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
     pub fn report_generic_bound_failure(
         &self,
+        generic_param_scope: LocalDefId,
         span: Span,
         origin: Option<SubregionOrigin<'tcx>>,
         bound_kind: GenericKind<'tcx>,
         sub: Region<'tcx>,
     ) {
-        let owner =
-            self.in_progress_typeck_results.map(|typeck_results| typeck_results.borrow().hir_owner);
-        self.construct_generic_bound_failure(span, origin, bound_kind, sub, owner).emit();
+        self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
+            .emit();
     }
 
     pub fn construct_generic_bound_failure(
         &self,
+        generic_param_scope: LocalDefId,
         span: Span,
         origin: Option<SubregionOrigin<'tcx>>,
         bound_kind: GenericKind<'tcx>,
         sub: Region<'tcx>,
-        owner: Option<LocalDefId>,
     ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
-        let hir = self.tcx.hir();
         // Attempt to obtain the span of the parameter so we can
         // suggest adding an explicit lifetime bound to it.
-        let generics = owner.map(|owner| {
-            let hir_id = hir.local_def_id_to_hir_id(owner);
-            let parent_id = hir.get_parent_item(hir_id);
-            (
-                // Parent item could be a `mod`, so we check the HIR before calling:
-                if let Some(Node::Item(Item {
-                    kind: ItemKind::Trait(..) | ItemKind::Impl { .. },
-                    ..
-                })) = hir.find_by_def_id(parent_id)
-                {
-                    Some(self.tcx.generics_of(parent_id))
-                } else {
-                    None
-                },
-                self.tcx.generics_of(owner.to_def_id()),
-                hir.span(hir_id),
-            )
-        });
-
-        let span = match generics {
-            // This is to get around the trait identity obligation, that has a `DUMMY_SP` as signal
-            // for other diagnostics, so we need to recover it here.
-            Some((_, _, node)) if span.is_dummy() => node,
-            _ => span,
-        };
-
+        let generics = self.tcx.generics_of(generic_param_scope);
         // type_param_span is (span, has_bounds)
-        let type_param_span = match (generics, bound_kind) {
-            (Some((_, ref generics, _)), GenericKind::Param(ref param)) => {
+        let type_param_span = match bound_kind {
+            GenericKind::Param(ref param) => {
                 // Account for the case where `param` corresponds to `Self`,
                 // which doesn't have the expected type argument.
                 if !(generics.has_self && param.index == 0) {
@@ -2346,30 +2325,23 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             }
             _ => None,
         };
-        let new_lt = generics
-            .as_ref()
-            .and_then(|(parent_g, g, _)| {
-                let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
-                let mut lts_names = g
-                    .params
-                    .iter()
+
+        let new_lt = {
+            let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
+            let lts_names =
+                iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p)))
+                    .flat_map(|g| &g.params)
                     .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
                     .map(|p| p.name.as_str())
                     .collect::<Vec<_>>();
-                if let Some(g) = parent_g {
-                    lts_names.extend(
-                        g.params
-                            .iter()
-                            .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
-                            .map(|p| p.name.as_str()),
-                    );
-                }
-                possible.find(|candidate| !lts_names.contains(&&candidate[..]))
-            })
-            .unwrap_or("'lt".to_string());
+            possible
+                .find(|candidate| !lts_names.contains(&&candidate[..]))
+                .unwrap_or("'lt".to_string())
+        };
+
         let add_lt_sugg = generics
-            .as_ref()
-            .and_then(|(_, g, _)| g.params.first())
+            .params
+            .first()
             .and_then(|param| param.def_id.as_local())
             .map(|def_id| (self.tcx.def_span(def_id).shrink_to_lo(), format!("{}, ", new_lt)));
 
@@ -2571,7 +2543,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 );
                 if let Some(infer::RelateParamBound(_, t, _)) = origin {
                     let return_impl_trait =
-                        owner.and_then(|owner| self.tcx.return_type_impl_trait(owner)).is_some();
+                        self.tcx.return_type_impl_trait(generic_param_scope).is_some();
                     let t = self.resolve_vars_if_possible(t);
                     match t.kind() {
                         // We've got:

diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
@@ -1301,7 +1301,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     /// result. After this, no more unification operations should be
     /// done -- or the compiler will panic -- but it is legal to use
     /// `resolve_vars_if_possible` as well as `fully_resolve`.
-    pub fn resolve_regions_and_report_errors(&self, outlives_env: &OutlivesEnvironment<'tcx>) {
+    pub fn resolve_regions_and_report_errors(
+        &self,
+        generic_param_scope: LocalDefId,
+        outlives_env: &OutlivesEnvironment<'tcx>,
+    ) {
         let errors = self.resolve_regions(outlives_env);
 
         if !self.is_tainted_by_errors() {
@@ -1310,7 +1314,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             // this infcx was in use.  This is totally hokey but
             // otherwise we have a hard time separating legit region
             // errors from silly ones.
-            self.report_region_errors(&errors);
+            self.report_region_errors(generic_param_scope, &errors);
         }
     }
 

diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -68,6 +68,7 @@ use crate::infer::{
 };
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use rustc_data_structures::undo_log::UndoLogs;
+use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::{self, Region, Ty, TyCtxt, TypeVisitable};
 use smallvec::smallvec;
@@ -163,14 +164,15 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
 
     pub fn check_region_obligations_and_report_errors(
         &self,
+        generic_param_scope: LocalDefId,
         outlives_env: &OutlivesEnvironment<'tcx>,
     ) {
         self.process_registered_region_obligations(
             outlives_env.region_bound_pairs(),
             outlives_env.param_env,
         );
 
-        self.resolve_regions_and_report_errors(outlives_env)
+        self.resolve_regions_and_report_errors(generic_param_scope, outlives_env)
     }
 }
 

diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -237,29 +237,37 @@ fn do_normalize_predicates<'tcx>(
         // cares about declarations like `'a: 'b`.
         let outlives_env = OutlivesEnvironment::new(elaborated_env);
 
-        infcx.resolve_regions_and_report_errors(&outlives_env);
+        // FIXME: It's very weird that we ignore region obligations but apparently
+        // still need to use `resolve_regions` as we need the resolved regions in
+        // the normalized predicates.
+        let errors = infcx.resolve_regions(&outlives_env);
+        if !errors.is_empty() {
+            tcx.sess.delay_span_bug(
+                span,
+                format!(
+                    "failed region resolution while normalizing {elaborated_env:?}: {errors:?}"
+                ),
+            );
+        }
 
-        let predicates = match infcx.fully_resolve(predicates) {
-            Ok(predicates) => predicates,
+        match infcx.fully_resolve(predicates) {
+            Ok(predicates) => Ok(predicates),
             Err(fixup_err) => {
                 // If we encounter a fixup error, it means that some type
                 // variable wound up unconstrained. I actually don't know
                 // if this can happen, and I certainly don't expect it to
                 // happen often, but if it did happen it probably
                 // represents a legitimate failure due to some kind of
-                // unconstrained variable, and it seems better not to ICE,
-                // all things considered.
-                let reported = tcx.sess.span_err(span, &fixup_err.to_string());
-                return Err(reported);
+                // unconstrained variable.
+                //
+                // @lcnr: Let's still ICE here for now. I want a test case
+                // for that.
+                span_bug!(
+                    span,
+                    "inference variables in normalized parameter environment: {}",
+                    fixup_err
+                );
             }
-        };
-        if predicates.needs_infer() {
-            let reported = tcx
-                .sess
-                .delay_span_bug(span, "encountered inference variables after `fully_resolve`");
-            Err(reported)
-        } else {
-            Ok(predicates)
         }
     })
 }

diff --git a/compiler/rustc_typeck/src/check/check.rs b/compiler/rustc_typeck/src/check/check.rs
@@ -767,7 +767,10 @@ fn check_opaque_meets_bounds<'tcx>(
             // Can have different predicates to their defining use
             hir::OpaqueTyOrigin::TyAlias => {
                 let outlives_environment = OutlivesEnvironment::new(param_env);
-                infcx.check_region_obligations_and_report_errors(&outlives_environment);
+                infcx.check_region_obligations_and_report_errors(
+                    defining_use_anchor,
+                    &outlives_environment,
+                );
             }
         }
 

diff --git a/compiler/rustc_typeck/src/check/compare_method.rs b/compiler/rustc_typeck/src/check/compare_method.rs
@@ -394,7 +394,10 @@ fn compare_predicate_entailment<'tcx>(
         // lifetime parameters.
         let mut outlives_environment = OutlivesEnvironment::new(param_env);
         outlives_environment.add_implied_bounds(infcx, wf_tys, impl_m_hir_id);
-        infcx.check_region_obligations_and_report_errors(&outlives_environment);
+        infcx.check_region_obligations_and_report_errors(
+            impl_m.def_id.expect_local(),
+            &outlives_environment,
+        );
 
         Ok(())
     })
@@ -1145,7 +1148,8 @@ pub(crate) fn compare_const_impl<'tcx>(
         }
 
         let outlives_environment = OutlivesEnvironment::new(param_env);
-        infcx.resolve_regions_and_report_errors(&outlives_environment);
+        infcx
+            .resolve_regions_and_report_errors(impl_c.def_id.expect_local(), &outlives_environment);
     });
 }
 
@@ -1262,7 +1266,10 @@ fn compare_type_predicate_entailment<'tcx>(
         // Finally, resolve all regions. This catches wily misuses of
         // lifetime parameters.
         let outlives_environment = OutlivesEnvironment::new(param_env);
-        infcx.check_region_obligations_and_report_errors(&outlives_environment);
+        infcx.check_region_obligations_and_report_errors(
+            impl_ty.def_id.expect_local(),
+            &outlives_environment,
+        );
 
         Ok(())
     })
@@ -1493,7 +1500,10 @@ pub fn check_type_bounds<'tcx>(
         };
         let mut outlives_environment = OutlivesEnvironment::new(param_env);
         outlives_environment.add_implied_bounds(&infcx, implied_bounds, impl_ty_hir_id);
-        infcx.check_region_obligations_and_report_errors(&outlives_environment);
+        infcx.check_region_obligations_and_report_errors(
+            impl_ty.def_id.expect_local(),
+            &outlives_environment,
+        );
 
         Ok(())
     })

diff --git a/compiler/rustc_typeck/src/check/wfcheck.rs b/compiler/rustc_typeck/src/check/wfcheck.rs
@@ -107,7 +107,7 @@ pub(super) fn enter_wf_checking_ctxt<'tcx, F>(
 
         let mut outlives_environment = OutlivesEnvironment::new(param_env);
         outlives_environment.add_implied_bounds(infcx, wf_tys, body_id);
-        infcx.check_region_obligations_and_report_errors(&outlives_environment);
+        infcx.check_region_obligations_and_report_errors(body_def_id, &outlives_environment);
     })
 }
 

diff --git a/compiler/rustc_typeck/src/coherence/builtin.rs b/compiler/rustc_typeck/src/coherence/builtin.rs
@@ -349,7 +349,7 @@ fn visit_implementation_of_dispatch_from_dyn<'tcx>(tcx: TyCtxt<'tcx>, impl_did:
 
                     // Finally, resolve all regions.
                     let outlives_env = OutlivesEnvironment::new(param_env);
-                    infcx.resolve_regions_and_report_errors(&outlives_env);
+                    infcx.resolve_regions_and_report_errors(impl_did, &outlives_env);
                 }
             }
             _ => {
@@ -606,7 +606,7 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: DefId) -> CoerceUn
 
         // Finally, resolve all regions.
         let outlives_env = OutlivesEnvironment::new(param_env);
-        infcx.resolve_regions_and_report_errors(&outlives_env);
+        infcx.resolve_regions_and_report_errors(impl_did, &outlives_env);
 
         CoerceUnsizedInfo { custom_kind: kind }
     })

diff --git a/compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs b/compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs
@@ -150,7 +150,7 @@ fn get_impl_substs<'tcx>(
 
     // Conservatively use an empty `ParamEnv`.
     let outlives_env = OutlivesEnvironment::new(ty::ParamEnv::empty());
-    infcx.resolve_regions_and_report_errors(&outlives_env);
+    infcx.resolve_regions_and_report_errors(impl1_def_id, &outlives_env);
     let Ok(impl2_substs) = infcx.fully_resolve(impl2_substs) else {
         let span = tcx.def_span(impl1_def_id);
         tcx.sess.emit_err(SubstsOnOverriddenImpl { span });

diff --git a/src/test/ui/builtin-superkinds/builtin-superkinds-self-type.stderr b/src/test/ui/builtin-superkinds/builtin-superkinds-self-type.stderr
@@ -2,15 +2,17 @@ error[E0310]: the parameter type `T` may not live long enough
   --> $DIR/builtin-superkinds-self-type.rs:10:16
    |
 LL | impl <T: Sync> Foo for T { }
-   |                ^^^
+   |                ^^^ ...so that the type `T` will meet its required lifetime bounds...
    |
-   = help: consider adding an explicit lifetime bound `T: 'static`...
-   = note: ...so that the type `T` will meet its required lifetime bounds...
 note: ...that is required by this bound
   --> $DIR/builtin-superkinds-self-type.rs:6:24
    |
 LL | trait Foo : Sized+Sync+'static {
    |                        ^^^^^^^
+help: consider adding an explicit lifetime bound...
+   |
+LL | impl <T: Sync + 'static> Foo for T { }
+   |               +++++++++
 
 error: aborting due to previous error
 

diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.stderr b/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.stderr
@@ -2,10 +2,12 @@ error[E0310]: the parameter type `T` may not live long enough
   --> $DIR/implied-bounds-unnorm-associated-type-3.rs:19:5
    |
 LL |     fn zero_copy_from<'b>(cart: &'b [T]) -> &'b [T] {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `[T]` will meet its required lifetime bounds
    |
-   = help: consider adding an explicit lifetime bound `T: 'static`...
-   = note: ...so that the type `[T]` will meet its required lifetime bounds
+help: consider adding an explicit lifetime bound...
+   |
+LL | impl<T: 'static> ZeroCopyFrom<[T]> for &'static [T] {
+   |       +++++++++
 
 error: aborting due to previous error