Don't print full paths in overlap errors

compiler/rustc_errors/src/lib.rs

@@ -1254,6 +1254,10 @@ impl HandlerInner {
         }
 
         if diagnostic.has_future_breakage() {
+            // Future breakages aren't emitted if they're Level::Allowed,
+            // but they still need to be constructed and stashed below,
+            // so they'll trigger the good-path bug check.
+            self.suppressed_expected_diag = true;
             self.future_breakage_diagnostics.push(diagnostic.clone());
         }
 

compiler/rustc_trait_selection/src/errors.rs

@@ -58,10 +58,10 @@ pub struct NoValueInOnUnimplemented {
     pub span: Span,
 }
 
-pub struct NegativePositiveConflict<'a> {
+pub struct NegativePositiveConflict<'tcx> {
     pub impl_span: Span,
-    pub trait_desc: &'a str,
-    pub self_desc: &'a Option<String>,
+    pub trait_desc: ty::TraitRef<'tcx>,
+    pub self_ty: Option<Ty<'tcx>>,
     pub negative_impl_span: Result<Span, Symbol>,
     pub positive_impl_span: Result<Span, Symbol>,
 }
@@ -73,10 +73,10 @@ impl IntoDiagnostic<'_> for NegativePositiveConflict<'_> {
         handler: &Handler,
     ) -> rustc_errors::DiagnosticBuilder<'_, ErrorGuaranteed> {
         let mut diag = handler.struct_err(fluent::trait_selection_negative_positive_conflict);
-        diag.set_arg("trait_desc", self.trait_desc);
+        diag.set_arg("trait_desc", self.trait_desc.print_only_trait_path().to_string());
         diag.set_arg(
             "self_desc",
-            self.self_desc.clone().map_or_else(|| String::from("none"), |ty| ty),
+            self.self_ty.map_or_else(|| "none".to_string(), |ty| ty.to_string()),
         );
         diag.set_span(self.impl_span);
         diag.code(rustc_errors::error_code!(E0751));

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -64,13 +64,13 @@ pub fn add_placeholder_note(err: &mut Diagnostic) {
 /// with a suitably-freshened `ImplHeader` with those types
 /// substituted. Otherwise, returns `None`.
 #[instrument(skip(tcx, skip_leak_check), level = "debug")]
-pub fn overlapping_impls(
-    tcx: TyCtxt<'_>,
+pub fn overlapping_impls<'tcx>(
+    tcx: TyCtxt<'tcx>,
     impl1_def_id: DefId,
     impl2_def_id: DefId,
     skip_leak_check: SkipLeakCheck,
     overlap_mode: OverlapMode,
-) -> Option<OverlapResult<'_>> {
+) -> Option<OverlapResult<'tcx>> {
     // Before doing expensive operations like entering an inference context, do
     // a quick check via fast_reject to tell if the impl headers could possibly
     // unify.

compiler/rustc_trait_selection/src/traits/specialize/mod.rs

@@ -17,9 +17,9 @@ use crate::infer::{InferCtxt, InferOk, TyCtxtInferExt};
 use crate::traits::select::IntercrateAmbiguityCause;
 use crate::traits::{self, coherence, FutureCompatOverlapErrorKind, ObligationCause};
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{struct_span_err, DiagnosticBuilder, EmissionGuarantee};
+use rustc_errors::{error_code, DelayDm, Diagnostic};
 use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_middle::ty::{self, ImplSubject, TyCtxt};
+use rustc_middle::ty::{self, ImplSubject, Ty, TyCtxt};
 use rustc_middle::ty::{InternalSubsts, SubstsRef};
 use rustc_session::lint::builtin::COHERENCE_LEAK_CHECK;
 use rustc_session::lint::builtin::ORDER_DEPENDENT_TRAIT_OBJECTS;
@@ -30,10 +30,10 @@ use super::SelectionContext;
 
 /// Information pertinent to an overlapping impl error.
 #[derive(Debug)]
-pub struct OverlapError {
+pub struct OverlapError<'tcx> {
     pub with_impl: DefId,
-    pub trait_desc: String,
-    pub self_desc: Option<String>,
+    pub trait_ref: ty::TraitRef<'tcx>,
+    pub self_ty: Option<Ty<'tcx>>,
     pub intercrate_ambiguity_causes: FxIndexSet<IntercrateAmbiguityCause>,
     pub involves_placeholder: bool,
 }
@@ -277,9 +277,9 @@ pub(super) fn specialization_graph_provider(
 // it negatively impacts perf.
 #[cold]
 #[inline(never)]
-fn report_overlap_conflict(
-    tcx: TyCtxt<'_>,
-    overlap: OverlapError,
+fn report_overlap_conflict<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    overlap: OverlapError<'tcx>,
     impl_def_id: LocalDefId,
     used_to_be_allowed: Option<FutureCompatOverlapErrorKind>,
     sg: &mut specialization_graph::Graph,
@@ -315,27 +315,27 @@ fn report_overlap_conflict(
     }
 }
 
-fn report_negative_positive_conflict(
-    tcx: TyCtxt<'_>,
-    overlap: &OverlapError,
+fn report_negative_positive_conflict<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    overlap: &OverlapError<'tcx>,
     local_impl_def_id: LocalDefId,
     negative_impl_def_id: DefId,
     positive_impl_def_id: DefId,
     sg: &mut specialization_graph::Graph,
 ) {
     let mut err = tcx.sess.create_err(NegativePositiveConflict {
         impl_span: tcx.def_span(local_impl_def_id),
-        trait_desc: &overlap.trait_desc,
-        self_desc: &overlap.self_desc,
+        trait_desc: overlap.trait_ref,
+        self_ty: overlap.self_ty,
         negative_impl_span: tcx.span_of_impl(negative_impl_def_id),
         positive_impl_span: tcx.span_of_impl(positive_impl_def_id),
     });
     sg.has_errored = Some(err.emit());
 }
 
-fn report_conflicting_impls(
-    tcx: TyCtxt<'_>,
-    overlap: OverlapError,
+fn report_conflicting_impls<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    overlap: OverlapError<'tcx>,
     impl_def_id: LocalDefId,
     used_to_be_allowed: Option<FutureCompatOverlapErrorKind>,
     sg: &mut specialization_graph::Graph,
@@ -345,12 +345,12 @@ fn report_conflicting_impls(
     // Work to be done after we've built the DiagnosticBuilder. We have to define it
     // now because the struct_lint methods don't return back the DiagnosticBuilder
     // that's passed in.
-    fn decorate<'a, 'b, G: EmissionGuarantee>(
-        tcx: TyCtxt<'_>,
-        overlap: OverlapError,
+    fn decorate<'tcx>(
+        tcx: TyCtxt<'tcx>,
+        overlap: &OverlapError<'tcx>,
         impl_span: Span,
-        err: &'b mut DiagnosticBuilder<'a, G>,
-    ) -> &'b mut DiagnosticBuilder<'a, G> {
+        err: &mut Diagnostic,
+    ) {
         match tcx.span_of_impl(overlap.with_impl) {
             Ok(span) => {
                 err.span_label(span, "first implementation here");
@@ -359,7 +359,7 @@ fn report_conflicting_impls(
                     impl_span,
                     format!(
                         "conflicting implementation{}",
-                        overlap.self_desc.map_or_else(String::new, |ty| format!(" for `{}`", ty))
+                        overlap.self_ty.map_or_else(String::new, |ty| format!(" for `{}`", ty))
                     ),
                 );
             }
@@ -381,26 +381,28 @@ fn report_conflicting_impls(
         if overlap.involves_placeholder {
             coherence::add_placeholder_note(err);
         }
-        err
     }
 
-    let msg = format!(
-        "conflicting implementations of trait `{}`{}{}",
-        overlap.trait_desc,
-        overlap.self_desc.as_deref().map_or_else(String::new, |ty| format!(" for type `{ty}`")),
-        match used_to_be_allowed {
-            Some(FutureCompatOverlapErrorKind::Issue33140) => ": (E0119)",
-            _ => "",
-        }
-    );
+    let msg = DelayDm(|| {
+        format!(
+            "conflicting implementations of trait `{}`{}{}",
+            overlap.trait_ref.print_only_trait_path(),
+            overlap.self_ty.map_or_else(String::new, |ty| format!(" for type `{ty}`")),
+            match used_to_be_allowed {
+                Some(FutureCompatOverlapErrorKind::Issue33140) => ": (E0119)",
+                _ => "",
+            }
+        )
+    });
 
     match used_to_be_allowed {
         None => {
             let reported = if overlap.with_impl.is_local()
                 || tcx.orphan_check_impl(impl_def_id).is_ok()
             {
-                let mut err = struct_span_err!(tcx.sess, impl_span, E0119, "{msg}",);
-                decorate(tcx, overlap, impl_span, &mut err);
+                let mut err = tcx.sess.struct_span_err(impl_span, msg);
+                err.code(error_code!(E0119));
+                decorate(tcx, &overlap, impl_span, &mut err);
                 Some(err.emit())
             } else {
                 Some(tcx.sess.delay_span_bug(impl_span, "impl should have failed the orphan check"))
@@ -417,7 +419,10 @@ fn report_conflicting_impls(
                 tcx.hir().local_def_id_to_hir_id(impl_def_id),
                 impl_span,
                 msg,
-                |err| decorate(tcx, overlap, impl_span, err),
+                |err| {
+                    decorate(tcx, &overlap, impl_span, err);
+                    err
+                },
             );
         }
     };

compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs

@@ -3,7 +3,6 @@ use super::OverlapError;
 use crate::traits;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::fast_reject::{self, SimplifiedType, TreatParams};
-use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
 
 pub use rustc_middle::traits::specialization_graph::*;
@@ -15,15 +14,15 @@ pub enum FutureCompatOverlapErrorKind {
 }
 
 #[derive(Debug)]
-pub struct FutureCompatOverlapError {
-    pub error: OverlapError,
+pub struct FutureCompatOverlapError<'tcx> {
+    pub error: OverlapError<'tcx>,
     pub kind: FutureCompatOverlapErrorKind,
 }
 
 /// The result of attempting to insert an impl into a group of children.
-enum Inserted {
+enum Inserted<'tcx> {
     /// The impl was inserted as a new child in this group of children.
-    BecameNewSibling(Option<FutureCompatOverlapError>),
+    BecameNewSibling(Option<FutureCompatOverlapError<'tcx>>),
 
     /// The impl should replace existing impls [X1, ..], because the impl specializes X1, X2, etc.
     ReplaceChildren(Vec<DefId>),
@@ -42,12 +41,12 @@ trait ChildrenExt<'tcx> {
         impl_def_id: DefId,
         simplified_self: Option<SimplifiedType>,
         overlap_mode: OverlapMode,
-    ) -> Result<Inserted, OverlapError>;
+    ) -> Result<Inserted<'tcx>, OverlapError<'tcx>>;
 }
 
-impl ChildrenExt<'_> for Children {
+impl<'tcx> ChildrenExt<'tcx> for Children {
     /// Insert an impl into this set of children without comparing to any existing impls.
-    fn insert_blindly(&mut self, tcx: TyCtxt<'_>, impl_def_id: DefId) {
+    fn insert_blindly(&mut self, tcx: TyCtxt<'tcx>, impl_def_id: DefId) {
         let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
         if let Some(st) = fast_reject::simplify_type(tcx, trait_ref.self_ty(), TreatParams::AsInfer)
         {
@@ -62,7 +61,7 @@ impl ChildrenExt<'_> for Children {
     /// Removes an impl from this set of children. Used when replacing
     /// an impl with a parent. The impl must be present in the list of
     /// children already.
-    fn remove_existing(&mut self, tcx: TyCtxt<'_>, impl_def_id: DefId) {
+    fn remove_existing(&mut self, tcx: TyCtxt<'tcx>, impl_def_id: DefId) {
         let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
         let vec: &mut Vec<DefId>;
         if let Some(st) = fast_reject::simplify_type(tcx, trait_ref.self_ty(), TreatParams::AsInfer)
@@ -82,11 +81,11 @@ impl ChildrenExt<'_> for Children {
     /// specialization relationships.
     fn insert(
         &mut self,
-        tcx: TyCtxt<'_>,
+        tcx: TyCtxt<'tcx>,
         impl_def_id: DefId,
         simplified_self: Option<SimplifiedType>,
         overlap_mode: OverlapMode,
-    ) -> Result<Inserted, OverlapError> {
+    ) -> Result<Inserted<'tcx>, OverlapError<'tcx>> {
         let mut last_lint = None;
         let mut replace_children = Vec::new();
 
@@ -103,30 +102,23 @@ impl ChildrenExt<'_> for Children {
                 impl_def_id, simplified_self, possible_sibling,
             );
 
-            let create_overlap_error = |overlap: traits::coherence::OverlapResult<'_>| {
+            let create_overlap_error = |overlap: traits::coherence::OverlapResult<'tcx>| {
                 let trait_ref = overlap.impl_header.trait_ref.unwrap();
                 let self_ty = trait_ref.self_ty();
 
-                // FIXME: should postpone string formatting until we decide to actually emit.
-                with_no_trimmed_paths!({
-                    OverlapError {
-                        with_impl: possible_sibling,
-                        trait_desc: trait_ref.print_only_trait_path().to_string(),
-                        // Only report the `Self` type if it has at least
-                        // some outer concrete shell; otherwise, it's
-                        // not adding much information.
-                        self_desc: if self_ty.has_concrete_skeleton() {
-                            Some(self_ty.to_string())
-                        } else {
-                            None
-                        },
-                        intercrate_ambiguity_causes: overlap.intercrate_ambiguity_causes,
-                        involves_placeholder: overlap.involves_placeholder,
-                    }
-                })
+                OverlapError {
+                    with_impl: possible_sibling,
+                    trait_ref,
+                    // Only report the `Self` type if it has at least
+                    // some outer concrete shell; otherwise, it's
+                    // not adding much information.
+                    self_ty: if self_ty.has_concrete_skeleton() { Some(self_ty) } else { None },
+                    intercrate_ambiguity_causes: overlap.intercrate_ambiguity_causes,
+                    involves_placeholder: overlap.involves_placeholder,
+                }
             };
 
-            let report_overlap_error = |overlap: traits::coherence::OverlapResult<'_>,
+            let report_overlap_error = |overlap: traits::coherence::OverlapResult<'tcx>,
                                         last_lint: &mut _| {
                 // Found overlap, but no specialization; error out or report future-compat warning.
 
@@ -255,31 +247,31 @@ where
     }
 }
 
-pub trait GraphExt {
+pub trait GraphExt<'tcx> {
     /// Insert a local impl into the specialization graph. If an existing impl
     /// conflicts with it (has overlap, but neither specializes the other),
     /// information about the area of overlap is returned in the `Err`.
     fn insert(
         &mut self,
-        tcx: TyCtxt<'_>,
+        tcx: TyCtxt<'tcx>,
         impl_def_id: DefId,
         overlap_mode: OverlapMode,
-    ) -> Result<Option<FutureCompatOverlapError>, OverlapError>;
+    ) -> Result<Option<FutureCompatOverlapError<'tcx>>, OverlapError<'tcx>>;
 
     /// Insert cached metadata mapping from a child impl back to its parent.
-    fn record_impl_from_cstore(&mut self, tcx: TyCtxt<'_>, parent: DefId, child: DefId);
+    fn record_impl_from_cstore(&mut self, tcx: TyCtxt<'tcx>, parent: DefId, child: DefId);
 }
 
-impl GraphExt for Graph {
+impl<'tcx> GraphExt<'tcx> for Graph {
     /// Insert a local impl into the specialization graph. If an existing impl
     /// conflicts with it (has overlap, but neither specializes the other),
     /// information about the area of overlap is returned in the `Err`.
     fn insert(
         &mut self,
-        tcx: TyCtxt<'_>,
+        tcx: TyCtxt<'tcx>,
         impl_def_id: DefId,
         overlap_mode: OverlapMode,
-    ) -> Result<Option<FutureCompatOverlapError>, OverlapError> {
+    ) -> Result<Option<FutureCompatOverlapError<'tcx>>, OverlapError<'tcx>> {
         assert!(impl_def_id.is_local());
 
         let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
@@ -376,7 +368,7 @@ impl GraphExt for Graph {
     }
 
     /// Insert cached metadata mapping from a child impl back to its parent.
-    fn record_impl_from_cstore(&mut self, tcx: TyCtxt<'_>, parent: DefId, child: DefId) {
+    fn record_impl_from_cstore(&mut self, tcx: TyCtxt<'tcx>, parent: DefId, child: DefId) {
         if self.parent.insert(child, parent).is_some() {
             bug!(
                 "When recording an impl from the crate store, information about its parent \

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-cross-crate.stderr

@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `go_trait::GoMut` for type `MyThingy`
+error[E0119]: conflicting implementations of trait `GoMut` for type `MyThingy`
   --> $DIR/coherence-blanket-conflicts-with-specific-cross-crate.rs:15:1
    |
 LL | impl GoMut for MyThingy {

src/test/ui/coherence/coherence-conflicting-negative-trait-impl.stderr

@@ -1,4 +1,4 @@
-error[E0751]: found both positive and negative implementation of trait `std::marker::Send` for type `TestType<_>`:
+error[E0751]: found both positive and negative implementation of trait `Send` for type `TestType<_>`:
   --> $DIR/coherence-conflicting-negative-trait-impl.rs:11:1
    |
 LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
@@ -7,7 +7,7 @@ LL |
 LL | impl<T: MyTrait> !Send for TestType<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
-error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<_>`
+error[E0119]: conflicting implementations of trait `Send` for type `TestType<_>`
   --> $DIR/coherence-conflicting-negative-trait-impl.rs:13:1
    |
 LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}

src/test/ui/coherence/coherence-impls-copy.stderr

@@ -9,7 +9,7 @@ LL | impl Copy for i32 {}
    |
    = note: define and implement a trait or new type instead
 
-error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `&NotSync`
+error[E0119]: conflicting implementations of trait `Copy` for type `&NotSync`
   --> $DIR/coherence-impls-copy.rs:28:1
    |
 LL | impl Copy for &'static NotSync {}