Rollup of 7 pull requests

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -45,12 +45,7 @@ pub(super) fn compare_impl_method<'tcx>(
     debug!("compare_impl_method(impl_trait_ref={:?})", impl_trait_ref);
 
     let _: Result<_, ErrorGuaranteed> = try {
-        compare_self_type(tcx, impl_m, trait_m, impl_trait_ref)?;
-        compare_number_of_generics(tcx, impl_m, trait_m, false)?;
-        compare_generic_param_kinds(tcx, impl_m, trait_m, false)?;
-        compare_number_of_method_arguments(tcx, impl_m, trait_m)?;
-        compare_synthetic_generics(tcx, impl_m, trait_m)?;
-        compare_asyncness(tcx, impl_m, trait_m)?;
+        check_method_is_structurally_compatible(tcx, impl_m, trait_m, impl_trait_ref, false)?;
         compare_method_predicate_entailment(
             tcx,
             impl_m,
@@ -61,6 +56,26 @@ pub(super) fn compare_impl_method<'tcx>(
     };
 }
 
+/// Checks a bunch of different properties of the impl/trait methods for
+/// compatibility, such as asyncness, number of argument, self receiver kind,
+/// and number of early- and late-bound generics.
+fn check_method_is_structurally_compatible<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    impl_m: ty::AssocItem,
+    trait_m: ty::AssocItem,
+    impl_trait_ref: ty::TraitRef<'tcx>,
+    delay: bool,
+) -> Result<(), ErrorGuaranteed> {
+    compare_self_type(tcx, impl_m, trait_m, impl_trait_ref, delay)?;
+    compare_number_of_generics(tcx, impl_m, trait_m, delay)?;
+    compare_generic_param_kinds(tcx, impl_m, trait_m, delay)?;
+    compare_number_of_method_arguments(tcx, impl_m, trait_m, delay)?;
+    compare_synthetic_generics(tcx, impl_m, trait_m, delay)?;
+    compare_asyncness(tcx, impl_m, trait_m, delay)?;
+    check_region_bounds_on_impl_item(tcx, impl_m, trait_m, delay)?;
+    Ok(())
+}
+
 /// This function is best explained by example. Consider a trait with it's implementation:
 ///
 /// ```rust
@@ -177,9 +192,6 @@ fn compare_method_predicate_entailment<'tcx>(
     let impl_m_predicates = tcx.predicates_of(impl_m.def_id);
     let trait_m_predicates = tcx.predicates_of(trait_m.def_id);
 
-    // Check region bounds.
-    check_region_bounds_on_impl_item(tcx, impl_m, trait_m, false)?;
-
     // Create obligations for each predicate declared by the impl
     // definition in the context of the trait's parameter
     // environment. We can't just use `impl_env.caller_bounds`,
@@ -534,6 +546,7 @@ fn compare_asyncness<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl_m: ty::AssocItem,
     trait_m: ty::AssocItem,
+    delay: bool,
 ) -> Result<(), ErrorGuaranteed> {
     if tcx.asyncness(trait_m.def_id) == hir::IsAsync::Async {
         match tcx.fn_sig(impl_m.def_id).skip_binder().skip_binder().output().kind() {
@@ -544,11 +557,14 @@ fn compare_asyncness<'tcx>(
                 // We don't know if it's ok, but at least it's already an error.
             }
             _ => {
-                return Err(tcx.sess.emit_err(crate::errors::AsyncTraitImplShouldBeAsync {
-                    span: tcx.def_span(impl_m.def_id),
-                    method_name: trait_m.name,
-                    trait_item_span: tcx.hir().span_if_local(trait_m.def_id),
-                }));
+                return Err(tcx
+                    .sess
+                    .create_err(crate::errors::AsyncTraitImplShouldBeAsync {
+                        span: tcx.def_span(impl_m.def_id),
+                        method_name: trait_m.name,
+                        trait_item_span: tcx.hir().span_if_local(trait_m.def_id),
+                    })
+                    .emit_unless(delay));
             }
         };
     }
@@ -602,9 +618,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
 
     // First, check a few of the same things as `compare_impl_method`,
     // just so we don't ICE during substitution later.
-    compare_number_of_generics(tcx, impl_m, trait_m, true)?;
-    compare_generic_param_kinds(tcx, impl_m, trait_m, true)?;
-    check_region_bounds_on_impl_item(tcx, impl_m, trait_m, true)?;
+    check_method_is_structurally_compatible(tcx, impl_m, trait_m, impl_trait_ref, true)?;
 
     let trait_to_impl_substs = impl_trait_ref.substs;
 
@@ -1097,6 +1111,7 @@ fn compare_self_type<'tcx>(
     impl_m: ty::AssocItem,
     trait_m: ty::AssocItem,
     impl_trait_ref: ty::TraitRef<'tcx>,
+    delay: bool,
 ) -> Result<(), ErrorGuaranteed> {
     // Try to give more informative error messages about self typing
     // mismatches. Note that any mismatch will also be detected
@@ -1145,7 +1160,7 @@ fn compare_self_type<'tcx>(
             } else {
                 err.note_trait_signature(trait_m.name, trait_m.signature(tcx));
             }
-            return Err(err.emit());
+            return Err(err.emit_unless(delay));
         }
 
         (true, false) => {
@@ -1166,7 +1181,7 @@ fn compare_self_type<'tcx>(
                 err.note_trait_signature(trait_m.name, trait_m.signature(tcx));
             }
 
-            return Err(err.emit());
+            return Err(err.emit_unless(delay));
         }
     }
 
@@ -1352,6 +1367,7 @@ fn compare_number_of_method_arguments<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl_m: ty::AssocItem,
     trait_m: ty::AssocItem,
+    delay: bool,
 ) -> Result<(), ErrorGuaranteed> {
     let impl_m_fty = tcx.fn_sig(impl_m.def_id);
     let trait_m_fty = tcx.fn_sig(trait_m.def_id);
@@ -1422,7 +1438,7 @@ fn compare_number_of_method_arguments<'tcx>(
             ),
         );
 
-        return Err(err.emit());
+        return Err(err.emit_unless(delay));
     }
 
     Ok(())
@@ -1432,6 +1448,7 @@ fn compare_synthetic_generics<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl_m: ty::AssocItem,
     trait_m: ty::AssocItem,
+    delay: bool,
 ) -> Result<(), ErrorGuaranteed> {
     // FIXME(chrisvittal) Clean up this function, list of FIXME items:
     //     1. Better messages for the span labels
@@ -1551,7 +1568,7 @@ fn compare_synthetic_generics<'tcx>(
                 }
                 _ => unreachable!(),
             }
-            error_found = Some(err.emit());
+            error_found = Some(err.emit_unless(delay));
         }
     }
     if let Some(reported) = error_found { Err(reported) } else { Ok(()) }

compiler/rustc_hir_analysis/src/impl_wf_check.rs

@@ -106,10 +106,23 @@ fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
                     if item.defaultness(tcx).has_value() {
                         cgp::parameters_for(&tcx.type_of(def_id).subst_identity(), true)
                     } else {
-                        Vec::new()
+                        vec![]
                     }
                 }
-                ty::AssocKind::Fn | ty::AssocKind::Const => Vec::new(),
+                ty::AssocKind::Fn => {
+                    if !tcx.lower_impl_trait_in_trait_to_assoc_ty()
+                        && item.defaultness(tcx).has_value()
+                        && tcx.impl_method_has_trait_impl_trait_tys(item.def_id)
+                        && let Ok(table) = tcx.collect_return_position_impl_trait_in_trait_tys(def_id)
+                    {
+                        table.values().copied().flat_map(|ty| {
+                            cgp::parameters_for(&ty.subst_identity(), true)
+                        }).collect()
+                    } else {
+                        vec![]
+                    }
+                }
+                ty::AssocKind::Const => vec![],
             }
         })
         .collect();

compiler/rustc_lint/src/builtin.rs

@@ -2124,12 +2124,16 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
             }
 
             let ty_generics = cx.tcx.generics_of(def_id);
+            let num_where_predicates = hir_generics
+                .predicates
+                .iter()
+                .filter(|predicate| predicate.in_where_clause())
+                .count();
 
             let mut bound_count = 0;
             let mut lint_spans = Vec::new();
             let mut where_lint_spans = Vec::new();
-            let mut dropped_predicate_count = 0;
-            let num_predicates = hir_generics.predicates.len();
+            let mut dropped_where_predicate_count = 0;
             for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
                 let (relevant_lifetimes, bounds, predicate_span, in_where_clause) =
                     match where_predicate {
@@ -2186,8 +2190,8 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                 bound_count += bound_spans.len();
 
                 let drop_predicate = bound_spans.len() == bounds.len();
-                if drop_predicate {
-                    dropped_predicate_count += 1;
+                if drop_predicate && in_where_clause {
+                    dropped_where_predicate_count += 1;
                 }
 
                 if drop_predicate {
@@ -2196,7 +2200,7 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                     } else if predicate_span.from_expansion() {
                         // Don't try to extend the span if it comes from a macro expansion.
                         where_lint_spans.push(predicate_span);
-                    } else if i + 1 < num_predicates {
+                    } else if i + 1 < num_where_predicates {
                         // If all the bounds on a predicate were inferable and there are
                         // further predicates, we want to eat the trailing comma.
                         let next_predicate_span = hir_generics.predicates[i + 1].span();
@@ -2224,9 +2228,10 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                 }
             }
 
-            // If all predicates are inferable, drop the entire clause
+            // If all predicates in where clause are inferable, drop the entire clause
             // (including the `where`)
-            if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
+            if hir_generics.has_where_clause_predicates
+                && dropped_where_predicate_count == num_where_predicates
             {
                 let where_span = hir_generics.where_clause_span;
                 // Extend the where clause back to the closing `>` of the