diff --git a/RELEASES.md b/RELEASES.md
index 2b65d070d5fd1..aa5f37fffebff 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,5 +1,5 @@
-Version 1.90 (2025-09-18)
-==========================
+Version 1.90.0 (2025-09-18)
+===========================
 
 <a id="1.90-Language"></a>
 
diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl
index e5405a7ad910c..5e10c5a77d97d 100644
--- a/compiler/rustc_ast_passes/messages.ftl
+++ b/compiler/rustc_ast_passes/messages.ftl
@@ -64,8 +64,6 @@ ast_passes_body_in_extern = incorrect `{$kind}` inside `extern` block
 
 ast_passes_bound_in_context = bounds on `type`s in {$ctx} have no effect
 
-ast_passes_c_variadic_associated_function = associated functions cannot have a C variable argument list
-
 ast_passes_c_variadic_bad_extern = `...` is not supported for `extern "{$abi}"` functions
     .label = `extern "{$abi}"` because of this
     .help = only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index dc221c2fb1abc..f773b02058ef1 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -696,7 +696,7 @@ impl<'a> AstValidator<'a> {
 
         match fn_ctxt {
             FnCtxt::Foreign => return,
-            FnCtxt::Free => match sig.header.ext {
+            FnCtxt::Free | FnCtxt::Assoc(_) => match sig.header.ext {
                 Extern::Implicit(_) => {
                     if !matches!(sig.header.safety, Safety::Unsafe(_)) {
                         self.dcx().emit_err(errors::CVariadicMustBeUnsafe {
@@ -726,11 +726,6 @@ impl<'a> AstValidator<'a> {
                     self.dcx().emit_err(err);
                 }
             },
-            FnCtxt::Assoc(_) => {
-                // For now, C variable argument lists are unsupported in associated functions.
-                let err = errors::CVariadicAssociatedFunction { span: variadic_param.span };
-                self.dcx().emit_err(err);
-            }
         }
     }
 
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index e09ca5b81c80c..fd75e999d1381 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -318,13 +318,6 @@ pub(crate) struct ExternItemAscii {
     pub block: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(ast_passes_c_variadic_associated_function)]
-pub(crate) struct CVariadicAssociatedFunction {
-    #[primary_span]
-    pub span: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(ast_passes_c_variadic_no_extern)]
 #[help]
diff --git a/compiler/rustc_borrowck/src/handle_placeholders.rs b/compiler/rustc_borrowck/src/handle_placeholders.rs
index 94379cdebf730..6be90994015f3 100644
--- a/compiler/rustc_borrowck/src/handle_placeholders.rs
+++ b/compiler/rustc_borrowck/src/handle_placeholders.rs
@@ -166,13 +166,9 @@ impl RegionTracker {
         }
     }
 
-    /// Determine if the tracked universes of the two SCCs are compatible.
-    pub(crate) fn universe_compatible_with(&self, other: Self) -> bool {
-        // HACK: We first check whether we can name the highest existential universe
-        // of `other`. This only exists to avoid errors in case that scc already
-        // depends on a placeholder it cannot name itself.
-        self.max_nameable_universe().can_name(other.max_nameable_universe())
-            || other.reachable_placeholders.can_be_named_by(self.max_nameable_universe())
+    /// Determine if we can name all the placeholders in `other`.
+    pub(crate) fn can_name_all_placeholders(&self, other: Self) -> bool {
+        other.reachable_placeholders.can_be_named_by(self.max_nameable_universe.0)
     }
 
     /// If this SCC reaches a placeholder it can't name, return it.
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index f57456949bb5e..5f4bfd9df48e5 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -571,11 +571,15 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
     }
 
-    /// Returns `true` if all the elements in the value of `scc_b` are nameable
+    /// Returns `true` if all the placeholders in the value of `scc_b` are nameable
     /// in `scc_a`. Used during constraint propagation, and only once
     /// the value of `scc_b` has been computed.
-    fn universe_compatible(&self, scc_b: ConstraintSccIndex, scc_a: ConstraintSccIndex) -> bool {
-        self.scc_annotations[scc_a].universe_compatible_with(self.scc_annotations[scc_b])
+    fn can_name_all_placeholders(
+        &self,
+        scc_a: ConstraintSccIndex,
+        scc_b: ConstraintSccIndex,
+    ) -> bool {
+        self.scc_annotations[scc_a].can_name_all_placeholders(self.scc_annotations[scc_b])
     }
 
     /// Once regions have been propagated, this method is used to see
@@ -964,16 +968,22 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             return true;
         }
 
+        let fr_static = self.universal_regions().fr_static;
+
         // If we are checking that `'sup: 'sub`, and `'sub` contains
         // some placeholder that `'sup` cannot name, then this is only
         // true if `'sup` outlives static.
-        if !self.universe_compatible(sub_region_scc, sup_region_scc) {
+        //
+        // Avoid infinite recursion if `sub_region` is already `'static`
+        if sub_region != fr_static
+            && !self.can_name_all_placeholders(sup_region_scc, sub_region_scc)
+        {
             debug!(
                 "sub universe `{sub_region_scc:?}` is not nameable \
                 by super `{sup_region_scc:?}`, promoting to static",
             );
 
-            return self.eval_outlives(sup_region, self.universal_regions().fr_static);
+            return self.eval_outlives(sup_region, fr_static);
         }
 
         // Both the `sub_region` and `sup_region` consist of the union
diff --git a/compiler/rustc_borrowck/src/type_check/canonical.rs b/compiler/rustc_borrowck/src/type_check/canonical.rs
index 2627ed899a933..aece0bda34692 100644
--- a/compiler/rustc_borrowck/src/type_check/canonical.rs
+++ b/compiler/rustc_borrowck/src/type_check/canonical.rs
@@ -230,8 +230,14 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         location: impl NormalizeLocation,
     ) -> Ty<'tcx> {
         let tcx = self.tcx();
+        let body = self.body;
+
+        let cause = ObligationCause::misc(
+            location.to_locations().span(body),
+            body.source.def_id().expect_local(),
+        );
+
         if self.infcx.next_trait_solver() {
-            let body = self.body;
             let param_env = self.infcx.param_env;
             // FIXME: Make this into a real type op?
             self.fully_perform_op(
@@ -241,10 +247,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     |ocx| {
                         let structurally_normalize = |ty| {
                             ocx.structurally_normalize_ty(
-                                &ObligationCause::misc(
-                                    location.to_locations().span(body),
-                                    body.source.def_id().expect_local(),
-                                ),
+                                &cause,
                                 param_env,
                                 ty,
                             )
@@ -253,6 +256,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                         let tail = tcx.struct_tail_raw(
                             ty,
+                            &cause,
                             structurally_normalize,
                             || {},
                         );
@@ -265,7 +269,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             .unwrap_or_else(|guar| Ty::new_error(tcx, guar))
         } else {
             let mut normalize = |ty| self.normalize(ty, location);
-            let tail = tcx.struct_tail_raw(ty, &mut normalize, || {});
+            let tail = tcx.struct_tail_raw(ty, &cause, &mut normalize, || {});
             normalize(tail)
         }
     }
diff --git a/compiler/rustc_const_eval/src/const_eval/valtrees.rs b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
index 37c6c4a61d8d6..7c41258ebfe5f 100644
--- a/compiler/rustc_const_eval/src/const_eval/valtrees.rs
+++ b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
@@ -1,6 +1,7 @@
 use rustc_abi::{BackendRepr, FieldIdx, VariantIdx};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_middle::mir::interpret::{EvalToValTreeResult, GlobalId, ValTreeCreationError};
+use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::layout::{LayoutCx, TyAndLayout};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::{bug, mir};
@@ -196,6 +197,7 @@ fn reconstruct_place_meta<'tcx>(
     // Traverse the type, and update `last_valtree` as we go.
     let tail = tcx.struct_tail_raw(
         layout.ty,
+        &ObligationCause::dummy(),
         |ty| ty,
         || {
             let branches = last_valtree.unwrap_branch();
diff --git a/compiler/rustc_hir_typeck/src/expectation.rs b/compiler/rustc_hir_typeck/src/expectation.rs
index 6d95b6917e296..2fbea5b61cfc6 100644
--- a/compiler/rustc_hir_typeck/src/expectation.rs
+++ b/compiler/rustc_hir_typeck/src/expectation.rs
@@ -1,3 +1,4 @@
+use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::{self, Ty};
 use rustc_span::Span;
 
@@ -74,8 +75,14 @@ impl<'a, 'tcx> Expectation<'tcx> {
     /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
     /// for examples of where this comes up,.
     pub(super) fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
+        let span = match ty.kind() {
+            ty::Adt(adt_def, _) => fcx.tcx.def_span(adt_def.did()),
+            _ => fcx.tcx.def_span(fcx.body_id),
+        };
+        let cause = ObligationCause::misc(span, fcx.body_id);
+
         // FIXME: This is not right, even in the old solver...
-        match fcx.tcx.struct_tail_raw(ty, |ty| ty, || {}).kind() {
+        match fcx.tcx.struct_tail_raw(ty, &cause, |ty| ty, || {}).kind() {
             ty::Slice(_) | ty::Str | ty::Dynamic(..) => ExpectRvalueLikeUnsized(ty),
             _ => ExpectHasType(ty),
         }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 7370124e800da..4563159314d15 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -424,6 +424,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if !ty.references_error() {
             let tail = self.tcx.struct_tail_raw(
                 ty,
+                &self.misc(span),
                 |ty| {
                     if self.next_trait_solver() {
                         self.try_structurally_resolve_type(span, ty)
diff --git a/compiler/rustc_middle/src/error.rs b/compiler/rustc_middle/src/error.rs
index dad402ec69616..e3e1393b5f9ae 100644
--- a/compiler/rustc_middle/src/error.rs
+++ b/compiler/rustc_middle/src/error.rs
@@ -71,6 +71,8 @@ pub enum TypeMismatchReason {
 #[diag(middle_recursion_limit_reached)]
 #[help]
 pub(crate) struct RecursionLimitReached<'tcx> {
+    #[primary_span]
+    pub span: Span,
     pub ty: Ty<'tcx>,
     pub suggested_limit: rustc_hir::limit::Limit,
 }
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index ab8a314295392..0c7bddf60d974 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -823,6 +823,9 @@ impl DynCompatibilityViolation {
             DynCompatibilityViolation::Method(name, MethodViolationCode::AsyncFn, _) => {
                 format!("method `{name}` is `async`").into()
             }
+            DynCompatibilityViolation::Method(name, MethodViolationCode::CVariadic, _) => {
+                format!("method `{name}` is C-variadic").into()
+            }
             DynCompatibilityViolation::Method(
                 name,
                 MethodViolationCode::WhereClauseReferencesSelf,
@@ -977,6 +980,9 @@ pub enum MethodViolationCode {
     /// e.g., `fn foo<A>()`
     Generic,
 
+    /// e.g., `fn (mut ap: ...)`
+    CVariadic,
+
     /// the method's receiver (`self` argument) can't be dispatched on
     UndispatchableReceiver(Option<Span>),
 }
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 9524057eebc6c..c477e65f5d6b3 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -22,6 +22,7 @@ use {rustc_abi as abi, rustc_hir as hir};
 
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::query::TyCtxtAt;
+use crate::traits::ObligationCause;
 use crate::ty::normalize_erasing_regions::NormalizationError;
 use crate::ty::{self, CoroutineArgsExt, Ty, TyCtxt, TypeVisitableExt};
 
@@ -384,6 +385,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
 
                 let tail = tcx.struct_tail_raw(
                     pointee,
+                    &ObligationCause::dummy(),
                     |ty| match tcx.try_normalize_erasing_regions(typing_env, ty) {
                         Ok(ty) => ty,
                         Err(e) => Ty::new_error_with_message(
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 2bea797799958..de35e5e847c81 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -23,6 +23,7 @@ use ty::util::IntTypeExt;
 
 use super::GenericParamDefKind;
 use crate::infer::canonical::Canonical;
+use crate::traits::ObligationCause;
 use crate::ty::InferTy::*;
 use crate::ty::{
     self, AdtDef, BoundRegionKind, Discr, GenericArg, GenericArgs, GenericArgsRef, List, ParamEnv,
@@ -1638,7 +1639,7 @@ impl<'tcx> Ty<'tcx> {
         tcx: TyCtxt<'tcx>,
         normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
     ) -> Result<Ty<'tcx>, Ty<'tcx>> {
-        let tail = tcx.struct_tail_raw(self, normalize, || {});
+        let tail = tcx.struct_tail_raw(self, &ObligationCause::dummy(), normalize, || {});
         match tail.kind() {
             // Sized types
             ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index b79b67c5927b0..4f039381e500d 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -24,6 +24,7 @@ use super::TypingEnv;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::mir;
 use crate::query::Providers;
+use crate::traits::ObligationCause;
 use crate::ty::layout::{FloatExt, IntegerExt};
 use crate::ty::{
     self, Asyncness, FallibleTypeFolder, GenericArgKind, GenericArgsRef, Ty, TyCtxt, TypeFoldable,
@@ -216,7 +217,12 @@ impl<'tcx> TyCtxt<'tcx> {
         typing_env: ty::TypingEnv<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self;
-        tcx.struct_tail_raw(ty, |ty| tcx.normalize_erasing_regions(typing_env, ty), || {})
+        tcx.struct_tail_raw(
+            ty,
+            &ObligationCause::dummy(),
+            |ty| tcx.normalize_erasing_regions(typing_env, ty),
+            || {},
+        )
     }
 
     /// Returns true if a type has metadata.
@@ -248,6 +254,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn struct_tail_raw(
         self,
         mut ty: Ty<'tcx>,
+        cause: &ObligationCause<'tcx>,
         mut normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
         // This is currently used to allow us to walk a ValTree
         // in lockstep with the type in order to get the ValTree branch that
@@ -261,9 +268,11 @@ impl<'tcx> TyCtxt<'tcx> {
                     Limit(0) => Limit(2),
                     limit => limit * 2,
                 };
-                let reported = self
-                    .dcx()
-                    .emit_err(crate::error::RecursionLimitReached { ty, suggested_limit });
+                let reported = self.dcx().emit_err(crate::error::RecursionLimitReached {
+                    span: cause.span,
+                    ty,
+                    suggested_limit,
+                });
                 return Ty::new_error(self, reported);
             }
             match *ty.kind() {
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index bcd11d6918d9a..3260dd712b9e4 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -426,6 +426,9 @@ fn virtual_call_violations_for_method<'tcx>(
     if let Some(code) = contains_illegal_impl_trait_in_trait(tcx, method.def_id, sig.output()) {
         errors.push(code);
     }
+    if sig.skip_binder().c_variadic {
+        errors.push(MethodViolationCode::CVariadic);
+    }
 
     // We can't monomorphize things like `fn foo<A>(...)`.
     let own_counts = tcx.generics_of(method.def_id).own_counts();
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 884d53732fe2a..042d6def84c33 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1057,6 +1057,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                     Some(LangItem::PointeeTrait) => {
                         let tail = selcx.tcx().struct_tail_raw(
                             self_ty,
+                            &obligation.cause,
                             |ty| {
                                 // We throw away any obligations we get from this, since we normalize
                                 // and confirm these obligations once again during confirmation
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index 643e3db8f83fe..c4cb43011adb0 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -10,6 +10,7 @@ use rustc_hashes::Hash64;
 use rustc_index::IndexVec;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
+use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::layout::{
     FloatExt, HasTyCtxt, IntegerExt, LayoutCx, LayoutError, LayoutOf, TyAndLayout,
 };
@@ -390,30 +391,31 @@ fn layout_of_uncached<'tcx>(
 
             let metadata = if let Some(metadata_def_id) = tcx.lang_items().metadata_type() {
                 let pointee_metadata = Ty::new_projection(tcx, metadata_def_id, [pointee]);
-                let metadata_ty =
-                    match tcx.try_normalize_erasing_regions(cx.typing_env, pointee_metadata) {
-                        Ok(metadata_ty) => metadata_ty,
-                        Err(mut err) => {
-                            // Usually `<Ty as Pointee>::Metadata` can't be normalized because
-                            // its struct tail cannot be normalized either, so try to get a
-                            // more descriptive layout error here, which will lead to less confusing
-                            // diagnostics.
-                            //
-                            // We use the raw struct tail function here to get the first tail
-                            // that is an alias, which is likely the cause of the normalization
-                            // error.
-                            match tcx.try_normalize_erasing_regions(
-                                cx.typing_env,
-                                tcx.struct_tail_raw(pointee, |ty| ty, || {}),
-                            ) {
-                                Ok(_) => {}
-                                Err(better_err) => {
-                                    err = better_err;
-                                }
+                let metadata_ty = match tcx
+                    .try_normalize_erasing_regions(cx.typing_env, pointee_metadata)
+                {
+                    Ok(metadata_ty) => metadata_ty,
+                    Err(mut err) => {
+                        // Usually `<Ty as Pointee>::Metadata` can't be normalized because
+                        // its struct tail cannot be normalized either, so try to get a
+                        // more descriptive layout error here, which will lead to less confusing
+                        // diagnostics.
+                        //
+                        // We use the raw struct tail function here to get the first tail
+                        // that is an alias, which is likely the cause of the normalization
+                        // error.
+                        match tcx.try_normalize_erasing_regions(
+                            cx.typing_env,
+                            tcx.struct_tail_raw(pointee, &ObligationCause::dummy(), |ty| ty, || {}),
+                        ) {
+                            Ok(_) => {}
+                            Err(better_err) => {
+                                err = better_err;
                             }
-                            return Err(error(cx, LayoutError::NormalizationFailure(pointee, err)));
                         }
-                    };
+                        return Err(error(cx, LayoutError::NormalizationFailure(pointee, err)));
+                    }
+                };
 
                 let metadata_layout = cx.layout_of(metadata_ty)?;
                 // If the metadata is a 1-zst, then the pointer is thin.
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index 18a9a7c22d9dd..e91e5055e9053 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -353,6 +353,7 @@ fn impl_self_is_guaranteed_unsized<'tcx>(tcx: TyCtxt<'tcx>, impl_def_id: DefId)
 
     let tail = tcx.struct_tail_raw(
         tcx.type_of(impl_def_id).instantiate_identity(),
+        &cause,
         |ty| {
             ocx.structurally_normalize_ty(&cause, param_env, ty).unwrap_or_else(|_| {
                 Ty::new_error_with_message(
diff --git a/library/coretests/tests/num/mod.rs b/library/coretests/tests/num/mod.rs
index 54e54f734f647..913f766ec1683 100644
--- a/library/coretests/tests/num/mod.rs
+++ b/library/coretests/tests/num/mod.rs
@@ -111,6 +111,13 @@ fn from_str_issue7588() {
     assert_eq!(s, None);
 }
 
+#[test]
+#[should_panic = "radix must lie in the range `[2, 36]`"]
+fn from_ascii_radix_panic() {
+    let radix = 1;
+    let _parsed = u64::from_str_radix("12345ABCD", radix);
+}
+
 #[test]
 fn test_int_from_str_overflow() {
     test_parse::<i8>("127", Ok(127));
diff --git a/tests/ui/c-variadic/inherent-method.rs b/tests/ui/c-variadic/inherent-method.rs
new file mode 100644
index 0000000000000..537bae7b3f0f4
--- /dev/null
+++ b/tests/ui/c-variadic/inherent-method.rs
@@ -0,0 +1,45 @@
+//@ run-pass
+#![feature(c_variadic)]
+
+#[repr(transparent)]
+struct S(i32);
+
+impl S {
+    unsafe extern "C" fn associated_function(mut ap: ...) -> i32 {
+        unsafe { ap.arg() }
+    }
+
+    unsafe extern "C" fn method_owned(self, mut ap: ...) -> i32 {
+        self.0 + unsafe { ap.arg::<i32>() }
+    }
+
+    unsafe extern "C" fn method_ref(&self, mut ap: ...) -> i32 {
+        self.0 + unsafe { ap.arg::<i32>() }
+    }
+
+    unsafe extern "C" fn method_mut(&mut self, mut ap: ...) -> i32 {
+        self.0 + unsafe { ap.arg::<i32>() }
+    }
+
+    unsafe extern "C" fn fat_pointer(self: Box<Self>, mut ap: ...) -> i32 {
+        self.0 + unsafe { ap.arg::<i32>() }
+    }
+}
+
+fn main() {
+    unsafe {
+        assert_eq!(S::associated_function(32), 32);
+        assert_eq!(S(100).method_owned(32), 132);
+        assert_eq!(S(100).method_ref(32), 132);
+        assert_eq!(S(100).method_mut(32), 132);
+        assert_eq!(S::fat_pointer(Box::new(S(100)), 32), 132);
+
+        type Method<T> = unsafe extern "C" fn(T, ...) -> i32;
+
+        assert_eq!((S::associated_function as unsafe extern "C" fn(...) -> i32)(32), 32);
+        assert_eq!((S::method_owned as Method<_>)(S(100), 32), 132);
+        assert_eq!((S::method_ref as Method<_>)(&S(100), 32), 132);
+        assert_eq!((S::method_mut as Method<_>)(&mut S(100), 32), 132);
+        assert_eq!((S::fat_pointer as Method<_>)(Box::new(S(100)), 32), 132);
+    }
+}
diff --git a/tests/ui/c-variadic/not-async.rs b/tests/ui/c-variadic/not-async.rs
index 45a7e1f8972bf..bdb51a9a43232 100644
--- a/tests/ui/c-variadic/not-async.rs
+++ b/tests/ui/c-variadic/not-async.rs
@@ -2,6 +2,14 @@
 #![feature(c_variadic)]
 #![crate_type = "lib"]
 
-async unsafe extern "C" fn cannot_be_async(x: isize, ...) {}
+async unsafe extern "C" fn fn_cannot_be_async(x: isize, ...) {}
 //~^ ERROR functions cannot be both `async` and C-variadic
 //~| ERROR hidden type for `impl Future<Output = ()>` captures lifetime that does not appear in bounds
+
+struct S;
+
+impl S {
+    async unsafe extern "C" fn method_cannot_be_async(x: isize, ...) {}
+    //~^ ERROR functions cannot be both `async` and C-variadic
+    //~| ERROR hidden type for `impl Future<Output = ()>` captures lifetime that does not appear in bounds
+}
diff --git a/tests/ui/c-variadic/not-async.stderr b/tests/ui/c-variadic/not-async.stderr
index b8caf0d8bd852..eab4c4f0822c4 100644
--- a/tests/ui/c-variadic/not-async.stderr
+++ b/tests/ui/c-variadic/not-async.stderr
@@ -1,19 +1,35 @@
 error: functions cannot be both `async` and C-variadic
   --> $DIR/not-async.rs:5:1
    |
-LL | async unsafe extern "C" fn cannot_be_async(x: isize, ...) {}
-   | ^^^^^ `async` because of this                        ^^^ C-variadic because of this
+LL | async unsafe extern "C" fn fn_cannot_be_async(x: isize, ...) {}
+   | ^^^^^ `async` because of this                           ^^^ C-variadic because of this
+
+error: functions cannot be both `async` and C-variadic
+  --> $DIR/not-async.rs:12:5
+   |
+LL |     async unsafe extern "C" fn method_cannot_be_async(x: isize, ...) {}
+   |     ^^^^^ `async` because of this                               ^^^ C-variadic because of this
 
 error[E0700]: hidden type for `impl Future<Output = ()>` captures lifetime that does not appear in bounds
-  --> $DIR/not-async.rs:5:59
+  --> $DIR/not-async.rs:5:62
    |
-LL | async unsafe extern "C" fn cannot_be_async(x: isize, ...) {}
-   | --------------------------------------------------------- ^^
+LL | async unsafe extern "C" fn fn_cannot_be_async(x: isize, ...) {}
+   | ------------------------------------------------------------ ^^
    | |
    | opaque type defined here
    |
-   = note: hidden type `{async fn body of cannot_be_async()}` captures lifetime `'_`
+   = note: hidden type `{async fn body of fn_cannot_be_async()}` captures lifetime `'_`
+
+error[E0700]: hidden type for `impl Future<Output = ()>` captures lifetime that does not appear in bounds
+  --> $DIR/not-async.rs:12:70
+   |
+LL |     async unsafe extern "C" fn method_cannot_be_async(x: isize, ...) {}
+   |     ---------------------------------------------------------------- ^^
+   |     |
+   |     opaque type defined here
+   |
+   = note: hidden type `{async fn body of S::method_cannot_be_async()}` captures lifetime `'_`
 
-error: aborting due to 2 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0700`.
diff --git a/tests/ui/c-variadic/not-dyn-compatible.rs b/tests/ui/c-variadic/not-dyn-compatible.rs
new file mode 100644
index 0000000000000..b40a13e584762
--- /dev/null
+++ b/tests/ui/c-variadic/not-dyn-compatible.rs
@@ -0,0 +1,35 @@
+// Traits where a method is c-variadic are not dyn compatible.
+//
+// Creating a function pointer from a method on an `&dyn T` value creates a ReifyShim.
+// This shim cannot reliably forward C-variadic arguments. Thus the trait as a whole
+// is dyn-incompatible to prevent invalid shims from being created.
+#![feature(c_variadic)]
+
+#[repr(transparent)]
+struct Struct(u64);
+
+trait Trait {
+    fn get(&self) -> u64;
+
+    unsafe extern "C" fn dyn_method_ref(&self, mut ap: ...) -> u64 {
+        self.get() + unsafe { ap.arg::<u64>() }
+    }
+}
+
+impl Trait for Struct {
+    fn get(&self) -> u64 {
+        self.0
+    }
+}
+
+fn main() {
+    unsafe {
+        let dyn_object: &dyn Trait = &Struct(64);
+        //~^ ERROR the trait `Trait` is not dyn compatible
+        assert_eq!(dyn_object.dyn_method_ref(100), 164);
+        assert_eq!(
+            (Trait::dyn_method_ref as unsafe extern "C" fn(_, ...) -> u64)(dyn_object, 100),
+            164
+        );
+    }
+}
diff --git a/tests/ui/c-variadic/not-dyn-compatible.stderr b/tests/ui/c-variadic/not-dyn-compatible.stderr
new file mode 100644
index 0000000000000..76630600c511f
--- /dev/null
+++ b/tests/ui/c-variadic/not-dyn-compatible.stderr
@@ -0,0 +1,21 @@
+error[E0038]: the trait `Trait` is not dyn compatible
+  --> $DIR/not-dyn-compatible.rs:27:30
+   |
+LL |         let dyn_object: &dyn Trait = &Struct(64);
+   |                              ^^^^^ `Trait` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
+  --> $DIR/not-dyn-compatible.rs:14:26
+   |
+LL | trait Trait {
+   |       ----- this trait is not dyn compatible...
+...
+LL |     unsafe extern "C" fn dyn_method_ref(&self, mut ap: ...) -> u64 {
+   |                          ^^^^^^^^^^^^^^ ...because method `dyn_method_ref` is C-variadic
+   = help: consider moving `dyn_method_ref` to another trait
+   = help: only type `Struct` implements `Trait`; consider using it directly instead.
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0038`.
diff --git a/tests/ui/c-variadic/trait-method.rs b/tests/ui/c-variadic/trait-method.rs
new file mode 100644
index 0000000000000..97da0706a3a18
--- /dev/null
+++ b/tests/ui/c-variadic/trait-method.rs
@@ -0,0 +1,73 @@
+//@ run-pass
+#![feature(c_variadic)]
+
+#[repr(transparent)]
+struct Struct(i32);
+
+impl Struct {
+    unsafe extern "C" fn associated_function(mut ap: ...) -> i32 {
+        unsafe { ap.arg() }
+    }
+
+    unsafe extern "C" fn method(&self, mut ap: ...) -> i32 {
+        self.0 + unsafe { ap.arg::<i32>() }
+    }
+}
+
+trait Trait: Sized {
+    fn get(&self) -> i32;
+
+    unsafe extern "C" fn trait_associated_function(mut ap: ...) -> i32 {
+        unsafe { ap.arg() }
+    }
+
+    unsafe extern "C" fn trait_method_owned(self, mut ap: ...) -> i32 {
+        self.get() + unsafe { ap.arg::<i32>() }
+    }
+
+    unsafe extern "C" fn trait_method_ref(&self, mut ap: ...) -> i32 {
+        self.get() + unsafe { ap.arg::<i32>() }
+    }
+
+    unsafe extern "C" fn trait_method_mut(&mut self, mut ap: ...) -> i32 {
+        self.get() + unsafe { ap.arg::<i32>() }
+    }
+
+    unsafe extern "C" fn trait_fat_pointer(self: Box<Self>, mut ap: ...) -> i32 {
+        self.get() + unsafe { ap.arg::<i32>() }
+    }
+}
+
+impl Trait for Struct {
+    fn get(&self) -> i32 {
+        self.0
+    }
+}
+
+fn main() {
+    unsafe {
+        assert_eq!(Struct::associated_function(32), 32);
+        assert_eq!(Struct(100).method(32), 132);
+
+        assert_eq!(Struct::trait_associated_function(32), 32);
+        assert_eq!(Struct(100).trait_method_owned(32), 132);
+        assert_eq!(Struct(100).trait_method_ref(32), 132);
+        assert_eq!(Struct(100).trait_method_mut(32), 132);
+        assert_eq!(Struct::trait_fat_pointer(Box::new(Struct(100)), 32), 132);
+
+        assert_eq!(<Struct as Trait>::trait_associated_function(32), 32);
+        assert_eq!(Trait::trait_method_owned(Struct(100), 32), 132);
+        assert_eq!(Trait::trait_method_ref(&Struct(100), 32), 132);
+        assert_eq!(Trait::trait_method_mut(&mut Struct(100), 32), 132);
+        assert_eq!(Trait::trait_fat_pointer(Box::new(Struct(100)), 32), 132);
+
+        type Associated = unsafe extern "C" fn(...) -> i32;
+        type Method<T> = unsafe extern "C" fn(T, ...) -> i32;
+
+        assert_eq!((Struct::trait_associated_function as Associated)(32), 32);
+        assert_eq!((Struct::trait_method_owned as Method<_>)(Struct(100), 32), 132);
+        assert_eq!((Struct::trait_method_ref as Method<_>)(&Struct(100), 32), 132);
+        assert_eq!((Struct::trait_method_mut as Method<_>)(&mut Struct(100), 32), 132);
+        assert_eq!((Struct::trait_fat_pointer as Method<_>)(Box::new(Struct(100)), 32), 132);
+    }
+}
diff --git a/tests/ui/c-variadic/unsupported-abi.rs b/tests/ui/c-variadic/unsupported-abi.rs
new file mode 100644
index 0000000000000..40179b164ce42
--- /dev/null
+++ b/tests/ui/c-variadic/unsupported-abi.rs
@@ -0,0 +1,123 @@
+//@ add-core-stubs
+//@ needs-llvm-components: x86
+//@ compile-flags: --target=i686-pc-windows-gnu --crate-type=rlib
+#![no_core]
+#![feature(no_core, lang_items, c_variadic)]
+
+// Test that ABIs for which C-variadics are not supported report an error.
+
+extern crate minicore;
+use minicore::*;
+
+#[rustfmt::skip]
+mod foreign {
+    extern "Rust"  { fn rust_foreign_explicit(_: ...); }
+    //~^ ERROR C-variadic functions with the "Rust" calling convention are not supported
+    extern "C"  { fn c_foreign(_: ...); }
+    extern "C-unwind"  { fn c_unwind_foreign(_: ...); }
+    extern "cdecl"  { fn cdecl_foreign(_: ...); }
+    extern "cdecl-unwind"  { fn cdecl_unwind_foreign(_: ...); }
+    extern "stdcall"  { fn stdcall_foreign(_: ...); }
+    //~^ ERROR C-variadic functions with the "stdcall" calling convention are not supported
+    extern "stdcall-unwind"  { fn stdcall_unwind_foreign(_: ...); }
+    //~^ ERROR C-variadic functions with the "stdcall-unwind" calling convention are not supported
+    extern "thiscall"  { fn thiscall_foreign(_: ...); }
+    //~^ ERROR C-variadic functions with the "thiscall" calling convention are not supported
+    extern "thiscall-unwind"  { fn thiscall_unwind_foreign(_: ...); }
+    //~^ ERROR C-variadic functions with the "thiscall-unwind" calling convention are not supported
+}
+
+#[lang = "va_list"]
+struct VaList(*mut u8);
+
+unsafe fn rust_free(_: ...) {}
+//~^ ERROR `...` is not supported for non-extern functions
+unsafe extern "Rust" fn rust_free_explicit(_: ...) {}
+//~^ ERROR `...` is not supported for `extern "Rust"` functions
+
+unsafe extern "C" fn c_free(_: ...) {}
+unsafe extern "C-unwind" fn c_unwind_free(_: ...) {}
+
+unsafe extern "cdecl" fn cdecl_free(_: ...) {}
+//~^ ERROR `...` is not supported for `extern "cdecl"` functions
+unsafe extern "cdecl-unwind" fn cdecl_unwind_free(_: ...) {}
+//~^ ERROR `...` is not supported for `extern "cdecl-unwind"` functions
+unsafe extern "stdcall" fn stdcall_free(_: ...) {}
+//~^ ERROR `...` is not supported for `extern "stdcall"` functions
+unsafe extern "stdcall-unwind" fn stdcall_unwind_free(_: ...) {}
+//~^ ERROR `...` is not supported for `extern "stdcall-unwind"` functions
+unsafe extern "thiscall" fn thiscall_free(_: ...) {}
+//~^ ERROR `...` is not supported for `extern "thiscall"` functions
+unsafe extern "thiscall-unwind" fn thiscall_unwind_free(_: ...) {}
+//~^ ERROR `...` is not supported for `extern "thiscall-unwind"` functions
+
+struct S;
+
+impl S {
+    unsafe fn rust_method(_: ...) {}
+    //~^ ERROR `...` is not supported for non-extern functions
+    unsafe extern "Rust" fn rust_method_explicit(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "Rust"` functions
+
+    unsafe extern "C" fn c_method(_: ...) {}
+    unsafe extern "C-unwind" fn c_unwind_method(_: ...) {}
+
+    unsafe extern "cdecl" fn cdecl_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "cdecl"` functions
+    unsafe extern "cdecl-unwind" fn cdecl_unwind_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "cdecl-unwind"` functions
+    unsafe extern "stdcall" fn stdcall_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "stdcall"` functions
+    unsafe extern "stdcall-unwind" fn stdcall_unwind_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "stdcall-unwind"` functions
+    unsafe extern "thiscall" fn thiscall_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "thiscall"` functions
+    unsafe extern "thiscall-unwind" fn thiscall_unwind_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "thiscall-unwind"` functions
+}
+
+trait T {
+    unsafe fn rust_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for non-extern functions
+    unsafe extern "Rust" fn rust_trait_method_explicit(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "Rust"` functions
+
+    unsafe extern "C" fn c_trait_method(_: ...) {}
+    unsafe extern "C-unwind" fn c_unwind_trait_method(_: ...) {}
+
+    unsafe extern "cdecl" fn cdecl_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "cdecl"` functions
+    unsafe extern "cdecl-unwind" fn cdecl_unwind_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "cdecl-unwind"` functions
+    unsafe extern "stdcall" fn stdcall_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "stdcall"` functions
+    unsafe extern "stdcall-unwind" fn stdcall_unwind_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "stdcall-unwind"` functions
+    unsafe extern "thiscall" fn thiscall_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "thiscall"` functions
+    unsafe extern "thiscall-unwind" fn thiscall_unwind_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "thiscall-unwind"` functions
+}
+
+impl T for S {
+    unsafe fn rust_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for non-extern functions
+    unsafe extern "Rust" fn rust_trait_method_explicit(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "Rust"` functions
+
+    unsafe extern "C" fn c_trait_method(_: ...) {}
+    unsafe extern "C-unwind" fn c_unwind_trait_method(_: ...) {}
+
+    unsafe extern "cdecl" fn cdecl_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "cdecl"` functions
+    unsafe extern "cdecl-unwind" fn cdecl_unwind_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "cdecl-unwind"` functions
+    unsafe extern "stdcall" fn stdcall_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "stdcall"` functions
+    unsafe extern "stdcall-unwind" fn stdcall_unwind_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "stdcall-unwind"` functions
+    unsafe extern "thiscall" fn thiscall_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "thiscall"` functions
+    unsafe extern "thiscall-unwind" fn thiscall_unwind_trait_method(_: ...) {}
+    //~^ ERROR `...` is not supported for `extern "thiscall-unwind"` functions
+}
diff --git a/tests/ui/c-variadic/unsupported-abi.stderr b/tests/ui/c-variadic/unsupported-abi.stderr
new file mode 100644
index 0000000000000..daed91714065a
--- /dev/null
+++ b/tests/ui/c-variadic/unsupported-abi.stderr
@@ -0,0 +1,345 @@
+error: `...` is not supported for non-extern functions
+  --> $DIR/unsupported-abi.rs:33:21
+   |
+LL | unsafe fn rust_free(_: ...) {}
+   |                     ^^^^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "Rust"` functions
+  --> $DIR/unsupported-abi.rs:35:44
+   |
+LL | unsafe extern "Rust" fn rust_free_explicit(_: ...) {}
+   |        -------------                       ^^^^^^
+   |        |
+   |        `extern "Rust"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "cdecl"` functions
+  --> $DIR/unsupported-abi.rs:41:37
+   |
+LL | unsafe extern "cdecl" fn cdecl_free(_: ...) {}
+   |        --------------               ^^^^^^
+   |        |
+   |        `extern "cdecl"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "cdecl-unwind"` functions
+  --> $DIR/unsupported-abi.rs:43:51
+   |
+LL | unsafe extern "cdecl-unwind" fn cdecl_unwind_free(_: ...) {}
+   |        ---------------------                      ^^^^^^
+   |        |
+   |        `extern "cdecl-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "stdcall"` functions
+  --> $DIR/unsupported-abi.rs:45:41
+   |
+LL | unsafe extern "stdcall" fn stdcall_free(_: ...) {}
+   |        ----------------                 ^^^^^^
+   |        |
+   |        `extern "stdcall"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "stdcall-unwind"` functions
+  --> $DIR/unsupported-abi.rs:47:55
+   |
+LL | unsafe extern "stdcall-unwind" fn stdcall_unwind_free(_: ...) {}
+   |        -----------------------                        ^^^^^^
+   |        |
+   |        `extern "stdcall-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "thiscall"` functions
+  --> $DIR/unsupported-abi.rs:49:43
+   |
+LL | unsafe extern "thiscall" fn thiscall_free(_: ...) {}
+   |        -----------------                  ^^^^^^
+   |        |
+   |        `extern "thiscall"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "thiscall-unwind"` functions
+  --> $DIR/unsupported-abi.rs:51:57
+   |
+LL | unsafe extern "thiscall-unwind" fn thiscall_unwind_free(_: ...) {}
+   |        ------------------------                         ^^^^^^
+   |        |
+   |        `extern "thiscall-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for non-extern functions
+  --> $DIR/unsupported-abi.rs:57:27
+   |
+LL |     unsafe fn rust_method(_: ...) {}
+   |                           ^^^^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "Rust"` functions
+  --> $DIR/unsupported-abi.rs:59:50
+   |
+LL |     unsafe extern "Rust" fn rust_method_explicit(_: ...) {}
+   |            -------------                         ^^^^^^
+   |            |
+   |            `extern "Rust"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "cdecl"` functions
+  --> $DIR/unsupported-abi.rs:65:43
+   |
+LL |     unsafe extern "cdecl" fn cdecl_method(_: ...) {}
+   |            --------------                 ^^^^^^
+   |            |
+   |            `extern "cdecl"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "cdecl-unwind"` functions
+  --> $DIR/unsupported-abi.rs:67:57
+   |
+LL |     unsafe extern "cdecl-unwind" fn cdecl_unwind_method(_: ...) {}
+   |            ---------------------                        ^^^^^^
+   |            |
+   |            `extern "cdecl-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "stdcall"` functions
+  --> $DIR/unsupported-abi.rs:69:47
+   |
+LL |     unsafe extern "stdcall" fn stdcall_method(_: ...) {}
+   |            ----------------                   ^^^^^^
+   |            |
+   |            `extern "stdcall"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "stdcall-unwind"` functions
+  --> $DIR/unsupported-abi.rs:71:61
+   |
+LL |     unsafe extern "stdcall-unwind" fn stdcall_unwind_method(_: ...) {}
+   |            -----------------------                          ^^^^^^
+   |            |
+   |            `extern "stdcall-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "thiscall"` functions
+  --> $DIR/unsupported-abi.rs:73:49
+   |
+LL |     unsafe extern "thiscall" fn thiscall_method(_: ...) {}
+   |            -----------------                    ^^^^^^
+   |            |
+   |            `extern "thiscall"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "thiscall-unwind"` functions
+  --> $DIR/unsupported-abi.rs:75:63
+   |
+LL |     unsafe extern "thiscall-unwind" fn thiscall_unwind_method(_: ...) {}
+   |            ------------------------                           ^^^^^^
+   |            |
+   |            `extern "thiscall-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for non-extern functions
+  --> $DIR/unsupported-abi.rs:80:33
+   |
+LL |     unsafe fn rust_trait_method(_: ...) {}
+   |                                 ^^^^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "Rust"` functions
+  --> $DIR/unsupported-abi.rs:82:56
+   |
+LL |     unsafe extern "Rust" fn rust_trait_method_explicit(_: ...) {}
+   |            -------------                               ^^^^^^
+   |            |
+   |            `extern "Rust"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "cdecl"` functions
+  --> $DIR/unsupported-abi.rs:88:49
+   |
+LL |     unsafe extern "cdecl" fn cdecl_trait_method(_: ...) {}
+   |            --------------                       ^^^^^^
+   |            |
+   |            `extern "cdecl"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "cdecl-unwind"` functions
+  --> $DIR/unsupported-abi.rs:90:63
+   |
+LL |     unsafe extern "cdecl-unwind" fn cdecl_unwind_trait_method(_: ...) {}
+   |            ---------------------                              ^^^^^^
+   |            |
+   |            `extern "cdecl-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "stdcall"` functions
+  --> $DIR/unsupported-abi.rs:92:53
+   |
+LL |     unsafe extern "stdcall" fn stdcall_trait_method(_: ...) {}
+   |            ----------------                         ^^^^^^
+   |            |
+   |            `extern "stdcall"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "stdcall-unwind"` functions
+  --> $DIR/unsupported-abi.rs:94:67
+   |
+LL |     unsafe extern "stdcall-unwind" fn stdcall_unwind_trait_method(_: ...) {}
+   |            -----------------------                                ^^^^^^
+   |            |
+   |            `extern "stdcall-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "thiscall"` functions
+  --> $DIR/unsupported-abi.rs:96:55
+   |
+LL |     unsafe extern "thiscall" fn thiscall_trait_method(_: ...) {}
+   |            -----------------                          ^^^^^^
+   |            |
+   |            `extern "thiscall"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "thiscall-unwind"` functions
+  --> $DIR/unsupported-abi.rs:98:69
+   |
+LL |     unsafe extern "thiscall-unwind" fn thiscall_unwind_trait_method(_: ...) {}
+   |            ------------------------                                 ^^^^^^
+   |            |
+   |            `extern "thiscall-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for non-extern functions
+  --> $DIR/unsupported-abi.rs:103:33
+   |
+LL |     unsafe fn rust_trait_method(_: ...) {}
+   |                                 ^^^^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "Rust"` functions
+  --> $DIR/unsupported-abi.rs:105:56
+   |
+LL |     unsafe extern "Rust" fn rust_trait_method_explicit(_: ...) {}
+   |            -------------                               ^^^^^^
+   |            |
+   |            `extern "Rust"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "cdecl"` functions
+  --> $DIR/unsupported-abi.rs:111:49
+   |
+LL |     unsafe extern "cdecl" fn cdecl_trait_method(_: ...) {}
+   |            --------------                       ^^^^^^
+   |            |
+   |            `extern "cdecl"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "cdecl-unwind"` functions
+  --> $DIR/unsupported-abi.rs:113:63
+   |
+LL |     unsafe extern "cdecl-unwind" fn cdecl_unwind_trait_method(_: ...) {}
+   |            ---------------------                              ^^^^^^
+   |            |
+   |            `extern "cdecl-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "stdcall"` functions
+  --> $DIR/unsupported-abi.rs:115:53
+   |
+LL |     unsafe extern "stdcall" fn stdcall_trait_method(_: ...) {}
+   |            ----------------                         ^^^^^^
+   |            |
+   |            `extern "stdcall"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "stdcall-unwind"` functions
+  --> $DIR/unsupported-abi.rs:117:67
+   |
+LL |     unsafe extern "stdcall-unwind" fn stdcall_unwind_trait_method(_: ...) {}
+   |            -----------------------                                ^^^^^^
+   |            |
+   |            `extern "stdcall-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "thiscall"` functions
+  --> $DIR/unsupported-abi.rs:119:55
+   |
+LL |     unsafe extern "thiscall" fn thiscall_trait_method(_: ...) {}
+   |            -----------------                          ^^^^^^
+   |            |
+   |            `extern "thiscall"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error: `...` is not supported for `extern "thiscall-unwind"` functions
+  --> $DIR/unsupported-abi.rs:121:69
+   |
+LL |     unsafe extern "thiscall-unwind" fn thiscall_unwind_trait_method(_: ...) {}
+   |            ------------------------                                 ^^^^^^
+   |            |
+   |            `extern "thiscall-unwind"` because of this
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
+
+error[E0045]: C-variadic functions with the "Rust" calling convention are not supported
+  --> $DIR/unsupported-abi.rs:14:22
+   |
+LL |     extern "Rust"  { fn rust_foreign_explicit(_: ...); }
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ C-variadic function must have a compatible calling convention
+
+error[E0045]: C-variadic functions with the "stdcall" calling convention are not supported
+  --> $DIR/unsupported-abi.rs:20:25
+   |
+LL |     extern "stdcall"  { fn stdcall_foreign(_: ...); }
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ C-variadic function must have a compatible calling convention
+
+error[E0045]: C-variadic functions with the "stdcall-unwind" calling convention are not supported
+  --> $DIR/unsupported-abi.rs:22:32
+   |
+LL |     extern "stdcall-unwind"  { fn stdcall_unwind_foreign(_: ...); }
+   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ C-variadic function must have a compatible calling convention
+
+error[E0045]: C-variadic functions with the "thiscall" calling convention are not supported
+  --> $DIR/unsupported-abi.rs:24:26
+   |
+LL |     extern "thiscall"  { fn thiscall_foreign(_: ...); }
+   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ C-variadic function must have a compatible calling convention
+
+error[E0045]: C-variadic functions with the "thiscall-unwind" calling convention are not supported
+  --> $DIR/unsupported-abi.rs:26:33
+   |
+LL |     extern "thiscall-unwind"  { fn thiscall_unwind_foreign(_: ...); }
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ C-variadic function must have a compatible calling convention
+
+error: aborting due to 37 previous errors
+
+For more information about this error, try `rustc --explain E0045`.
diff --git a/tests/ui/did_you_mean/recursion_limit_deref.rs b/tests/ui/did_you_mean/recursion_limit_deref.rs
index e53007388af25..3ae956b751d84 100644
--- a/tests/ui/did_you_mean/recursion_limit_deref.rs
+++ b/tests/ui/did_you_mean/recursion_limit_deref.rs
@@ -1,3 +1,6 @@
+//~ ERROR reached the recursion limit finding the struct tail for `K`
+//~| ERROR reached the recursion limit finding the struct tail for `Bottom`
+
 // Test that the recursion limit can be changed and that the compiler
 // suggests a fix. In this case, we have a long chain of Deref impls
 // which will cause an overflow during the autoderef loop.
@@ -9,6 +12,7 @@
 macro_rules! link {
     ($outer:ident, $inner:ident) => {
         struct $outer($inner);
+        //~^ ERROR reached the recursion limit finding the struct tail for `Bottom`
 
         impl $outer {
             fn new() -> $outer {
@@ -51,6 +55,3 @@ fn main() {
     let x: &Bottom = &t; //~ ERROR mismatched types
     //~^ error recursion limit
 }
-
-//~? ERROR reached the recursion limit finding the struct tail for `K`
-//~? ERROR reached the recursion limit finding the struct tail for `Bottom`
diff --git a/tests/ui/did_you_mean/recursion_limit_deref.stderr b/tests/ui/did_you_mean/recursion_limit_deref.stderr
index 23341ec6bdc27..faa85dc5ae98c 100644
--- a/tests/ui/did_you_mean/recursion_limit_deref.stderr
+++ b/tests/ui/did_you_mean/recursion_limit_deref.stderr
@@ -6,8 +6,20 @@ error: reached the recursion limit finding the struct tail for `Bottom`
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "20"]`
 
+error: reached the recursion limit finding the struct tail for `Bottom`
+  --> $DIR/recursion_limit_deref.rs:14:9
+   |
+LL |         struct $outer($inner);
+   |         ^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | link!(A, B);
+   | ----------- in this macro invocation
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "20"]`
+   = note: this error originates in the macro `link` (in Nightly builds, run with -Z macro-backtrace for more info)
+
 error[E0055]: reached the recursion limit while auto-dereferencing `J`
-  --> $DIR/recursion_limit_deref.rs:51:22
+  --> $DIR/recursion_limit_deref.rs:55:22
    |
 LL |     let x: &Bottom = &t;
    |                      ^^ deref recursion limit reached
@@ -15,7 +27,7 @@ LL |     let x: &Bottom = &t;
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "20"]` attribute to your crate (`recursion_limit_deref`)
 
 error[E0308]: mismatched types
-  --> $DIR/recursion_limit_deref.rs:51:22
+  --> $DIR/recursion_limit_deref.rs:55:22
    |
 LL |     let x: &Bottom = &t;
    |            -------   ^^ expected `&Bottom`, found `&Top`
@@ -25,7 +37,7 @@ LL |     let x: &Bottom = &t;
    = note: expected reference `&Bottom`
               found reference `&Top`
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
 Some errors have detailed explanations: E0055, E0308.
 For more information about an error, try `rustc --explain E0055`.
diff --git a/tests/ui/feature-gates/feature-gate-c_variadic.rs b/tests/ui/feature-gates/feature-gate-c_variadic.rs
index 88d91dbd081fb..649816b48d784 100644
--- a/tests/ui/feature-gates/feature-gate-c_variadic.rs
+++ b/tests/ui/feature-gates/feature-gate-c_variadic.rs
@@ -6,5 +6,4 @@ pub unsafe extern "C" fn test(_: i32, ap: ...) {}
 trait Trait {
     unsafe extern "C" fn trait_test(_: i32, ap: ...) {}
     //~^ ERROR C-variadic functions are unstable
-    //~| ERROR associated functions cannot have a C variable argument list
 }
diff --git a/tests/ui/feature-gates/feature-gate-c_variadic.stderr b/tests/ui/feature-gates/feature-gate-c_variadic.stderr
index 808aa20948d03..ae880093b980c 100644
--- a/tests/ui/feature-gates/feature-gate-c_variadic.stderr
+++ b/tests/ui/feature-gates/feature-gate-c_variadic.stderr
@@ -1,9 +1,3 @@
-error: associated functions cannot have a C variable argument list
-  --> $DIR/feature-gate-c_variadic.rs:7:45
-   |
-LL |     unsafe extern "C" fn trait_test(_: i32, ap: ...) {}
-   |                                             ^^^^^^^
-
 error[E0658]: C-variadic functions are unstable
   --> $DIR/feature-gate-c_variadic.rs:3:1
    |
@@ -24,6 +18,6 @@ LL |     unsafe extern "C" fn trait_test(_: i32, ap: ...) {}
    = help: add `#![feature(c_variadic)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.rs b/tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.rs
index f7117368ece7b..b8ea353df9385 100644
--- a/tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.rs
+++ b/tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.rs
@@ -1,4 +1,17 @@
-//~ ERROR reached the recursion limit while instantiating `<VirtualWrapper<
+//~ ERROR reached the recursion limit finding the struct tail for `[u8; 256]`
+//~| ERROR reached the recursion limit finding the struct tail for `[u8; 256]`
+//~| ERROR reached the recursion limit finding the struct tail for `[u8; 256]`
+//~| ERROR reached the recursion limit finding the struct tail for `[u8; 256]`
+//~| ERROR reached the recursion limit finding the struct tail for `SomeData<256>`
+//~| ERROR reached the recursion limit finding the struct tail for `SomeData<256>`
+//~| ERROR reached the recursion limit finding the struct tail for `SomeData<256>`
+//~| ERROR reached the recursion limit finding the struct tail for `SomeData<256>`
+//~| ERROR reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
+//~| ERROR reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
+//~| ERROR reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
+//~| ERROR reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
+//~| ERROR reached the recursion limit while instantiating `<VirtualWrapper<..., 1> as MyTrait>::virtualize`
+
 //@ build-fail
 //@ compile-flags: --diagnostic-width=100 -Zwrite-long-types-to-disk=yes
 
@@ -72,16 +85,3 @@ fn main() {
     let test = SomeData([0; 256]);
     test.virtualize();
 }
-
-//~? ERROR reached the recursion limit finding the struct tail for `[u8; 256]`
-//~? ERROR reached the recursion limit finding the struct tail for `[u8; 256]`
-//~? ERROR reached the recursion limit finding the struct tail for `[u8; 256]`
-//~? ERROR reached the recursion limit finding the struct tail for `[u8; 256]`
-//~? ERROR reached the recursion limit finding the struct tail for `SomeData<256>`
-//~? ERROR reached the recursion limit finding the struct tail for `SomeData<256>`
-//~? ERROR reached the recursion limit finding the struct tail for `SomeData<256>`
-//~? ERROR reached the recursion limit finding the struct tail for `SomeData<256>`
-//~? ERROR reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
-//~? ERROR reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
-//~? ERROR reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
-//~? ERROR reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
diff --git a/tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.stderr b/tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.stderr
index faf9cbe2318c4..deccc88e64fa5 100644
--- a/tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.stderr
+++ b/tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.stderr
@@ -18,7 +18,7 @@ error: reached the recursion limit finding the struct tail for `[u8; 256]`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 note: the above error was encountered while instantiating `fn virtualize_my_trait::<VirtualWrapper<..., 1>>`
-  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:25:18
+  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:38:18
    |
 LL |         unsafe { virtualize_my_trait(L, self) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -46,7 +46,7 @@ error: reached the recursion limit finding the struct tail for `SomeData<256>`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 note: the above error was encountered while instantiating `fn virtualize_my_trait::<VirtualWrapper<..., 1>>`
-  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:25:18
+  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:38:18
    |
 LL |         unsafe { virtualize_my_trait(L, self) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -74,7 +74,7 @@ error: reached the recursion limit finding the struct tail for `VirtualWrapper<S
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 note: the above error was encountered while instantiating `fn virtualize_my_trait::<VirtualWrapper<..., 1>>`
-  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:25:18
+  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:38:18
    |
 LL |         unsafe { virtualize_my_trait(L, self) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -85,7 +85,7 @@ LL |         unsafe { virtualize_my_trait(L, self) }
 error: reached the recursion limit while instantiating `<VirtualWrapper<..., 1> as MyTrait>::virtualize`
    |
 note: `<VirtualWrapper<T, L> as MyTrait>::virtualize` defined here
-  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:24:5
+  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:37:5
    |
 LL |     fn virtualize(&self) -> &dyn MyTrait {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/infinite/infinite-struct.rs b/tests/ui/infinite/infinite-struct.rs
index fd47a4ec9cc6a..d784455824604 100644
--- a/tests/ui/infinite/infinite-struct.rs
+++ b/tests/ui/infinite/infinite-struct.rs
@@ -1,6 +1,7 @@
 struct Take(Take);
 //~^ ERROR has infinite size
 //~| ERROR cycle
+//~| ERROR reached the recursion limit finding the struct tail for `Take`
 
 // check that we don't hang trying to find the tail of a recursive struct (#79437)
 fn foo() -> Take {
@@ -15,5 +16,3 @@ struct Foo { //~ ERROR has infinite size
 struct Bar<T>([T; 1]);
 
 fn main() {}
-
-//~? ERROR reached the recursion limit finding the struct tail for `Take`
diff --git a/tests/ui/infinite/infinite-struct.stderr b/tests/ui/infinite/infinite-struct.stderr
index 5896aec399dc4..0d1ec4989aa53 100644
--- a/tests/ui/infinite/infinite-struct.stderr
+++ b/tests/ui/infinite/infinite-struct.stderr
@@ -10,7 +10,7 @@ LL | struct Take(Box<Take>);
    |             ++++    +
 
 error[E0072]: recursive type `Foo` has infinite size
-  --> $DIR/infinite-struct.rs:11:1
+  --> $DIR/infinite-struct.rs:12:1
    |
 LL | struct Foo {
    | ^^^^^^^^^^
@@ -23,6 +23,10 @@ LL |     x: Bar<Box<Foo>>,
    |            ++++   +
 
 error: reached the recursion limit finding the struct tail for `Take`
+  --> $DIR/infinite-struct.rs:1:1
+   |
+LL | struct Take(Take);
+   | ^^^^^^^^^^^
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
 
diff --git a/tests/ui/invalid/issue-114435-layout-type-err.rs b/tests/ui/invalid/issue-114435-layout-type-err.rs
index 07f310478d3c9..ae04759af5df2 100644
--- a/tests/ui/invalid/issue-114435-layout-type-err.rs
+++ b/tests/ui/invalid/issue-114435-layout-type-err.rs
@@ -1,3 +1,4 @@
+//~ ERROR reached the recursion limit finding the struct tail for `Bottom`
 //@ check-fail
 //@ compile-flags: --crate-type lib -Cdebuginfo=2
 
@@ -40,5 +41,3 @@ link!(J, K);
 link!(K, Bottom);
 
 fn main() {}
-
-//~? ERROR reached the recursion limit finding the struct tail for `Bottom`
diff --git a/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-5.rs b/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-5.rs
new file mode 100644
index 0000000000000..16039f177b4de
--- /dev/null
+++ b/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-5.rs
@@ -0,0 +1,13 @@
+// Regression test for #91831
+
+struct Foo<'a>(&'a i32);
+
+impl<'a> Foo<'a> {
+    fn modify(&'a mut self) {}
+}
+
+fn bar(foo: &mut Foo) {
+    foo.modify(); //~ ERROR lifetime may not live long enough
+}
+
+fn main() {}
diff --git a/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-5.stderr b/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-5.stderr
new file mode 100644
index 0000000000000..f02b65230b6eb
--- /dev/null
+++ b/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-5.stderr
@@ -0,0 +1,20 @@
+error: lifetime may not live long enough
+  --> $DIR/ex3-both-anon-regions-one-is-struct-5.rs:10:5
+   |
+LL | fn bar(foo: &mut Foo) {
+   |        ---  - let's call the lifetime of this reference `'1`
+   |        |
+   |        has type `&mut Foo<'2>`
+LL |     foo.modify();
+   |     ^^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+   = note: requirement occurs because of a mutable reference to `Foo<'_>`
+   = note: mutable references are invariant over their type parameter
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
+help: consider introducing a named lifetime parameter
+   |
+LL | fn bar<'a>(foo: &'a mut Foo<'a>) {
+   |       ++++       ++        ++++
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/parser/variadic-ffi-semantic-restrictions.rs b/tests/ui/parser/variadic-ffi-semantic-restrictions.rs
index 4db056f15a51f..415472176d9c4 100644
--- a/tests/ui/parser/variadic-ffi-semantic-restrictions.rs
+++ b/tests/ui/parser/variadic-ffi-semantic-restrictions.rs
@@ -53,30 +53,30 @@ struct X;
 
 impl X {
     fn i_f1(x: isize, ...) {}
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     fn i_f2(...) {}
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     fn i_f3(..., x: isize, ...) {}
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     //~| ERROR `...` must be the last argument of a C-variadic function
     fn i_f4(..., x: isize, ...) {}
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     //~| ERROR `...` must be the last argument of a C-variadic function
     const fn i_f5(x: isize, ...) {}
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     //~| ERROR functions cannot be both `const` and C-variadic
     //~| ERROR destructor of `VaListImpl<'_>` cannot be evaluated at compile-time
 }
 
 trait T {
     fn t_f1(x: isize, ...) {}
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     fn t_f2(x: isize, ...);
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     fn t_f3(...) {}
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     fn t_f4(...);
-    //~^ ERROR associated functions cannot have a C variable argument list
+    //~^ ERROR `...` is not supported for non-extern functions
     fn t_f5(..., x: isize) {}
     //~^ ERROR `...` must be the last argument of a C-variadic function
     fn t_f6(..., x: isize);
diff --git a/tests/ui/parser/variadic-ffi-semantic-restrictions.stderr b/tests/ui/parser/variadic-ffi-semantic-restrictions.stderr
index 0cd78318de6a8..da9c9b0f76099 100644
--- a/tests/ui/parser/variadic-ffi-semantic-restrictions.stderr
+++ b/tests/ui/parser/variadic-ffi-semantic-restrictions.stderr
@@ -132,17 +132,21 @@ error: `...` must be the last argument of a C-variadic function
 LL |     fn e_f2(..., x: isize);
    |             ^^^
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:55:23
    |
 LL |     fn i_f1(x: isize, ...) {}
    |                       ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:57:13
    |
 LL |     fn i_f2(...) {}
    |             ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
 error: `...` must be the last argument of a C-variadic function
   --> $DIR/variadic-ffi-semantic-restrictions.rs:59:13
@@ -150,11 +154,13 @@ error: `...` must be the last argument of a C-variadic function
 LL |     fn i_f3(..., x: isize, ...) {}
    |             ^^^
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:59:28
    |
 LL |     fn i_f3(..., x: isize, ...) {}
    |                            ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
 error: `...` must be the last argument of a C-variadic function
   --> $DIR/variadic-ffi-semantic-restrictions.rs:62:13
@@ -162,11 +168,13 @@ error: `...` must be the last argument of a C-variadic function
 LL |     fn i_f4(..., x: isize, ...) {}
    |             ^^^
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:62:28
    |
 LL |     fn i_f4(..., x: isize, ...) {}
    |                            ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
 error: functions cannot be both `const` and C-variadic
   --> $DIR/variadic-ffi-semantic-restrictions.rs:65:5
@@ -176,35 +184,45 @@ LL |     const fn i_f5(x: isize, ...) {}
    |     |
    |     `const` because of this
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:65:29
    |
 LL |     const fn i_f5(x: isize, ...) {}
    |                             ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:72:23
    |
 LL |     fn t_f1(x: isize, ...) {}
    |                       ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:74:23
    |
 LL |     fn t_f2(x: isize, ...);
    |                       ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:76:13
    |
 LL |     fn t_f3(...) {}
    |             ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
-error: associated functions cannot have a C variable argument list
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:78:13
    |
 LL |     fn t_f4(...);
    |             ^^^
+   |
+   = help: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
 
 error: `...` must be the last argument of a C-variadic function
   --> $DIR/variadic-ffi-semantic-restrictions.rs:80:13
diff --git a/tests/ui/traits/solver-cycles/129541-recursive-struct.rs b/tests/ui/traits/solver-cycles/129541-recursive-struct.rs
index 723179302e30a..c5c2c27b28267 100644
--- a/tests/ui/traits/solver-cycles/129541-recursive-struct.rs
+++ b/tests/ui/traits/solver-cycles/129541-recursive-struct.rs
@@ -1,3 +1,4 @@
+//~ ERROR reached the recursion limit finding the struct tail for `<[Hello] as Normalize>::Assoc`
 // Regression test for #129541
 
 //@ revisions: unique_curr unique_next multiple_curr multiple_next
@@ -24,5 +25,3 @@ struct Hello {
 }
 
 fn main() {}
-
-//~? ERROR reached the recursion limit finding the struct tail for `<[Hello] as Normalize>::Assoc`