Rollup merge of #146597 - modhanami:add-struct-tail-recursion-limit-span, r=oli-obk

Add span for struct tail recursion limit error

Fixes rust-lang/rust#135629

Changes
1. Add span to RecursionLimitReached
2. Add ObligationCause parameter to struct_tail_raw
4. Update call sites to pass nearby ObligationCause or create one
5. Update affected .stderr

11 files changed, 66 insertions, 34 deletions

diff --git a/compiler/rustc_borrowck/src/type_check/canonical.rs b/compiler/rustc_borrowck/src/type_check/canonical.rs
index 2627ed899a9..aece0bda346 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 37c6c4a61d8..7c41258ebfe 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 6d95b6917e2..2fbea5b61cf 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 7370124e800..4563159314d 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 dad402ec696..e3e1393b5f9 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/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 9524057eebc..c477e65f5d6 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 2bea7977999..de35e5e847c 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 b79b67c5927..4f039381e50 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/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 884d53732fe..042d6def84c 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 643e3db8f83..c4cb43011ad 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 18a9a7c22d9..e91e5055e90 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(