pass `sub_relations` into canonical queries

14 files changed, 342 insertions, 318 deletions

diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index 40d3e8acaa4..be68609502a 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
@@ -6,6 +6,7 @@
 //! [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html
 
 use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::sso::SsoHashMap;
 use rustc_index::Idx;
 use rustc_middle::bug;
 use rustc_middle::ty::{
@@ -293,6 +294,7 @@ struct Canonicalizer<'cx, 'tcx> {
     // Note that indices is only used once `var_values` is big enough to be
     // heap-allocated.
     indices: FxHashMap<GenericArg<'tcx>, BoundVar>,
+    sub_root_lookup_table: SsoHashMap<ty::TyVid, usize>,
     canonicalize_mode: &'cx dyn CanonicalizeMode,
     needs_canonical_flags: TypeFlags,
 
@@ -361,7 +363,8 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
                             // FIXME: perf problem described in #55921.
                             ui = ty::UniverseIndex::ROOT;
                         }
-                        self.canonicalize_ty_var(CanonicalVarKind::Ty(ui), t)
+                        let sub_root = self.get_or_insert_sub_root(vid);
+                        self.canonicalize_ty_var(CanonicalVarKind::Ty { ui, sub_root }, t)
                     }
                 }
             }
@@ -559,6 +562,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
             variables: SmallVec::from_slice(base.variables),
             query_state,
             indices: FxHashMap::default(),
+            sub_root_lookup_table: Default::default(),
             binder_index: ty::INNERMOST,
         };
         if canonicalizer.query_state.var_values.spilled() {
@@ -657,6 +661,13 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
         }
     }
 
+    fn get_or_insert_sub_root(&mut self, vid: ty::TyVid) -> ty::BoundVar {
+        let root_vid = self.infcx.unwrap().sub_root_var(vid);
+        let idx =
+            *self.sub_root_lookup_table.entry(root_vid).or_insert_with(|| self.variables.len());
+        ty::BoundVar::from(idx)
+    }
+
     /// Replaces the universe indexes used in `var_values` with their index in
     /// `query_state.universe_map`. This minimizes the maximum universe used in
     /// the canonicalized value.
@@ -679,7 +690,9 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
                 CanonicalVarKind::Int | CanonicalVarKind::Float => {
                     return kind;
                 }
-                CanonicalVarKind::Ty(u) => CanonicalVarKind::Ty(reverse_universe_map[&u]),
+                CanonicalVarKind::Ty { ui, sub_root } => {
+                    CanonicalVarKind::Ty { ui: reverse_universe_map[&ui], sub_root }
+                }
                 CanonicalVarKind::Region(u) => CanonicalVarKind::Region(reverse_universe_map[&u]),
                 CanonicalVarKind::Const(u) => CanonicalVarKind::Const(reverse_universe_map[&u]),
                 CanonicalVarKind::PlaceholderTy(placeholder) => {
diff --git a/compiler/rustc_infer/src/infer/canonical/mod.rs b/compiler/rustc_infer/src/infer/canonical/mod.rs
index 223fb8419ec..4e1ea52af4c 100644
--- a/compiler/rustc_infer/src/infer/canonical/mod.rs
+++ b/compiler/rustc_infer/src/infer/canonical/mod.rs
@@ -84,13 +84,12 @@ impl<'tcx> InferCtxt<'tcx> {
         variables: &List<CanonicalVarKind<'tcx>>,
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> CanonicalVarValues<'tcx> {
-        CanonicalVarValues {
-            var_values: self.tcx.mk_args_from_iter(
-                variables
-                    .iter()
-                    .map(|kind| self.instantiate_canonical_var(span, kind, &universe_map)),
-            ),
+        let mut var_values = Vec::with_capacity(variables.len());
+        for info in variables.iter() {
+            let value = self.instantiate_canonical_var(span, info, &var_values, &universe_map);
+            var_values.push(value);
         }
+        CanonicalVarValues { var_values: self.tcx.mk_args(&var_values) }
     }
 
     /// Given the "info" about a canonical variable, creates a fresh
@@ -105,10 +104,22 @@ impl<'tcx> InferCtxt<'tcx> {
         &self,
         span: Span,
         kind: CanonicalVarKind<'tcx>,
+        previous_var_values: &[GenericArg<'tcx>],
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> GenericArg<'tcx> {
         match kind {
-            CanonicalVarKind::Ty(ui) => self.next_ty_var_in_universe(span, universe_map(ui)).into(),
+            CanonicalVarKind::Ty { ui, sub_root } => {
+                let vid = self.next_ty_vid_in_universe(span, universe_map(ui));
+                // Fetch the `sub_root` in case it exists.
+                if let Some(prev) = previous_var_values.get(sub_root.as_usize()) {
+                    if let &ty::Infer(ty::TyVar(sub_root)) = prev.expect_ty().kind() {
+                        self.inner.borrow_mut().type_variables().sub(vid, sub_root);
+                    } else {
+                        unreachable!()
+                    }
+                }
+                Ty::new_var(self.tcx, vid).into()
+            }
 
             CanonicalVarKind::Int => self.next_int_var().into(),
 
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index 09578598114..22c9c4edccc 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -13,6 +13,7 @@ use std::iter;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::bug;
+use rustc_middle::infer::canonical::CanonicalVarKind;
 use rustc_middle::ty::{self, BoundVar, GenericArg, GenericArgKind, Ty, TyCtxt, TypeFoldable};
 use tracing::{debug, instrument};
 
@@ -413,26 +414,27 @@ impl<'tcx> InferCtxt<'tcx> {
         let mut opt_values: IndexVec<BoundVar, Option<GenericArg<'tcx>>> =
             IndexVec::from_elem_n(None, query_response.variables.len());
 
-        // In terms of our example above, we are iterating over pairs like:
-        // [(?A, Vec<?0>), ('static, '?1), (?B, ?0)]
         for (original_value, result_value) in iter::zip(&original_values.var_values, result_values)
         {
             match result_value.kind() {
                 GenericArgKind::Type(result_value) => {
-                    // e.g., here `result_value` might be `?0` in the example above...
-                    if let ty::Bound(debruijn, b) = *result_value.kind() {
-                        // ...in which case we would set `canonical_vars[0]` to `Some(?U)`.
-
+                    // We disable the instantiation guess for inference variables
+                    // and only use it for placeholders. We need to handle the
+                    // `sub_root` of type inference variables which would make this
+                    // more involved. They are also a lot rarer than region variables.
+                    if let ty::Bound(debruijn, b) = *result_value.kind()
+                        && !matches!(
+                            query_response.variables[b.var.as_usize()],
+                            CanonicalVarKind::Ty { .. }
+                        )
+                    {
                         // We only allow a `ty::INNERMOST` index in generic parameters.
                         assert_eq!(debruijn, ty::INNERMOST);
                         opt_values[b.var] = Some(*original_value);
                     }
                 }
                 GenericArgKind::Lifetime(result_value) => {
-                    // e.g., here `result_value` might be `'?1` in the example above...
                     if let ty::ReBound(debruijn, b) = result_value.kind() {
-                        // ... in which case we would set `canonical_vars[0]` to `Some('static)`.
-
                         // We only allow a `ty::INNERMOST` index in generic parameters.
                         assert_eq!(debruijn, ty::INNERMOST);
                         opt_values[b.var] = Some(*original_value);
@@ -440,8 +442,6 @@ impl<'tcx> InferCtxt<'tcx> {
                 }
                 GenericArgKind::Const(result_value) => {
                     if let ty::ConstKind::Bound(debruijn, b) = result_value.kind() {
-                        // ...in which case we would set `canonical_vars[0]` to `Some(const X)`.
-
                         // We only allow a `ty::INNERMOST` index in generic parameters.
                         assert_eq!(debruijn, ty::INNERMOST);
                         opt_values[b.var] = Some(*original_value);
@@ -453,32 +453,31 @@ impl<'tcx> InferCtxt<'tcx> {
         // Create result arguments: if we found a value for a
         // given variable in the loop above, use that. Otherwise, use
         // a fresh inference variable.
-        let result_args = CanonicalVarValues {
-            var_values: self.tcx.mk_args_from_iter(
-                query_response.variables.iter().enumerate().map(|(index, var_kind)| {
-                    if var_kind.universe() != ty::UniverseIndex::ROOT {
-                        // A variable from inside a binder of the query. While ideally these shouldn't
-                        // exist at all, we have to deal with them for now.
-                        self.instantiate_canonical_var(cause.span, var_kind, |u| {
-                            universe_map[u.as_usize()]
-                        })
-                    } else if var_kind.is_existential() {
-                        match opt_values[BoundVar::new(index)] {
-                            Some(k) => k,
-                            None => self.instantiate_canonical_var(cause.span, var_kind, |u| {
-                                universe_map[u.as_usize()]
-                            }),
-                        }
-                    } else {
-                        // For placeholders which were already part of the input, we simply map this
-                        // universal bound variable back the placeholder of the input.
-                        opt_values[BoundVar::new(index)].expect(
-                            "expected placeholder to be unified with itself during response",
-                        )
-                    }
-                }),
-            ),
-        };
+        let mut var_values = Vec::with_capacity(query_response.variables.len());
+        for (index, kind) in query_response.variables.iter().enumerate() {
+            let value = if kind.universe() != ty::UniverseIndex::ROOT {
+                // A variable from inside a binder of the query. While ideally these shouldn't
+                // exist at all, we have to deal with them for now.
+                self.instantiate_canonical_var(cause.span, kind, &var_values, |u| {
+                    universe_map[u.as_usize()]
+                })
+            } else if kind.is_existential() {
+                match opt_values[BoundVar::new(index)] {
+                    Some(k) => k,
+                    None => self.instantiate_canonical_var(cause.span, kind, &var_values, |u| {
+                        universe_map[u.as_usize()]
+                    }),
+                }
+            } else {
+                // For placeholders which were already part of the input, we simply map this
+                // universal bound variable back the placeholder of the input.
+                opt_values[BoundVar::new(index)]
+                    .expect("expected placeholder to be unified with itself during response")
+            };
+            var_values.push(value);
+        }
+
+        let result_args = CanonicalVarValues { var_values: self.tcx.mk_args(&var_values) };
 
         let mut obligations = PredicateObligations::new();
 
diff --git a/compiler/rustc_infer/src/infer/context.rs b/compiler/rustc_infer/src/infer/context.rs
index efd623fac78..b76931caaa5 100644
--- a/compiler/rustc_infer/src/infer/context.rs
+++ b/compiler/rustc_infer/src/infer/context.rs
@@ -59,6 +59,10 @@ impl<'tcx> rustc_type_ir::InferCtxtLike for InferCtxt<'tcx> {
         self.root_var(var)
     }
 
+    fn sub_root_ty_var(&self, var: ty::TyVid) -> ty::TyVid {
+        self.sub_root_var(var)
+    }
+
     fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid {
         self.root_const_var(var)
     }
diff --git a/compiler/rustc_next_trait_solver/src/canonicalizer.rs b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
index 7a8ee09650e..d42c62439f6 100644
--- a/compiler/rustc_next_trait_solver/src/canonicalizer.rs
+++ b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
@@ -67,6 +67,7 @@ pub struct Canonicalizer<'a, D: SolverDelegate<Interner = I>, I: Interner> {
     variables: &'a mut Vec<I::GenericArg>,
     var_kinds: Vec<CanonicalVarKind<I>>,
     variable_lookup_table: HashMap<I::GenericArg, usize>,
+    sub_root_lookup_table: HashMap<ty::TyVid, usize>,
     binder_index: ty::DebruijnIndex,
 
     /// We only use the debruijn index during lookup. We don't need to
@@ -88,6 +89,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
             variables,
             variable_lookup_table: Default::default(),
+            sub_root_lookup_table: Default::default(),
             var_kinds: Vec::new(),
             binder_index: ty::INNERMOST,
 
@@ -132,6 +134,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
                         variables: &mut variables,
                         variable_lookup_table: Default::default(),
+                        sub_root_lookup_table: Default::default(),
                         var_kinds: Vec::new(),
                         binder_index: ty::INNERMOST,
 
@@ -139,6 +142,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
                     };
                     let param_env = param_env.fold_with(&mut env_canonicalizer);
                     debug_assert_eq!(env_canonicalizer.binder_index, ty::INNERMOST);
+                    debug_assert!(env_canonicalizer.sub_root_lookup_table.is_empty());
                     CanonicalParamEnvCacheEntry {
                         param_env,
                         variable_lookup_table: env_canonicalizer.variable_lookup_table,
@@ -164,6 +168,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
                 variables,
                 variable_lookup_table: Default::default(),
+                sub_root_lookup_table: Default::default(),
                 var_kinds: Vec::new(),
                 binder_index: ty::INNERMOST,
 
@@ -171,6 +176,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
             };
             let param_env = param_env.fold_with(&mut env_canonicalizer);
             debug_assert_eq!(env_canonicalizer.binder_index, ty::INNERMOST);
+            debug_assert!(env_canonicalizer.sub_root_lookup_table.is_empty());
             (param_env, env_canonicalizer.variable_lookup_table, env_canonicalizer.var_kinds)
         }
     }
@@ -199,6 +205,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
             variables,
             variable_lookup_table,
+            sub_root_lookup_table: Default::default(),
             var_kinds,
             binder_index: ty::INNERMOST,
 
@@ -265,6 +272,13 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
         ty::BoundVar::from(idx)
     }
 
+    fn get_or_insert_sub_root(&mut self, vid: ty::TyVid) -> ty::BoundVar {
+        let root_vid = self.delegate.sub_root_ty_var(vid);
+        let idx =
+            *self.sub_root_lookup_table.entry(root_vid).or_insert_with(|| self.variables.len());
+        ty::BoundVar::from(idx)
+    }
+
     fn finalize(self) -> (ty::UniverseIndex, I::CanonicalVarKinds) {
         let mut var_kinds = self.var_kinds;
         // See the rustc-dev-guide section about how we deal with universes
@@ -312,16 +326,15 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
                         "ty vid should have been resolved fully before canonicalization"
                     );
 
-                    match self.canonicalize_mode {
-                        CanonicalizeMode::Input { .. } => {
-                            CanonicalVarKind::Ty(ty::UniverseIndex::ROOT)
-                        }
-                        CanonicalizeMode::Response { .. } => {
-                            CanonicalVarKind::Ty(self.delegate.universe_of_ty(vid).unwrap_or_else(
-                                || panic!("ty var should have been resolved: {t:?}"),
-                            ))
-                        }
-                    }
+                    let sub_root = self.get_or_insert_sub_root(vid);
+                    let ui = match self.canonicalize_mode {
+                        CanonicalizeMode::Input { .. } => ty::UniverseIndex::ROOT,
+                        CanonicalizeMode::Response { .. } => self
+                            .delegate
+                            .universe_of_ty(vid)
+                            .unwrap_or_else(|| panic!("ty var should have been resolved: {t:?}")),
+                    };
+                    CanonicalVarKind::Ty { ui, sub_root }
                 }
                 ty::IntVar(vid) => {
                     debug_assert_eq!(
diff --git a/compiler/rustc_next_trait_solver/src/delegate.rs b/compiler/rustc_next_trait_solver/src/delegate.rs
index 7b932010d49..4460e9ad2f1 100644
--- a/compiler/rustc_next_trait_solver/src/delegate.rs
+++ b/compiler/rustc_next_trait_solver/src/delegate.rs
@@ -57,12 +57,14 @@ pub trait SolverDelegate: Deref<Target = Self::Infcx> + Sized {
     where
         V: TypeFoldable<Self::Interner>;
 
-    fn instantiate_canonical_var_with_infer(
+    fn instantiate_canonical_var(
         &self,
         kind: ty::CanonicalVarKind<Self::Interner>,
         span: <Self::Interner as Interner>::Span,
+        var_values: &[<Self::Interner as Interner>::GenericArg],
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> <Self::Interner as Interner>::GenericArg;
+
     fn add_item_bounds_for_hidden_type(
         &self,
         def_id: <Self::Interner as Interner>::DefId,
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
index 6f9f4067384..8d7a55c55be 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
@@ -16,7 +16,8 @@ use rustc_type_ir::data_structures::HashSet;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::relate::solver_relating::RelateExt;
 use rustc_type_ir::{
-    self as ty, Canonical, CanonicalVarValues, InferCtxtLike, Interner, TypeFoldable,
+    self as ty, Canonical, CanonicalVarKind, CanonicalVarValues, InferCtxtLike, Interner,
+    TypeFoldable,
 };
 use tracing::{debug, instrument, trace};
 
@@ -336,7 +337,16 @@ where
         {
             match result_value.kind() {
                 ty::GenericArgKind::Type(t) => {
-                    if let ty::Bound(debruijn, b) = t.kind() {
+                    // We disable the instantiation guess for inference variables
+                    // and only use it for placeholders. We need to handle the
+                    // `sub_root` of type inference variables which would make this
+                    // more involved. They are also a lot rarer than region variables.
+                    if let ty::Bound(debruijn, b) = t.kind()
+                        && !matches!(
+                            response.variables.get(b.var().as_usize()).unwrap(),
+                            CanonicalVarKind::Ty { .. }
+                        )
+                    {
                         assert_eq!(debruijn, ty::INNERMOST);
                         opt_values[b.var()] = Some(*original_value);
                     }
@@ -356,38 +366,37 @@ where
             }
         }
 
-        let var_values = delegate.cx().mk_args_from_iter(
-            response.variables.iter().enumerate().map(|(index, var_kind)| {
-                if var_kind.universe() != ty::UniverseIndex::ROOT {
-                    // A variable from inside a binder of the query. While ideally these shouldn't
-                    // exist at all (see the FIXME at the start of this method), we have to deal with
-                    // them for now.
-                    delegate.instantiate_canonical_var_with_infer(var_kind, span, |idx| {
-                        prev_universe + idx.index()
-                    })
-                } else if var_kind.is_existential() {
-                    // As an optimization we sometimes avoid creating a new inference variable here.
-                    //
-                    // All new inference variables we create start out in the current universe of the caller.
-                    // This is conceptually wrong as these inference variables would be able to name
-                    // more placeholders then they should be able to. However the inference variables have
-                    // to "come from somewhere", so by equating them with the original values of the caller
-                    // later on, we pull them down into their correct universe again.
-                    if let Some(v) = opt_values[ty::BoundVar::from_usize(index)] {
-                        v
-                    } else {
-                        delegate
-                            .instantiate_canonical_var_with_infer(var_kind, span, |_| prev_universe)
-                    }
+        let mut var_values = Vec::with_capacity(response.variables.len());
+        for (index, kind) in response.variables.iter().enumerate() {
+            let value = if kind.universe() != ty::UniverseIndex::ROOT {
+                // A variable from inside a binder of the query. While ideally these shouldn't
+                // exist at all (see the FIXME at the start of this method), we have to deal with
+                // them for now.
+                delegate.instantiate_canonical_var(kind, span, &var_values, |idx| {
+                    prev_universe + idx.index()
+                })
+            } else if kind.is_existential() {
+                // As an optimization we sometimes avoid creating a new inference variable here.
+                //
+                // All new inference variables we create start out in the current universe of the caller.
+                // This is conceptually wrong as these inference variables would be able to name
+                // more placeholders then they should be able to. However the inference variables have
+                // to "come from somewhere", so by equating them with the original values of the caller
+                // later on, we pull them down into their correct universe again.
+                if let Some(v) = opt_values[ty::BoundVar::from_usize(index)] {
+                    v
                 } else {
-                    // For placeholders which were already part of the input, we simply map this
-                    // universal bound variable back the placeholder of the input.
-                    original_values[var_kind.expect_placeholder_index()]
+                    delegate.instantiate_canonical_var(kind, span, &var_values, |_| prev_universe)
                 }
-            }),
-        );
+            } else {
+                // For placeholders which were already part of the input, we simply map this
+                // universal bound variable back the placeholder of the input.
+                original_values[kind.expect_placeholder_index()]
+            };
+            var_values.push(value)
+        }
 
-        CanonicalVarValues { var_values }
+        CanonicalVarValues { var_values: delegate.cx().mk_args(&var_values) }
     }
 
     /// Unify the `original_values` with the `var_values` returned by the canonical query..
diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs
index a2db21796a2..91b83e6cbbe 100644
--- a/compiler/rustc_next_trait_solver/src/solve/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs
@@ -418,6 +418,11 @@ pub struct GoalEvaluation<I: Interner> {
     pub has_changed: HasChanged,
     /// If the [`Certainty`] was `Maybe`, then keep track of whether the goal has changed
     /// before rerunning it.
+    ///
+    /// We knowingly ignore the `sub_root` of our inference variables here. This means we
+    /// may not reevaluate a goal even though a change to the `sub_root` could cause a goal
+    /// to make progress. Tracking them adds additional complexity for an incredibly minor
+    /// type inference improvement. We could look into properly handling this in the future.
     pub stalled_on: Option<GoalStalledOn<I>>,
 }
 
diff --git a/compiler/rustc_trait_selection/src/solve/delegate.rs b/compiler/rustc_trait_selection/src/solve/delegate.rs
index 448fc025be6..44230624ddb 100644
--- a/compiler/rustc_trait_selection/src/solve/delegate.rs
+++ b/compiler/rustc_trait_selection/src/solve/delegate.rs
@@ -237,13 +237,14 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
         canonical.instantiate(self.tcx, &values)
     }
 
-    fn instantiate_canonical_var_with_infer(
+    fn instantiate_canonical_var(
         &self,
         kind: CanonicalVarKind<'tcx>,
         span: Span,
+        var_values: &[ty::GenericArg<'tcx>],
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> ty::GenericArg<'tcx> {
-        self.0.instantiate_canonical_var(span, kind, universe_map)
+        self.0.instantiate_canonical_var(span, kind, var_values, universe_map)
     }
 
     fn add_item_bounds_for_hidden_type(
diff --git a/compiler/rustc_type_ir/src/canonical.rs b/compiler/rustc_type_ir/src/canonical.rs
index cd509ed3f72..04bf9008035 100644
--- a/compiler/rustc_type_ir/src/canonical.rs
+++ b/compiler/rustc_type_ir/src/canonical.rs
@@ -91,7 +91,11 @@ impl<I: Interner, V: fmt::Display> fmt::Display for Canonical<I, V> {
 )]
 pub enum CanonicalVarKind<I: Interner> {
     /// General type variable `?T` that can be unified with arbitrary types.
-    Ty(UniverseIndex),
+    ///
+    /// We also store the index of the first type variable which is sub-unified
+    /// with this one. If there is no inference variable related to this one,
+    /// its `sub_root` just points to itself.
+    Ty { ui: UniverseIndex, sub_root: ty::BoundVar },
 
     /// Integral type variable `?I` (that can only be unified with integral types).
     Int,
@@ -122,7 +126,7 @@ impl<I: Interner> Eq for CanonicalVarKind<I> {}
 impl<I: Interner> CanonicalVarKind<I> {
     pub fn universe(self) -> UniverseIndex {
         match self {
-            CanonicalVarKind::Ty(ui) => ui,
+            CanonicalVarKind::Ty { ui, sub_root: _ } => ui,
             CanonicalVarKind::Region(ui) => ui,
             CanonicalVarKind::Const(ui) => ui,
             CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.universe(),
@@ -138,7 +142,7 @@ impl<I: Interner> CanonicalVarKind<I> {
     /// the updated universe is not the root.
     pub fn with_updated_universe(self, ui: UniverseIndex) -> CanonicalVarKind<I> {
         match self {
-            CanonicalVarKind::Ty(_) => CanonicalVarKind::Ty(ui),
+            CanonicalVarKind::Ty { ui: _, sub_root } => CanonicalVarKind::Ty { ui, sub_root },
             CanonicalVarKind::Region(_) => CanonicalVarKind::Region(ui),
             CanonicalVarKind::Const(_) => CanonicalVarKind::Const(ui),
 
@@ -160,7 +164,7 @@ impl<I: Interner> CanonicalVarKind<I> {
 
     pub fn is_existential(self) -> bool {
         match self {
-            CanonicalVarKind::Ty(_)
+            CanonicalVarKind::Ty { .. }
             | CanonicalVarKind::Int
             | CanonicalVarKind::Float
             | CanonicalVarKind::Region(_)
@@ -174,7 +178,7 @@ impl<I: Interner> CanonicalVarKind<I> {
     pub fn is_region(self) -> bool {
         match self {
             CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => true,
-            CanonicalVarKind::Ty(_)
+            CanonicalVarKind::Ty { .. }
             | CanonicalVarKind::Int
             | CanonicalVarKind::Float
             | CanonicalVarKind::PlaceholderTy(_)
@@ -185,7 +189,7 @@ impl<I: Interner> CanonicalVarKind<I> {
 
     pub fn expect_placeholder_index(self) -> usize {
         match self {
-            CanonicalVarKind::Ty(_)
+            CanonicalVarKind::Ty { .. }
             | CanonicalVarKind::Int
             | CanonicalVarKind::Float
             | CanonicalVarKind::Region(_)
@@ -275,7 +279,7 @@ impl<I: Interner> CanonicalVarValues<I> {
             var_values: cx.mk_args_from_iter(infos.iter().enumerate().map(
                 |(i, kind)| -> I::GenericArg {
                     match kind {
-                        CanonicalVarKind::Ty(_)
+                        CanonicalVarKind::Ty { .. }
                         | CanonicalVarKind::Int
                         | CanonicalVarKind::Float
                         | CanonicalVarKind::PlaceholderTy(_) => {
diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs
index 3fac50ff9cc..7fec869f100 100644
--- a/compiler/rustc_type_ir/src/infer_ctxt.rs
+++ b/compiler/rustc_type_ir/src/infer_ctxt.rs
@@ -158,6 +158,7 @@ pub trait InferCtxtLike: Sized {
     fn universe_of_ct(&self, ct: ty::ConstVid) -> Option<ty::UniverseIndex>;
 
     fn root_ty_var(&self, var: ty::TyVid) -> ty::TyVid;
+    fn sub_root_ty_var(&self, var: ty::TyVid) -> ty::TyVid;
     fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid;
 
     fn opportunistic_resolve_ty_var(&self, vid: ty::TyVid) -> <Self::Interner as Interner>::Ty;
diff --git a/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir b/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
index 906e5828aba..a18d7e7478f 100644
--- a/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
+++ b/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
@@ -1,30 +1,30 @@
 // MIR for `address_of_reborrow` after SimplifyCfg-initial
 
 | User Type Annotations
-| 0: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:8:10: 8:18, inferred_ty: *const [i32; 10]
+| 0: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:8:10: 8:18, inferred_ty: *const [i32; 10]
 | 1: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [Region(U0)] }, span: $DIR/address_of.rs:10:10: 10:25, inferred_ty: *const dyn std::marker::Send
-| 2: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:14:12: 14:20, inferred_ty: *const [i32; 10]
-| 3: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:14:12: 14:20, inferred_ty: *const [i32; 10]
+| 2: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:14:12: 14:20, inferred_ty: *const [i32; 10]
+| 3: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:14:12: 14:20, inferred_ty: *const [i32; 10]
 | 4: user_ty: Canonical { value: Ty(*const [i32; 10]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:15:12: 15:28, inferred_ty: *const [i32; 10]
 | 5: user_ty: Canonical { value: Ty(*const [i32; 10]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:15:12: 15:28, inferred_ty: *const [i32; 10]
 | 6: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [Region(U0)] }, span: $DIR/address_of.rs:16:12: 16:27, inferred_ty: *const dyn std::marker::Send
 | 7: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [Region(U0)] }, span: $DIR/address_of.rs:16:12: 16:27, inferred_ty: *const dyn std::marker::Send
 | 8: user_ty: Canonical { value: Ty(*const [i32]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:17:12: 17:24, inferred_ty: *const [i32]
 | 9: user_ty: Canonical { value: Ty(*const [i32]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:17:12: 17:24, inferred_ty: *const [i32]
-| 10: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:19:10: 19:18, inferred_ty: *const [i32; 10]
+| 10: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:19:10: 19:18, inferred_ty: *const [i32; 10]
 | 11: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [Region(U0)] }, span: $DIR/address_of.rs:21:10: 21:25, inferred_ty: *const dyn std::marker::Send
-| 12: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:24:12: 24:20, inferred_ty: *const [i32; 10]
-| 13: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:24:12: 24:20, inferred_ty: *const [i32; 10]
+| 12: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:24:12: 24:20, inferred_ty: *const [i32; 10]
+| 13: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:24:12: 24:20, inferred_ty: *const [i32; 10]
 | 14: user_ty: Canonical { value: Ty(*const [i32; 10]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:25:12: 25:28, inferred_ty: *const [i32; 10]
 | 15: user_ty: Canonical { value: Ty(*const [i32; 10]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:25:12: 25:28, inferred_ty: *const [i32; 10]
 | 16: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [Region(U0)] }, span: $DIR/address_of.rs:26:12: 26:27, inferred_ty: *const dyn std::marker::Send
 | 17: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [Region(U0)] }, span: $DIR/address_of.rs:26:12: 26:27, inferred_ty: *const dyn std::marker::Send
 | 18: user_ty: Canonical { value: Ty(*const [i32]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:27:12: 27:24, inferred_ty: *const [i32]
 | 19: user_ty: Canonical { value: Ty(*const [i32]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:27:12: 27:24, inferred_ty: *const [i32]
-| 20: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:29:10: 29:16, inferred_ty: *mut [i32; 10]
+| 20: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:29:10: 29:16, inferred_ty: *mut [i32; 10]
 | 21: user_ty: Canonical { value: Ty(*mut dyn std::marker::Send), max_universe: U0, variables: [Region(U0)] }, span: $DIR/address_of.rs:31:10: 31:23, inferred_ty: *mut dyn std::marker::Send
-| 22: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:34:12: 34:18, inferred_ty: *mut [i32; 10]
-| 23: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [Ty(U0)] }, span: $DIR/address_of.rs:34:12: 34:18, inferred_ty: *mut [i32; 10]
+| 22: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:34:12: 34:18, inferred_ty: *mut [i32; 10]
+| 23: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [Ty { ui: U0, sub_root: 0 }] }, span: $DIR/address_of.rs:34:12: 34:18, inferred_ty: *mut [i32; 10]
 | 24: user_ty: Canonical { value: Ty(*mut [i32; 10]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:35:12: 35:26, inferred_ty: *mut [i32; 10]
 | 25: user_ty: Canonical { value: Ty(*mut [i32; 10]), max_universe: U0, variables: [] }, span: $DIR/address_of.rs:35:12: 35:26, inferred_ty: *mut [i32; 10]
 | 26: user_ty: Canonical { value: Ty(*mut dyn std::marker::Send), max_universe: U0, variables: [Region(U0)] }, span: $DIR/address_of.rs:36:12: 36:25, inferred_ty: *mut dyn std::marker::Send
diff --git a/tests/ui/error-emitter/multiline-removal-suggestion.svg b/tests/ui/error-emitter/multiline-removal-suggestion.svg
index 9c9bd163ecd..7a88ac55b23 100644
--- a/tests/ui/error-emitter/multiline-removal-suggestion.svg
+++ b/tests/ui/error-emitter/multiline-removal-suggestion.svg
@@ -1,4 +1,4 @@
-<svg width="2322px" height="4322px" xmlns="http://www.w3.org/2000/svg">
+<svg width="2238px" height="3890px" xmlns="http://www.w3.org/2000/svg">
   <style>
     .fg { fill: #AAAAAA }
     .bg { background: #000000 }
@@ -129,375 +129,327 @@
 </tspan>
     <tspan x="10px" y="982px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: the following trait bounds were not satisfied:</tspan>
 </tspan>
-    <tspan x="10px" y="1000px"><tspan>           `&lt;Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:16:10: 16:13}&gt;&gt; as IntoIterator&gt;::IntoIter = _`</tspan>
+    <tspan x="10px" y="1000px"><tspan>           `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:14:8: 14:23}&gt;&gt;: Iterator`</tspan>
 </tspan>
-    <tspan x="10px" y="1018px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:14:8: 14:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="1018px"><tspan>           which is required by `&amp;mut Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:14:8: 14:23}&gt;&gt;: Iterator`</tspan>
 </tspan>
-    <tspan x="10px" y="1036px"><tspan>           `&lt;Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:16:10: 16:13}&gt;&gt; as IntoIterator&gt;::Item = _`</tspan>
+    <tspan x="10px" y="1036px">
 </tspan>
-    <tspan x="10px" y="1054px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:14:8: 14:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="1054px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="1072px"><tspan>           `Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:16:10: 16:13}&gt;&gt;: IntoIterator`</tspan>
+    <tspan x="10px" y="1072px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:32:6</tspan>
 </tspan>
-    <tspan x="10px" y="1090px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:14:8: 14:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="1090px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1108px"><tspan>           `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:14:8: 14:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="1108px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 .flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="1126px"><tspan>           which is required by `&amp;mut Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:14:8: 14:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="1126px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                  </tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="1144px">
+    <tspan x="10px" y="1144px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1162px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="1162px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
 </tspan>
-    <tspan x="10px" y="1180px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:32:6</tspan>
+    <tspan x="10px" y="1180px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
 </tspan>
-    <tspan x="10px" y="1198px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1198px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `flatten`</tspan>
 </tspan>
-    <tspan x="10px" y="1216px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 .flatten()</tspan>
+    <tspan x="10px" y="1216px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL</tspan>
 </tspan>
-    <tspan x="10px" y="1234px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                  </tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="1234px"><tspan class="fg-ansi256-014 bold">help</tspan><tspan>: consider removing this method call, as the receiver has type `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;` and `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;: Iterator` trivially holds</tspan>
 </tspan>
     <tspan x="10px" y="1252px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1270px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
+    <tspan x="10px" y="1270px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">- </tspan><tspan>            ts.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="1288px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
+    <tspan x="10px" y="1288px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">-                 .map(|t| (is_true, t))</tspan>
 </tspan>
-    <tspan x="10px" y="1306px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `flatten`</tspan>
+    <tspan x="10px" y="1306px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-010">+ </tspan><tspan>            ts.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="1324px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL</tspan>
+    <tspan x="10px" y="1324px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1342px"><tspan class="fg-ansi256-014 bold">help</tspan><tspan>: consider removing this method call, as the receiver has type `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;` and `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;: Iterator` trivially holds</tspan>
+    <tspan x="10px" y="1342px">
 </tspan>
-    <tspan x="10px" y="1360px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1360px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="1378px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">- </tspan><tspan>            ts.into_iter()</tspan>
+    <tspan x="10px" y="1378px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:28:2</tspan>
 </tspan>
-    <tspan x="10px" y="1396px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">-                 .map(|t| (is_true, t))</tspan>
+    <tspan x="10px" y="1396px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1414px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-010">+ </tspan><tspan>            ts.into_iter()</tspan>
+    <tspan x="10px" y="1414px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">/</tspan><tspan>     hm.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="1432px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1432px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
 </tspan>
-    <tspan x="10px" y="1450px">
+    <tspan x="10px" y="1450px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>             ts.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="1468px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="1468px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>                 .map(|t| (is_true, t))</tspan>
 </tspan>
-    <tspan x="10px" y="1486px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:28:2</tspan>
+    <tspan x="10px" y="1486px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>                 .flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="1504px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1504px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         })</tspan>
 </tspan>
-    <tspan x="10px" y="1522px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">/</tspan><tspan>     hm.into_iter()</tspan>
+    <tspan x="10px" y="1522px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|__________^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="1540px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
+    <tspan x="10px" y="1540px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1558px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>             ts.into_iter()</tspan>
+    <tspan x="10px" y="1558px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
 </tspan>
-    <tspan x="10px" y="1576px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>                 .map(|t| (is_true, t))</tspan>
+    <tspan x="10px" y="1576px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
 </tspan>
-    <tspan x="10px" y="1594px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>                 .flatten()</tspan>
+    <tspan x="10px" y="1594px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `Flatten`</tspan>
 </tspan>
-    <tspan x="10px" y="1612px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         })</tspan>
+    <tspan x="10px" y="1612px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/adapters/flatten.rs:LL:COL</tspan>
 </tspan>
-    <tspan x="10px" y="1630px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|__________^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="1630px">
 </tspan>
-    <tspan x="10px" y="1648px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1648px"><tspan class="fg-ansi256-009 bold">error[E0599]</tspan><tspan class="bold">: the method `collect` exists for struct `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;`, but its trait bounds were not satisfied</tspan>
 </tspan>
-    <tspan x="10px" y="1666px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
+    <tspan x="10px" y="1666px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:35:4</tspan>
 </tspan>
-    <tspan x="10px" y="1684px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
+    <tspan x="10px" y="1684px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1702px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `Flatten`</tspan>
+    <tspan x="10px" y="1702px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">/</tspan><tspan>     hm.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="1720px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/adapters/flatten.rs:LL:COL</tspan>
+    <tspan x="10px" y="1720px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
 </tspan>
-    <tspan x="10px" y="1738px">
+    <tspan x="10px" y="1738px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>             ts.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="1756px"><tspan class="fg-ansi256-009 bold">error[E0599]</tspan><tspan class="bold">: the method `collect` exists for struct `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;`, but its trait bounds were not satisfied</tspan>
+    <tspan x="10px" y="1756px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 .map(|t| (is_true, t))</tspan>
 </tspan>
-    <tspan x="10px" y="1774px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:35:4</tspan>
+    <tspan x="10px" y="1774px"><tspan class="fg-ansi256-012 bold">...</tspan><tspan>  </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1792px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1792px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="1810px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">/</tspan><tspan>     hm.into_iter()</tspan>
+    <tspan x="10px" y="1810px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .collect()</tspan>
 </tspan>
-    <tspan x="10px" y="1828px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
+    <tspan x="10px" y="1828px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         </tspan><tspan class="fg-ansi256-012 bold">-</tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">method cannot be called due to unsatisfied trait bounds</tspan>
 </tspan>
-    <tspan x="10px" y="1846px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>             ts.into_iter()</tspan>
+    <tspan x="10px" y="1846px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|_________|</tspan>
 </tspan>
-    <tspan x="10px" y="1864px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 .map(|t| (is_true, t))</tspan>
+    <tspan x="10px" y="1864px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1882px"><tspan class="fg-ansi256-012 bold">...</tspan><tspan>  </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1882px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="1900px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .flatten()</tspan>
+    <tspan x="10px" y="1900px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: the following trait bounds were not satisfied:</tspan>
 </tspan>
-    <tspan x="10px" y="1918px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .collect()</tspan>
+    <tspan x="10px" y="1918px"><tspan>           `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;: Iterator`</tspan>
 </tspan>
-    <tspan x="10px" y="1936px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         </tspan><tspan class="fg-ansi256-012 bold">-</tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">method cannot be called due to unsatisfied trait bounds</tspan>
+    <tspan x="10px" y="1936px"><tspan>           which is required by `&amp;mut Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;: Iterator`</tspan>
 </tspan>
-    <tspan x="10px" y="1954px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|_________|</tspan>
+    <tspan x="10px" y="1954px">
 </tspan>
-    <tspan x="10px" y="1972px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1972px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="1990px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="1990px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:43:7</tspan>
 </tspan>
-    <tspan x="10px" y="2008px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: the following trait bounds were not satisfied:</tspan>
+    <tspan x="10px" y="2008px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2026px"><tspan>           `&lt;Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:31:10: 31:13}&gt;&gt; as IntoIterator&gt;::IntoIter = _`</tspan>
+    <tspan x="10px" y="2026px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>             }).flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="2044px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="2044px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                </tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="2062px"><tspan>           `&lt;Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:31:10: 31:13}&gt;&gt; as IntoIterator&gt;::Item = _`</tspan>
+    <tspan x="10px" y="2062px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2080px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="2080px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
 </tspan>
-    <tspan x="10px" y="2098px"><tspan>           `Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:31:10: 31:13}&gt;&gt;: IntoIterator`</tspan>
+    <tspan x="10px" y="2098px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
 </tspan>
-    <tspan x="10px" y="2116px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="2116px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `flatten`</tspan>
 </tspan>
-    <tspan x="10px" y="2134px"><tspan>           `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="2134px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL</tspan>
 </tspan>
-    <tspan x="10px" y="2152px"><tspan>           which is required by `&amp;mut Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:29:8: 29:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="2152px"><tspan class="fg-ansi256-014 bold">help</tspan><tspan>: consider removing this method call, as the receiver has type `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;` and `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;: Iterator` trivially holds</tspan>
 </tspan>
-    <tspan x="10px" y="2170px">
+    <tspan x="10px" y="2170px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2188px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="2188px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">- </tspan><tspan>            ts.into_iter()</tspan><tspan class="fg-ansi256-009">.map(|t| {</tspan>
 </tspan>
-    <tspan x="10px" y="2206px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:43:7</tspan>
+    <tspan x="10px" y="2206px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">-                 (is_true, t)</tspan>
 </tspan>
-    <tspan x="10px" y="2224px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="2224px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">-             })</tspan><tspan>.flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="2242px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>             }).flatten()</tspan>
+    <tspan x="10px" y="2242px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-010">+ </tspan><tspan>            ts.into_iter().flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="2260px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                </tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="2260px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2278px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="2278px">
 </tspan>
-    <tspan x="10px" y="2296px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
+    <tspan x="10px" y="2296px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="2314px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
+    <tspan x="10px" y="2314px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:39:2</tspan>
 </tspan>
-    <tspan x="10px" y="2332px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `flatten`</tspan>
+    <tspan x="10px" y="2332px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2350px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL</tspan>
+    <tspan x="10px" y="2350px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">/</tspan><tspan>     hm.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="2368px"><tspan class="fg-ansi256-014 bold">help</tspan><tspan>: consider removing this method call, as the receiver has type `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;` and `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;: Iterator` trivially holds</tspan>
+    <tspan x="10px" y="2368px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
 </tspan>
-    <tspan x="10px" y="2386px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="2386px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>             ts.into_iter().map(|t| {</tspan>
 </tspan>
-    <tspan x="10px" y="2404px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">- </tspan><tspan>            ts.into_iter()</tspan><tspan class="fg-ansi256-009">.map(|t| {</tspan>
+    <tspan x="10px" y="2404px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>                 (is_true, t)</tspan>
 </tspan>
-    <tspan x="10px" y="2422px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">-                 (is_true, t)</tspan>
+    <tspan x="10px" y="2422px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>             }).flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="2440px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">-             })</tspan><tspan>.flatten()</tspan>
+    <tspan x="10px" y="2440px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         })</tspan>
 </tspan>
-    <tspan x="10px" y="2458px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-010">+ </tspan><tspan>            ts.into_iter().flatten()</tspan>
+    <tspan x="10px" y="2458px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|__________^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
     <tspan x="10px" y="2476px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2494px">
+    <tspan x="10px" y="2494px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
 </tspan>
-    <tspan x="10px" y="2512px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="2512px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
 </tspan>
-    <tspan x="10px" y="2530px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:39:2</tspan>
+    <tspan x="10px" y="2530px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `Flatten`</tspan>
 </tspan>
-    <tspan x="10px" y="2548px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="2548px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/adapters/flatten.rs:LL:COL</tspan>
 </tspan>
-    <tspan x="10px" y="2566px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">/</tspan><tspan>     hm.into_iter()</tspan>
+    <tspan x="10px" y="2566px">
 </tspan>
-    <tspan x="10px" y="2584px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
+    <tspan x="10px" y="2584px"><tspan class="fg-ansi256-009 bold">error[E0599]</tspan><tspan class="bold">: the method `collect` exists for struct `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;`, but its trait bounds were not satisfied</tspan>
 </tspan>
-    <tspan x="10px" y="2602px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>             ts.into_iter().map(|t| {</tspan>
+    <tspan x="10px" y="2602px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:46:4</tspan>
 </tspan>
-    <tspan x="10px" y="2620px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>                 (is_true, t)</tspan>
+    <tspan x="10px" y="2620px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2638px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>             }).flatten()</tspan>
+    <tspan x="10px" y="2638px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">/</tspan><tspan>     hm.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="2656px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         })</tspan>
+    <tspan x="10px" y="2656px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
 </tspan>
-    <tspan x="10px" y="2674px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|__________^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="2674px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>             ts.into_iter().map(|t| {</tspan>
 </tspan>
-    <tspan x="10px" y="2692px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="2692px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 (is_true, t)</tspan>
 </tspan>
-    <tspan x="10px" y="2710px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
+    <tspan x="10px" y="2710px"><tspan class="fg-ansi256-012 bold">...</tspan><tspan>  </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2728px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
+    <tspan x="10px" y="2728px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="2746px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `Flatten`</tspan>
+    <tspan x="10px" y="2746px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .collect()</tspan>
 </tspan>
-    <tspan x="10px" y="2764px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/adapters/flatten.rs:LL:COL</tspan>
+    <tspan x="10px" y="2764px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         </tspan><tspan class="fg-ansi256-012 bold">-</tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">method cannot be called due to unsatisfied trait bounds</tspan>
 </tspan>
-    <tspan x="10px" y="2782px">
+    <tspan x="10px" y="2782px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|_________|</tspan>
 </tspan>
-    <tspan x="10px" y="2800px"><tspan class="fg-ansi256-009 bold">error[E0599]</tspan><tspan class="bold">: the method `collect` exists for struct `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;`, but its trait bounds were not satisfied</tspan>
+    <tspan x="10px" y="2800px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2818px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:46:4</tspan>
+    <tspan x="10px" y="2818px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2836px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="2836px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: the following trait bounds were not satisfied:</tspan>
 </tspan>
-    <tspan x="10px" y="2854px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">/</tspan><tspan>     hm.into_iter()</tspan>
+    <tspan x="10px" y="2854px"><tspan>           `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;: Iterator`</tspan>
 </tspan>
-    <tspan x="10px" y="2872px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
+    <tspan x="10px" y="2872px"><tspan>           which is required by `&amp;mut Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;: Iterator`</tspan>
 </tspan>
-    <tspan x="10px" y="2890px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>             ts.into_iter().map(|t| {</tspan>
+    <tspan x="10px" y="2890px">
 </tspan>
-    <tspan x="10px" y="2908px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 (is_true, t)</tspan>
+    <tspan x="10px" y="2908px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="2926px"><tspan class="fg-ansi256-012 bold">...</tspan><tspan>  </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="2926px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:53:28</tspan>
 </tspan>
-    <tspan x="10px" y="2944px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .flatten()</tspan>
+    <tspan x="10px" y="2944px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="2962px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .collect()</tspan>
+    <tspan x="10px" y="2962px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 .map(|t| (is_true, t)).flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="2980px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         </tspan><tspan class="fg-ansi256-012 bold">-</tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">method cannot be called due to unsatisfied trait bounds</tspan>
+    <tspan x="10px" y="2980px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                                        </tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="2998px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|_________|</tspan>
+    <tspan x="10px" y="2998px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="3016px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="3016px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
 </tspan>
-    <tspan x="10px" y="3034px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="3034px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
 </tspan>
-    <tspan x="10px" y="3052px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: the following trait bounds were not satisfied:</tspan>
+    <tspan x="10px" y="3052px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `flatten`</tspan>
 </tspan>
-    <tspan x="10px" y="3070px"><tspan>           `&lt;Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:41:23: 41:26}&gt;&gt; as IntoIterator&gt;::IntoIter = _`</tspan>
+    <tspan x="10px" y="3070px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL</tspan>
 </tspan>
-    <tspan x="10px" y="3088px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="3088px"><tspan class="fg-ansi256-014 bold">help</tspan><tspan>: consider removing this method call, as the receiver has type `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;` and `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;: Iterator` trivially holds</tspan>
 </tspan>
-    <tspan x="10px" y="3106px"><tspan>           `&lt;Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:41:23: 41:26}&gt;&gt; as IntoIterator&gt;::Item = _`</tspan>
+    <tspan x="10px" y="3106px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="3124px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="3124px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">- </tspan><tspan>            ts.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="3142px"><tspan>           `Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:41:23: 41:26}&gt;&gt;: IntoIterator`</tspan>
+    <tspan x="10px" y="3142px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">-                 .map(|t| (is_true, t))</tspan><tspan>.flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="3160px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="3160px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-010">+ </tspan><tspan>            ts.into_iter().flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="3178px"><tspan>           `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="3178px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="3196px"><tspan>           which is required by `&amp;mut Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:40:8: 40:23}&gt;&gt;: Iterator`</tspan>
+    <tspan x="10px" y="3196px">
 </tspan>
-    <tspan x="10px" y="3214px">
+    <tspan x="10px" y="3214px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="3232px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="3232px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:50:2</tspan>
 </tspan>
-    <tspan x="10px" y="3250px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:53:28</tspan>
+    <tspan x="10px" y="3250px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="3268px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="3268px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">/</tspan><tspan>     hm.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="3286px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 .map(|t| (is_true, t)).flatten()</tspan>
+    <tspan x="10px" y="3286px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
 </tspan>
-    <tspan x="10px" y="3304px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                                        </tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="3304px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>             ts.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="3322px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="3322px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>                 .map(|t| (is_true, t)).flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="3340px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
+    <tspan x="10px" y="3340px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         })</tspan>
 </tspan>
-    <tspan x="10px" y="3358px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
+    <tspan x="10px" y="3358px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|__________^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
 </tspan>
-    <tspan x="10px" y="3376px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `flatten`</tspan>
+    <tspan x="10px" y="3376px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="3394px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL</tspan>
+    <tspan x="10px" y="3394px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
 </tspan>
-    <tspan x="10px" y="3412px"><tspan class="fg-ansi256-014 bold">help</tspan><tspan>: consider removing this method call, as the receiver has type `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;` and `std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;: Iterator` trivially holds</tspan>
+    <tspan x="10px" y="3412px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
 </tspan>
-    <tspan x="10px" y="3430px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="3430px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `Flatten`</tspan>
 </tspan>
-    <tspan x="10px" y="3448px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">- </tspan><tspan>            ts.into_iter()</tspan>
+    <tspan x="10px" y="3448px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/adapters/flatten.rs:LL:COL</tspan>
 </tspan>
-    <tspan x="10px" y="3466px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-009">-                 .map(|t| (is_true, t))</tspan><tspan>.flatten()</tspan>
+    <tspan x="10px" y="3466px">
 </tspan>
-    <tspan x="10px" y="3484px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-010">+ </tspan><tspan>            ts.into_iter().flatten()</tspan>
+    <tspan x="10px" y="3484px"><tspan class="fg-ansi256-009 bold">error[E0599]</tspan><tspan class="bold">: the method `collect` exists for struct `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;`, but its trait bounds were not satisfied</tspan>
 </tspan>
-    <tspan x="10px" y="3502px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="3502px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:56:4</tspan>
 </tspan>
-    <tspan x="10px" y="3520px">
+    <tspan x="10px" y="3520px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="3538px"><tspan class="fg-ansi256-009 bold">error[E0277]</tspan><tspan class="bold">: `(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="3538px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">/</tspan><tspan>     hm.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="3556px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:50:2</tspan>
+    <tspan x="10px" y="3556px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
 </tspan>
-    <tspan x="10px" y="3574px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="3574px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>             ts.into_iter()</tspan>
 </tspan>
-    <tspan x="10px" y="3592px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">/</tspan><tspan>     hm.into_iter()</tspan>
+    <tspan x="10px" y="3592px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 .map(|t| (is_true, t)).flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="3610px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
+    <tspan x="10px" y="3610px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         })</tspan>
 </tspan>
-    <tspan x="10px" y="3628px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>             ts.into_iter()</tspan>
+    <tspan x="10px" y="3628px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .flatten()</tspan>
 </tspan>
-    <tspan x="10px" y="3646px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>                 .map(|t| (is_true, t)).flatten()</tspan>
+    <tspan x="10px" y="3646px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .collect()</tspan>
 </tspan>
-    <tspan x="10px" y="3664px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|</tspan><tspan>         })</tspan>
+    <tspan x="10px" y="3664px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         </tspan><tspan class="fg-ansi256-012 bold">-</tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">method cannot be called due to unsatisfied trait bounds</tspan>
 </tspan>
-    <tspan x="10px" y="3682px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">|__________^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">`(bool, HashSet&lt;u8&gt;)` is not an iterator</tspan>
+    <tspan x="10px" y="3682px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|_________|</tspan>
 </tspan>
     <tspan x="10px" y="3700px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="3718px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">help</tspan><tspan>: the trait `Iterator` is not implemented for `(bool, HashSet&lt;u8&gt;)`</tspan>
+    <tspan x="10px" y="3718px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
 </tspan>
-    <tspan x="10px" y="3736px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: required for `(bool, HashSet&lt;u8&gt;)` to implement `IntoIterator`</tspan>
+    <tspan x="10px" y="3736px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: the following trait bounds were not satisfied:</tspan>
 </tspan>
-    <tspan x="10px" y="3754px"><tspan class="fg-ansi256-010 bold">note</tspan><tspan>: required by a bound in `Flatten`</tspan>
+    <tspan x="10px" y="3754px"><tspan>           `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;: Iterator`</tspan>
 </tspan>
-    <tspan x="10px" y="3772px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$SRC_DIR/core/src/iter/adapters/flatten.rs:LL:COL</tspan>
+    <tspan x="10px" y="3772px"><tspan>           which is required by `&amp;mut Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;: Iterator`</tspan>
 </tspan>
     <tspan x="10px" y="3790px">
 </tspan>
-    <tspan x="10px" y="3808px"><tspan class="fg-ansi256-009 bold">error[E0599]</tspan><tspan class="bold">: the method `collect` exists for struct `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;`, but its trait bounds were not satisfied</tspan>
+    <tspan x="10px" y="3808px"><tspan class="fg-ansi256-009 bold">error</tspan><tspan class="bold">: aborting due to 12 previous errors</tspan>
 </tspan>
-    <tspan x="10px" y="3826px"><tspan>  </tspan><tspan class="fg-ansi256-012 bold">--&gt; </tspan><tspan>$DIR/multiline-removal-suggestion.rs:56:4</tspan>
+    <tspan x="10px" y="3826px">
 </tspan>
-    <tspan x="10px" y="3844px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
+    <tspan x="10px" y="3844px"><tspan class="bold">Some errors have detailed explanations: E0277, E0599.</tspan>
 </tspan>
-    <tspan x="10px" y="3862px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">/</tspan><tspan>     hm.into_iter()</tspan>
+    <tspan x="10px" y="3862px"><tspan class="bold">For more information about an error, try `rustc --explain E0277`.</tspan>
 </tspan>
-    <tspan x="10px" y="3880px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .map(|(is_true, ts)| {</tspan>
-</tspan>
-    <tspan x="10px" y="3898px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>             ts.into_iter()</tspan>
-</tspan>
-    <tspan x="10px" y="3916px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>                 .map(|t| (is_true, t)).flatten()</tspan>
-</tspan>
-    <tspan x="10px" y="3934px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         })</tspan>
-</tspan>
-    <tspan x="10px" y="3952px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .flatten()</tspan>
-</tspan>
-    <tspan x="10px" y="3970px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         .collect()</tspan>
-</tspan>
-    <tspan x="10px" y="3988px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan>         </tspan><tspan class="fg-ansi256-012 bold">-</tspan><tspan class="fg-ansi256-009 bold">^^^^^^^</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">method cannot be called due to unsatisfied trait bounds</tspan>
-</tspan>
-    <tspan x="10px" y="4006px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">|_________|</tspan>
-</tspan>
-    <tspan x="10px" y="4024px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
-</tspan>
-    <tspan x="10px" y="4042px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">|</tspan>
-</tspan>
-    <tspan x="10px" y="4060px"><tspan>   </tspan><tspan class="fg-ansi256-012 bold">= </tspan><tspan class="bold">note</tspan><tspan>: the following trait bounds were not satisfied:</tspan>
-</tspan>
-    <tspan x="10px" y="4078px"><tspan>           `&lt;Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:53:10: 53:13}&gt;&gt; as IntoIterator&gt;::IntoIter = _`</tspan>
-</tspan>
-    <tspan x="10px" y="4096px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;: Iterator`</tspan>
-</tspan>
-    <tspan x="10px" y="4114px"><tspan>           `&lt;Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:53:10: 53:13}&gt;&gt; as IntoIterator&gt;::Item = _`</tspan>
-</tspan>
-    <tspan x="10px" y="4132px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;: Iterator`</tspan>
-</tspan>
-    <tspan x="10px" y="4150px"><tspan>           `Flatten&lt;Map&lt;std::vec::IntoIter&lt;HashSet&lt;u8&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:53:10: 53:13}&gt;&gt;: IntoIterator`</tspan>
-</tspan>
-    <tspan x="10px" y="4168px"><tspan>           which is required by `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;: Iterator`</tspan>
-</tspan>
-    <tspan x="10px" y="4186px"><tspan>           `Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;: Iterator`</tspan>
-</tspan>
-    <tspan x="10px" y="4204px"><tspan>           which is required by `&amp;mut Flatten&lt;Map&lt;std::collections::hash_map::IntoIter&lt;bool, Vec&lt;HashSet&lt;u8&gt;&gt;&gt;, {closure@$DIR/multiline-removal-suggestion.rs:51:8: 51:23}&gt;&gt;: Iterator`</tspan>
-</tspan>
-    <tspan x="10px" y="4222px">
-</tspan>
-    <tspan x="10px" y="4240px"><tspan class="fg-ansi256-009 bold">error</tspan><tspan class="bold">: aborting due to 12 previous errors</tspan>
-</tspan>
-    <tspan x="10px" y="4258px">
-</tspan>
-    <tspan x="10px" y="4276px"><tspan class="bold">Some errors have detailed explanations: E0277, E0599.</tspan>
-</tspan>
-    <tspan x="10px" y="4294px"><tspan class="bold">For more information about an error, try `rustc --explain E0277`.</tspan>
-</tspan>
-    <tspan x="10px" y="4312px">
+    <tspan x="10px" y="3880px">
 </tspan>
   </text>
 
diff --git a/tests/ui/impl-trait/recursive-in-exhaustiveness.next.stderr b/tests/ui/impl-trait/recursive-in-exhaustiveness.next.stderr
index 45df8cc9c0c..10e8dbf41cc 100644
--- a/tests/ui/impl-trait/recursive-in-exhaustiveness.next.stderr
+++ b/tests/ui/impl-trait/recursive-in-exhaustiveness.next.stderr
@@ -1,14 +1,24 @@
-error[E0282]: type annotations needed
-  --> $DIR/recursive-in-exhaustiveness.rs:19:17
+error[E0282]: type annotations needed for `(_,)`
+  --> $DIR/recursive-in-exhaustiveness.rs:19:9
    |
 LL |     let (x,) = (build(x),);
-   |                 ^^^^^^^^ cannot infer type
+   |         ^^^^
+   |
+help: consider giving this pattern a type, where the placeholders `_` are specified
+   |
+LL |     let (x,): (_,) = (build(x),);
+   |             ++++++
 
-error[E0282]: type annotations needed
-  --> $DIR/recursive-in-exhaustiveness.rs:29:17
+error[E0282]: type annotations needed for `((_,),)`
+  --> $DIR/recursive-in-exhaustiveness.rs:29:9
    |
 LL |     let (x,) = (build2(x),);
-   |                 ^^^^^^^^^ cannot infer type
+   |         ^^^^
+   |
+help: consider giving this pattern a type, where the placeholders `_` are specified
+   |
+LL |     let (x,): ((_,),) = (build2(x),);
+   |             +++++++++
 
 error[E0282]: type annotations needed
   --> $DIR/recursive-in-exhaustiveness.rs:40:5