Auto merge of #142074 - oli-obk:its-finally-gone, r=petrochenkov

Remove CollectItemTypesVisitor

I always felt like we were very unnecessarily walking the HIR, let's see if perf agrees

There is lots to ~~improve~~ consolidate further here, as we still have 3 item wfchecks:

* check_item (matching on the hir::ItemKind)
    * actually doing trait solver based checks (by using HIR spans)
* lower_item (matching on the hir::ItemKind after loading it again??)
    * just ensure_ok-ing a bunch of queries
* check_item_type (matching on DefKind)
    * some type based checks, mostly ensure_ok-ing a bunch of queries

fixes rust-lang/rust#121429

11 files changed, 204 insertions, 230 deletions

diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 102fc2a63be..8c52f5dbbbe 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -702,6 +702,29 @@ fn check_static_linkage(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 }
 
 pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
+    let generics = tcx.generics_of(def_id);
+
+    for param in &generics.own_params {
+        match param.kind {
+            ty::GenericParamDefKind::Lifetime { .. } => {}
+            ty::GenericParamDefKind::Type { has_default, .. } => {
+                if has_default {
+                    tcx.ensure_ok().type_of(param.def_id);
+                }
+            }
+            ty::GenericParamDefKind::Const { has_default, .. } => {
+                tcx.ensure_ok().type_of(param.def_id);
+                if has_default {
+                    // need to store default and type of default
+                    let ct = tcx.const_param_default(param.def_id).skip_binder();
+                    if let ty::ConstKind::Unevaluated(uv) = ct.kind() {
+                        tcx.ensure_ok().type_of(uv.def);
+                    }
+                }
+            }
+        }
+    }
+
     match tcx.def_kind(def_id) {
         DefKind::Static { .. } => {
             check_static_inhabited(tcx, def_id);
@@ -770,6 +793,16 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
             } else {
                 check_opaque(tcx, def_id);
             }
+
+            tcx.ensure_ok().predicates_of(def_id);
+            tcx.ensure_ok().explicit_item_bounds(def_id);
+            tcx.ensure_ok().explicit_item_self_bounds(def_id);
+            tcx.ensure_ok().item_bounds(def_id);
+            tcx.ensure_ok().item_self_bounds(def_id);
+            if tcx.is_conditionally_const(def_id) {
+                tcx.ensure_ok().explicit_implied_const_bounds(def_id);
+                tcx.ensure_ok().const_conditions(def_id);
+            }
         }
         DefKind::TyAlias => {
             check_type_alias_type_params_are_used(tcx, def_id);
@@ -827,6 +860,15 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
                 }
             }
         }
+        DefKind::Closure => {
+            // This is guaranteed to be called by metadata encoding,
+            // we still call it in wfcheck eagerly to ensure errors in codegen
+            // attrs prevent lints from spamming the output.
+            tcx.ensure_ok().codegen_fn_attrs(def_id);
+            // We do not call `type_of` for closures here as that
+            // depends on typecheck and would therefore hide
+            // any further errors in case one typeck fails.
+        }
         _ => {}
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index 237b8ae8b89..b8dc01cbc03 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -40,7 +40,6 @@ use tracing::{debug, instrument};
 use {rustc_ast as ast, rustc_hir as hir};
 
 use crate::autoderef::Autoderef;
-use crate::collect::CollectItemTypesVisitor;
 use crate::constrained_generic_params::{Parameter, identify_constrained_generic_params};
 use crate::errors::InvalidReceiverTyHint;
 use crate::{errors, fluent_generated as fluent};
@@ -195,7 +194,9 @@ fn check_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGua
         hir::Node::TraitItem(item) => check_trait_item(tcx, item),
         hir::Node::ImplItem(item) => check_impl_item(tcx, item),
         hir::Node::ForeignItem(item) => check_foreign_item(tcx, item),
-        hir::Node::OpaqueTy(_) => Ok(crate::check::check::check_item_type(tcx, def_id)),
+        hir::Node::ConstBlock(_) | hir::Node::Expr(_) | hir::Node::OpaqueTy(_) => {
+            Ok(crate::check::check::check_item_type(tcx, def_id))
+        }
         _ => unreachable!("{node:?}"),
     };
 
@@ -229,7 +230,8 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) -> Result<()
         ?item.owner_id,
         item.name = ? tcx.def_path_str(def_id)
     );
-    CollectItemTypesVisitor { tcx }.visit_item(item);
+    crate::collect::lower_item(tcx, item.item_id());
+    crate::collect::reject_placeholder_type_signatures_in_item(tcx, item);
 
     let res = match item.kind {
         // Right now we check that every default trait implementation
@@ -350,8 +352,6 @@ fn check_foreign_item<'tcx>(
 ) -> Result<(), ErrorGuaranteed> {
     let def_id = item.owner_id.def_id;
 
-    CollectItemTypesVisitor { tcx }.visit_foreign_item(item);
-
     debug!(
         ?item.owner_id,
         item.name = ? tcx.def_path_str(def_id)
@@ -374,7 +374,7 @@ fn check_trait_item<'tcx>(
 ) -> Result<(), ErrorGuaranteed> {
     let def_id = trait_item.owner_id.def_id;
 
-    CollectItemTypesVisitor { tcx }.visit_trait_item(trait_item);
+    crate::collect::lower_trait_item(tcx, trait_item.trait_item_id());
 
     let (method_sig, span) = match trait_item.kind {
         hir::TraitItemKind::Fn(ref sig, _) => (Some(sig), trait_item.span),
@@ -939,7 +939,7 @@ fn check_impl_item<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl_item: &'tcx hir::ImplItem<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
-    CollectItemTypesVisitor { tcx }.visit_impl_item(impl_item);
+    crate::collect::lower_impl_item(tcx, impl_item.impl_item_id());
 
     let (method_sig, span) = match impl_item.kind {
         hir::ImplItemKind::Fn(ref sig, _) => (Some(sig), impl_item.span),
@@ -2411,6 +2411,7 @@ fn check_type_wf(tcx: TyCtxt<'_>, (): ()) -> Result<(), ErrorGuaranteed> {
         .and(
             items.par_foreign_items(|item| tcx.ensure_ok().check_well_formed(item.owner_id.def_id)),
         )
+        .and(items.par_nested_bodies(|item| tcx.ensure_ok().check_well_formed(item)))
         .and(items.par_opaques(|item| tcx.ensure_ok().check_well_formed(item)));
     super::entry::check_for_entry_fn(tcx);
 
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index a649e7d67af..e1df0d60452 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -28,11 +28,10 @@ use rustc_errors::{
 };
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_hir::intravisit::{self, InferKind, Visitor, VisitorExt, walk_generics};
+use rustc_hir::intravisit::{InferKind, Visitor, VisitorExt, walk_generics};
 use rustc_hir::{self as hir, GenericParamKind, HirId, Node, PreciseCapturingArgKind};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::{DynCompatibilityViolation, ObligationCause};
-use rustc_middle::hir::nested_filter;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{Discr, IntTypeExt};
 use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, Ty, TyCtxt, TypingMode, fold_regions};
@@ -148,10 +147,6 @@ impl<'v> Visitor<'v> for HirPlaceholderCollector {
     }
 }
 
-pub(crate) struct CollectItemTypesVisitor<'tcx> {
-    pub tcx: TyCtxt<'tcx>,
-}
-
 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
@@ -243,7 +238,7 @@ pub(crate) fn placeholder_type_error_diag<'cx, 'tcx>(
     err
 }
 
-fn reject_placeholder_type_signatures_in_item<'tcx>(
+pub(super) fn reject_placeholder_type_signatures_in_item<'tcx>(
     tcx: TyCtxt<'tcx>,
     item: &'tcx hir::Item<'tcx>,
 ) {
@@ -274,81 +269,6 @@ fn reject_placeholder_type_signatures_in_item<'tcx>(
     );
 }
 
-impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
-    type NestedFilter = nested_filter::OnlyBodies;
-
-    fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
-        self.tcx
-    }
-
-    fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
-        lower_item(self.tcx, item.item_id());
-        reject_placeholder_type_signatures_in_item(self.tcx, item);
-        intravisit::walk_item(self, item);
-    }
-
-    fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
-        for param in generics.params {
-            match param.kind {
-                hir::GenericParamKind::Lifetime { .. } => {}
-                hir::GenericParamKind::Type { default: Some(_), .. } => {
-                    self.tcx.ensure_ok().type_of(param.def_id);
-                }
-                hir::GenericParamKind::Type { .. } => {}
-                hir::GenericParamKind::Const { default, .. } => {
-                    self.tcx.ensure_ok().type_of(param.def_id);
-                    if let Some(default) = default {
-                        // need to store default and type of default
-                        self.tcx.ensure_ok().const_param_default(param.def_id);
-                        if let hir::ConstArgKind::Anon(ac) = default.kind {
-                            self.tcx.ensure_ok().type_of(ac.def_id);
-                        }
-                    }
-                }
-            }
-        }
-        intravisit::walk_generics(self, generics);
-    }
-
-    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
-        if let hir::ExprKind::Closure(closure) = expr.kind {
-            self.tcx.ensure_ok().generics_of(closure.def_id);
-            self.tcx.ensure_ok().codegen_fn_attrs(closure.def_id);
-            // We do not call `type_of` for closures here as that
-            // depends on typecheck and would therefore hide
-            // any further errors in case one typeck fails.
-        }
-        intravisit::walk_expr(self, expr);
-    }
-
-    /// Don't call `type_of` on opaque types, since that depends on type checking function bodies.
-    /// `check_item_type` ensures that it's called instead.
-    fn visit_opaque_ty(&mut self, opaque: &'tcx hir::OpaqueTy<'tcx>) {
-        let def_id = opaque.def_id;
-        self.tcx.ensure_ok().generics_of(def_id);
-        self.tcx.ensure_ok().predicates_of(def_id);
-        self.tcx.ensure_ok().explicit_item_bounds(def_id);
-        self.tcx.ensure_ok().explicit_item_self_bounds(def_id);
-        self.tcx.ensure_ok().item_bounds(def_id);
-        self.tcx.ensure_ok().item_self_bounds(def_id);
-        if self.tcx.is_conditionally_const(def_id) {
-            self.tcx.ensure_ok().explicit_implied_const_bounds(def_id);
-            self.tcx.ensure_ok().const_conditions(def_id);
-        }
-        intravisit::walk_opaque_ty(self, opaque);
-    }
-
-    fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
-        lower_trait_item(self.tcx, trait_item.trait_item_id());
-        intravisit::walk_trait_item(self, trait_item);
-    }
-
-    fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
-        lower_impl_item(self.tcx, impl_item.impl_item_id());
-        intravisit::walk_impl_item(self, impl_item);
-    }
-}
-
 ///////////////////////////////////////////////////////////////////////////
 // Utility types and common code for the above passes.
 
@@ -669,7 +589,7 @@ fn get_new_lifetime_name<'tcx>(
 }
 
 #[instrument(level = "debug", skip_all)]
-fn lower_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
+pub(super) fn lower_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
     let it = tcx.hir_item(item_id);
     debug!(item = ?it.kind.ident(), id = %it.hir_id());
     let def_id = item_id.owner_id.def_id;
@@ -790,7 +710,7 @@ fn lower_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
     }
 }
 
-fn lower_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
+pub(crate) fn lower_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
     let trait_item = tcx.hir_trait_item(trait_item_id);
     let def_id = trait_item_id.owner_id;
     tcx.ensure_ok().generics_of(def_id);
@@ -861,7 +781,7 @@ fn lower_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
     tcx.ensure_ok().predicates_of(def_id);
 }
 
-fn lower_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
+pub(super) fn lower_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
     let def_id = impl_item_id.owner_id;
     tcx.ensure_ok().generics_of(def_id);
     tcx.ensure_ok().type_of(def_id);
diff --git a/compiler/rustc_middle/src/hir/mod.rs b/compiler/rustc_middle/src/hir/mod.rs
index a28dcb0cb8e..d1f5caaafb2 100644
--- a/compiler/rustc_middle/src/hir/mod.rs
+++ b/compiler/rustc_middle/src/hir/mod.rs
@@ -71,6 +71,7 @@ impl ModuleItems {
         self.opaques.iter().copied()
     }
 
+    /// Closures and inline consts
     pub fn nested_bodies(&self) -> impl Iterator<Item = LocalDefId> {
         self.nested_bodies.iter().copied()
     }
@@ -79,6 +80,14 @@ impl ModuleItems {
         self.owners().map(|id| id.def_id)
     }
 
+    /// Closures and inline consts
+    pub fn par_nested_bodies(
+        &self,
+        f: impl Fn(LocalDefId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
+    ) -> Result<(), ErrorGuaranteed> {
+        try_par_for_each_in(&self.nested_bodies[..], |&&id| f(id))
+    }
+
     pub fn par_items(
         &self,
         f: impl Fn(ItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
diff --git a/tests/crashes/121429.rs b/tests/crashes/121429.rs
deleted file mode 100644
index e407754db5c..00000000000
--- a/tests/crashes/121429.rs
+++ /dev/null
@@ -1,14 +0,0 @@
-//@ known-bug: #121429
-
-#![feature(generic_const_exprs)]
-
-struct FixedI8<const X: usize>;
-const FRAC_LHS: usize = 0;
-const FRAC_RHS: usize = 1;
-
-pub trait True {}
-
-impl<const N: usize = { const { 3 } }> PartialEq<FixedI8<FRAC_RHS>> for FixedI8<FRAC_LHS> where
-    If<{}>: True
-{
-}
diff --git a/tests/ui/associated-inherent-types/issue-109299-1.stderr b/tests/ui/associated-inherent-types/issue-109299-1.stderr
index 940ccd7e400..6bc7a539680 100644
--- a/tests/ui/associated-inherent-types/issue-109299-1.stderr
+++ b/tests/ui/associated-inherent-types/issue-109299-1.stderr
@@ -1,3 +1,11 @@
+error: unconstrained opaque type
+  --> $DIR/issue-109299-1.rs:10:10
+   |
+LL | type X = impl for<T> Fn() -> Lexer<T>::Cursor;
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `X` must be used in combination with a concrete type within the same crate
+
 error[E0220]: associated type `Cursor` not found for `Lexer<T>` in the current scope
   --> $DIR/issue-109299-1.rs:10:40
    |
@@ -23,14 +31,6 @@ LL | type X = impl for<T> Fn() -> Lexer<T>::Cursor;
            - `Lexer<i32>`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: unconstrained opaque type
-  --> $DIR/issue-109299-1.rs:10:10
-   |
-LL | type X = impl for<T> Fn() -> Lexer<T>::Cursor;
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `X` must be used in combination with a concrete type within the same crate
-
 error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0220`.
diff --git a/tests/ui/associated-type-bounds/duplicate.stderr b/tests/ui/associated-type-bounds/duplicate.stderr
index 1ce212a9ff3..68fbb345f6f 100644
--- a/tests/ui/associated-type-bounds/duplicate.stderr
+++ b/tests/ui/associated-type-bounds/duplicate.stderr
@@ -199,16 +199,6 @@ LL | fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
    |                              `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:133:42
-   |
-LL | fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
   --> $DIR/duplicate.rs:139:42
    |
 LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
@@ -217,32 +207,12 @@ LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
    |                              `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:139:42
-   |
-LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:145:45
-   |
-LL | fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
-   |                              -------------  ^^^^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
   --> $DIR/duplicate.rs:145:45
    |
 LL | fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
    |                              -------------  ^^^^^^^^^^^^^ re-bound here
    |                              |
    |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
   --> $DIR/duplicate.rs:151:40
@@ -341,60 +311,6 @@ LL | type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
    |                        `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:189:40
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:189:40
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:193:40
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:193:40
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:197:43
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |                            -------------  ^^^^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:197:43
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |                            -------------  ^^^^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
   --> $DIR/duplicate.rs:202:36
    |
 LL | trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
@@ -664,6 +580,16 @@ LL |     type A: Iterator<Item: 'static, Item: 'static>;
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:133:42
+   |
+LL | fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
+   |                              ----------  ^^^^^^^^^^ re-bound here
+   |                              |
+   |                              `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error[E0282]: type annotations needed
   --> $DIR/duplicate.rs:136:5
    |
@@ -675,6 +601,16 @@ help: consider specifying the generic argument
 LL |     iter::empty::<T>()
    |                +++++
 
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:139:42
+   |
+LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
+   |                              ----------  ^^^^^^^^^^ re-bound here
+   |                              |
+   |                              `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error[E0282]: type annotations needed
   --> $DIR/duplicate.rs:142:5
    |
@@ -686,6 +622,16 @@ help: consider specifying the generic argument
 LL |     iter::empty::<T>()
    |                +++++
 
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:145:45
+   |
+LL | fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
+   |                              -------------  ^^^^^^^^^^^^^ re-bound here
+   |                              |
+   |                              `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error[E0282]: type annotations needed
   --> $DIR/duplicate.rs:148:5
    |
@@ -729,6 +675,24 @@ LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
    |
    = note: `ETAI4` must be used in combination with a concrete type within the same crate
 
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:189:40
+   |
+LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
+   |                            ----------  ^^^^^^^^^^ re-bound here
+   |                            |
+   |                            `Item` bound here first
+
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:189:40
+   |
+LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
+   |                            ----------  ^^^^^^^^^^ re-bound here
+   |                            |
+   |                            `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error: unconstrained opaque type
   --> $DIR/duplicate.rs:193:14
    |
@@ -737,6 +701,24 @@ LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
    |
    = note: `ETAI5` must be used in combination with a concrete type within the same crate
 
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:193:40
+   |
+LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
+   |                            ----------  ^^^^^^^^^^ re-bound here
+   |                            |
+   |                            `Item` bound here first
+
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:193:40
+   |
+LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
+   |                            ----------  ^^^^^^^^^^ re-bound here
+   |                            |
+   |                            `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error: unconstrained opaque type
   --> $DIR/duplicate.rs:197:14
    |
@@ -745,6 +727,24 @@ LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
    |
    = note: `ETAI6` must be used in combination with a concrete type within the same crate
 
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:197:43
+   |
+LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
+   |                            -------------  ^^^^^^^^^^^^^ re-bound here
+   |                            |
+   |                            `Item` bound here first
+
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate.rs:197:43
+   |
+LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
+   |                            -------------  ^^^^^^^^^^^^^ re-bound here
+   |                            |
+   |                            `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error: aborting due to 87 previous errors
 
 Some errors have detailed explanations: E0282, E0719.
diff --git a/tests/ui/query-system/issue-83479.rs b/tests/ui/query-system/issue-83479.rs
index 32676dfe9c8..94ceccf49f4 100644
--- a/tests/ui/query-system/issue-83479.rs
+++ b/tests/ui/query-system/issue-83479.rs
@@ -8,6 +8,7 @@ type PairCoupledTypes: Trait<
     }],
 > = impl Trait<
     //~^ ERROR: cannot find trait `Trait` in this scope
+    //~| ERROR: unconstrained opaque type
     [u32; {
         static FOO: usize; //~ ERROR: free static item without body
     }],
diff --git a/tests/ui/query-system/issue-83479.stderr b/tests/ui/query-system/issue-83479.stderr
index 7cb41f5cbe5..79764d01b3b 100644
--- a/tests/ui/query-system/issue-83479.stderr
+++ b/tests/ui/query-system/issue-83479.stderr
@@ -20,7 +20,7 @@ LL |         static FOO: usize;
    |                          help: provide a definition for the static: `= <expr>;`
 
 error: free static item without body
-  --> $DIR/issue-83479.rs:12:9
+  --> $DIR/issue-83479.rs:13:9
    |
 LL |         static FOO: usize;
    |         ^^^^^^^^^^^^^^^^^-
@@ -39,6 +39,21 @@ error[E0405]: cannot find trait `Trait` in this scope
 LL | > = impl Trait<
    |          ^^^^^ not found in this scope
 
-error: aborting due to 5 previous errors
+error: unconstrained opaque type
+  --> $DIR/issue-83479.rs:9:5
+   |
+LL |   > = impl Trait<
+   |  _____^
+LL | |
+LL | |
+LL | |     [u32; {
+LL | |         static FOO: usize;
+LL | |     }],
+LL | | >;
+   | |_^
+   |
+   = note: `PairCoupledTypes` must be used in combination with a concrete type within the same crate
+
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0405`.
diff --git a/tests/ui/traits/associated_type_bound/116464-invalid-assoc-type-suggestion-in-trait-impl.stderr b/tests/ui/traits/associated_type_bound/116464-invalid-assoc-type-suggestion-in-trait-impl.stderr
index a22d88b7c59..eedaae43f9a 100644
--- a/tests/ui/traits/associated_type_bound/116464-invalid-assoc-type-suggestion-in-trait-impl.stderr
+++ b/tests/ui/traits/associated_type_bound/116464-invalid-assoc-type-suggestion-in-trait-impl.stderr
@@ -49,23 +49,6 @@ LL | fn func<T: Trait<u32, String>>(t: T) -> impl Trait<(), Assoc = i32> {
    |                                                        +++++++
 
 error[E0107]: trait takes 1 generic argument but 2 generic arguments were supplied
-  --> $DIR/116464-invalid-assoc-type-suggestion-in-trait-impl.rs:19:46
-   |
-LL | fn func<T: Trait<u32, String>>(t: T) -> impl Trait<(), i32> {
-   |                                              ^^^^^ expected 1 generic argument
-   |
-note: trait defined here, with 1 generic parameter: `T`
-  --> $DIR/116464-invalid-assoc-type-suggestion-in-trait-impl.rs:5:11
-   |
-LL | pub trait Trait<T> {
-   |           ^^^^^ -
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-help: replace the generic bound with the associated type
-   |
-LL | fn func<T: Trait<u32, String>>(t: T) -> impl Trait<(), Assoc = i32> {
-   |                                                        +++++++
-
-error[E0107]: trait takes 1 generic argument but 2 generic arguments were supplied
   --> $DIR/116464-invalid-assoc-type-suggestion-in-trait-impl.rs:26:18
    |
 LL | struct Struct<T: Trait<u32, String>> {
@@ -127,6 +110,23 @@ note: struct defined here, with 1 generic parameter: `T`
 LL | struct Struct<T: Trait<u32, String>> {
    |        ^^^^^^ -
 
+error[E0107]: trait takes 1 generic argument but 2 generic arguments were supplied
+  --> $DIR/116464-invalid-assoc-type-suggestion-in-trait-impl.rs:19:46
+   |
+LL | fn func<T: Trait<u32, String>>(t: T) -> impl Trait<(), i32> {
+   |                                              ^^^^^ expected 1 generic argument
+   |
+note: trait defined here, with 1 generic parameter: `T`
+  --> $DIR/116464-invalid-assoc-type-suggestion-in-trait-impl.rs:5:11
+   |
+LL | pub trait Trait<T> {
+   |           ^^^^^ -
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: replace the generic bound with the associated type
+   |
+LL | fn func<T: Trait<u32, String>>(t: T) -> impl Trait<(), Assoc = i32> {
+   |                                                        +++++++
+
 error: aborting due to 9 previous errors
 
 Some errors have detailed explanations: E0107, E0207.
diff --git a/tests/ui/traits/const-traits/const-impl-trait.stderr b/tests/ui/traits/const-traits/const-impl-trait.stderr
index 27d7957c001..6783cec3960 100644
--- a/tests/ui/traits/const-traits/const-impl-trait.stderr
+++ b/tests/ui/traits/const-traits/const-impl-trait.stderr
@@ -33,13 +33,14 @@ note: `PartialEq` can't be used with `~const` because it isn't annotated with `#
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
 
 error: `~const` can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:17:11
+  --> $DIR/const-impl-trait.rs:16:13
    |
-LL | ) -> impl ~const PartialEq + ~const Destruct {
-   |           ^^^^^^ can't be applied to `PartialEq`
+LL |     x: impl ~const PartialEq + ~const Destruct,
+   |             ^^^^^^ can't be applied to `PartialEq`
    |
 note: `PartialEq` can't be used with `~const` because it isn't annotated with `#[const_trait]`
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `~const` can only be applied to `#[const_trait]` traits
   --> $DIR/const-impl-trait.rs:17:11
@@ -49,7 +50,6 @@ LL | ) -> impl ~const PartialEq + ~const Destruct {
    |
 note: `PartialEq` can't be used with `~const` because it isn't annotated with `#[const_trait]`
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `~const` can only be applied to `#[const_trait]` traits
   --> $DIR/const-impl-trait.rs:17:11
@@ -62,32 +62,32 @@ note: `PartialEq` can't be used with `~const` because it isn't annotated with `#
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `~const` can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:16:13
+  --> $DIR/const-impl-trait.rs:23:22
    |
-LL |     x: impl ~const PartialEq + ~const Destruct,
-   |             ^^^^^^ can't be applied to `PartialEq`
+LL |     fn huh() -> impl ~const PartialEq + ~const Destruct + Copy;
+   |                      ^^^^^^ can't be applied to `PartialEq`
    |
 note: `PartialEq` can't be used with `~const` because it isn't annotated with `#[const_trait]`
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `~const` can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:23:22
+  --> $DIR/const-impl-trait.rs:27:22
    |
-LL |     fn huh() -> impl ~const PartialEq + ~const Destruct + Copy;
+LL |     fn huh() -> impl ~const PartialEq + ~const Destruct + Copy {
    |                      ^^^^^^ can't be applied to `PartialEq`
    |
 note: `PartialEq` can't be used with `~const` because it isn't annotated with `#[const_trait]`
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
 
 error: `~const` can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:27:22
+  --> $DIR/const-impl-trait.rs:17:11
    |
-LL |     fn huh() -> impl ~const PartialEq + ~const Destruct + Copy {
-   |                      ^^^^^^ can't be applied to `PartialEq`
+LL | ) -> impl ~const PartialEq + ~const Destruct {
+   |           ^^^^^^ can't be applied to `PartialEq`
    |
 note: `PartialEq` can't be used with `~const` because it isn't annotated with `#[const_trait]`
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `~const` can only be applied to `#[const_trait]` traits
   --> $DIR/const-impl-trait.rs:27:22