Auto merge of #131158 - matthiaskrgr:rollup-3x2vado, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #130863 (Relax a debug assertion for dyn principal *equality* in codegen)
 - #131016 (Apple: Do not specify an SDK version in `rlib` object files)
 - #131140 (Handle `rustc_hir_analysis` cases of `potential_query_instability` lint)
 - #131141 (mpmc doctest: make sure main thread waits for child threads)
 - #131150 (only query `params_in_repr` if def kind is adt)
 - #131151 (Replace zero-width whitespace with a visible `\` in the PR template)
 - #131152 (Improve const traits diagnostics for new desugaring)

r? `@ghost`
`@rustbot` modify labels: rollup

50 files changed, 538 insertions, 279 deletions

diff --git a/.github/pull_request_template.md b/.github/pull_request_template.md
index fd54a153a16..ecf8f993f90 100644
--- a/.github/pull_request_template.md
+++ b/.github/pull_request_template.md
@@ -7,6 +7,6 @@ tracking issue or there are none, feel free to ignore this.
 This PR will get automatically assigned to a reviewer. In case you would like
 a specific user to review your work, you can assign it to them by using
 
-    r​? <reviewer name>
+    r\? <reviewer name> (with the `\` removed)
 -->
 <!-- homu-ignore:end -->
diff --git a/Cargo.lock b/Cargo.lock
index 5b0b0368c93..452770edf7b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3451,6 +3451,7 @@ dependencies = [
  "rustc_span",
  "rustc_symbol_mangling",
  "rustc_target",
+ "rustc_trait_selection",
  "rustc_type_ir",
  "serde_json",
  "smallvec",
diff --git a/compiler/rustc_codegen_cranelift/src/unsize.rs b/compiler/rustc_codegen_cranelift/src/unsize.rs
index 339628053a9..5c297ebfadb 100644
--- a/compiler/rustc_codegen_cranelift/src/unsize.rs
+++ b/compiler/rustc_codegen_cranelift/src/unsize.rs
@@ -2,6 +2,7 @@
 //!
 //! [`PointerCoercion::Unsize`]: `rustc_middle::ty::adjustment::PointerCoercion::Unsize`
 
+use rustc_codegen_ssa::base::validate_trivial_unsize;
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
 
 use crate::base::codegen_panic_nounwind;
@@ -34,20 +35,8 @@ pub(crate) fn unsized_info<'tcx>(
             let old_info =
                 old_info.expect("unsized_info: missing old info for trait upcasting coercion");
             if data_a.principal_def_id() == data_b.principal_def_id() {
-                // Codegen takes advantage of the additional assumption, where if the
-                // principal trait def id of what's being casted doesn't change,
-                // then we don't need to adjust the vtable at all. This
-                // corresponds to the fact that `dyn Tr<A>: Unsize<dyn Tr<B>>`
-                // requires that `A = B`; we don't allow *upcasting* objects
-                // between the same trait with different args. If we, for
-                // some reason, were to relax the `Unsize` trait, it could become
-                // unsound, so let's assert here that the trait refs are *equal*.
-                //
-                // We can use `assert_eq` because the binders should have been anonymized,
-                // and because higher-ranked equality now requires the binders are equal.
-                debug_assert_eq!(
-                    data_a.principal(),
-                    data_b.principal(),
+                debug_assert!(
+                    validate_trivial_unsize(fx.tcx, data_a, data_b),
                     "NOP unsize vtable changed principal trait ref: {data_a} -> {data_b}"
                 );
                 return old_info;
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index f316a0a6cfc..58baf40b581 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -34,6 +34,7 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_symbol_mangling = { path = "../rustc_symbol_mangling" }
 rustc_target = { path = "../rustc_target" }
+rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_type_ir = { path = "../rustc_type_ir" }
 serde_json = "1.0.59"
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index a23cc512926..e7b1c63a822 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -2959,11 +2959,12 @@ pub(crate) fn are_upstream_rust_objects_already_included(sess: &Session) -> bool
     }
 }
 
-/// We need to communicate four things to the linker on Apple/Darwin targets:
+/// We need to communicate five things to the linker on Apple/Darwin targets:
 /// - The architecture.
 /// - The operating system (and that it's an Apple platform).
-/// - The deployment target.
 /// - The environment / ABI.
+/// - The deployment target.
+/// - The SDK version.
 fn add_apple_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
     if !sess.target.is_like_osx {
         return;
@@ -3039,7 +3040,38 @@ fn add_apple_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavo
         let (major, minor, patch) = current_apple_deployment_target(&sess.target);
         let min_version = format!("{major}.{minor}.{patch}");
 
-        // Lie about the SDK version, we don't know it here
+        // The SDK version is used at runtime when compiling with a newer SDK / version of Xcode:
+        // - By dyld to give extra warnings and errors, see e.g.:
+        //   <https://github.com/apple-oss-distributions/dyld/blob/dyld-1165.3/common/MachOFile.cpp#L3029>
+        //   <https://github.com/apple-oss-distributions/dyld/blob/dyld-1165.3/common/MachOFile.cpp#L3738-L3857>
+        // - By system frameworks to change certain behaviour. For example, the default value of
+        //   `-[NSView wantsBestResolutionOpenGLSurface]` is `YES` when the SDK version is >= 10.15.
+        //   <https://developer.apple.com/documentation/appkit/nsview/1414938-wantsbestresolutionopenglsurface?language=objc>
+        //
+        // We do not currently know the actual SDK version though, so we have a few options:
+        // 1. Use the minimum version supported by rustc.
+        // 2. Use the same as the deployment target.
+        // 3. Use an arbitary recent version.
+        // 4. Omit the version.
+        //
+        // The first option is too low / too conservative, and means that users will not get the
+        // same behaviour from a binary compiled with rustc as with one compiled by clang.
+        //
+        // The second option is similarly conservative, and also wrong since if the user specified a
+        // higher deployment target than the SDK they're compiling/linking with, the runtime might
+        // make invalid assumptions about the capabilities of the binary.
+        //
+        // The third option requires that `rustc` is periodically kept up to date with Apple's SDK
+        // version, and is also wrong for similar reasons as above.
+        //
+        // The fourth option is bad because while `ld`, `otool`, `vtool` and such understand it to
+        // mean "absent" or `n/a`, dyld doesn't actually understand it, and will end up interpreting
+        // it as 0.0, which is again too low/conservative.
+        //
+        // Currently, we lie about the SDK version, and choose the second option.
+        //
+        // FIXME(madsmtm): Parse the SDK version from the SDK root instead.
+        // <https://github.com/rust-lang/rust/issues/129432>
         let sdk_version = &*min_version;
 
         // From the man page for ld64 (`man ld`):
@@ -3053,11 +3085,13 @@ fn add_apple_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavo
         cmd.link_args(&["-platform_version", platform_name, &*min_version, sdk_version]);
     } else {
         // cc == Cc::Yes
+        //
         // We'd _like_ to use `-target` everywhere, since that can uniquely
-        // communicate all the required details, but that doesn't work on GCC,
-        // and since we don't know whether the `cc` compiler is Clang, GCC, or
-        // something else, we fall back to other options that also work on GCC
-        // when compiling for macOS.
+        // communicate all the required details except for the SDK version
+        // (which is read by Clang itself from the SDKROOT), but that doesn't
+        // work on GCC, and since we don't know whether the `cc` compiler is
+        // Clang, GCC, or something else, we fall back to other options that
+        // also work on GCC when compiling for macOS.
         //
         // Targets other than macOS are ill-supported by GCC (it doesn't even
         // support e.g. `-miphoneos-version-min`), so in those cases we can
diff --git a/compiler/rustc_codegen_ssa/src/back/metadata.rs b/compiler/rustc_codegen_ssa/src/back/metadata.rs
index 06433484ea3..8857fda1e97 100644
--- a/compiler/rustc_codegen_ssa/src/back/metadata.rs
+++ b/compiler/rustc_codegen_ssa/src/back/metadata.rs
@@ -402,13 +402,17 @@ fn macho_object_build_version_for_target(target: &Target) -> object::write::Mach
     let platform =
         rustc_target::spec::current_apple_platform(target).expect("unknown Apple target OS");
     let min_os = rustc_target::spec::current_apple_deployment_target(target);
-    let (sdk_major, sdk_minor) =
-        rustc_target::spec::current_apple_sdk_version(platform).expect("unknown Apple target OS");
 
     let mut build_version = object::write::MachOBuildVersion::default();
     build_version.platform = platform;
     build_version.minos = pack_version(min_os);
-    build_version.sdk = pack_version((sdk_major, sdk_minor, 0));
+    // The version here does not _really_ matter, since it is only used at runtime, and we specify
+    // it when linking the final binary, so we will omit the version. This is also what LLVM does,
+    // and the tooling also allows this (and shows the SDK version as `n/a`). Finally, it is the
+    // semantically correct choice, as the SDK has not influenced the binary generated by rustc at
+    // this point in time.
+    build_version.sdk = 0;
+
     build_version
 }
 
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 5c67600e4ee..d91c0f0790d 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -27,6 +27,9 @@ use rustc_session::config::{self, CrateType, EntryFnType, OptLevel, OutputType};
 use rustc_span::symbol::sym;
 use rustc_span::{DUMMY_SP, Symbol};
 use rustc_target::abi::FIRST_VARIANT;
+use rustc_trait_selection::infer::at::ToTrace;
+use rustc_trait_selection::infer::{BoundRegionConversionTime, TyCtxtInferExt};
+use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt};
 use tracing::{debug, info};
 
 use crate::assert_module_sources::CguReuse;
@@ -101,6 +104,54 @@ pub fn compare_simd_types<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     bx.sext(cmp, ret_ty)
 }
 
+/// Codegen takes advantage of the additional assumption, where if the
+/// principal trait def id of what's being casted doesn't change,
+/// then we don't need to adjust the vtable at all. This
+/// corresponds to the fact that `dyn Tr<A>: Unsize<dyn Tr<B>>`
+/// requires that `A = B`; we don't allow *upcasting* objects
+/// between the same trait with different args. If we, for
+/// some reason, were to relax the `Unsize` trait, it could become
+/// unsound, so let's validate here that the trait refs are subtypes.
+pub fn validate_trivial_unsize<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    source_data: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
+    target_data: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
+) -> bool {
+    match (source_data.principal(), target_data.principal()) {
+        (Some(hr_source_principal), Some(hr_target_principal)) => {
+            let infcx = tcx.infer_ctxt().build();
+            let universe = infcx.universe();
+            let ocx = ObligationCtxt::new(&infcx);
+            infcx.enter_forall(hr_target_principal, |target_principal| {
+                let source_principal = infcx.instantiate_binder_with_fresh_vars(
+                    DUMMY_SP,
+                    BoundRegionConversionTime::HigherRankedType,
+                    hr_source_principal,
+                );
+                let Ok(()) = ocx.eq_trace(
+                    &ObligationCause::dummy(),
+                    ty::ParamEnv::reveal_all(),
+                    ToTrace::to_trace(
+                        &ObligationCause::dummy(),
+                        hr_target_principal,
+                        hr_source_principal,
+                    ),
+                    target_principal,
+                    source_principal,
+                ) else {
+                    return false;
+                };
+                if !ocx.select_all_or_error().is_empty() {
+                    return false;
+                }
+                infcx.leak_check(universe, None).is_ok()
+            })
+        }
+        (None, None) => true,
+        _ => false,
+    }
+}
+
 /// Retrieves the information we are losing (making dynamic) in an unsizing
 /// adjustment.
 ///
@@ -133,12 +184,8 @@ fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 // between the same trait with different args. If we, for
                 // some reason, were to relax the `Unsize` trait, it could become
                 // unsound, so let's assert here that the trait refs are *equal*.
-                //
-                // We can use `assert_eq` because the binders should have been anonymized,
-                // and because higher-ranked equality now requires the binders are equal.
-                debug_assert_eq!(
-                    data_a.principal(),
-                    data_b.principal(),
+                debug_assert!(
+                    validate_trivial_unsize(cx.tcx(), data_a, data_b),
                     "NOP unsize vtable changed principal trait ref: {data_a} -> {data_b}"
                 );
 
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index 70b0b3f5788..02d23b95d46 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -2,7 +2,7 @@ use std::cell::LazyCell;
 use std::ops::{ControlFlow, Deref};
 
 use hir::intravisit::{self, Visitor};
-use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
+use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, ErrorGuaranteed, pluralize, struct_span_code_err};
 use rustc_hir::ItemKind;
@@ -404,7 +404,7 @@ fn check_trait_item<'tcx>(
 /// ```
 fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
     // Associates every GAT's def_id to a list of possibly missing bounds detected by this lint.
-    let mut required_bounds_by_item = FxHashMap::default();
+    let mut required_bounds_by_item = FxIndexMap::default();
     let associated_items = tcx.associated_items(trait_def_id);
 
     // Loop over all GATs together, because if this lint suggests adding a where-clause bound
@@ -430,7 +430,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
             // Gather the bounds with which all other items inside of this trait constrain the GAT.
             // This is calculated by taking the intersection of the bounds that each item
             // constrains the GAT with individually.
-            let mut new_required_bounds: Option<FxHashSet<ty::Clause<'_>>> = None;
+            let mut new_required_bounds: Option<FxIndexSet<ty::Clause<'_>>> = None;
             for item in associated_items.in_definition_order() {
                 let item_def_id = item.def_id.expect_local();
                 // Skip our own GAT, since it does not constrain itself at all.
@@ -589,7 +589,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
 fn augment_param_env<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-    new_predicates: Option<&FxHashSet<ty::Clause<'tcx>>>,
+    new_predicates: Option<&FxIndexSet<ty::Clause<'tcx>>>,
 ) -> ty::ParamEnv<'tcx> {
     let Some(new_predicates) = new_predicates else {
         return param_env;
@@ -625,9 +625,9 @@ fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
     wf_tys: &FxIndexSet<Ty<'tcx>>,
     gat_def_id: LocalDefId,
     gat_generics: &'tcx ty::Generics,
-) -> Option<FxHashSet<ty::Clause<'tcx>>> {
+) -> Option<FxIndexSet<ty::Clause<'tcx>>> {
     // The bounds we that we would require from `to_check`
-    let mut bounds = FxHashSet::default();
+    let mut bounds = FxIndexSet::default();
 
     let (regions, types) = GATArgsCollector::visit(gat_def_id.to_def_id(), to_check);
 
@@ -789,18 +789,18 @@ fn test_region_obligations<'tcx>(
 struct GATArgsCollector<'tcx> {
     gat: DefId,
     // Which region appears and which parameter index its instantiated with
-    regions: FxHashSet<(ty::Region<'tcx>, usize)>,
+    regions: FxIndexSet<(ty::Region<'tcx>, usize)>,
     // Which params appears and which parameter index its instantiated with
-    types: FxHashSet<(Ty<'tcx>, usize)>,
+    types: FxIndexSet<(Ty<'tcx>, usize)>,
 }
 
 impl<'tcx> GATArgsCollector<'tcx> {
     fn visit<T: TypeFoldable<TyCtxt<'tcx>>>(
         gat: DefId,
         t: T,
-    ) -> (FxHashSet<(ty::Region<'tcx>, usize)>, FxHashSet<(Ty<'tcx>, usize)>) {
+    ) -> (FxIndexSet<(ty::Region<'tcx>, usize)>, FxIndexSet<(Ty<'tcx>, usize)>) {
         let mut visitor =
-            GATArgsCollector { gat, regions: FxHashSet::default(), types: FxHashSet::default() };
+            GATArgsCollector { gat, regions: FxIndexSet::default(), types: FxIndexSet::default() };
         t.visit_with(&mut visitor);
         (visitor.regions, visitor.types)
     }
diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
index b8066b4b47d..d1c888a185e 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
@@ -1,4 +1,4 @@
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap, IndexEntry};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet, IndexEntry};
 use rustc_errors::codes::*;
 use rustc_errors::struct_span_code_err;
 use rustc_hir as hir;
@@ -215,7 +215,7 @@ impl<'tcx> InherentOverlapChecker<'tcx> {
 
             struct ConnectedRegion {
                 idents: SmallVec<[Symbol; 8]>,
-                impl_blocks: FxHashSet<usize>,
+                impl_blocks: FxIndexSet<usize>,
             }
             let mut connected_regions: IndexVec<RegionId, _> = Default::default();
             // Reverse map from the Symbol to the connected region id.
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 2186952720f..6dd3a06ef37 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -23,7 +23,7 @@ mod lint;
 use std::slice;
 
 use rustc_ast::TraitObjectSyntax;
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
+use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, FatalError, struct_span_code_err,
@@ -2394,8 +2394,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     #[instrument(level = "trace", skip(self, generate_err))]
     fn validate_late_bound_regions<'cx>(
         &'cx self,
-        constrained_regions: FxHashSet<ty::BoundRegionKind>,
-        referenced_regions: FxHashSet<ty::BoundRegionKind>,
+        constrained_regions: FxIndexSet<ty::BoundRegionKind>,
+        referenced_regions: FxIndexSet<ty::BoundRegionKind>,
         generate_err: impl Fn(&str) -> Diag<'cx>,
     ) {
         for br in referenced_regions.difference(&constrained_regions) {
diff --git a/compiler/rustc_hir_analysis/src/lib.rs b/compiler/rustc_hir_analysis/src/lib.rs
index 92d85d48a42..7d40a7746b9 100644
--- a/compiler/rustc_hir_analysis/src/lib.rs
+++ b/compiler/rustc_hir_analysis/src/lib.rs
@@ -58,7 +58,6 @@ This API is completely unstable and subject to change.
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![allow(rustc::diagnostic_outside_of_impl)]
-#![allow(rustc::potential_query_instability)]
 #![allow(rustc::untranslatable_diagnostic)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
diff --git a/compiler/rustc_middle/src/macros.rs b/compiler/rustc_middle/src/macros.rs
index d385be007d3..39816c17b98 100644
--- a/compiler/rustc_middle/src/macros.rs
+++ b/compiler/rustc_middle/src/macros.rs
@@ -67,7 +67,7 @@ macro_rules! TrivialLiftImpls {
     };
 }
 
-/// Used for types that are `Copy` and which **do not care arena
+/// Used for types that are `Copy` and which **do not care about arena
 /// allocated data** (i.e., don't need to be folded).
 #[macro_export]
 macro_rules! TrivialTypeTraversalImpls {
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 2b1212a5eb5..c4a28845085 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -186,7 +186,7 @@ pub struct ResolverGlobalCtxt {
     pub proc_macros: Vec<LocalDefId>,
     /// Mapping from ident span to path span for paths that don't exist as written, but that
     /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
-    pub confused_type_with_std_module: FxHashMap<Span, Span>,
+    pub confused_type_with_std_module: FxIndexMap<Span, Span>,
     pub doc_link_resolutions: FxHashMap<LocalDefId, DocLinkResMap>,
     pub doc_link_traits_in_scope: FxHashMap<LocalDefId, Vec<DefId>>,
     pub all_macro_rules: FxHashMap<Symbol, Res<ast::NodeId>>,
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 8fd4c30457f..7ada5fd93ba 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1951,19 +1951,18 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
     fn pretty_print_bound_constness(
         &mut self,
-        trait_ref: ty::TraitRef<'tcx>,
+        constness: ty::BoundConstness,
     ) -> Result<(), PrintError> {
         define_scoped_cx!(self);
 
-        let Some(idx) = self.tcx().generics_of(trait_ref.def_id).host_effect_index else {
-            return Ok(());
-        };
-        let arg = trait_ref.args.const_at(idx);
-
-        if arg == self.tcx().consts.false_ {
-            p!("const ");
-        } else if arg != self.tcx().consts.true_ && !arg.has_infer() {
-            p!("~const ");
+        match constness {
+            ty::BoundConstness::NotConst => {}
+            ty::BoundConstness::Const => {
+                p!("const ");
+            }
+            ty::BoundConstness::ConstIfConst => {
+                p!("~const ");
+            }
         }
         Ok(())
     }
@@ -2948,6 +2947,15 @@ impl<'tcx> ty::TraitPredicate<'tcx> {
     }
 }
 
+#[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
+pub struct TraitPredPrintWithBoundConstness<'tcx>(ty::TraitPredicate<'tcx>, ty::BoundConstness);
+
+impl<'tcx> fmt::Debug for TraitPredPrintWithBoundConstness<'tcx> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
 #[extension(pub trait PrintPolyTraitPredicateExt<'tcx>)]
 impl<'tcx> ty::PolyTraitPredicate<'tcx> {
     fn print_modifiers_and_trait_path(
@@ -2955,6 +2963,13 @@ impl<'tcx> ty::PolyTraitPredicate<'tcx> {
     ) -> ty::Binder<'tcx, TraitPredPrintModifiersAndPath<'tcx>> {
         self.map_bound(TraitPredPrintModifiersAndPath)
     }
+
+    fn print_with_bound_constness(
+        self,
+        constness: ty::BoundConstness,
+    ) -> ty::Binder<'tcx, TraitPredPrintWithBoundConstness<'tcx>> {
+        self.map_bound(|trait_pred| TraitPredPrintWithBoundConstness(trait_pred, constness))
+    }
 }
 
 #[derive(Debug, Copy, Clone, Lift)]
@@ -3052,7 +3067,6 @@ define_print! {
 
     ty::TraitPredicate<'tcx> {
         p!(print(self.trait_ref.self_ty()), ": ");
-        p!(pretty_print_bound_constness(self.trait_ref));
         if let ty::PredicatePolarity::Negative = self.polarity {
             p!("!");
         }
@@ -3184,13 +3198,21 @@ define_print_and_forward_display! {
     }
 
     TraitPredPrintModifiersAndPath<'tcx> {
-        p!(pretty_print_bound_constness(self.0.trait_ref));
         if let ty::PredicatePolarity::Negative = self.0.polarity {
             p!("!")
         }
         p!(print(self.0.trait_ref.print_trait_sugared()));
     }
 
+    TraitPredPrintWithBoundConstness<'tcx> {
+        p!(print(self.0.trait_ref.self_ty()), ": ");
+        p!(pretty_print_bound_constness(self.1));
+        if let ty::PredicatePolarity::Negative = self.0.polarity {
+            p!("!");
+        }
+        p!(print(self.0.trait_ref.print_trait_sugared()))
+    }
+
     PrintClosureAsImpl<'tcx> {
         p!(pretty_closure_as_impl(self.closure))
     }
diff --git a/compiler/rustc_middle/src/ty/visit.rs b/compiler/rustc_middle/src/ty/visit.rs
index 78d83004c14..4efaccefcf7 100644
--- a/compiler/rustc_middle/src/ty/visit.rs
+++ b/compiler/rustc_middle/src/ty/visit.rs
@@ -1,6 +1,6 @@
 use std::ops::ControlFlow;
 
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_type_ir::fold::TypeFoldable;
 pub use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
 
@@ -110,7 +110,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn collect_constrained_late_bound_regions<T>(
         self,
         value: Binder<'tcx, T>,
-    ) -> FxHashSet<ty::BoundRegionKind>
+    ) -> FxIndexSet<ty::BoundRegionKind>
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
@@ -121,7 +121,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn collect_referenced_late_bound_regions<T>(
         self,
         value: Binder<'tcx, T>,
-    ) -> FxHashSet<ty::BoundRegionKind>
+    ) -> FxIndexSet<ty::BoundRegionKind>
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
@@ -132,7 +132,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         value: Binder<'tcx, T>,
         just_constrained: bool,
-    ) -> FxHashSet<ty::BoundRegionKind>
+    ) -> FxIndexSet<ty::BoundRegionKind>
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
@@ -148,7 +148,7 @@ impl<'tcx> TyCtxt<'tcx> {
 /// into a hash set.
 struct LateBoundRegionsCollector {
     current_index: ty::DebruijnIndex,
-    regions: FxHashSet<ty::BoundRegionKind>,
+    regions: FxIndexSet<ty::BoundRegionKind>,
 
     /// `true` if we only want regions that are known to be
     /// "constrained" when you equate this type with another type. In
diff --git a/compiler/rustc_middle/src/values.rs b/compiler/rustc_middle/src/values.rs
index c98d88e22d4..48ca38344cf 100644
--- a/compiler/rustc_middle/src/values.rs
+++ b/compiler/rustc_middle/src/values.rs
@@ -358,7 +358,7 @@ fn find_item_ty_spans(
     match ty.kind {
         hir::TyKind::Path(hir::QPath::Resolved(_, path)) => {
             if let Res::Def(kind, def_id) = path.res
-                && !matches!(kind, DefKind::TyAlias)
+                && matches!(kind, DefKind::Enum | DefKind::Struct | DefKind::Union)
             {
                 let check_params = def_id.as_local().map_or(true, |def_id| {
                     if def_id == needle {
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index b84408cd0cb..0c1a0038f9c 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -1188,7 +1188,7 @@ pub struct Resolver<'ra, 'tcx> {
     /// A list of proc macro LocalDefIds, written out in the order in which
     /// they are declared in the static array generated by proc_macro_harness.
     proc_macros: Vec<NodeId>,
-    confused_type_with_std_module: FxHashMap<Span, Span>,
+    confused_type_with_std_module: FxIndexMap<Span, Span>,
     /// Whether lifetime elision was successful.
     lifetime_elision_allowed: FxHashSet<NodeId>,
 
diff --git a/compiler/rustc_target/src/spec/base/apple/mod.rs b/compiler/rustc_target/src/spec/base/apple/mod.rs
index 81b5a936d35..73763cf034c 100644
--- a/compiler/rustc_target/src/spec/base/apple/mod.rs
+++ b/compiler/rustc_target/src/spec/base/apple/mod.rs
@@ -158,23 +158,6 @@ pub(crate) fn base(
     (opts, llvm_target(os, arch, abi), arch.target_arch())
 }
 
-pub fn sdk_version(platform: u32) -> Option<(u16, u8)> {
-    // NOTE: These values are from an arbitrary point in time but shouldn't make it into the final
-    // binary since the final link command will have the current SDK version passed to it.
-    match platform {
-        object::macho::PLATFORM_MACOS => Some((13, 1)),
-        object::macho::PLATFORM_IOS
-        | object::macho::PLATFORM_IOSSIMULATOR
-        | object::macho::PLATFORM_TVOS
-        | object::macho::PLATFORM_TVOSSIMULATOR
-        | object::macho::PLATFORM_MACCATALYST => Some((16, 2)),
-        object::macho::PLATFORM_WATCHOS | object::macho::PLATFORM_WATCHOSSIMULATOR => Some((9, 1)),
-        // FIXME: Upgrade to `object-rs` 0.33+ implementation with visionOS platform definition
-        11 | 12 => Some((1, 0)),
-        _ => None,
-    }
-}
-
 pub fn platform(target: &Target) -> Option<u32> {
     Some(match (&*target.os, &*target.abi) {
         ("macos", _) => object::macho::PLATFORM_MACOS,
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index d1fcfe4adef..c557091242e 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -61,7 +61,7 @@ pub mod crt_objects;
 mod base;
 pub use base::apple::{
     deployment_target_for_target as current_apple_deployment_target,
-    platform as current_apple_platform, sdk_version as current_apple_sdk_version,
+    platform as current_apple_platform,
 };
 pub use base::avr_gnu::ef_avr_arch;
 
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
index 34a0f182ab4..5af117a3f48 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@@ -19,8 +19,8 @@ use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::print::{
-    FmtPrinter, Print, PrintTraitPredicateExt as _, PrintTraitRefExt as _,
-    with_forced_trimmed_paths,
+    FmtPrinter, Print, PrintPolyTraitPredicateExt, PrintTraitPredicateExt as _,
+    PrintTraitRefExt as _, with_forced_trimmed_paths,
 };
 use rustc_middle::ty::{
     self, ToPolyTraitRef, TraitRef, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, Upcast,
@@ -154,6 +154,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         } else {
                             (leaf_trait_predicate, &obligation)
                         };
+
+                        let (main_trait_predicate, leaf_trait_predicate, predicate_constness) = self.get_effects_trait_pred_override(main_trait_predicate, leaf_trait_predicate, span);
+
                         let main_trait_ref = main_trait_predicate.to_poly_trait_ref();
                         let leaf_trait_ref = leaf_trait_predicate.to_poly_trait_ref();
 
@@ -164,9 +167,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             return guar;
                         }
 
-                        // FIXME(effects)
-                        let predicate_is_const = false;
-
                         if let Err(guar) = leaf_trait_predicate.error_reported()
                         {
                             return guar;
@@ -227,7 +227,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         let err_msg = self.get_standard_error_message(
                             main_trait_predicate,
                             message,
-                            predicate_is_const,
+                            predicate_constness,
                             append_const_msg,
                             post_message,
                         );
@@ -286,7 +286,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         }
 
                         if tcx.is_lang_item(leaf_trait_ref.def_id(), LangItem::Drop)
-                            && predicate_is_const
+                            && matches!(predicate_constness, ty::BoundConstness::ConstIfConst | ty::BoundConstness::Const)
                         {
                             err.note("`~const Drop` was renamed to `~const Destruct`");
                             err.note("See <https://github.com/rust-lang/rust/pull/94901> for more details");
@@ -2187,29 +2187,34 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         &self,
         trait_predicate: ty::PolyTraitPredicate<'tcx>,
         message: Option<String>,
-        predicate_is_const: bool,
+        predicate_constness: ty::BoundConstness,
         append_const_msg: Option<AppendConstMessage>,
         post_message: String,
     ) -> String {
         message
             .and_then(|cannot_do_this| {
-                match (predicate_is_const, append_const_msg) {
+                match (predicate_constness, append_const_msg) {
                     // do nothing if predicate is not const
-                    (false, _) => Some(cannot_do_this),
+                    (ty::BoundConstness::NotConst, _) => Some(cannot_do_this),
                     // suggested using default post message
-                    (true, Some(AppendConstMessage::Default)) => {
-                        Some(format!("{cannot_do_this} in const contexts"))
-                    }
+                    (
+                        ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst,
+                        Some(AppendConstMessage::Default),
+                    ) => Some(format!("{cannot_do_this} in const contexts")),
                     // overridden post message
-                    (true, Some(AppendConstMessage::Custom(custom_msg, _))) => {
-                        Some(format!("{cannot_do_this}{custom_msg}"))
-                    }
+                    (
+                        ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst,
+                        Some(AppendConstMessage::Custom(custom_msg, _)),
+                    ) => Some(format!("{cannot_do_this}{custom_msg}")),
                     // fallback to generic message
-                    (true, None) => None,
+                    (ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst, None) => None,
                 }
             })
             .unwrap_or_else(|| {
-                format!("the trait bound `{trait_predicate}` is not satisfied{post_message}")
+                format!(
+                    "the trait bound `{}` is not satisfied{post_message}",
+                    trait_predicate.print_with_bound_constness(predicate_constness)
+                )
             })
     }
 
@@ -2333,6 +2338,51 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         }
     }
 
+    /// For effects predicates such as `<u32 as Add>::Effects: Compat<host>`, pretend that the
+    /// predicate that failed was `u32: Add`. Return the constness of such predicate to later
+    /// print as `u32: ~const Add`.
+    fn get_effects_trait_pred_override(
+        &self,
+        p: ty::PolyTraitPredicate<'tcx>,
+        leaf: ty::PolyTraitPredicate<'tcx>,
+        span: Span,
+    ) -> (ty::PolyTraitPredicate<'tcx>, ty::PolyTraitPredicate<'tcx>, ty::BoundConstness) {
+        let trait_ref = p.to_poly_trait_ref();
+        if !self.tcx.is_lang_item(trait_ref.def_id(), LangItem::EffectsCompat) {
+            return (p, leaf, ty::BoundConstness::NotConst);
+        }
+
+        let Some(ty::Alias(ty::AliasTyKind::Projection, projection)) =
+            trait_ref.self_ty().no_bound_vars().map(Ty::kind)
+        else {
+            return (p, leaf, ty::BoundConstness::NotConst);
+        };
+
+        let constness = trait_ref.skip_binder().args.const_at(1);
+
+        let constness = if constness == self.tcx.consts.true_ || constness.is_ct_infer() {
+            ty::BoundConstness::NotConst
+        } else if constness == self.tcx.consts.false_ {
+            ty::BoundConstness::Const
+        } else if matches!(constness.kind(), ty::ConstKind::Param(_)) {
+            ty::BoundConstness::ConstIfConst
+        } else {
+            self.dcx().span_bug(span, format!("Unknown constness argument: {constness:?}"));
+        };
+
+        let new_pred = p.map_bound(|mut trait_pred| {
+            trait_pred.trait_ref = projection.trait_ref(self.tcx);
+            trait_pred
+        });
+
+        let new_leaf = leaf.map_bound(|mut trait_pred| {
+            trait_pred.trait_ref = projection.trait_ref(self.tcx);
+            trait_pred
+        });
+
+        (new_pred, new_leaf, constness)
+    }
+
     fn add_tuple_trait_message(
         &self,
         obligation_cause_code: &ObligationCauseCode<'tcx>,
diff --git a/compiler/rustc_type_ir/src/predicate.rs b/compiler/rustc_type_ir/src/predicate.rs
index 76065c10d19..8146181df6c 100644
--- a/compiler/rustc_type_ir/src/predicate.rs
+++ b/compiler/rustc_type_ir/src/predicate.rs
@@ -755,3 +755,10 @@ impl fmt::Display for BoundConstness {
         }
     }
 }
+
+impl<I> Lift<I> for BoundConstness {
+    type Lifted = BoundConstness;
+    fn lift_to_interner(self, _: I) -> Option<Self::Lifted> {
+        Some(self)
+    }
+}
diff --git a/library/std/src/sync/mpmc/mod.rs b/library/std/src/sync/mpmc/mod.rs
index 77a67f4fd38..44e146a89ba 100644
--- a/library/std/src/sync/mpmc/mod.rs
+++ b/library/std/src/sync/mpmc/mod.rs
@@ -66,29 +66,31 @@
 //! use std::thread;
 //! use std::sync::mpmc::channel;
 //!
-//! // Create a shared channel that can be sent along from many threads
-//! // where tx is the sending half (tx for transmission), and rx is the receiving
-//! // half (rx for receiving).
-//! let (tx, rx) = channel();
-//! for i in 0..10 {
-//!     let tx = tx.clone();
-//!     thread::spawn(move || {
-//!         tx.send(i).unwrap();
-//!     });
-//! }
+//! thread::scope(|s| {
+//!     // Create a shared channel that can be sent along from many threads
+//!     // where tx is the sending half (tx for transmission), and rx is the receiving
+//!     // half (rx for receiving).
+//!     let (tx, rx) = channel();
+//!     for i in 0..10 {
+//!         let tx = tx.clone();
+//!         s.spawn(move || {
+//!             tx.send(i).unwrap();
+//!         });
+//!     }
 //!
-//! for _ in 0..5 {
-//!     let rx1 = rx.clone();
-//!     let rx2 = rx.clone();
-//!     thread::spawn(move || {
-//!         let j = rx1.recv().unwrap();
-//!         assert!(0 <= j && j < 10);
-//!     });
-//!     thread::spawn(move || {
-//!         let j = rx2.recv().unwrap();
-//!         assert!(0 <= j && j < 10);
-//!     });
-//! }
+//!     for _ in 0..5 {
+//!         let rx1 = rx.clone();
+//!         let rx2 = rx.clone();
+//!         s.spawn(move || {
+//!             let j = rx1.recv().unwrap();
+//!             assert!(0 <= j && j < 10);
+//!         });
+//!         s.spawn(move || {
+//!             let j = rx2.recv().unwrap();
+//!             assert!(0 <= j && j < 10);
+//!         });
+//!     }
+//! })
 //! ```
 //!
 //! Propagating panics:
diff --git a/tests/crashes/128327.rs b/tests/crashes/128327.rs
deleted file mode 100644
index a63f758c317..00000000000
--- a/tests/crashes/128327.rs
+++ /dev/null
@@ -1,5 +0,0 @@
-//@ known-bug: rust-lang/rust#128327
-
-use std::ops::Deref;
-struct Apple((Apple, <&'static [f64] as Deref>::Target(Banana ? Citron)));
-fn main(){}
diff --git a/tests/run-make/apple-sdk-version/foo.rs b/tests/run-make/apple-sdk-version/foo.rs
new file mode 100644
index 00000000000..f328e4d9d04
--- /dev/null
+++ b/tests/run-make/apple-sdk-version/foo.rs
@@ -0,0 +1 @@
+fn main() {}
diff --git a/tests/run-make/apple-sdk-version/rmake.rs b/tests/run-make/apple-sdk-version/rmake.rs
new file mode 100644
index 00000000000..6463ec00403
--- /dev/null
+++ b/tests/run-make/apple-sdk-version/rmake.rs
@@ -0,0 +1,95 @@
+//! Test codegen when setting SDK version on Apple platforms.
+//!
+//! This is important since its a compatibility hazard. The linker will
+//! generate load commands differently based on what minimum OS it can assume.
+//!
+//! See https://github.com/rust-lang/rust/issues/129432.
+
+//@ only-apple
+
+use run_make_support::{apple_os, cmd, run_in_tmpdir, rustc, target};
+
+/// Run vtool to check the `sdk` field in LC_BUILD_VERSION.
+///
+/// On lower deployment targets, LC_VERSION_MIN_MACOSX, LC_VERSION_MIN_IPHONEOS and similar
+/// are used instead of LC_BUILD_VERSION, but both name the relevant variable `sdk`.
+#[track_caller]
+fn has_sdk_version(file: &str, version: &str) {
+    cmd("vtool")
+        .arg("-show-build")
+        .arg(file)
+        .run()
+        .assert_stdout_contains(format!("sdk {version}"));
+}
+
+fn main() {
+    // Fetch rustc's inferred deployment target.
+    let current_deployment_target =
+        rustc().target(target()).print("deployment-target").run().stdout_utf8();
+    let current_deployment_target =
+        current_deployment_target.strip_prefix("deployment_target=").unwrap().trim();
+
+    // Fetch current SDK version via. xcrun.
+    //
+    // Assumes a standard Xcode distribution, where e.g. the macOS SDK's Mac Catalyst
+    // and the iPhone Simulator version is the same as for the iPhone SDK.
+    let sdk_name = match apple_os() {
+        "macos" => "macosx",
+        "ios" => "iphoneos",
+        "watchos" => "watchos",
+        "tvos" => "appletvos",
+        "visionos" => "xros",
+        _ => unreachable!(),
+    };
+    let current_sdk_version =
+        cmd("xcrun").arg("--show-sdk-version").arg("--sdk").arg(sdk_name).run().stdout_utf8();
+    let current_sdk_version = current_sdk_version.trim();
+
+    // Check the SDK version in the object file produced by the codegen backend.
+    rustc().target(target()).crate_type("lib").emit("obj").input("foo.rs").output("foo.o").run();
+    // Set to 0, which means not set or "n/a".
+    has_sdk_version("foo.o", "n/a");
+
+    // Check the SDK version in the .rmeta file, as set in `create_object_file`.
+    //
+    // This is just to ensure that we don't set some odd version in `create_object_file`,
+    // if the rmeta file is packed in a different way in the future, this can safely be removed.
+    rustc().target(target()).crate_type("rlib").input("foo.rs").output("libfoo.rlib").run();
+    // Extra .rmeta file (which is encoded as an object file).
+    cmd("ar").arg("-x").arg("libfoo.rlib").arg("lib.rmeta").run();
+    has_sdk_version("lib.rmeta", "n/a");
+
+    // Test that version makes it to the linker.
+    for (crate_type, file_ext) in [("bin", ""), ("dylib", ".dylib")] {
+        // Non-simulator watchOS targets don't support dynamic linking,
+        // for simplicity we disable the test on all watchOS targets.
+        if crate_type == "dylib" && apple_os() == "watchos" {
+            continue;
+        }
+
+        // Test with clang
+        let file_name = format!("foo_cc{file_ext}");
+        rustc()
+            .target(target())
+            .crate_type("bin")
+            .arg("-Clinker-flavor=gcc")
+            .input("foo.rs")
+            .output(&file_name)
+            .run();
+        has_sdk_version(&file_name, current_sdk_version);
+
+        // Test with ld64
+        let file_name = format!("foo_ld{file_ext}");
+        rustc()
+            .target(target())
+            .crate_type("bin")
+            .arg("-Clinker-flavor=ld")
+            .input("foo.rs")
+            .output(&file_name)
+            .run();
+        // FIXME(madsmtm): This uses the current deployment target
+        // instead of the current SDK version like Clang does.
+        // https://github.com/rust-lang/rust/issues/129432
+        has_sdk_version(&file_name, current_deployment_target);
+    }
+}
diff --git a/tests/ui/codegen/sub-principals-in-codegen.rs b/tests/ui/codegen/sub-principals-in-codegen.rs
new file mode 100644
index 00000000000..178c10da596
--- /dev/null
+++ b/tests/ui/codegen/sub-principals-in-codegen.rs
@@ -0,0 +1,8 @@
+//@ build-pass
+
+// Regression test for an overly aggressive assertion in #130855.
+
+fn main() {
+    let subtype: &(dyn for<'a> Fn(&'a i32) -> &'a i32) = &|x| x;
+    let supertype: &(dyn Fn(&'static i32) -> &'static i32) = subtype;
+}
diff --git a/tests/ui/generic-associated-types/self-outlives-lint.stderr b/tests/ui/generic-associated-types/self-outlives-lint.stderr
index 9e9b2e18abe..58172bf06b5 100644
--- a/tests/ui/generic-associated-types/self-outlives-lint.stderr
+++ b/tests/ui/generic-associated-types/self-outlives-lint.stderr
@@ -108,17 +108,6 @@ LL |     type Bar<'b>;
    = note: this bound is currently required to ensure that impls have maximum flexibility
    = note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information
 
-error: missing required bound on `Iterator`
-  --> $DIR/self-outlives-lint.rs:142:5
-   |
-LL |     type Iterator<'a>: Iterator<Item = Self::Item<'a>>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-
-   |                                                       |
-   |                                                       help: add the required where clause: `where Self: 'a`
-   |
-   = note: this bound is currently required to ensure that impls have maximum flexibility
-   = note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information
-
 error: missing required bound on `Item`
   --> $DIR/self-outlives-lint.rs:140:5
    |
@@ -130,6 +119,17 @@ LL |     type Item<'a>;
    = note: this bound is currently required to ensure that impls have maximum flexibility
    = note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information
 
+error: missing required bound on `Iterator`
+  --> $DIR/self-outlives-lint.rs:142:5
+   |
+LL |     type Iterator<'a>: Iterator<Item = Self::Item<'a>>;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-
+   |                                                       |
+   |                                                       help: add the required where clause: `where Self: 'a`
+   |
+   = note: this bound is currently required to ensure that impls have maximum flexibility
+   = note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information
+
 error: missing required bound on `Item`
   --> $DIR/self-outlives-lint.rs:148:5
    |
diff --git a/tests/ui/infinite/auxiliary/alias.rs b/tests/ui/infinite/auxiliary/alias.rs
index 59add7eb18b..5ae124e8aba 100644
--- a/tests/ui/infinite/auxiliary/alias.rs
+++ b/tests/ui/infinite/auxiliary/alias.rs
@@ -1,2 +1,5 @@
 pub struct W<T>(T);
 pub type Wrapper<T> = W<T>;
+pub trait Trait {
+    type T;
+}
diff --git a/tests/ui/infinite/infinite-assoc.rs b/tests/ui/infinite/infinite-assoc.rs
new file mode 100644
index 00000000000..d128a7e0d2d
--- /dev/null
+++ b/tests/ui/infinite/infinite-assoc.rs
@@ -0,0 +1,16 @@
+//@ aux-build: alias.rs
+
+// issue#128327
+
+extern crate alias;
+
+use alias::Trait;
+struct S;
+impl Trait for S {
+    type T = ();
+}
+struct A((A, <S as Trait>::T<NOT_EXIST?>));
+//~^ ERROR: invalid `?` in type
+//~| ERROR: recursive type `A` has infinite size
+
+fn main() {}
diff --git a/tests/ui/infinite/infinite-assoc.stderr b/tests/ui/infinite/infinite-assoc.stderr
new file mode 100644
index 00000000000..e6b91f13241
--- /dev/null
+++ b/tests/ui/infinite/infinite-assoc.stderr
@@ -0,0 +1,25 @@
+error: invalid `?` in type
+  --> $DIR/infinite-assoc.rs:12:39
+   |
+LL | struct A((A, <S as Trait>::T<NOT_EXIST?>));
+   |                                       ^ `?` is only allowed on expressions, not types
+   |
+help: if you meant to express that the type might not contain a value, use the `Option` wrapper type
+   |
+LL | struct A((A, <S as Trait>::T<Option<NOT_EXIST>>));
+   |                              +++++++         ~
+
+error[E0072]: recursive type `A` has infinite size
+  --> $DIR/infinite-assoc.rs:12:1
+   |
+LL | struct A((A, <S as Trait>::T<NOT_EXIST?>));
+   | ^^^^^^^^  - recursive without indirection
+   |
+help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle
+   |
+LL | struct A((Box<A>, <S as Trait>::T<NOT_EXIST?>));
+   |           ++++ +
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0072`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage-0.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage-0.stderr
index fb491453b37..8288c660ce7 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage-0.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage-0.stderr
@@ -3,11 +3,11 @@ error: using `#![feature(effects)]` without enabling next trait solver globally
    = note: the next trait solver must be enabled globally for the effects feature to work correctly
    = help: use `-Znext-solver` to enable
 
-error[E0277]: the trait bound `Trait::{synthetic#0}: Compat` is not satisfied
+error[E0277]: the trait bound `<T as Trait>::Assoc: Trait` is not satisfied
   --> $DIR/assoc-type-const-bound-usage-0.rs:13:5
    |
 LL |     T::Assoc::func()
-   |     ^^^^^^^^ the trait `Compat` is not implemented for `Trait::{synthetic#0}`
+   |     ^^^^^^^^ the trait `Trait` is not implemented for `<T as Trait>::Assoc`
    |
 note: required by a bound in `Trait::func`
   --> $DIR/assoc-type-const-bound-usage-0.rs:6:1
@@ -17,12 +17,16 @@ LL | #[const_trait]
 ...
 LL |     fn func() -> i32;
    |        ---- required by a bound in this associated function
+help: consider further restricting the associated type
+   |
+LL | const fn unqualified<T: ~const Trait>() -> i32 where <T as Trait>::Assoc: Trait {
+   |                                                ++++++++++++++++++++++++++++++++
 
-error[E0277]: the trait bound `Trait::{synthetic#0}: Compat` is not satisfied
+error[E0277]: the trait bound `<T as Trait>::Assoc: Trait` is not satisfied
   --> $DIR/assoc-type-const-bound-usage-0.rs:17:5
    |
 LL |     <T as Trait>::Assoc::func()
-   |     ^^^^^^^^^^^^^^^^^^^ the trait `Compat` is not implemented for `Trait::{synthetic#0}`
+   |     ^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `<T as Trait>::Assoc`
    |
 note: required by a bound in `Trait::func`
   --> $DIR/assoc-type-const-bound-usage-0.rs:6:1
@@ -32,6 +36,10 @@ LL | #[const_trait]
 ...
 LL |     fn func() -> i32;
    |        ---- required by a bound in this associated function
+help: consider further restricting the associated type
+   |
+LL | const fn qualified<T: ~const Trait>() -> i32 where <T as Trait>::Assoc: Trait {
+   |                                              ++++++++++++++++++++++++++++++++
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage-1.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage-1.stderr
index 392b310a4c9..0792d090321 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage-1.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage-1.stderr
@@ -3,11 +3,11 @@ error: using `#![feature(effects)]` without enabling next trait solver globally
    = note: the next trait solver must be enabled globally for the effects feature to work correctly
    = help: use `-Znext-solver` to enable
 
-error[E0277]: the trait bound `Trait::{synthetic#0}: Compat` is not satisfied
+error[E0277]: the trait bound `<T as Trait>::Assoc: Trait` is not satisfied
   --> $DIR/assoc-type-const-bound-usage-1.rs:15:44
    |
 LL | fn unqualified<T: const Trait>() -> Type<{ T::Assoc::func() }> {
-   |                                            ^^^^^^^^ the trait `Compat` is not implemented for `Trait::{synthetic#0}`
+   |                                            ^^^^^^^^ the trait `Trait` is not implemented for `<T as Trait>::Assoc`
    |
 note: required by a bound in `Trait::func`
   --> $DIR/assoc-type-const-bound-usage-1.rs:7:1
@@ -17,12 +17,16 @@ LL | #[const_trait]
 ...
 LL |     fn func() -> i32;
    |        ---- required by a bound in this associated function
+help: consider further restricting the associated type
+   |
+LL | fn unqualified<T: const Trait>() -> Type<{ T::Assoc::func() }> where <T as Trait>::Assoc: Trait {
+   |                                                                ++++++++++++++++++++++++++++++++
 
-error[E0277]: the trait bound `Trait::{synthetic#0}: Compat` is not satisfied
+error[E0277]: the trait bound `<T as Trait>::Assoc: Trait` is not satisfied
   --> $DIR/assoc-type-const-bound-usage-1.rs:19:42
    |
 LL | fn qualified<T: const Trait>() -> Type<{ <T as Trait>::Assoc::func() }> {
-   |                                          ^^^^^^^^^^^^^^^^^^^ the trait `Compat` is not implemented for `Trait::{synthetic#0}`
+   |                                          ^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `<T as Trait>::Assoc`
    |
 note: required by a bound in `Trait::func`
   --> $DIR/assoc-type-const-bound-usage-1.rs:7:1
@@ -32,6 +36,10 @@ LL | #[const_trait]
 ...
 LL |     fn func() -> i32;
    |        ---- required by a bound in this associated function
+help: consider further restricting the associated type
+   |
+LL | fn qualified<T: const Trait>() -> Type<{ <T as Trait>::Assoc::func() }> where <T as Trait>::Assoc: Trait {
+   |                                                                         ++++++++++++++++++++++++++++++++
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.rs
index bb9e9045f8f..878f9a713a0 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.rs
@@ -1,4 +1,6 @@
-#![feature(const_trait_impl, effects)] //~ WARN the feature `effects` is incomplete
+//@ compile-flags: -Znext-solver
+#![allow(incomplete_features)]
+#![feature(const_trait_impl, effects)]
 
 #[const_trait]
 pub trait Plus {
@@ -23,7 +25,7 @@ pub const fn add_i32(a: i32, b: i32) -> i32 {
 
 pub const fn add_u32(a: u32, b: u32) -> u32 {
     a.plus(b)
-    //~^ ERROR the trait bound
+    //~^ ERROR the trait bound `u32: ~const Plus`
 }
 
 fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr
index 73ea1422bf9..5d2333d94fe 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr
@@ -1,33 +1,22 @@
-warning: the feature `effects` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/call-const-trait-method-fail.rs:1:30
-   |
-LL | #![feature(const_trait_impl, effects)]
-   |                              ^^^^^^^
-   |
-   = note: see issue #102090 <https://github.com/rust-lang/rust/issues/102090> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-error: using `#![feature(effects)]` without enabling next trait solver globally
-   |
-   = note: the next trait solver must be enabled globally for the effects feature to work correctly
-   = help: use `-Znext-solver` to enable
-
-error[E0277]: the trait bound `Runtime: ~const Compat` is not satisfied
-  --> $DIR/call-const-trait-method-fail.rs:25:5
+error[E0277]: the trait bound `u32: ~const Plus` is not satisfied
+  --> $DIR/call-const-trait-method-fail.rs:27:5
    |
 LL |     a.plus(b)
-   |     ^ the trait `~const Compat` is not implemented for `Runtime`
+   |     ^ the trait `Plus` is not implemented for `u32`
    |
-   = help: the trait `Compat` is implemented for `Runtime`
 note: required by a bound in `Plus::plus`
-  --> $DIR/call-const-trait-method-fail.rs:3:1
+  --> $DIR/call-const-trait-method-fail.rs:5:1
    |
 LL | #[const_trait]
    | ^^^^^^^^^^^^^^ required by this bound in `Plus::plus`
 LL | pub trait Plus {
 LL |     fn plus(self, rhs: Self) -> Self;
    |        ---- required by a bound in this associated function
+help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
+   |
+LL | pub const fn add_u32(a: u32, b: u32) -> u32 where u32: Plus {
+   |                                             +++++++++++++++
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.rs
index 74e33ca72ff..f9e79d41752 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.rs
@@ -1,4 +1,6 @@
-#![feature(const_trait_impl, effects)] //~ WARN the feature `effects` is incomplete
+//@ compile-flags: -Znext-solver
+#![allow(incomplete_features)]
+#![feature(const_trait_impl, effects)]
 
 struct S;
 
@@ -21,7 +23,6 @@ const fn equals_self<T: ~const Foo>(t: &T) -> bool {
 // it not using the impl.
 
 pub const EQ: bool = equals_self(&S);
-//~^ ERROR: the trait bound `Runtime: const Compat` is not satisfied
-// FIXME(effects) diagnostic
+//~^ ERROR: the trait bound `S: const Foo` is not satisfied
 
 fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.stderr
index b2a98041c1c..68c9fc40010 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.stderr
@@ -1,32 +1,21 @@
-warning: the feature `effects` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/call-generic-method-nonconst.rs:1:30
-   |
-LL | #![feature(const_trait_impl, effects)]
-   |                              ^^^^^^^
-   |
-   = note: see issue #102090 <https://github.com/rust-lang/rust/issues/102090> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-error: using `#![feature(effects)]` without enabling next trait solver globally
-   |
-   = note: the next trait solver must be enabled globally for the effects feature to work correctly
-   = help: use `-Znext-solver` to enable
-
-error[E0277]: the trait bound `Runtime: const Compat` is not satisfied
-  --> $DIR/call-generic-method-nonconst.rs:23:34
+error[E0277]: the trait bound `S: const Foo` is not satisfied
+  --> $DIR/call-generic-method-nonconst.rs:25:34
    |
 LL | pub const EQ: bool = equals_self(&S);
-   |                      ----------- ^^ the trait `const Compat` is not implemented for `Runtime`
+   |                      ----------- ^^ the trait `Foo` is not implemented for `S`
    |                      |
    |                      required by a bound introduced by this call
    |
-   = help: the trait `Compat` is implemented for `Runtime`
 note: required by a bound in `equals_self`
-  --> $DIR/call-generic-method-nonconst.rs:16:25
+  --> $DIR/call-generic-method-nonconst.rs:18:25
    |
 LL | const fn equals_self<T: ~const Foo>(t: &T) -> bool {
    |                         ^^^^^^^^^^ required by this bound in `equals_self`
+help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
+   |
+LL | pub const EQ: bool where S: Foo = equals_self(&S);
+   |                    ++++++++++++
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.rs
index 2fd58b05178..a0333153f85 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.rs
@@ -1,4 +1,6 @@
-#![feature(const_trait_impl, effects)] //~ WARN the feature `effects` is incomplete
+//@ compile-flags: -Znext-solver
+#![allow(incomplete_features)]
+#![feature(const_trait_impl, effects)]
 
 #[const_trait]
 trait ConstDefaultFn: Sized {
@@ -22,7 +24,7 @@ impl const ConstDefaultFn for ConstImpl {
 
 const fn test() {
     NonConstImpl.a();
-    //~^ ERROR the trait bound
+    //~^ ERROR the trait bound `NonConstImpl: ~const ConstDefaultFn` is not satisfied
     ConstImpl.a();
 }
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.stderr
index 02f9dffba32..0809d9c1e1d 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.stderr
@@ -1,33 +1,22 @@
-warning: the feature `effects` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/const-default-method-bodies.rs:1:30
-   |
-LL | #![feature(const_trait_impl, effects)]
-   |                              ^^^^^^^
-   |
-   = note: see issue #102090 <https://github.com/rust-lang/rust/issues/102090> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-error: using `#![feature(effects)]` without enabling next trait solver globally
-   |
-   = note: the next trait solver must be enabled globally for the effects feature to work correctly
-   = help: use `-Znext-solver` to enable
-
-error[E0277]: the trait bound `Runtime: ~const Compat` is not satisfied
-  --> $DIR/const-default-method-bodies.rs:24:18
+error[E0277]: the trait bound `NonConstImpl: ~const ConstDefaultFn` is not satisfied
+  --> $DIR/const-default-method-bodies.rs:26:18
    |
 LL |     NonConstImpl.a();
-   |                  ^ the trait `~const Compat` is not implemented for `Runtime`
+   |                  ^ the trait `ConstDefaultFn` is not implemented for `NonConstImpl`
    |
-   = help: the trait `Compat` is implemented for `Runtime`
 note: required by a bound in `ConstDefaultFn::a`
-  --> $DIR/const-default-method-bodies.rs:3:1
+  --> $DIR/const-default-method-bodies.rs:5:1
    |
 LL | #[const_trait]
    | ^^^^^^^^^^^^^^ required by this bound in `ConstDefaultFn::a`
 ...
 LL |     fn a(self) {
    |        - required by a bound in this associated function
+help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
+   |
+LL | const fn test() where NonConstImpl: ConstDefaultFn {
+   |                 ++++++++++++++++++++++++++++++++++
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-fns-are-early-bound.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-fns-are-early-bound.stderr
index 7aa3aa8c6bb..9eda9d98ec5 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-fns-are-early-bound.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-fns-are-early-bound.stderr
@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `FnOnce<()>::{synthetic#0}: const Compat` is not satisfied
+error[E0277]: the trait bound `fn() {foo}: const FnOnce()` is not satisfied
   --> $DIR/const-fns-are-early-bound.rs:31:17
    |
 LL |     is_const_fn(foo);
-   |     ----------- ^^^ the trait `const Compat` is not implemented for `FnOnce<()>::{synthetic#0}`
+   |     ----------- ^^^ the trait `FnOnce()` is not implemented for fn item `fn() {foo}`
    |     |
    |     required by a bound introduced by this call
    |
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr
index b7209827c22..a34bae843c8 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr
@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `cross_crate::MyTrait::{synthetic#0}: ~const Compat` is not satisfied
+error[E0277]: the trait bound `cross_crate::NonConst: ~const cross_crate::MyTrait` is not satisfied
   --> $DIR/cross-crate.rs:19:14
    |
 LL |     NonConst.func();
-   |              ^^^^ the trait `~const Compat` is not implemented for `cross_crate::MyTrait::{synthetic#0}`
+   |              ^^^^ the trait `cross_crate::MyTrait` is not implemented for `cross_crate::NonConst`
    |
 note: required by a bound in `func`
   --> $DIR/auxiliary/cross-crate.rs:5:1
@@ -12,6 +12,10 @@ LL | #[const_trait]
 ...
 LL |     fn func(self);
    |        ---- required by a bound in this associated function
+help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
+   |
+LL | const fn const_context() where cross_crate::NonConst: cross_crate::MyTrait {
+   |                          +++++++++++++++++++++++++++++++++++++++++++++++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.rs
index 64f23824b39..0c2d93775a4 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.rs
@@ -1,4 +1,6 @@
-#![feature(const_trait_impl, effects)] //~ WARN the feature `effects` is incomplete
+//@ compile-flags: -Znext-solver
+#![allow(incomplete_features)]
+#![feature(const_trait_impl, effects)]
 
 #[const_trait]
 pub trait Tr {
@@ -6,7 +8,7 @@ pub trait Tr {
 
     fn b(&self) {
         ().a()
-        //~^ ERROR the trait bound
+        //~^ ERROR the trait bound `(): ~const Tr` is not satisfied
     }
 }
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr
index 1b5aa9c9191..d0f22c0b9b6 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr
@@ -1,33 +1,22 @@
-warning: the feature `effects` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/default-method-body-is-const-same-trait-ck.rs:1:30
-   |
-LL | #![feature(const_trait_impl, effects)]
-   |                              ^^^^^^^
-   |
-   = note: see issue #102090 <https://github.com/rust-lang/rust/issues/102090> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-error: using `#![feature(effects)]` without enabling next trait solver globally
-   |
-   = note: the next trait solver must be enabled globally for the effects feature to work correctly
-   = help: use `-Znext-solver` to enable
-
-error[E0277]: the trait bound `Runtime: ~const Compat` is not satisfied
-  --> $DIR/default-method-body-is-const-same-trait-ck.rs:8:12
+error[E0277]: the trait bound `(): ~const Tr` is not satisfied
+  --> $DIR/default-method-body-is-const-same-trait-ck.rs:10:12
    |
 LL |         ().a()
-   |            ^ the trait `~const Compat` is not implemented for `Runtime`
+   |            ^ the trait `Tr` is not implemented for `()`
    |
-   = help: the trait `Compat` is implemented for `Runtime`
 note: required by a bound in `Tr::a`
-  --> $DIR/default-method-body-is-const-same-trait-ck.rs:3:1
+  --> $DIR/default-method-body-is-const-same-trait-ck.rs:5:1
    |
 LL | #[const_trait]
    | ^^^^^^^^^^^^^^ required by this bound in `Tr::a`
 LL | pub trait Tr {
 LL |     fn a(&self) {}
    |        - required by a bound in this associated function
+help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
+   |
+LL | pub trait Tr where (): Tr {
+   |              ++++++++++++
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.rs
index 0d659744e70..93a6f385e47 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.rs
@@ -17,8 +17,7 @@ trait Bar: ~const Foo {}
 
 const fn foo<T: Bar>(x: &T) {
     x.a();
-    //[yy,yn]~^ ERROR the trait bound
-    // FIXME(effects) diagnostic
+    //[yy,yn]~^ ERROR the trait bound `T: ~const Foo`
 }
 
 fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yn.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yn.stderr
index d4064e01ef1..873c57ec71f 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yn.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yn.stderr
@@ -10,11 +10,11 @@ note: this trait is not a `#[const_trait]`, so it cannot have `~const` trait bou
 LL | trait Bar: ~const Foo {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `Foo::{synthetic#0}: ~const Compat` is not satisfied
+error[E0277]: the trait bound `T: ~const Foo` is not satisfied
   --> $DIR/super-traits-fail-2.rs:19:7
    |
 LL |     x.a();
-   |       ^ the trait `~const Compat` is not implemented for `Foo::{synthetic#0}`
+   |       ^ the trait `Foo` is not implemented for `T`
    |
 note: required by a bound in `Foo::a`
   --> $DIR/super-traits-fail-2.rs:6:25
@@ -24,10 +24,10 @@ LL | #[cfg_attr(any(yy, yn), const_trait)]
 LL | trait Foo {
 LL |     fn a(&self);
    |        - required by a bound in this associated function
-help: consider further restricting the associated type
+help: consider further restricting this bound
    |
-LL | const fn foo<T: Bar>(x: &T) where Foo::{synthetic#0}: ~const Compat {
-   |                             +++++++++++++++++++++++++++++++++++++++
+LL | const fn foo<T: Bar + Foo>(x: &T) {
+   |                     +++++
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yy.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yy.stderr
index 9f9f96c6b48..bea3aea2f3a 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yy.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yy.stderr
@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `Foo::{synthetic#0}: ~const Compat` is not satisfied
+error[E0277]: the trait bound `T: ~const Foo` is not satisfied
   --> $DIR/super-traits-fail-2.rs:19:7
    |
 LL |     x.a();
-   |       ^ the trait `~const Compat` is not implemented for `Foo::{synthetic#0}`
+   |       ^ the trait `Foo` is not implemented for `T`
    |
 note: required by a bound in `Foo::a`
   --> $DIR/super-traits-fail-2.rs:6:25
@@ -12,10 +12,10 @@ LL | #[cfg_attr(any(yy, yn), const_trait)]
 LL | trait Foo {
 LL |     fn a(&self);
    |        - required by a bound in this associated function
-help: consider further restricting the associated type
+help: consider further restricting this bound
    |
-LL | const fn foo<T: Bar>(x: &T) where Foo::{synthetic#0}: ~const Compat {
-   |                             +++++++++++++++++++++++++++++++++++++++
+LL | const fn foo<T: Bar + Foo>(x: &T) {
+   |                     +++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.rs
index c7e224dcce0..b5643b11700 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.rs
@@ -20,7 +20,7 @@ trait Bar: ~const Foo {}
 const fn foo<T: ~const Bar>(x: &T) {
     //[yn,nn]~^ ERROR: `~const` can only be applied to `#[const_trait]`
     x.a();
-    //[yn]~^ ERROR: the trait bound
+    //[yn]~^ ERROR: the trait bound `T: ~const Foo` is not satisfied
 }
 
 fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yn.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yn.stderr
index 0b48633a10e..bbc95948a59 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yn.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yn.stderr
@@ -16,11 +16,11 @@ error: `~const` can only be applied to `#[const_trait]` traits
 LL | const fn foo<T: ~const Bar>(x: &T) {
    |                        ^^^
 
-error[E0277]: the trait bound `Foo::{synthetic#0}: ~const Compat` is not satisfied
+error[E0277]: the trait bound `T: ~const Foo` is not satisfied
   --> $DIR/super-traits-fail-3.rs:22:7
    |
 LL |     x.a();
-   |       ^ the trait `~const Compat` is not implemented for `Foo::{synthetic#0}`
+   |       ^ the trait `Foo` is not implemented for `T`
    |
 note: required by a bound in `Foo::a`
   --> $DIR/super-traits-fail-3.rs:8:25
@@ -30,10 +30,10 @@ LL | #[cfg_attr(any(yy, yn), const_trait)]
 LL | trait Foo {
 LL |     fn a(&self);
    |        - required by a bound in this associated function
-help: consider further restricting the associated type
+help: consider further restricting this bound
    |
-LL | const fn foo<T: ~const Bar>(x: &T) where Foo::{synthetic#0}: ~const Compat {
-   |                                    +++++++++++++++++++++++++++++++++++++++
+LL | const fn foo<T: ~const Bar + Foo>(x: &T) {
+   |                            +++++
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/trait-where-clause-const.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/trait-where-clause-const.stderr
index 979f1e798e0..eaa981ec744 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/trait-where-clause-const.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/trait-where-clause-const.stderr
@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `Foo::{synthetic#0}: Compat` is not satisfied
+error[E0277]: the trait bound `T: Foo` is not satisfied
   --> $DIR/trait-where-clause-const.rs:22:5
    |
 LL |     T::b();
-   |     ^ the trait `Compat` is not implemented for `Foo::{synthetic#0}`
+   |     ^ the trait `Foo` is not implemented for `T`
    |
 note: required by a bound in `Foo::b`
   --> $DIR/trait-where-clause-const.rs:13:1
@@ -12,10 +12,6 @@ LL | #[const_trait]
 ...
 LL |     fn b() where Self: ~const Bar;
    |        - required by a bound in this associated function
-help: consider further restricting the associated type
-   |
-LL | const fn test1<T: ~const Foo + Bar>() where Foo::{synthetic#0}: Compat {
-   |                                       ++++++++++++++++++++++++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/trait-where-clause-const.rs:22:5
@@ -26,11 +22,11 @@ LL |     T::b();
    = note: expected constant `host`
               found constant `true`
 
-error[E0277]: the trait bound `Foo::{synthetic#0}: Compat` is not satisfied
+error[E0277]: the trait bound `T: Foo` is not satisfied
   --> $DIR/trait-where-clause-const.rs:25:5
    |
 LL |     T::c::<T>();
-   |     ^ the trait `Compat` is not implemented for `Foo::{synthetic#0}`
+   |     ^ the trait `Foo` is not implemented for `T`
    |
 note: required by a bound in `Foo::c`
   --> $DIR/trait-where-clause-const.rs:13:1
@@ -40,10 +36,6 @@ LL | #[const_trait]
 ...
 LL |     fn c<T: ~const Bar>();
    |        - required by a bound in this associated function
-help: consider further restricting the associated type
-   |
-LL | const fn test1<T: ~const Foo + Bar>() where Foo::{synthetic#0}: Compat {
-   |                                       ++++++++++++++++++++++++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/trait-where-clause-const.rs:25:5
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/unsatisfied-const-trait-bound.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/unsatisfied-const-trait-bound.rs
index 5fffe54fc1a..d336719f52e 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/unsatisfied-const-trait-bound.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/unsatisfied-const-trait-bound.rs
@@ -19,7 +19,6 @@ impl Trait for Ty {
 }
 
 fn main() {
-    // FIXME(effects): improve diagnostics on this
     require::<Ty>();
 }
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/unsatisfied-const-trait-bound.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/unsatisfied-const-trait-bound.stderr
index 0806ffa4b5d..848aa68689b 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/unsatisfied-const-trait-bound.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/unsatisfied-const-trait-bound.stderr
@@ -7,7 +7,7 @@ LL | #![feature(const_trait_impl, effects, generic_const_exprs)]
    = help: remove one of these features
 
 error[E0308]: mismatched types
-  --> $DIR/unsatisfied-const-trait-bound.rs:30:37
+  --> $DIR/unsatisfied-const-trait-bound.rs:29:37
    |
 LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
    |                                     ^^^^^^^^^ expected `false`, found `true`
@@ -16,7 +16,7 @@ LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
               found constant `true`
 
 error[E0308]: mismatched types
-  --> $DIR/unsatisfied-const-trait-bound.rs:34:50
+  --> $DIR/unsatisfied-const-trait-bound.rs:33:50
    |
 LL | const fn accept1<T: ~const Trait>(_: Container<{ T::make() }>) {}
    |                                                  ^^^^^^^^^ expected `false`, found `host`
@@ -24,17 +24,21 @@ LL | const fn accept1<T: ~const Trait>(_: Container<{ T::make() }>) {}
    = note: expected constant `false`
               found constant `host`
 
-error[E0277]: the trait bound `Trait::{synthetic#0}: const Compat` is not satisfied
-  --> $DIR/unsatisfied-const-trait-bound.rs:23:15
+error[E0277]: the trait bound `Ty: const Trait` is not satisfied
+  --> $DIR/unsatisfied-const-trait-bound.rs:22:15
    |
 LL |     require::<Ty>();
-   |               ^^ the trait `const Compat` is not implemented for `Trait::{synthetic#0}`
+   |               ^^ the trait `Trait` is not implemented for `Ty`
    |
 note: required by a bound in `require`
   --> $DIR/unsatisfied-const-trait-bound.rs:8:15
    |
 LL | fn require<T: const Trait>() {}
    |               ^^^^^^^^^^^ required by this bound in `require`
+help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
+   |
+LL | fn main() where Ty: Trait {
+   |           +++++++++++++++
 
 error: aborting due to 4 previous errors