diff --git a/Cargo.lock b/Cargo.lock
index 5c936ca40e167..af8cbfe3d6182 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3212,6 +3212,7 @@ dependencies = [
  "rustc_trait_selection",
  "rustc_ty_utils",
  "serde_json",
+ "time",
  "tracing",
  "windows",
 ]
@@ -4815,6 +4816,33 @@ dependencies = [
 name = "tier-check"
 version = "0.1.0"
 
+[[package]]
+name = "time"
+version = "0.3.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea9e1b3cf1243ae005d9e74085d4d542f3125458f3a81af210d901dcd7411efd"
+dependencies = [
+ "itoa",
+ "serde",
+ "time-core",
+ "time-macros",
+]
+
+[[package]]
+name = "time-core"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7300fbefb4dadc1af235a9cef3737cea692a9d97e1b9cbcd4ebdae6f8868e6fb"
+
+[[package]]
+name = "time-macros"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "372950940a5f07bf38dbe211d7283c9e6d7327df53794992d293e534c733d09b"
+dependencies = [
+ "time-core",
+]
+
 [[package]]
 name = "tinystr"
 version = "0.7.1"
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index ececa29b23155..1c5d7a7c68e92 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -362,7 +362,7 @@ pub struct CodegenContext<B: WriteBackendMethods> {
 
 impl<B: WriteBackendMethods> CodegenContext<B> {
     pub fn create_diag_handler(&self) -> Handler {
-        Handler::with_emitter(true, None, Box::new(self.diag_emitter.clone()))
+        Handler::with_emitter(true, None, Box::new(self.diag_emitter.clone()), None)
     }
 
     pub fn config(&self, kind: ModuleKind) -> &ModuleConfig {
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index 24c1fe43d0c68..ca1106384fd33 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -700,8 +700,13 @@ where
             assert_eq!(src.layout.size, dest.layout.size);
         }
 
+        // Setting `nonoverlapping` here only has an effect when we don't hit the fast-path above,
+        // but that should at least match what LLVM does where `memcpy` is also only used when the
+        // type does not have Scalar/ScalarPair layout.
+        // (Or as the `Assign` docs put it, assignments "not producing primitives" must be
+        // non-overlapping.)
         self.mem_copy(
-            src.ptr, src.align, dest.ptr, dest.align, dest_size, /*nonoverlapping*/ false,
+            src.ptr, src.align, dest.ptr, dest.align, dest_size, /*nonoverlapping*/ true,
         )
     }
 
diff --git a/compiler/rustc_driver_impl/Cargo.toml b/compiler/rustc_driver_impl/Cargo.toml
index 67352c55c9019..a7b01618ade39 100644
--- a/compiler/rustc_driver_impl/Cargo.toml
+++ b/compiler/rustc_driver_impl/Cargo.toml
@@ -6,6 +6,7 @@ edition = "2021"
 [lib]
 
 [dependencies]
+time = { version = "0.3", default-features = false, features = ["formatting", ] }
 tracing = { version = "0.1.35" }
 serde_json = "1.0.59"
 rustc_log = { path = "../rustc_log" }
diff --git a/compiler/rustc_driver_impl/messages.ftl b/compiler/rustc_driver_impl/messages.ftl
index 22b4ec6b0d1b1..9b2f2c3386078 100644
--- a/compiler/rustc_driver_impl/messages.ftl
+++ b/compiler/rustc_driver_impl/messages.ftl
@@ -3,7 +3,11 @@ driver_impl_ice_bug_report = we would appreciate a bug report: {$bug_report_url}
 driver_impl_ice_exclude_cargo_defaults = some of the compiler flags provided by cargo are hidden
 
 driver_impl_ice_flags = compiler flags: {$flags}
+driver_impl_ice_path = please attach the file at `{$path}` to your bug report
+driver_impl_ice_path_error = the ICE couldn't be written to `{$path}`: {$error}
+driver_impl_ice_path_error_env = the environment variable `RUSTC_ICE` is set to `{$env_var}`
 driver_impl_ice_version = rustc {$version} running on {$triple}
+
 driver_impl_rlink_empty_version_number = The input does not contain version number
 
 driver_impl_rlink_encoding_version_mismatch = .rlink file was produced with encoding version `{$version_array}`, but the current version is `{$rlink_version}`
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 9352fe3147e59..2149480732f1c 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -7,6 +7,8 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(lazy_cell)]
 #![feature(decl_macro)]
+#![feature(ice_to_disk)]
+#![feature(let_chains)]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]
 #![deny(rustc::untranslatable_diagnostic)]
@@ -57,8 +59,11 @@ use std::panic::{self, catch_unwind};
 use std::path::PathBuf;
 use std::process::{self, Command, Stdio};
 use std::str;
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::OnceLock;
-use std::time::Instant;
+use std::time::{Instant, SystemTime};
+use time::format_description::well_known::Rfc3339;
+use time::OffsetDateTime;
 
 #[allow(unused_macros)]
 macro do_not_use_print($($t:tt)*) {
@@ -297,6 +302,7 @@ fn run_compiler(
         input: Input::File(PathBuf::new()),
         output_file: ofile,
         output_dir: odir,
+        ice_file: ice_path().clone(),
         file_loader,
         locale_resources: DEFAULT_LOCALE_RESOURCES,
         lint_caps: Default::default(),
@@ -1295,9 +1301,29 @@ pub fn catch_with_exit_code(f: impl FnOnce() -> interface::Result<()>) -> i32 {
     }
 }
 
-/// Stores the default panic hook, from before [`install_ice_hook`] was called.
-static DEFAULT_HOOK: OnceLock<Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send + 'static>> =
-    OnceLock::new();
+pub static ICE_PATH: OnceLock<Option<PathBuf>> = OnceLock::new();
+
+pub fn ice_path() -> &'static Option<PathBuf> {
+    ICE_PATH.get_or_init(|| {
+        if !rustc_feature::UnstableFeatures::from_environment(None).is_nightly_build() {
+            return None;
+        }
+        if let Ok("0") = std::env::var("RUST_BACKTRACE").as_deref() {
+            return None;
+        }
+        let mut path = match std::env::var("RUSTC_ICE").as_deref() {
+            // Explicitly opting out of writing ICEs to disk.
+            Ok("0") => return None,
+            Ok(s) => PathBuf::from(s),
+            Err(_) => std::env::current_dir().unwrap_or_default(),
+        };
+        let now: OffsetDateTime = SystemTime::now().into();
+        let file_now = now.format(&Rfc3339).unwrap_or(String::new());
+        let pid = std::process::id();
+        path.push(format!("rustc-ice-{file_now}-{pid}.txt"));
+        Some(path)
+    })
+}
 
 /// Installs a panic hook that will print the ICE message on unexpected panics.
 ///
@@ -1321,8 +1347,6 @@ pub fn install_ice_hook(bug_report_url: &'static str, extra_info: fn(&Handler))
         std::env::set_var("RUST_BACKTRACE", "full");
     }
 
-    let default_hook = DEFAULT_HOOK.get_or_init(panic::take_hook);
-
     panic::set_hook(Box::new(move |info| {
         // If the error was caused by a broken pipe then this is not a bug.
         // Write the error and return immediately. See #98700.
@@ -1339,7 +1363,7 @@ pub fn install_ice_hook(bug_report_url: &'static str, extra_info: fn(&Handler))
         // Invoke the default handler, which prints the actual panic message and optionally a backtrace
         // Don't do this for delayed bugs, which already emit their own more useful backtrace.
         if !info.payload().is::<rustc_errors::DelayedBugPanic>() {
-            (*default_hook)(info);
+            std::panic_hook_with_disk_dump(info, ice_path().as_deref());
 
             // Separate the output with an empty line
             eprintln!();
@@ -1371,7 +1395,7 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str, extra_info:
         false,
         TerminalUrl::No,
     ));
-    let handler = rustc_errors::Handler::with_emitter(true, None, emitter);
+    let handler = rustc_errors::Handler::with_emitter(true, None, emitter, None);
 
     // a .span_bug or .bug call has already printed what
     // it wants to print.
@@ -1382,10 +1406,40 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str, extra_info:
     }
 
     handler.emit_note(session_diagnostics::IceBugReport { bug_report_url });
-    handler.emit_note(session_diagnostics::IceVersion {
-        version: util::version_str!().unwrap_or("unknown_version"),
-        triple: config::host_triple(),
-    });
+
+    let version = util::version_str!().unwrap_or("unknown_version");
+    let triple = config::host_triple();
+
+    static FIRST_PANIC: AtomicBool = AtomicBool::new(true);
+
+    let file = if let Some(path) = ice_path().as_ref() {
+        // Create the ICE dump target file.
+        match crate::fs::File::options().create(true).append(true).open(&path) {
+            Ok(mut file) => {
+                handler
+                    .emit_note(session_diagnostics::IcePath { path: path.display().to_string() });
+                if FIRST_PANIC.swap(false, Ordering::SeqCst) {
+                    let _ = write!(file, "\n\nrustc version: {version}\nplatform: {triple}");
+                }
+                Some(file)
+            }
+            Err(err) => {
+                // The path ICE couldn't be written to disk, provide feedback to the user as to why.
+                handler.emit_warning(session_diagnostics::IcePathError {
+                    path: path.display().to_string(),
+                    error: err.to_string(),
+                    env_var: std::env::var("RUSTC_ICE")
+                        .ok()
+                        .map(|env_var| session_diagnostics::IcePathErrorEnv { env_var }),
+                });
+                handler.emit_note(session_diagnostics::IceVersion { version, triple });
+                None
+            }
+        }
+    } else {
+        handler.emit_note(session_diagnostics::IceVersion { version, triple });
+        None
+    };
 
     if let Some((flags, excluded_cargo_defaults)) = extra_compiler_flags() {
         handler.emit_note(session_diagnostics::IceFlags { flags: flags.join(" ") });
@@ -1399,7 +1453,7 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str, extra_info:
 
     let num_frames = if backtrace { None } else { Some(2) };
 
-    interface::try_print_query_stack(&handler, num_frames);
+    interface::try_print_query_stack(&handler, num_frames, file);
 
     // We don't trust this callback not to panic itself, so run it at the end after we're sure we've
     // printed all the relevant info.
diff --git a/compiler/rustc_driver_impl/src/session_diagnostics.rs b/compiler/rustc_driver_impl/src/session_diagnostics.rs
index 638b368f70214..f7f06b7d0f2b8 100644
--- a/compiler/rustc_driver_impl/src/session_diagnostics.rs
+++ b/compiler/rustc_driver_impl/src/session_diagnostics.rs
@@ -1,4 +1,4 @@
-use rustc_macros::Diagnostic;
+use rustc_macros::{Diagnostic, Subdiagnostic};
 
 #[derive(Diagnostic)]
 #[diag(driver_impl_rlink_unable_to_read)]
@@ -56,6 +56,27 @@ pub(crate) struct IceVersion<'a> {
     pub triple: &'a str,
 }
 
+#[derive(Diagnostic)]
+#[diag(driver_impl_ice_path)]
+pub(crate) struct IcePath {
+    pub path: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(driver_impl_ice_path_error)]
+pub(crate) struct IcePathError {
+    pub path: String,
+    pub error: String,
+    #[subdiagnostic]
+    pub env_var: Option<IcePathErrorEnv>,
+}
+
+#[derive(Subdiagnostic)]
+#[note(driver_impl_ice_path_error_env)]
+pub(crate) struct IcePathErrorEnv {
+    pub env_var: String,
+}
+
 #[derive(Diagnostic)]
 #[diag(driver_impl_ice_flags)]
 pub(crate) struct IceFlags {
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index f3ee83fd4d218..1879ece59e329 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -226,7 +226,7 @@ fn register_functions(bundle: &mut FluentBundle) {
 pub type LazyFallbackBundle = Lrc<Lazy<FluentBundle, impl FnOnce() -> FluentBundle>>;
 
 /// Return the default `FluentBundle` with standard "en-US" diagnostic messages.
-#[instrument(level = "trace")]
+#[instrument(level = "trace", skip(resources))]
 pub fn fallback_fluent_bundle(
     resources: Vec<&'static str>,
     with_directionality_markers: bool,
@@ -242,7 +242,6 @@ pub fn fallback_fluent_bundle(
         for resource in resources {
             let resource = FluentResource::try_new(resource.to_string())
                 .expect("failed to parse fallback fluent resource");
-            trace!(?resource);
             fallback_bundle.add_resource_overriding(resource);
         }
 
@@ -355,6 +354,13 @@ impl DiagnosticMessage {
             }
         }
     }
+
+    pub fn as_str(&self) -> Option<&str> {
+        match self {
+            DiagnosticMessage::Eager(s) | DiagnosticMessage::Str(s) => Some(s),
+            DiagnosticMessage::FluentIdentifier(_, _) => None,
+        }
+    }
 }
 
 impl From<String> for DiagnosticMessage {
diff --git a/compiler/rustc_errors/src/json/tests.rs b/compiler/rustc_errors/src/json/tests.rs
index 671dc449eaa73..db0dd4ffe8e17 100644
--- a/compiler/rustc_errors/src/json/tests.rs
+++ b/compiler/rustc_errors/src/json/tests.rs
@@ -64,7 +64,7 @@ fn test_positions(code: &str, span: (u32, u32), expected_output: SpanTestData) {
         );
 
         let span = Span::with_root_ctxt(BytePos(span.0), BytePos(span.1));
-        let handler = Handler::with_emitter(true, None, Box::new(je));
+        let handler = Handler::with_emitter(true, None, Box::new(je), None);
         handler.span_err(span, "foo");
 
         let bytes = output.lock().unwrap();
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index b9db25103a3a8..31410c39d368e 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -47,9 +47,10 @@ use std::borrow::Cow;
 use std::error::Report;
 use std::fmt;
 use std::hash::Hash;
+use std::io::Write;
 use std::num::NonZeroUsize;
 use std::panic;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 
 use termcolor::{Color, ColorSpec};
 
@@ -461,6 +462,10 @@ struct HandlerInner {
     ///
     /// [RFC-2383]: https://rust-lang.github.io/rfcs/2383-lint-reasons.html
     fulfilled_expectations: FxHashSet<LintExpectationId>,
+
+    /// The file where the ICE information is stored. This allows delayed_span_bug backtraces to be
+    /// stored along side the main panic backtrace.
+    ice_file: Option<PathBuf>,
 }
 
 /// A key denoting where from a diagnostic was stashed.
@@ -550,6 +555,7 @@ impl Handler {
         sm: Option<Lrc<SourceMap>>,
         fluent_bundle: Option<Lrc<FluentBundle>>,
         fallback_bundle: LazyFallbackBundle,
+        ice_file: Option<PathBuf>,
     ) -> Self {
         Self::with_tty_emitter_and_flags(
             color_config,
@@ -557,6 +563,7 @@ impl Handler {
             fluent_bundle,
             fallback_bundle,
             HandlerFlags { can_emit_warnings, treat_err_as_bug, ..Default::default() },
+            ice_file,
         )
     }
 
@@ -566,6 +573,7 @@ impl Handler {
         fluent_bundle: Option<Lrc<FluentBundle>>,
         fallback_bundle: LazyFallbackBundle,
         flags: HandlerFlags,
+        ice_file: Option<PathBuf>,
     ) -> Self {
         let emitter = Box::new(EmitterWriter::stderr(
             color_config,
@@ -579,23 +587,26 @@ impl Handler {
             flags.track_diagnostics,
             TerminalUrl::No,
         ));
-        Self::with_emitter_and_flags(emitter, flags)
+        Self::with_emitter_and_flags(emitter, flags, ice_file)
     }
 
     pub fn with_emitter(
         can_emit_warnings: bool,
         treat_err_as_bug: Option<NonZeroUsize>,
         emitter: Box<dyn Emitter + sync::Send>,
+        ice_file: Option<PathBuf>,
     ) -> Self {
         Handler::with_emitter_and_flags(
             emitter,
             HandlerFlags { can_emit_warnings, treat_err_as_bug, ..Default::default() },
+            ice_file,
         )
     }
 
     pub fn with_emitter_and_flags(
         emitter: Box<dyn Emitter + sync::Send>,
         flags: HandlerFlags,
+        ice_file: Option<PathBuf>,
     ) -> Self {
         Self {
             flags,
@@ -618,6 +629,7 @@ impl Handler {
                 check_unstable_expect_diagnostics: false,
                 unstable_expect_diagnostics: Vec::new(),
                 fulfilled_expectations: Default::default(),
+                ice_file,
             }),
         }
     }
@@ -1657,8 +1669,21 @@ impl HandlerInner {
         explanation: impl Into<DiagnosticMessage> + Copy,
     ) {
         let mut no_bugs = true;
+        // If backtraces are enabled, also print the query stack
+        let backtrace = std::env::var_os("RUST_BACKTRACE").map_or(true, |x| &x != "0");
         for bug in bugs {
-            let mut bug = bug.decorate();
+            if let Some(file) = self.ice_file.as_ref()
+                && let Ok(mut out) = std::fs::File::options().append(true).open(file)
+            {
+                let _ = write!(
+                    &mut out,
+                    "\n\ndelayed span bug: {}\n{}",
+                    bug.inner.styled_message().iter().filter_map(|(msg, _)| msg.as_str()).collect::<String>(),
+                    &bug.note
+                );
+            }
+            let mut bug =
+                if backtrace || self.ice_file.is_none() { bug.decorate() } else { bug.inner };
 
             if no_bugs {
                 // Put the overall explanation before the `DelayedBug`s, to
diff --git a/compiler/rustc_expand/src/tests.rs b/compiler/rustc_expand/src/tests.rs
index 8a5e09475ff13..6490e52955db8 100644
--- a/compiler/rustc_expand/src/tests.rs
+++ b/compiler/rustc_expand/src/tests.rs
@@ -161,7 +161,7 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
             false,
             TerminalUrl::No,
         );
-        let handler = Handler::with_emitter(true, None, Box::new(emitter));
+        let handler = Handler::with_emitter(true, None, Box::new(emitter), None);
         #[allow(rustc::untranslatable_diagnostic)]
         handler.span_err(msp, "foo");
 
diff --git a/compiler/rustc_hir_analysis/messages.ftl b/compiler/rustc_hir_analysis/messages.ftl
index 0738961d6ce48..166760166c108 100644
--- a/compiler/rustc_hir_analysis/messages.ftl
+++ b/compiler/rustc_hir_analysis/messages.ftl
@@ -248,6 +248,9 @@ hir_analysis_static_specialize = cannot specialize on `'static` lifetime
 
 hir_analysis_substs_on_overridden_impl = could not resolve substs on overridden impl
 
+hir_analysis_tait_forward_compat = item constrains opaque type that is not in its signature
+    .note = this item must mention the opaque type in its signature in order to be able to register hidden types
+
 hir_analysis_target_feature_on_main = `main` function is not allowed to have `#[target_feature]`
 
 hir_analysis_too_large_static = extern static is too large for the current architecture
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index f4779a3f26533..957a6bb348109 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -6,7 +6,7 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::DUMMY_SP;
 
-use crate::errors::UnconstrainedOpaqueType;
+use crate::errors::{TaitForwardCompat, UnconstrainedOpaqueType};
 
 /// Checks "defining uses" of opaque `impl Trait` types to ensure that they meet the restrictions
 /// laid for "higher-order pattern unification".
@@ -139,6 +139,15 @@ impl TaitConstraintLocator<'_> {
                 continue;
             }
             constrained = true;
+            if !self.tcx.opaque_types_defined_by(item_def_id).contains(&self.def_id) {
+                self.tcx.sess.emit_err(TaitForwardCompat {
+                    span: hidden_type.span,
+                    item_span: self
+                        .tcx
+                        .def_ident_span(item_def_id)
+                        .unwrap_or_else(|| self.tcx.def_span(item_def_id)),
+                });
+            }
             let concrete_type =
                 self.tcx.erase_regions(hidden_type.remap_generic_params_to_declaration_params(
                     opaque_type_key,
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 205e26d0edaac..c2d2e5f7e50f6 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -184,6 +184,16 @@ pub struct UnconstrainedOpaqueType {
     pub what: &'static str,
 }
 
+#[derive(Diagnostic)]
+#[diag(hir_analysis_tait_forward_compat)]
+#[note]
+pub struct TaitForwardCompat {
+    #[primary_span]
+    pub span: Span,
+    #[note]
+    pub item_span: Span,
+}
+
 pub struct MissingTypeParams {
     pub span: Span,
     pub def_span: Span,
diff --git a/compiler/rustc_hir_analysis/src/variance/mod.rs b/compiler/rustc_hir_analysis/src/variance/mod.rs
index 49aee6b59a28c..066e7449189ea 100644
--- a/compiler/rustc_hir_analysis/src/variance/mod.rs
+++ b/compiler/rustc_hir_analysis/src/variance/mod.rs
@@ -7,7 +7,7 @@ use rustc_arena::DroplessArena;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, CrateVariancesMap, ImplTraitInTraitData, SubstsRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, CrateVariancesMap, SubstsRef, Ty, TyCtxt};
 use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable};
 use std::ops::ControlFlow;
 
@@ -59,13 +59,6 @@ fn variances_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Variance] {
         DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder => {
             return variance_of_opaque(tcx, item_def_id);
         }
-        DefKind::AssocTy => {
-            if let Some(ImplTraitInTraitData::Trait { .. }) =
-                tcx.opt_rpitit_info(item_def_id.to_def_id())
-            {
-                return variance_of_opaque(tcx, item_def_id);
-            }
-        }
         _ => {}
     }
 
@@ -125,7 +118,8 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
                 // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) check whether this is necessary
                 // at all for RPITITs.
                 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
-                    if self.tcx.is_impl_trait_in_trait(*def_id) =>
+                    if self.tcx.is_impl_trait_in_trait(*def_id)
+                        && !self.tcx.lower_impl_trait_in_trait_to_assoc_ty() =>
                 {
                     self.visit_opaque(*def_id, substs)
                 }
diff --git a/compiler/rustc_hir_typeck/src/inherited.rs b/compiler/rustc_hir_typeck/src/inherited.rs
index 05e5db9f0f3a3..d5619af2aae17 100644
--- a/compiler/rustc_hir_typeck/src/inherited.rs
+++ b/compiler/rustc_hir_typeck/src/inherited.rs
@@ -80,7 +80,7 @@ impl<'tcx> Inherited<'tcx> {
         let infcx = tcx
             .infer_ctxt()
             .ignoring_regions()
-            .with_opaque_type_inference(DefiningAnchor::Bind(hir_owner.def_id))
+            .with_opaque_type_inference(DefiningAnchor::Bind(def_id))
             .build();
         let typeck_results = RefCell::new(ty::TypeckResults::new(hir_owner));
 
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 19f82fbd3bf73..42f4531c0efd3 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -394,8 +394,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut pat_ty = ty;
         if let hir::ExprKind::Lit(Spanned { node: ast::LitKind::ByteStr(..), .. }) = lt.kind {
             let expected = self.structurally_resolve_type(span, expected);
-            if let ty::Ref(_, inner_ty, _) = expected.kind()
-                && matches!(inner_ty.kind(), ty::Slice(_))
+            if let ty::Ref(_, inner_ty, _) = *expected.kind()
+                && self.try_structurally_resolve_type(span, inner_ty).is_slice()
             {
                 let tcx = self.tcx;
                 trace!(?lt.hir_id.local_id, "polymorphic byte string lit");
diff --git a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
index c9a8f8131dffb..63613b59020fb 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
@@ -257,7 +257,7 @@ impl<T> Trait<T> for X {
                             );
                         }
                     }
-                    (ty::Alias(ty::Opaque, alias), _) | (_, ty::Alias(ty::Opaque, alias)) if alias.def_id.is_local() && matches!(tcx.def_kind(body_owner_def_id), DefKind::AssocFn | DefKind::AssocConst) => {
+                    (ty::Alias(ty::Opaque, alias), _) | (_, ty::Alias(ty::Opaque, alias)) if alias.def_id.is_local() && matches!(tcx.def_kind(body_owner_def_id), DefKind::Fn | DefKind::Static(_) | DefKind::Const | DefKind::AssocFn | DefKind::AssocConst) => {
                         if tcx.is_type_alias_impl_trait(alias.def_id) {
                             if !tcx.opaque_types_defined_by(body_owner_def_id.expect_local()).contains(&alias.def_id.expect_local()) {
                                 let sp = tcx.def_ident_span(body_owner_def_id).unwrap_or_else(|| tcx.def_span(body_owner_def_id));
diff --git a/compiler/rustc_infer/src/infer/opaque_types.rs b/compiler/rustc_infer/src/infer/opaque_types.rs
index 3098b8bc2f9b2..5927f79a18333 100644
--- a/compiler/rustc_infer/src/infer/opaque_types.rs
+++ b/compiler/rustc_infer/src/infer/opaque_types.rs
@@ -473,17 +473,6 @@ where
                 }
             }
 
-            ty::Alias(ty::Projection, proj) if self.tcx.is_impl_trait_in_trait(proj.def_id) => {
-                // Skip lifetime parameters that are not captures.
-                let variances = self.tcx.variances_of(proj.def_id);
-
-                for (v, s) in std::iter::zip(variances, proj.substs.iter()) {
-                    if *v != ty::Variance::Bivariant {
-                        s.visit_with(self);
-                    }
-                }
-            }
-
             _ => {
                 ty.super_visit_with(self);
             }
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 953c2e4b8f86f..4e1668c8a8cf0 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -255,6 +255,7 @@ pub struct Config {
     pub input: Input,
     pub output_dir: Option<PathBuf>,
     pub output_file: Option<OutFileName>,
+    pub ice_file: Option<PathBuf>,
     pub file_loader: Option<Box<dyn FileLoader + Send + Sync>>,
     pub locale_resources: &'static [&'static str],
 
@@ -315,6 +316,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 config.lint_caps,
                 config.make_codegen_backend,
                 registry.clone(),
+                config.ice_file,
             );
 
             if let Some(parse_sess_created) = config.parse_sess_created {
@@ -346,7 +348,11 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
     )
 }
 
-pub fn try_print_query_stack(handler: &Handler, num_frames: Option<usize>) {
+pub fn try_print_query_stack(
+    handler: &Handler,
+    num_frames: Option<usize>,
+    file: Option<std::fs::File>,
+) {
     eprintln!("query stack during panic:");
 
     // Be careful relying on global state here: this code is called from
@@ -358,7 +364,8 @@ pub fn try_print_query_stack(handler: &Handler, num_frames: Option<usize>) {
                 QueryCtxt::new(icx.tcx),
                 icx.query,
                 handler,
-                num_frames
+                num_frames,
+                file,
             ))
         } else {
             0
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 09141afd13707..5c6c3491b388c 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -67,6 +67,7 @@ fn mk_session(handler: &mut EarlyErrorHandler, matches: getopts::Matches) -> (Se
         None,
         None,
         "",
+        None,
     );
     (sess, cfg)
 }
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 035ea2414f767..12d33f06309b7 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -70,6 +70,7 @@ pub fn create_session(
         Box<dyn FnOnce(&config::Options) -> Box<dyn CodegenBackend> + Send>,
     >,
     descriptions: Registry,
+    ice_file: Option<PathBuf>,
 ) -> (Session, Box<dyn CodegenBackend>) {
     let codegen_backend = if let Some(make_codegen_backend) = make_codegen_backend {
         make_codegen_backend(&sopts)
@@ -111,6 +112,7 @@ pub fn create_session(
         file_loader,
         target_override,
         rustc_version_str().unwrap_or("unknown"),
+        ice_file,
     );
 
     codegen_backend.init(&sess);
diff --git a/compiler/rustc_query_system/src/query/job.rs b/compiler/rustc_query_system/src/query/job.rs
index f45f7ca5da6dd..e964ba851bdf6 100644
--- a/compiler/rustc_query_system/src/query/job.rs
+++ b/compiler/rustc_query_system/src/query/job.rs
@@ -13,6 +13,7 @@ use rustc_session::Session;
 use rustc_span::Span;
 
 use std::hash::Hash;
+use std::io::Write;
 use std::num::NonZeroU64;
 
 #[cfg(parallel_compiler)]
@@ -617,30 +618,50 @@ pub fn print_query_stack<Qcx: QueryContext>(
     mut current_query: Option<QueryJobId>,
     handler: &Handler,
     num_frames: Option<usize>,
+    mut file: Option<std::fs::File>,
 ) -> usize {
     // Be careful relying on global state here: this code is called from
     // a panic hook, which means that the global `Handler` may be in a weird
     // state if it was responsible for triggering the panic.
-    let mut i = 0;
+    let mut count_printed = 0;
+    let mut count_total = 0;
     let query_map = qcx.try_collect_active_jobs();
 
+    if let Some(ref mut file) = file {
+        let _ = writeln!(file, "\n\nquery stack during panic:");
+    }
     while let Some(query) = current_query {
-        if Some(i) == num_frames {
-            break;
-        }
         let Some(query_info) = query_map.as_ref().and_then(|map| map.get(&query)) else {
             break;
         };
-        let mut diag = Diagnostic::new(
-            Level::FailureNote,
-            format!("#{} [{:?}] {}", i, query_info.query.dep_kind, query_info.query.description),
-        );
-        diag.span = query_info.job.span.into();
-        handler.force_print_diagnostic(diag);
+        if Some(count_printed) < num_frames || num_frames.is_none() {
+            // Only print to stderr as many stack frames as `num_frames` when present.
+            let mut diag = Diagnostic::new(
+                Level::FailureNote,
+                format!(
+                    "#{} [{:?}] {}",
+                    count_printed, query_info.query.dep_kind, query_info.query.description
+                ),
+            );
+            diag.span = query_info.job.span.into();
+            handler.force_print_diagnostic(diag);
+            count_printed += 1;
+        }
+
+        if let Some(ref mut file) = file {
+            let _ = writeln!(
+                file,
+                "#{} [{:?}] {}",
+                count_total, query_info.query.dep_kind, query_info.query.description
+            );
+        }
 
         current_query = query_info.job.parent;
-        i += 1;
+        count_total += 1;
     }
 
-    i
+    if let Some(ref mut file) = file {
+        let _ = writeln!(file, "end of query stack");
+    }
+    count_printed
 }
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index 194f7201ff357..0a0ec927209a3 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -229,6 +229,7 @@ impl ParseSess {
             Some(sm.clone()),
             None,
             fallback_bundle,
+            None,
         );
         ParseSess::with_span_handler(handler, sm)
     }
@@ -259,12 +260,20 @@ impl ParseSess {
     pub fn with_silent_emitter(fatal_note: Option<String>) -> Self {
         let fallback_bundle = fallback_fluent_bundle(Vec::new(), false);
         let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-        let fatal_handler =
-            Handler::with_tty_emitter(ColorConfig::Auto, false, None, None, None, fallback_bundle);
+        let fatal_handler = Handler::with_tty_emitter(
+            ColorConfig::Auto,
+            false,
+            None,
+            None,
+            None,
+            fallback_bundle,
+            None,
+        );
         let handler = Handler::with_emitter(
             false,
             None,
             Box::new(SilentEmitter { fatal_handler, fatal_note }),
+            None,
         );
         ParseSess::with_span_handler(handler, sm)
     }
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 5be122ffbdeb0..7922394081e31 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -1392,6 +1392,7 @@ pub fn build_session(
     file_loader: Option<Box<dyn FileLoader + Send + Sync + 'static>>,
     target_override: Option<Target>,
     cfg_version: &'static str,
+    ice_file: Option<PathBuf>,
 ) -> Session {
     // FIXME: This is not general enough to make the warning lint completely override
     // normal diagnostic warnings, since the warning lint can also be denied and changed
@@ -1440,6 +1441,7 @@ pub fn build_session(
     let span_diagnostic = rustc_errors::Handler::with_emitter_and_flags(
         emitter,
         sopts.unstable_opts.diagnostic_handler_flags(can_emit_warnings),
+        ice_file,
     );
 
     let self_profiler = if let SwitchWithOptPath::Enabled(ref d) = sopts.unstable_opts.self_profile
@@ -1731,7 +1733,7 @@ pub struct EarlyErrorHandler {
 impl EarlyErrorHandler {
     pub fn new(output: ErrorOutputType) -> Self {
         let emitter = mk_emitter(output);
-        Self { handler: rustc_errors::Handler::with_emitter(true, None, emitter) }
+        Self { handler: rustc_errors::Handler::with_emitter(true, None, emitter, None) }
     }
 
     pub fn abort_if_errors(&self) {
@@ -1745,7 +1747,7 @@ impl EarlyErrorHandler {
         self.handler.abort_if_errors();
 
         let emitter = mk_emitter(output);
-        self.handler = Handler::with_emitter(true, None, emitter);
+        self.handler = Handler::with_emitter(true, None, emitter, None);
     }
 
     #[allow(rustc::untranslatable_diagnostic)]
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index e2ee347b639a1..1af8323b6e993 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -11,7 +11,7 @@ mod fulfill;
 pub mod misc;
 mod object_safety;
 pub mod outlives_bounds;
-mod project;
+pub mod project;
 pub mod query;
 #[cfg_attr(not(bootstrap), allow(hidden_glob_reexports))]
 mod select;
diff --git a/compiler/rustc_ty_utils/src/opaque_types.rs b/compiler/rustc_ty_utils/src/opaque_types.rs
index 29de8bf0e53f5..570c3b245cd41 100644
--- a/compiler/rustc_ty_utils/src/opaque_types.rs
+++ b/compiler/rustc_ty_utils/src/opaque_types.rs
@@ -1,5 +1,7 @@
 use rustc_data_structures::fx::FxHashSet;
+use rustc_hir::intravisit::Visitor;
 use rustc_hir::{def::DefKind, def_id::LocalDefId};
+use rustc_hir::{intravisit, CRATE_HIR_ID};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{CheckRegions, NotUniqueParam};
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -51,7 +53,7 @@ impl<'tcx> OpaqueTypeCollector<'tcx> {
 
     fn parent(&self) -> Option<LocalDefId> {
         match self.tcx.def_kind(self.item) {
-            DefKind::Fn => None,
+            DefKind::AnonConst | DefKind::InlineConst | DefKind::Fn | DefKind::TyAlias => None,
             DefKind::AssocFn | DefKind::AssocTy | DefKind::AssocConst => {
                 Some(self.tcx.local_parent(self.item))
             }
@@ -61,6 +63,73 @@ impl<'tcx> OpaqueTypeCollector<'tcx> {
             ),
         }
     }
+
+    /// Returns `true` if `opaque_hir_id` is a sibling or a child of a sibling of `self.item`.
+    ///
+    /// Example:
+    /// ```ignore UNSOLVED (is this a bug?)
+    /// # #![feature(type_alias_impl_trait)]
+    /// pub mod foo {
+    ///     pub mod bar {
+    ///         pub trait Bar { /* ... */ }
+    ///         pub type Baz = impl Bar;
+    ///
+    ///         # impl Bar for () {}
+    ///         fn f1() -> Baz { /* ... */ }
+    ///     }
+    ///     fn f2() -> bar::Baz { /* ... */ }
+    /// }
+    /// ```
+    ///
+    /// and `opaque_def_id` is the `DefId` of the definition of the opaque type `Baz`.
+    /// For the above example, this function returns `true` for `f1` and `false` for `f2`.
+    #[instrument(level = "trace", skip(self), ret)]
+    fn check_tait_defining_scope(&self, opaque_def_id: LocalDefId) -> bool {
+        let mut hir_id = self.tcx.hir().local_def_id_to_hir_id(self.item);
+        let opaque_hir_id = self.tcx.hir().local_def_id_to_hir_id(opaque_def_id);
+
+        // Named opaque types can be defined by any siblings or children of siblings.
+        let scope = self.tcx.hir().get_defining_scope(opaque_hir_id);
+        // We walk up the node tree until we hit the root or the scope of the opaque type.
+        while hir_id != scope && hir_id != CRATE_HIR_ID {
+            hir_id = self.tcx.hir().get_parent_item(hir_id).into();
+        }
+        // Syntactically, we are allowed to define the concrete type if:
+        hir_id == scope
+    }
+
+    fn collect_body_and_predicate_taits(&mut self) {
+        // Look at all where bounds.
+        self.tcx.predicates_of(self.item).instantiate_identity(self.tcx).visit_with(self);
+        // An item is allowed to constrain opaques declared within its own body (but not nested within
+        // nested functions).
+        self.collect_taits_declared_in_body();
+    }
+
+    #[instrument(level = "trace", skip(self))]
+    fn collect_taits_declared_in_body(&mut self) {
+        let body = self.tcx.hir().body(self.tcx.hir().body_owned_by(self.item)).value;
+        struct TaitInBodyFinder<'a, 'tcx> {
+            collector: &'a mut OpaqueTypeCollector<'tcx>,
+        }
+        impl<'v> intravisit::Visitor<'v> for TaitInBodyFinder<'_, '_> {
+            #[instrument(level = "trace", skip(self))]
+            fn visit_nested_item(&mut self, id: rustc_hir::ItemId) {
+                let id = id.owner_id.def_id;
+                if let DefKind::TyAlias = self.collector.tcx.def_kind(id) {
+                    let items = self.collector.tcx.opaque_types_defined_by(id);
+                    self.collector.opaques.extend(items);
+                }
+            }
+            #[instrument(level = "trace", skip(self))]
+            // Recurse into these, as they are type checked with their parent
+            fn visit_nested_body(&mut self, id: rustc_hir::BodyId) {
+                let body = self.collector.tcx.hir().body(id);
+                self.visit_body(body);
+            }
+        }
+        TaitInBodyFinder { collector: self }.visit_expr(body);
+    }
 }
 
 impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
@@ -73,6 +142,21 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
                     return ControlFlow::Continue(());
                 }
 
+                // TAITs outside their defining scopes are ignored.
+                let origin = self.tcx.opaque_type_origin(alias_ty.def_id.expect_local());
+                trace!(?origin);
+                match origin {
+                    rustc_hir::OpaqueTyOrigin::FnReturn(_)
+                    | rustc_hir::OpaqueTyOrigin::AsyncFn(_) => {}
+                    rustc_hir::OpaqueTyOrigin::TyAlias { in_assoc_ty } => {
+                        if !in_assoc_ty {
+                            if !self.check_tait_defining_scope(alias_ty.def_id.expect_local()) {
+                                return ControlFlow::Continue(());
+                            }
+                        }
+                    }
+                }
+
                 self.opaques.push(alias_ty.def_id.expect_local());
 
                 match self.tcx.uses_unique_generic_params(alias_ty.substs, CheckRegions::Bound) {
@@ -188,33 +272,36 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
 fn opaque_types_defined_by<'tcx>(tcx: TyCtxt<'tcx>, item: LocalDefId) -> &'tcx [LocalDefId] {
     let kind = tcx.def_kind(item);
     trace!(?kind);
-    // FIXME(type_alias_impl_trait): This is definitely still wrong except for RPIT and impl trait in assoc types.
+    let mut collector = OpaqueTypeCollector::new(tcx, item);
     match kind {
+        // Walk over the signature of the function-like to find the opaques.
+        DefKind::AssocFn | DefKind::Fn => {
+            let ty_sig = tcx.fn_sig(item).subst_identity();
+            let hir_sig = tcx.hir().get_by_def_id(item).fn_sig().unwrap();
+            // Walk over the inputs and outputs manually in order to get good spans for them.
+            collector.visit_spanned(hir_sig.decl.output.span(), ty_sig.output());
+            for (hir, ty) in hir_sig.decl.inputs.iter().zip(ty_sig.inputs().iter()) {
+                collector.visit_spanned(hir.span, ty.map_bound(|x| *x));
+            }
+            collector.collect_body_and_predicate_taits();
+        }
+        // Walk over the type of the item to find opaques.
+        DefKind::Static(_) | DefKind::Const | DefKind::AssocConst | DefKind::AnonConst => {
+            let span = match tcx.hir().get_by_def_id(item).ty() {
+                Some(ty) => ty.span,
+                _ => tcx.def_span(item),
+            };
+            collector.visit_spanned(span, tcx.type_of(item).subst_identity());
+            collector.collect_body_and_predicate_taits();
+        }
         // We're also doing this for `AssocTy` for the wf checks in `check_opaque_meets_bounds`
-        DefKind::Fn | DefKind::AssocFn | DefKind::AssocTy | DefKind::AssocConst => {
-            let mut collector = OpaqueTypeCollector::new(tcx, item);
-            match kind {
-                // Walk over the signature of the function-like to find the opaques.
-                DefKind::AssocFn | DefKind::Fn => {
-                    let ty_sig = tcx.fn_sig(item).subst_identity();
-                    let hir_sig = tcx.hir().get_by_def_id(item).fn_sig().unwrap();
-                    // Walk over the inputs and outputs manually in order to get good spans for them.
-                    collector.visit_spanned(hir_sig.decl.output.span(), ty_sig.output());
-                    for (hir, ty) in hir_sig.decl.inputs.iter().zip(ty_sig.inputs().iter()) {
-                        collector.visit_spanned(hir.span, ty.map_bound(|x| *x));
-                    }
-                }
-                // Walk over the type of the item to find opaques.
-                DefKind::AssocTy | DefKind::AssocConst => {
-                    let span = match tcx.hir().get_by_def_id(item).ty() {
-                        Some(ty) => ty.span,
-                        _ => tcx.def_span(item),
-                    };
-                    collector.visit_spanned(span, tcx.type_of(item).subst_identity());
-                }
-                _ => unreachable!(),
+        DefKind::TyAlias | DefKind::AssocTy => {
+            tcx.type_of(item).subst_identity().visit_with(&mut collector);
+        }
+        DefKind::OpaqueTy => {
+            for (pred, span) in tcx.explicit_item_bounds(item).subst_identity_iter_copied() {
+                collector.visit_spanned(span, pred);
             }
-            tcx.arena.alloc_from_iter(collector.opaques)
         }
         DefKind::Mod
         | DefKind::Struct
@@ -222,31 +309,26 @@ fn opaque_types_defined_by<'tcx>(tcx: TyCtxt<'tcx>, item: LocalDefId) -> &'tcx [
         | DefKind::Enum
         | DefKind::Variant
         | DefKind::Trait
-        | DefKind::TyAlias
         | DefKind::ForeignTy
         | DefKind::TraitAlias
         | DefKind::TyParam
-        | DefKind::Const
         | DefKind::ConstParam
-        | DefKind::Static(_)
         | DefKind::Ctor(_, _)
         | DefKind::Macro(_)
         | DefKind::ExternCrate
         | DefKind::Use
         | DefKind::ForeignMod
-        | DefKind::AnonConst
-        | DefKind::InlineConst
-        | DefKind::OpaqueTy
         | DefKind::ImplTraitPlaceholder
         | DefKind::Field
         | DefKind::LifetimeParam
         | DefKind::GlobalAsm
-        | DefKind::Impl { .. }
-        | DefKind::Closure
-        | DefKind::Generator => {
-            span_bug!(tcx.def_span(item), "{kind:?} is type checked as part of its parent")
+        | DefKind::Impl { .. } => {}
+        // Closures and generators are type checked with their parent, so there is no difference here.
+        DefKind::Closure | DefKind::Generator | DefKind::InlineConst => {
+            return tcx.opaque_types_defined_by(tcx.local_parent(item));
         }
     }
+    tcx.arena.alloc_from_iter(collector.opaques)
 }
 
 pub(super) fn provide(providers: &mut Providers) {
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 72b9ad3480b32..0c91841fd81e2 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -605,6 +605,9 @@ pub mod alloc;
 mod panicking;
 mod personality;
 
+#[unstable(feature = "ice_to_disk", issue = "none")]
+pub use panicking::panic_hook_with_disk_dump;
+
 #[path = "../../backtrace/src/lib.rs"]
 #[allow(dead_code, unused_attributes, fuzzy_provenance_casts)]
 mod backtrace_rs;
diff --git a/library/std/src/panicking.rs b/library/std/src/panicking.rs
index a6a370409c0e2..0e90d618ad434 100644
--- a/library/std/src/panicking.rs
+++ b/library/std/src/panicking.rs
@@ -234,7 +234,16 @@ where
     *hook = Hook::Custom(Box::new(move |info| hook_fn(&prev, info)));
 }
 
+/// The default panic handler.
 fn default_hook(info: &PanicInfo<'_>) {
+    panic_hook_with_disk_dump(info, None)
+}
+
+#[unstable(feature = "ice_to_disk", issue = "none")]
+/// The implementation of the default panic handler.
+///
+/// It can also write the backtrace to a given `path`. This functionality is used only by `rustc`.
+pub fn panic_hook_with_disk_dump(info: &PanicInfo<'_>, path: Option<&crate::path::Path>) {
     // If this is a double panic, make sure that we print a backtrace
     // for this panic. Otherwise only print it if logging is enabled.
     let backtrace = if panic_count::get_count() >= 2 {
@@ -256,7 +265,7 @@ fn default_hook(info: &PanicInfo<'_>) {
     let thread = thread_info::current_thread();
     let name = thread.as_ref().and_then(|t| t.name()).unwrap_or("<unnamed>");
 
-    let write = |err: &mut dyn crate::io::Write| {
+    let write = |err: &mut dyn crate::io::Write, backtrace: Option<BacktraceStyle>| {
         let _ = writeln!(err, "thread '{name}' panicked at '{msg}', {location}");
 
         static FIRST_PANIC: AtomicBool = AtomicBool::new(true);
@@ -270,10 +279,19 @@ fn default_hook(info: &PanicInfo<'_>) {
             }
             Some(BacktraceStyle::Off) => {
                 if FIRST_PANIC.swap(false, Ordering::SeqCst) {
-                    let _ = writeln!(
-                        err,
-                        "note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace"
-                    );
+                    if let Some(path) = path {
+                        let _ = writeln!(
+                            err,
+                            "note: a backtrace for this error was stored at `{}`",
+                            path.display(),
+                        );
+                    } else {
+                        let _ = writeln!(
+                            err,
+                            "note: run with `RUST_BACKTRACE=1` environment variable to display a \
+                             backtrace"
+                        );
+                    }
                 }
             }
             // If backtraces aren't supported, do nothing.
@@ -281,11 +299,17 @@ fn default_hook(info: &PanicInfo<'_>) {
         }
     };
 
+    if let Some(path) = path
+        && let Ok(mut out) = crate::fs::File::options().create(true).write(true).open(&path)
+    {
+        write(&mut out, BacktraceStyle::full());
+    }
+
     if let Some(local) = set_output_capture(None) {
-        write(&mut *local.lock().unwrap_or_else(|e| e.into_inner()));
+        write(&mut *local.lock().unwrap_or_else(|e| e.into_inner()), backtrace);
         set_output_capture(Some(local));
     } else if let Some(mut out) = panic_output() {
-        write(&mut out);
+        write(&mut out, backtrace);
     }
 }
 
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 0182d50773d77..f663b58c7380e 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1479,8 +1479,97 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
     Item::from_def_id_and_parts(assoc_item.def_id, Some(assoc_item.name), kind, cx)
 }
 
+/// The goal of this function is to return the first `Path` which is not private (ie not private
+/// or `doc(hidden)`). If it's not possible, it'll return the "end type".
+///
+/// If the path is not a re-export or is public, it'll return `None`.
+fn first_non_private(
+    cx: &mut DocContext<'_>,
+    hir_id: hir::HirId,
+    path: &hir::Path<'_>,
+) -> Option<Path> {
+    let (parent_def_id, mut ident) = match &path.segments[..] {
+        [] => return None,
+        // Relative paths are available in the same scope as the owner.
+        [leaf] => (cx.tcx.local_parent(hir_id.owner.def_id), leaf.ident),
+        // So are self paths.
+        [parent, leaf] if parent.ident.name == kw::SelfLower => {
+            (cx.tcx.local_parent(hir_id.owner.def_id), leaf.ident)
+        }
+        // Crate paths are not. We start from the crate root.
+        [parent, leaf] if matches!(parent.ident.name, kw::Crate | kw::PathRoot) => {
+            (LOCAL_CRATE.as_def_id().as_local()?, leaf.ident)
+        }
+        [parent, leaf] if parent.ident.name == kw::Super => {
+            let parent_mod = cx.tcx.parent_module(hir_id);
+            if let Some(super_parent) = cx.tcx.opt_local_parent(parent_mod) {
+                (super_parent, leaf.ident)
+            } else {
+                // If we can't find the parent of the parent, then the parent is already the crate.
+                (LOCAL_CRATE.as_def_id().as_local()?, leaf.ident)
+            }
+        }
+        // Absolute paths are not. We start from the parent of the item.
+        [.., parent, leaf] => (parent.res.opt_def_id()?.as_local()?, leaf.ident),
+    };
+    let target_def_id = path.res.opt_def_id()?;
+    // First we try to get the `DefId` of the item.
+    for child in
+        cx.tcx.module_children_local(parent_def_id).iter().filter(move |c| c.ident == ident)
+    {
+        if let Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) = child.res {
+            continue;
+        }
+
+        if let Some(def_id) = child.res.opt_def_id() && target_def_id == def_id {
+            let mut last_path_res = None;
+            'reexps: for reexp in child.reexport_chain.iter() {
+                if let Some(use_def_id) = reexp.id() &&
+                    let Some(local_use_def_id) = use_def_id.as_local()
+                {
+                    let hir = cx.tcx.hir();
+                    for item_id in hir.module_items(cx.tcx.local_parent(local_use_def_id)) {
+                        let item = hir.item(item_id);
+                        if item.ident == ident && let hir::ItemKind::Use(path, _) = item.kind {
+                            for res in &path.res {
+                                if let Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) = res {
+                                    continue;
+                                }
+                                if !cx.tcx.is_doc_hidden(use_def_id) &&
+                                    cx.tcx.local_visibility(local_use_def_id).is_public() {
+                                    break 'reexps;
+                                }
+                                ident = path.segments.last().unwrap().ident;
+                                last_path_res = Some((path, res));
+                                continue 'reexps;
+                            }
+                        }
+                    }
+                }
+            }
+            if !child.reexport_chain.is_empty() {
+                // So in here, we use the data we gathered from iterating the reexports. If
+                // `last_path_res` is set, it can mean two things:
+                //
+                // 1. We found a public reexport.
+                // 2. We didn't find a public reexport so it's the "end type" path.
+                if let Some((path, res)) = last_path_res {
+                    let path = hir::Path { segments: path.segments, res: *res, span: path.span };
+                    return Some(clean_path(&path, cx));
+                }
+                // If `last_path_res` is `None`, it can mean two things:
+                //
+                // 1. The re-export is public, no need to change anything, just use the path as is.
+                // 2. Nothing was found, so let's just return the original path.
+                return None;
+            }
+        }
+    }
+    None
+}
+
 fn clean_qpath<'tcx>(hir_ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type {
-    let hir::Ty { hir_id: _, span, ref kind } = *hir_ty;
+    let hir::Ty { hir_id, span, ref kind } = *hir_ty;
     let hir::TyKind::Path(qpath) = kind else { unreachable!() };
 
     match qpath {
@@ -1497,7 +1586,12 @@ fn clean_qpath<'tcx>(hir_ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type
             if let Some(expanded) = maybe_expand_private_type_alias(cx, path) {
                 expanded
             } else {
-                let path = clean_path(path, cx);
+                // First we check if it's a private re-export.
+                let path = if let Some(path) = first_non_private(cx, hir_id, &path) {
+                    path
+                } else {
+                    clean_path(path, cx)
+                };
                 resolve_type(cx, path)
             }
         }
@@ -1649,7 +1743,7 @@ fn maybe_expand_private_type_alias<'tcx>(
         }
     }
 
-    Some(cx.enter_alias(substs, def_id.to_def_id(), |cx| clean_ty(ty, cx)))
+    Some(cx.enter_alias(substs, def_id.to_def_id(), |cx| clean_ty(&ty, cx)))
 }
 
 pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type {
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 9687b8b18878e..bf4ac4b4f3bb2 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -176,6 +176,7 @@ pub(crate) fn new_handler(
     rustc_errors::Handler::with_emitter_and_flags(
         emitter,
         unstable_opts.diagnostic_handler_flags(true),
+        None,
     )
 }
 
@@ -296,6 +297,7 @@ pub(crate) fn create_config(
         }),
         make_codegen_backend: None,
         registry: rustc_driver::diagnostics_registry(),
+        ice_file: None,
     }
 }
 
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 217257316c84f..ab3807a609a9a 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -108,6 +108,7 @@ pub(crate) fn run(options: RustdocOptions) -> Result<(), ErrorGuaranteed> {
         override_queries: None,
         make_codegen_backend: None,
         registry: rustc_driver::diagnostics_registry(),
+        ice_file: None,
     };
 
     let test_args = options.test_args.clone();
@@ -586,7 +587,7 @@ pub(crate) fn make_test(
             );
 
             // FIXME(misdreavus): pass `-Z treat-err-as-bug` to the doctest parser
-            let handler = Handler::with_emitter(false, None, Box::new(emitter));
+            let handler = Handler::with_emitter(false, None, Box::new(emitter), None);
             let sess = ParseSess::with_span_handler(handler, sm);
 
             let mut found_main = false;
@@ -774,7 +775,7 @@ fn check_if_attr_is_complete(source: &str, edition: Edition) -> bool {
                 TerminalUrl::No,
             );
 
-            let handler = Handler::with_emitter(false, None, Box::new(emitter));
+            let handler = Handler::with_emitter(false, None, Box::new(emitter), None);
             let sess = ParseSess::with_span_handler(handler, sm);
             let mut parser =
                 match maybe_new_parser_from_source_str(&sess, filename, source.to_owned()) {
diff --git a/src/librustdoc/passes/lint/check_code_block_syntax.rs b/src/librustdoc/passes/lint/check_code_block_syntax.rs
index f489f5081daa2..544cc07f27ad8 100644
--- a/src/librustdoc/passes/lint/check_code_block_syntax.rs
+++ b/src/librustdoc/passes/lint/check_code_block_syntax.rs
@@ -40,7 +40,7 @@ fn check_rust_syntax(
     let emitter = BufferEmitter { buffer: Lrc::clone(&buffer), fallback_bundle };
 
     let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-    let handler = Handler::with_emitter(false, None, Box::new(emitter));
+    let handler = Handler::with_emitter(false, None, Box::new(emitter), None);
     let source = dox[code_block.code].to_owned();
     let sess = ParseSess::with_span_handler(handler, sm);
 
diff --git a/src/tools/clippy/clippy_lints/src/doc.rs b/src/tools/clippy/clippy_lints/src/doc.rs
index 87d88f707529c..7599c37b8d8ce 100644
--- a/src/tools/clippy/clippy_lints/src/doc.rs
+++ b/src/tools/clippy/clippy_lints/src/doc.rs
@@ -724,7 +724,7 @@ fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
                     false,
                     TerminalUrl::No,
                 );
-                let handler = Handler::with_emitter(false, None, Box::new(emitter));
+                let handler = Handler::with_emitter(false, None, Box::new(emitter), None);
                 let sess = ParseSess::with_span_handler(handler, sm);
 
                 let mut parser = match maybe_new_parser_from_source_str(&sess, filename, code) {
diff --git a/src/tools/miri/tests/fail/overlapping_assignment.rs b/src/tools/miri/tests/fail/overlapping_assignment.rs
new file mode 100644
index 0000000000000..84994c179f9ea
--- /dev/null
+++ b/src/tools/miri/tests/fail/overlapping_assignment.rs
@@ -0,0 +1,23 @@
+#![feature(core_intrinsics)]
+#![feature(custom_mir)]
+
+use std::intrinsics::mir::*;
+
+// It's not that easy to fool the MIR validity check
+// which wants to prevent overlapping assignments...
+// So we use two separate pointer arguments, and then arrange for them to alias.
+#[custom_mir(dialect = "runtime", phase = "optimized")]
+pub fn self_copy(ptr1: *mut [i32; 4], ptr2: *mut [i32; 4]) {
+    mir! {
+        {
+            *ptr1 = *ptr2; //~ERROR: overlapping ranges
+            Return()
+        }
+    }
+}
+
+pub fn main() {
+    let mut x = [0; 4];
+    let ptr = std::ptr::addr_of_mut!(x);
+    self_copy(ptr, ptr);
+}
diff --git a/src/tools/miri/tests/fail/overlapping_assignment.stderr b/src/tools/miri/tests/fail/overlapping_assignment.stderr
new file mode 100644
index 0000000000000..42a000dfcc6c7
--- /dev/null
+++ b/src/tools/miri/tests/fail/overlapping_assignment.stderr
@@ -0,0 +1,20 @@
+error: Undefined Behavior: `copy_nonoverlapping` called on overlapping ranges
+  --> $DIR/overlapping_assignment.rs:LL:CC
+   |
+LL |             *ptr1 = *ptr2;
+   |             ^^^^^^^^^^^^^ `copy_nonoverlapping` called on overlapping ranges
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE:
+   = note: inside `self_copy` at $DIR/overlapping_assignment.rs:LL:CC
+note: inside `main`
+  --> $DIR/overlapping_assignment.rs:LL:CC
+   |
+LL |     self_copy(ptr, ptr);
+   |     ^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+
diff --git a/src/tools/rustfmt/src/parse/session.rs b/src/tools/rustfmt/src/parse/session.rs
index 81b5015dde33d..92d2425cd3b92 100644
--- a/src/tools/rustfmt/src/parse/session.rs
+++ b/src/tools/rustfmt/src/parse/session.rs
@@ -162,6 +162,7 @@ fn default_handler(
             ignore_path_set,
             can_reset,
         }),
+        None,
     )
 }
 
@@ -233,7 +234,7 @@ impl ParseSess {
     }
 
     pub(crate) fn set_silent_emitter(&mut self) {
-        self.parse_sess.span_diagnostic = Handler::with_emitter(true, None, silent_emitter());
+        self.parse_sess.span_diagnostic = Handler::with_emitter(true, None, silent_emitter(), None);
     }
 
     pub(crate) fn span_to_filename(&self, span: Span) -> FileName {
diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index ecc84c1618c0f..8a448c7ef6fce 100644
--- a/src/tools/tidy/src/deps.rs
+++ b/src/tools/tidy/src/deps.rs
@@ -246,6 +246,9 @@ const PERMITTED_RUSTC_DEPENDENCIES: &[&str] = &[
     "thiserror-impl",
     "thorin-dwp",
     "thread_local",
+    "time",
+    "time-core",
+    "time-macros",
     "tinystr",
     "tinyvec",
     "tinyvec_macros",
diff --git a/tests/run-make-fulldeps/issue-19371/foo.rs b/tests/run-make-fulldeps/issue-19371/foo.rs
index 9cca6200050bd..42a94b519cb9e 100644
--- a/tests/run-make-fulldeps/issue-19371/foo.rs
+++ b/tests/run-make-fulldeps/issue-19371/foo.rs
@@ -52,6 +52,7 @@ fn compile(code: String, output: PathBuf, sysroot: PathBuf) {
         input,
         output_file: Some(OutFileName::Real(output)),
         output_dir: None,
+        ice_file: None,
         file_loader: None,
         locale_resources: &[],
         lint_caps: Default::default(),
diff --git a/tests/run-make/dump-ice-to-disk/Makefile b/tests/run-make/dump-ice-to-disk/Makefile
new file mode 100644
index 0000000000000..4f33d590237b3
--- /dev/null
+++ b/tests/run-make/dump-ice-to-disk/Makefile
@@ -0,0 +1,9 @@
+include ../tools.mk
+
+# ignore-windows
+
+export RUSTC := $(RUSTC_ORIGINAL)
+export TMPDIR := $(TMPDIR)
+
+all:
+	bash check.sh
diff --git a/tests/run-make/dump-ice-to-disk/check.sh b/tests/run-make/dump-ice-to-disk/check.sh
new file mode 100644
index 0000000000000..91109596a451f
--- /dev/null
+++ b/tests/run-make/dump-ice-to-disk/check.sh
@@ -0,0 +1,58 @@
+#!/bin/sh
+
+# Default nightly behavior (write ICE to current directory)
+# FIXME(estebank): these are failing on CI, but passing locally.
+# $RUSTC src/lib.rs -Z treat-err-as-bug=1 1>$TMPDIR/rust-test-default.log 2>&1
+# default=$(cat ./rustc-ice-*.txt | wc -l)
+# rm ./rustc-ice-*.txt
+
+# Explicit directory set
+export RUSTC_ICE=$TMPDIR
+$RUSTC src/lib.rs -Z treat-err-as-bug=1 1>$TMPDIR/rust-test-default-set.log 2>&1
+default_set=$(cat $TMPDIR/rustc-ice-*.txt | wc -l)
+content=$(cat $TMPDIR/rustc-ice-*.txt)
+rm $TMPDIR/rustc-ice-*.txt
+RUST_BACKTRACE=short $RUSTC src/lib.rs -Z treat-err-as-bug=1 1>$TMPDIR/rust-test-short.log 2>&1
+short=$(cat $TMPDIR/rustc-ice-*.txt | wc -l)
+rm $TMPDIR/rustc-ice-*.txt
+RUST_BACKTRACE=full $RUSTC src/lib.rs -Z treat-err-as-bug=1 1>$TMPDIR/rust-test-full.log 2>&1
+full=$(cat $TMPDIR/rustc-ice-*.txt | wc -l)
+rm $TMPDIR/rustc-ice-*.txt
+
+# Explicitly disabling ICE dump
+export RUSTC_ICE=0
+$RUSTC src/lib.rs -Z treat-err-as-bug=1 1>$TMPDIR/rust-test-disabled.log 2>&1
+should_be_empty_tmp=$(ls -l $TMPDIR/rustc-ice-*.txt | wc -l)
+should_be_empty_dot=$(ls -l ./rustc-ice-*.txt | wc -l)
+
+echo "#### ICE Dump content:"
+echo $content
+echo "#### default length:"
+echo $default
+echo "#### short length:"
+echo $short
+echo "#### default_set length:"
+echo $default_set
+echo "#### full length:"
+echo $full
+echo "#### should_be_empty_dot length:"
+echo $should_be_empty_dot
+echo "#### should_be_empty_tmp length:"
+echo $should_be_empty_tmp
+
+## Verify that a the ICE dump file is created in the appropriate directories, that
+## their lengths are the same regardless of other backtrace configuration options,
+## that the file is not created when asked to (RUSTC_ICE=0) and that the file
+## contains at least part of the expected content.
+if [ $short -eq $default_set ] &&
+    #[ $default -eq $short ] &&
+    [ $default_set -eq $full ] &&
+    [[ $content == *"thread 'rustc' panicked at "* ]] &&
+    [[ $content == *"stack backtrace:"* ]] &&
+    #[ $default -gt 0 ] &&
+    [ $should_be_empty_dot -eq 0 ] &&
+    [ $should_be_empty_tmp -eq 0 ]; then
+    exit 0
+else
+    exit 1
+fi
diff --git a/tests/run-make/dump-ice-to-disk/src/lib.rs b/tests/run-make/dump-ice-to-disk/src/lib.rs
new file mode 100644
index 0000000000000..b23b7f830d739
--- /dev/null
+++ b/tests/run-make/dump-ice-to-disk/src/lib.rs
@@ -0,0 +1,7 @@
+fn func(s: &str) {
+    println!("{}", s);
+}
+
+fn main() {
+    func(1);
+}
diff --git a/tests/run-make/exit-code/Makefile b/tests/run-make/exit-code/Makefile
index 6458b71688fff..155e5cd112344 100644
--- a/tests/run-make/exit-code/Makefile
+++ b/tests/run-make/exit-code/Makefile
@@ -5,7 +5,7 @@ all:
 	$(RUSTC) success.rs; [ $$? -eq 0 ]
 	$(RUSTC) --invalid-arg-foo; [ $$? -eq 1 ]
 	$(RUSTC) compile-error.rs; [ $$? -eq 1 ]
-	$(RUSTC) -Ztreat-err-as-bug compile-error.rs; [ $$? -eq 101 ]
+	RUSTC_ICE=0 $(RUSTC) -Ztreat-err-as-bug compile-error.rs; [ $$? -eq 101 ]
 	$(RUSTDOC) -o $(TMPDIR)/exit-code success.rs; [ $$? -eq 0 ]
 	$(RUSTDOC) --invalid-arg-foo; [ $$? -eq 1 ]
 	$(RUSTDOC) compile-error.rs; [ $$? -eq 1 ]
diff --git a/tests/run-make/short-ice/check.sh b/tests/run-make/short-ice/check.sh
index 96cd8fe86bc30..435bce04e8e34 100644
--- a/tests/run-make/short-ice/check.sh
+++ b/tests/run-make/short-ice/check.sh
@@ -1,5 +1,5 @@
 #!/bin/sh
-
+export RUSTC_ICE=0
 RUST_BACKTRACE=1 $RUSTC src/lib.rs -Z treat-err-as-bug=1 1>$TMPDIR/rust-test-1.log 2>&1
 RUST_BACKTRACE=full $RUSTC src/lib.rs -Z treat-err-as-bug=1 1>$TMPDIR/rust-test-2.log 2>&1
 
diff --git a/tests/rustdoc-ui/ice-bug-report-url.rs b/tests/rustdoc-ui/ice-bug-report-url.rs
index 8ede91cf8f4f4..7689d78d31f33 100644
--- a/tests/rustdoc-ui/ice-bug-report-url.rs
+++ b/tests/rustdoc-ui/ice-bug-report-url.rs
@@ -1,4 +1,5 @@
 // compile-flags: -Ztreat-err-as-bug
+// rustc-env:RUSTC_ICE=0
 // failure-status: 101
 // error-pattern: aborting due to
 // error-pattern: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-rustdoc&template=ice.md
diff --git a/tests/rustdoc-ui/ice-bug-report-url.stderr b/tests/rustdoc-ui/ice-bug-report-url.stderr
index 98c08b9a8944b..7d9f05f8f4ed0 100644
--- a/tests/rustdoc-ui/ice-bug-report-url.stderr
+++ b/tests/rustdoc-ui/ice-bug-report-url.stderr
@@ -1,5 +1,5 @@
 error: expected one of `->`, `where`, or `{`, found `<eof>`
-  --> $DIR/ice-bug-report-url.rs:13:10
+  --> $DIR/ice-bug-report-url.rs:14:10
    |
 LL | fn wrong()
    |          ^ expected one of `->`, `where`, or `{`
diff --git a/tests/rustdoc/issue-81141-private-reexport-in-public-api-2.rs b/tests/rustdoc/issue-81141-private-reexport-in-public-api-2.rs
new file mode 100644
index 0000000000000..4e9d188bbf8d1
--- /dev/null
+++ b/tests/rustdoc/issue-81141-private-reexport-in-public-api-2.rs
@@ -0,0 +1,13 @@
+// edition:2015
+
+#![crate_name = "foo"]
+
+use external::Public as Private;
+
+pub mod external {
+    pub struct Public;
+
+    // @has 'foo/external/fn.make.html'
+    // @has - '//*[@class="rust item-decl"]/code' 'pub fn make() -> Public'
+    pub fn make() -> ::Private { super::Private }
+}
diff --git a/tests/rustdoc/issue-81141-private-reexport-in-public-api.rs b/tests/rustdoc/issue-81141-private-reexport-in-public-api.rs
new file mode 100644
index 0000000000000..bd54d02c6ec8f
--- /dev/null
+++ b/tests/rustdoc/issue-81141-private-reexport-in-public-api.rs
@@ -0,0 +1,124 @@
+// This test ensures that if a private re-export is present in a public API, it'll be
+// replaced by the first public item in the re-export chain or by the private item.
+
+#![crate_name = "foo"]
+
+use crate::bar::Bar as Alias;
+
+pub use crate::bar::Bar as Whatever;
+use crate::Whatever as Whatever2;
+use crate::Whatever2 as Whatever3;
+pub use crate::bar::Inner as Whatever4;
+
+mod bar {
+    pub struct Bar;
+    pub use self::Bar as Inner;
+}
+
+// @has 'foo/fn.bar.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar() -> Bar'
+pub fn bar() -> Alias {
+    Alias
+}
+
+// @has 'foo/fn.bar2.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar2() -> Whatever'
+pub fn bar2() -> Whatever3 {
+    Whatever
+}
+
+// @has 'foo/fn.bar3.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar3() -> Whatever4'
+pub fn bar3() -> Whatever4 {
+    Whatever
+}
+
+// @has 'foo/fn.bar4.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar4() -> Bar'
+pub fn bar4() -> crate::Alias {
+    Alias
+}
+
+// @has 'foo/fn.bar5.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar5() -> Whatever'
+pub fn bar5() -> crate::Whatever3 {
+    Whatever
+}
+
+// @has 'foo/fn.bar6.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar6() -> Whatever4'
+pub fn bar6() -> crate::Whatever4 {
+    Whatever
+}
+
+
+// @has 'foo/fn.bar7.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar7() -> Bar'
+pub fn bar7() -> self::Alias {
+    Alias
+}
+
+// @has 'foo/fn.bar8.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar8() -> Whatever'
+pub fn bar8() -> self::Whatever3 {
+    Whatever
+}
+
+// @has 'foo/fn.bar9.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar9() -> Whatever4'
+pub fn bar9() -> self::Whatever4 {
+    Whatever
+}
+
+mod nested {
+    pub(crate) use crate::Alias;
+    pub(crate) use crate::Whatever3;
+    pub(crate) use crate::Whatever4;
+    pub(crate) use crate::nested as nested2;
+}
+
+// @has 'foo/fn.bar10.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar10() -> Bar'
+pub fn bar10() -> nested::Alias {
+    Alias
+}
+
+// @has 'foo/fn.bar11.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar11() -> Whatever'
+pub fn bar11() -> nested::Whatever3 {
+    Whatever
+}
+
+// @has 'foo/fn.bar12.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar12() -> Whatever4'
+pub fn bar12() -> nested::Whatever4 {
+    Whatever
+}
+
+// @has 'foo/fn.bar13.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar13() -> Bar'
+pub fn bar13() -> nested::nested2::Alias {
+    Alias
+}
+
+// @has 'foo/fn.bar14.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar14() -> Whatever'
+pub fn bar14() -> nested::nested2::Whatever3 {
+    Whatever
+}
+
+// @has 'foo/fn.bar15.html'
+// @has - '//*[@class="rust item-decl"]/code' 'pub fn bar15() -> Whatever4'
+pub fn bar15() -> nested::nested2::Whatever4 {
+    Whatever
+}
+
+use external::Public as Private;
+
+pub mod external {
+    pub struct Public;
+
+    // @has 'foo/external/fn.make.html'
+    // @has - '//*[@class="rust item-decl"]/code' 'pub fn make() -> Public'
+    pub fn make() -> super::Private { super::Private }
+}
diff --git a/tests/ui/const-generics/late-bound-vars/in_closure.rs b/tests/ui/const-generics/late-bound-vars/in_closure.rs
index 00fb535f04879..a6ac79506a536 100644
--- a/tests/ui/const-generics/late-bound-vars/in_closure.rs
+++ b/tests/ui/const-generics/late-bound-vars/in_closure.rs
@@ -1,4 +1,5 @@
 // failure-status: 101
+// rustc-env:RUSTC_ICE=0
 // known-bug: unknown
 // error-pattern:internal compiler error
 // normalize-stderr-test "internal compiler error.*" -> ""
diff --git a/tests/ui/const-generics/late-bound-vars/simple.rs b/tests/ui/const-generics/late-bound-vars/simple.rs
index 5d19aaf0b9555..518333f099eed 100644
--- a/tests/ui/const-generics/late-bound-vars/simple.rs
+++ b/tests/ui/const-generics/late-bound-vars/simple.rs
@@ -1,5 +1,6 @@
 // failure-status: 101
 // known-bug: unknown
+// rustc-env:RUSTC_ICE=0
 // error-pattern:internal compiler error
 // normalize-stderr-test "internal compiler error.*" -> ""
 // normalize-stderr-test "DefId\([^)]*\)" -> "..."
diff --git a/tests/ui/consts/const-eval/const-eval-query-stack.rs b/tests/ui/consts/const-eval/const-eval-query-stack.rs
index 81f28c1755deb..e9b2fb9d87c12 100644
--- a/tests/ui/consts/const-eval/const-eval-query-stack.rs
+++ b/tests/ui/consts/const-eval/const-eval-query-stack.rs
@@ -1,10 +1,12 @@
 // compile-flags: -Ztreat-err-as-bug=1
 // failure-status: 101
 // rustc-env:RUST_BACKTRACE=1
+// rustc-env:RUSTC_ICE=0
 // normalize-stderr-test "\nerror: .*unexpectedly panicked.*\n\n" -> ""
 // normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
 // normalize-stderr-test "note: compiler flags.*\n\n" -> ""
 // normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
+// normalize-stderr-test "note: please attach the file at `.*` to your bug report\n\n" -> ""
 // normalize-stderr-test "thread.*panicked.*\n" -> ""
 // normalize-stderr-test "stack backtrace:\n" -> ""
 // normalize-stderr-test "\s\d{1,}: .*\n" -> ""
diff --git a/tests/ui/consts/const-eval/const-eval-query-stack.stderr b/tests/ui/consts/const-eval/const-eval-query-stack.stderr
index 01fb8153cf384..f34cb71902fc6 100644
--- a/tests/ui/consts/const-eval/const-eval-query-stack.stderr
+++ b/tests/ui/consts/const-eval/const-eval-query-stack.stderr
@@ -1,5 +1,5 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const-eval-query-stack.rs:16:16
+  --> $DIR/const-eval-query-stack.rs:18:16
    |
 LL | const X: i32 = 1 / 0;
    |                ^^^^^ attempt to divide `1_i32` by zero
diff --git a/tests/ui/feature-gates/feature-gate-type_alias_impl_trait.rs b/tests/ui/feature-gates/feature-gate-type_alias_impl_trait.rs
index 0d019b1f50206..3f49020bbea38 100644
--- a/tests/ui/feature-gates/feature-gate-type_alias_impl_trait.rs
+++ b/tests/ui/feature-gates/feature-gate-type_alias_impl_trait.rs
@@ -11,7 +11,7 @@ fn define() -> Bar {
 
 type Foo2 = impl Debug;
 
-fn define2() {
+fn define2(_: Foo2) {
     let x = || -> Foo2 { 42 };
 }
 
@@ -20,13 +20,13 @@ type Foo3 = impl Debug;
 fn define3(x: Foo3) {
     let y: i32 = x;
 }
-fn define3_1() {
+fn define3_1(_: Foo3) {
     define3(42)
 }
 
 type Foo4 = impl Debug;
 
-fn define4() {
+fn define4(_: Foo4) {
     let y: Foo4 = 42;
 }
 
diff --git a/tests/ui/generic-associated-types/issue-90014-tait.rs b/tests/ui/generic-associated-types/issue-90014-tait.rs
new file mode 100644
index 0000000000000..bc3a4e1296513
--- /dev/null
+++ b/tests/ui/generic-associated-types/issue-90014-tait.rs
@@ -0,0 +1,23 @@
+//! This test is reporting the wrong error. We need
+//! more inherent associated type tests that use opaque types
+//! in general. Some variant of this test should compile successfully.
+// known-bug: unknown
+// edition:2018
+
+#![feature(impl_trait_in_assoc_type, inherent_associated_types)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+
+struct Foo<'a>(&'a mut ());
+
+impl Foo<'_> {
+    type Fut<'a> = impl Future<Output = ()>;
+    //^ ERROR: the type `&mut ()` does not fulfill the required lifetime
+
+    fn make_fut<'a>(&'a self) -> Self::Fut<'a> {
+        async { () }
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/generic-associated-types/issue-90014-tait.stderr b/tests/ui/generic-associated-types/issue-90014-tait.stderr
new file mode 100644
index 0000000000000..8330a387ecd55
--- /dev/null
+++ b/tests/ui/generic-associated-types/issue-90014-tait.stderr
@@ -0,0 +1,22 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-90014-tait.rs:19:9
+   |
+LL |     type Fut<'a> = impl Future<Output = ()>;
+   |                    ------------------------ the expected future
+...
+LL |     fn make_fut<'a>(&'a self) -> Self::Fut<'a> {
+   |                                  ------------- expected `Foo<'_>::Fut<'a>` because of return type
+LL |         async { () }
+   |         ^^^^^^^^^^^^ expected future, found `async` block
+   |
+   = note: expected opaque type `Foo<'_>::Fut<'a>`
+            found `async` block `[async block@$DIR/issue-90014-tait.rs:19:9: 19:21]`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/issue-90014-tait.rs:18:8
+   |
+LL |     fn make_fut<'a>(&'a self) -> Self::Fut<'a> {
+   |        ^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/generic-associated-types/issue-90014-tait2.rs b/tests/ui/generic-associated-types/issue-90014-tait2.rs
new file mode 100644
index 0000000000000..dacbc93dec880
--- /dev/null
+++ b/tests/ui/generic-associated-types/issue-90014-tait2.rs
@@ -0,0 +1,46 @@
+//! This test checks that opaque type collection doesn't try to normalize the projection
+//! without respecting its binders (which would ICE).
+//! Unfortunately we don't even reach opaque type collection, as we ICE in typeck before that.
+// known-bug: #109281
+// failure-status: 101
+// error-pattern:internal compiler error
+// normalize-stderr-test "internal compiler error.*" -> ""
+// normalize-stderr-test "DefId\([^)]*\)" -> "..."
+// normalize-stderr-test "\nerror: internal compiler error.*\n\n" -> ""
+// normalize-stderr-test "note:.*unexpectedly panicked.*\n\n" -> ""
+// normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
+// normalize-stderr-test "note: compiler flags.*\n\n" -> ""
+// normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
+// normalize-stderr-test "thread.*panicked.*\n" -> ""
+// normalize-stderr-test "stack backtrace:\n" -> ""
+// normalize-stderr-test "\s\d{1,}: .*\n" -> ""
+// normalize-stderr-test "\s at .*\n" -> ""
+// normalize-stderr-test ".*note: Some details.*\n" -> ""
+// normalize-stderr-test "\n\n[ ]*\n" -> ""
+// normalize-stderr-test "compiler/.*: projection" -> "projection"
+// edition:2018
+
+#![feature(type_alias_impl_trait)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+
+struct Foo<'a>(&'a mut ());
+
+type Fut<'a> = impl Future<Output = ()>;
+
+trait Trait<'x> {
+    type Thing;
+}
+
+impl<'x, T: 'x> Trait<'x> for (T,) {
+    type Thing = T;
+}
+
+impl Foo<'_> {
+    fn make_fut(&self) -> Box<dyn for<'a> Trait<'a, Thing = Fut<'a>>> {
+        Box::new((async { () },))
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/generic-associated-types/issue-90014-tait2.stderr b/tests/ui/generic-associated-types/issue-90014-tait2.stderr
new file mode 100644
index 0000000000000..3187be3334c5f
--- /dev/null
+++ b/tests/ui/generic-associated-types/issue-90014-tait2.stderr
@@ -0,0 +1,12 @@
+error: 
+  --> $DIR/issue-90014-tait2.rs:41:27
+   |
+LL |     fn make_fut(&self) -> Box<dyn for<'a> Trait<'a, Thing = Fut<'a>>> {
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^query stack during panic:
+#0 [typeck] type-checking `<impl at $DIR/issue-90014-tait2.rs:40:1: 40:13>::make_fut`
+#1 [type_of] computing type of `Fut::{opaque#0}`
+#2 [check_mod_item_types] checking item types in top-level module
+#3 [analysis] running analysis passes on this crate
+end of query stack
+error: aborting due to previous error
+
diff --git a/tests/ui/impl-trait/deduce-signature-from-supertrait.rs b/tests/ui/impl-trait/deduce-signature-from-supertrait.rs
index d2c3479203573..7a51aac44e2e8 100644
--- a/tests/ui/impl-trait/deduce-signature-from-supertrait.rs
+++ b/tests/ui/impl-trait/deduce-signature-from-supertrait.rs
@@ -8,8 +8,10 @@ impl<T: Fn(i32)> SuperExpectation for T {}
 
 type Foo = impl SuperExpectation;
 
-fn main() {
+fn bop(_: Foo) {
     let _: Foo = |x| {
         let _ = x.to_string();
     };
 }
+
+fn main() {}
diff --git a/tests/ui/impl-trait/in-assoc-type.rs b/tests/ui/impl-trait/in-assoc-type.rs
index 36c54bdd6de34..38ad2fa6f02ee 100644
--- a/tests/ui/impl-trait/in-assoc-type.rs
+++ b/tests/ui/impl-trait/in-assoc-type.rs
@@ -1,3 +1,6 @@
+//! This test checks that we don't allow registering hidden types for
+//! opaque types from other impls.
+
 #![feature(impl_trait_in_assoc_type)]
 
 trait Foo<T> {
diff --git a/tests/ui/impl-trait/in-assoc-type.stderr b/tests/ui/impl-trait/in-assoc-type.stderr
index ab3f3a14410d0..af60da07cac31 100644
--- a/tests/ui/impl-trait/in-assoc-type.stderr
+++ b/tests/ui/impl-trait/in-assoc-type.stderr
@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/in-assoc-type.rs:17:22
+  --> $DIR/in-assoc-type.rs:20:22
    |
 LL |     type Bar = impl std::fmt::Debug;
    |                -------------------- the expected opaque type
@@ -12,7 +12,7 @@ LL |     fn foo(&self) -> <Self as Foo<()>>::Bar {}
    = note: expected opaque type `<() as Foo<()>>::Bar`
                 found unit type `()`
 note: this item must have the opaque type in its signature in order to be able to register hidden types
-  --> $DIR/in-assoc-type.rs:17:8
+  --> $DIR/in-assoc-type.rs:20:8
    |
 LL |     fn foo(&self) -> <Self as Foo<()>>::Bar {}
    |        ^^^
diff --git a/tests/ui/impl-trait/issues/issue-70877.rs b/tests/ui/impl-trait/issues/issue-70877.rs
index 8169cfafac711..df7722986744d 100644
--- a/tests/ui/impl-trait/issues/issue-70877.rs
+++ b/tests/ui/impl-trait/issues/issue-70877.rs
@@ -25,12 +25,12 @@ fn ham() -> Foo {
     Bar(1)
 }
 
-fn oof() -> impl std::fmt::Debug {
+fn oof(_: Foo) -> impl std::fmt::Debug {
     let mut bar = ham();
     let func = bar.next().unwrap();
     return func(&"oof"); //~ ERROR opaque type's hidden type cannot be another opaque type
 }
 
 fn main() {
-    let _ = oof();
+    let _ = oof(ham());
 }
diff --git a/tests/ui/impl-trait/issues/issue-70877.stderr b/tests/ui/impl-trait/issues/issue-70877.stderr
index 8813bff3c353e..ee140e6f6c43d 100644
--- a/tests/ui/impl-trait/issues/issue-70877.stderr
+++ b/tests/ui/impl-trait/issues/issue-70877.stderr
@@ -5,10 +5,10 @@ LL |     return func(&"oof");
    |            ^^^^^^^^^^^^ one of the two opaque types used here has to be outside its defining scope
    |
 note: opaque type whose hidden type is being assigned
-  --> $DIR/issue-70877.rs:28:13
+  --> $DIR/issue-70877.rs:28:19
    |
-LL | fn oof() -> impl std::fmt::Debug {
-   |             ^^^^^^^^^^^^^^^^^^^^
+LL | fn oof(_: Foo) -> impl std::fmt::Debug {
+   |                   ^^^^^^^^^^^^^^^^^^^^
 note: opaque type being used as hidden type
   --> $DIR/issue-70877.rs:4:15
    |
diff --git a/tests/ui/impl-trait/issues/issue-74282.rs b/tests/ui/impl-trait/issues/issue-74282.rs
index 654de0cd0253c..51bd5f67ed574 100644
--- a/tests/ui/impl-trait/issues/issue-74282.rs
+++ b/tests/ui/impl-trait/issues/issue-74282.rs
@@ -3,9 +3,12 @@
 type Closure = impl Fn() -> u64;
 struct Anonymous(Closure);
 
-fn main() {
+fn bop(_: Closure) {
     let y = || -> Closure { || 3 };
-    Anonymous(|| { //~ ERROR mismatched types
-        3 //~^ ERROR mismatched types
+    Anonymous(|| {
+        //~^ ERROR mismatched types
+        3 //~^^ ERROR mismatched types
     })
 }
+
+fn main() {}
diff --git a/tests/ui/impl-trait/issues/issue-74282.stderr b/tests/ui/impl-trait/issues/issue-74282.stderr
index 724f3c5d6747c..d43e9fee0b359 100644
--- a/tests/ui/impl-trait/issues/issue-74282.stderr
+++ b/tests/ui/impl-trait/issues/issue-74282.stderr
@@ -8,6 +8,7 @@ LL |       Anonymous(|| {
    |  _____---------_^
    | |     |
    | |     arguments to this struct are incorrect
+LL | |
 LL | |         3
 LL | |     })
    | |_____^ expected opaque type, found closure
@@ -25,15 +26,20 @@ LL | struct Anonymous(Closure);
 error[E0308]: mismatched types
   --> $DIR/issue-74282.rs:8:5
    |
-LL |   fn main() {
-   |             - expected `()` because of default return type
-LL |       let y = || -> Closure { || 3 };
 LL | /     Anonymous(|| {
+LL | |
 LL | |         3
 LL | |     })
-   | |      ^- help: consider using a semicolon here: `;`
-   | |______|
-   |        expected `()`, found `Anonymous`
+   | |______^ expected `()`, found `Anonymous`
+   |
+help: consider using a semicolon here
+   |
+LL |     });
+   |       +
+help: try adding a return type
+   |
+LL | fn bop(_: Closure) -> Anonymous {
+   |                    ++++++++++++
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/impl-trait/issues/issue-78722-2.rs b/tests/ui/impl-trait/issues/issue-78722-2.rs
new file mode 100644
index 0000000000000..cf5361e1e602c
--- /dev/null
+++ b/tests/ui/impl-trait/issues/issue-78722-2.rs
@@ -0,0 +1,22 @@
+//! test that we cannot register hidden types for opaque types
+//! declared outside an anonymous constant.
+// edition:2018
+
+#![feature(type_alias_impl_trait)]
+
+type F = impl core::future::Future<Output = u8>;
+
+struct Bug {
+    V1: [(); {
+        fn concrete_use() -> F {
+            //~^ ERROR future that resolves to `u8`, but it resolves to `()`
+            async {}
+        }
+        let f: F = async { 1 };
+        //~^ ERROR item constrains opaque type that is not in its signature
+        //~| ERROR `async` blocks are not allowed in constants
+        1
+    }],
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/issues/issue-78722-2.stderr b/tests/ui/impl-trait/issues/issue-78722-2.stderr
new file mode 100644
index 0000000000000..6db603e775175
--- /dev/null
+++ b/tests/ui/impl-trait/issues/issue-78722-2.stderr
@@ -0,0 +1,32 @@
+error[E0658]: `async` blocks are not allowed in constants
+  --> $DIR/issue-78722-2.rs:15:20
+   |
+LL |         let f: F = async { 1 };
+   |                    ^^^^^^^^^^^
+   |
+   = note: see issue #85368 <https://github.com/rust-lang/rust/issues/85368> for more information
+   = help: add `#![feature(const_async_blocks)]` to the crate attributes to enable
+
+error[E0271]: expected `[async block@$DIR/issue-78722-2.rs:13:13: 13:21]` to be a future that resolves to `u8`, but it resolves to `()`
+  --> $DIR/issue-78722-2.rs:11:30
+   |
+LL |         fn concrete_use() -> F {
+   |                              ^ expected `()`, found `u8`
+
+error: item constrains opaque type that is not in its signature
+  --> $DIR/issue-78722-2.rs:15:20
+   |
+LL |         let f: F = async { 1 };
+   |                    ^^^^^^^^^^^
+   |
+   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
+note: this item must mention the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/issue-78722-2.rs:15:20
+   |
+LL |         let f: F = async { 1 };
+   |                    ^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0271, E0658.
+For more information about an error, try `rustc --explain E0271`.
diff --git a/tests/ui/impl-trait/issues/issue-78722.rs b/tests/ui/impl-trait/issues/issue-78722.rs
index 7b5ab5f229835..75ccc8d8e8a9a 100644
--- a/tests/ui/impl-trait/issues/issue-78722.rs
+++ b/tests/ui/impl-trait/issues/issue-78722.rs
@@ -2,10 +2,9 @@
 
 #![feature(type_alias_impl_trait)]
 
-type F = impl core::future::Future<Output = u8>;
-
 struct Bug {
     V1: [(); {
+        type F = impl core::future::Future<Output = u8>;
         fn concrete_use() -> F {
             //~^ ERROR to be a future that resolves to `u8`, but it resolves to `()`
             async {}
diff --git a/tests/ui/impl-trait/issues/issue-78722.stderr b/tests/ui/impl-trait/issues/issue-78722.stderr
index 05a2c135cf7c7..36340a0bab41a 100644
--- a/tests/ui/impl-trait/issues/issue-78722.stderr
+++ b/tests/ui/impl-trait/issues/issue-78722.stderr
@@ -1,5 +1,5 @@
 error[E0658]: `async` blocks are not allowed in constants
-  --> $DIR/issue-78722.rs:13:20
+  --> $DIR/issue-78722.rs:12:20
    |
 LL |         let f: F = async { 1 };
    |                    ^^^^^^^^^^^
@@ -7,8 +7,8 @@ LL |         let f: F = async { 1 };
    = note: see issue #85368 <https://github.com/rust-lang/rust/issues/85368> for more information
    = help: add `#![feature(const_async_blocks)]` to the crate attributes to enable
 
-error[E0271]: expected `[async block@$DIR/issue-78722.rs:11:13: 11:21]` to be a future that resolves to `u8`, but it resolves to `()`
-  --> $DIR/issue-78722.rs:9:30
+error[E0271]: expected `[async block@$DIR/issue-78722.rs:10:13: 10:21]` to be a future that resolves to `u8`, but it resolves to `()`
+  --> $DIR/issue-78722.rs:8:30
    |
 LL |         fn concrete_use() -> F {
    |                              ^ expected `()`, found `u8`
diff --git a/tests/ui/impl-trait/issues/issue-86800.rs b/tests/ui/impl-trait/issues/issue-86800.rs
index ec4fda322d04f..6319ba4fd0cc5 100644
--- a/tests/ui/impl-trait/issues/issue-86800.rs
+++ b/tests/ui/impl-trait/issues/issue-86800.rs
@@ -2,6 +2,7 @@
 
 // edition:2021
 // compile-flags:-Z treat-err-as-bug=1
+// rustc-env:RUSTC_ICE=0
 // error-pattern: aborting due to `-Z treat-err-as-bug=1`
 // failure-status:101
 // normalize-stderr-test ".*note: .*\n\n" -> ""
diff --git a/tests/ui/impl-trait/issues/issue-86800.stderr b/tests/ui/impl-trait/issues/issue-86800.stderr
index facab390d1524..040b9281e47c9 100644
--- a/tests/ui/impl-trait/issues/issue-86800.stderr
+++ b/tests/ui/impl-trait/issues/issue-86800.stderr
@@ -1,5 +1,5 @@
 error: unconstrained opaque type
-  --> $DIR/issue-86800.rs:31:34
+  --> $DIR/issue-86800.rs:32:34
    |
 LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResult<O>>;
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/impl-trait/normalize-tait-in-const.rs b/tests/ui/impl-trait/normalize-tait-in-const.rs
index d2e34c00b6422..151fc49e0e645 100644
--- a/tests/ui/impl-trait/normalize-tait-in-const.rs
+++ b/tests/ui/impl-trait/normalize-tait-in-const.rs
@@ -4,6 +4,7 @@
 // normalize-stderr-test "thread 'rustc' panicked.*\n" -> ""
 // normalize-stderr-test "(error: internal compiler error: [^:]+):\d+:\d+: " -> "$1:LL:CC: "
 // rustc-env:RUST_BACKTRACE=0
+// rustc-env:RUSTC_ICE=0
 
 #![feature(type_alias_impl_trait)]
 #![feature(const_trait_impl)]
diff --git a/tests/ui/layout/valid_range_oob.rs b/tests/ui/layout/valid_range_oob.rs
index 74aa47fe40549..35003dd6bf39e 100644
--- a/tests/ui/layout/valid_range_oob.rs
+++ b/tests/ui/layout/valid_range_oob.rs
@@ -2,6 +2,7 @@
 // normalize-stderr-test "note: .*\n\n" -> ""
 // normalize-stderr-test "thread 'rustc' panicked.*\n" -> ""
 // rustc-env:RUST_BACKTRACE=0
+// rustc-env:RUSTC_ICE=0
 
 #![feature(rustc_attrs)]
 
diff --git a/tests/ui/lint/issue-99387.rs b/tests/ui/lint/issue-99387.rs
index 616eb935e93d4..ba5031167e33d 100644
--- a/tests/ui/lint/issue-99387.rs
+++ b/tests/ui/lint/issue-99387.rs
@@ -1,4 +1,5 @@
-// check-pass
+//! Test that we don't follow through projections to find
+//! opaque types.
 
 #![feature(type_alias_impl_trait)]
 #![allow(private_in_public)]
@@ -18,6 +19,7 @@ impl<'a> Tr for &'a () {
 }
 
 pub fn ohno<'a>() -> <&'a () as Tr>::Item {
+    //~^ ERROR item constrains opaque type that is not in its signature
     None.into_iter()
 }
 
diff --git a/tests/ui/lint/issue-99387.stderr b/tests/ui/lint/issue-99387.stderr
new file mode 100644
index 0000000000000..3a46ce7e1952d
--- /dev/null
+++ b/tests/ui/lint/issue-99387.stderr
@@ -0,0 +1,15 @@
+error: item constrains opaque type that is not in its signature
+  --> $DIR/issue-99387.rs:21:22
+   |
+LL | pub fn ohno<'a>() -> <&'a () as Tr>::Item {
+   |                      ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
+note: this item must mention the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/issue-99387.rs:21:8
+   |
+LL | pub fn ohno<'a>() -> <&'a () as Tr>::Item {
+   |        ^^^^
+
+error: aborting due to previous error
+
diff --git a/tests/ui/mir/validate/storage-live.rs b/tests/ui/mir/validate/storage-live.rs
index ed3c26ed6da5a..34aed6a4ee95b 100644
--- a/tests/ui/mir/validate/storage-live.rs
+++ b/tests/ui/mir/validate/storage-live.rs
@@ -1,4 +1,5 @@
 // compile-flags: -Zvalidate-mir -Ztreat-err-as-bug
+// rustc-env:RUSTC_ICE=0
 // failure-status: 101
 // error-pattern: broken MIR in
 // error-pattern: StorageLive(_1) which already has storage here
diff --git a/tests/ui/mir/validate/storage-live.stderr b/tests/ui/mir/validate/storage-live.stderr
index 720fb0a90b08b..57292a239257c 100644
--- a/tests/ui/mir/validate/storage-live.stderr
+++ b/tests/ui/mir/validate/storage-live.stderr
@@ -1,6 +1,6 @@
 error: internal compiler error: broken MIR in Item(DefId(0:8 ~ storage_live[HASH]::multiple_storage)) (before pass CheckPackedRef) at bb0[1]:
                                 StorageLive(_1) which already has storage here
-  --> $DIR/storage-live.rs:22:13
+  --> $DIR/storage-live.rs:23:13
    |
 LL |             StorageLive(a);
    |             ^^^^^^^^^^^^^^
diff --git a/tests/ui/panics/default-backtrace-ice.rs b/tests/ui/panics/default-backtrace-ice.rs
index b40203c339d05..00f8bdf44578d 100644
--- a/tests/ui/panics/default-backtrace-ice.rs
+++ b/tests/ui/panics/default-backtrace-ice.rs
@@ -1,4 +1,5 @@
 // unset-rustc-env:RUST_BACKTRACE
+// rustc-env:RUSTC_ICE=0
 // compile-flags:-Z treat-err-as-bug=1
 // error-pattern:stack backtrace:
 // failure-status:101
diff --git a/tests/ui/panics/default-backtrace-ice.stderr b/tests/ui/panics/default-backtrace-ice.stderr
index 815ce4dd01528..6e3ec24cfe232 100644
--- a/tests/ui/panics/default-backtrace-ice.stderr
+++ b/tests/ui/panics/default-backtrace-ice.stderr
@@ -1,5 +1,5 @@
 error[E0425]: cannot find value `missing_ident` in this scope
-  --> $DIR/default-backtrace-ice.rs:21:13
+  --> $DIR/default-backtrace-ice.rs:22:13
    |
 LL | fn main() { missing_ident; }
    |             ^^^^^^^^^^^^^ not found in this scope
diff --git a/tests/ui/recursion/issue-95134.rs b/tests/ui/recursion/issue-95134.rs
index 2f1cffa2fa907..0071791ec013d 100644
--- a/tests/ui/recursion/issue-95134.rs
+++ b/tests/ui/recursion/issue-95134.rs
@@ -3,6 +3,7 @@
 // compile-flags: -Copt-level=0
 // dont-check-failure-status
 // dont-check-compiler-stderr
+// rustc-env:RUSTC_ICE=0
 
 pub fn encode_num<Writer: ExampleWriter>(n: u32, mut writer: Writer) -> Result<(), Writer::Error> {
     if n > 15 {
diff --git a/tests/ui/traits/new-solver/dont-remap-tait-substs.rs b/tests/ui/traits/new-solver/dont-remap-tait-substs.rs
index 028222f4e6dba..309bee8aa8c2c 100644
--- a/tests/ui/traits/new-solver/dont-remap-tait-substs.rs
+++ b/tests/ui/traits/new-solver/dont-remap-tait-substs.rs
@@ -12,7 +12,7 @@ type Foo<T: Send, U> = impl NeedsSend<T>;
 trait NeedsSend<T> {}
 impl<T: Send> NeedsSend<T> for T {}
 
-fn define<A, B: Send>(a: A, b: B) {
+fn define<A, B: Send>(a: A, b: B, _: Foo<B, A>) {
     let y: Option<Foo<B, A>> = Some(b);
 }
 
diff --git a/tests/ui/traits/new-solver/dont-type_of-tait-in-defining-scope.rs b/tests/ui/traits/new-solver/dont-type_of-tait-in-defining-scope.rs
index 5a0dcd0e8ccea..08f14d7494d79 100644
--- a/tests/ui/traits/new-solver/dont-type_of-tait-in-defining-scope.rs
+++ b/tests/ui/traits/new-solver/dont-type_of-tait-in-defining-scope.rs
@@ -12,11 +12,13 @@ type Foo = impl Sized;
 
 fn needs_send<T: Send>() {}
 
-fn test() {
+fn test(_: Foo) {
     needs_send::<Foo>();
     //[not_send]~^ ERROR type annotations needed: cannot satisfy `Foo: Send`
 }
 
-fn main() {
+fn defines(_: Foo) {
     let _: Foo = ();
 }
+
+fn main() {}
diff --git a/tests/ui/traits/new-solver/slice-match-byte-lit.rs b/tests/ui/traits/new-solver/slice-match-byte-lit.rs
index 5f9c0df645036..4f848062595da 100644
--- a/tests/ui/traits/new-solver/slice-match-byte-lit.rs
+++ b/tests/ui/traits/new-solver/slice-match-byte-lit.rs
@@ -1,5 +1,5 @@
 // compile-flags: -Ztrait-solver=next
-// known-bug: rust-lang/trait-system-refactor-initiative#38
+// check-pass
 
 fn test(s: &[u8]) {
     match &s[0..3] {
diff --git a/tests/ui/traits/new-solver/slice-match-byte-lit.stderr b/tests/ui/traits/new-solver/slice-match-byte-lit.stderr
deleted file mode 100644
index cd48a6d184339..0000000000000
--- a/tests/ui/traits/new-solver/slice-match-byte-lit.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error[E0271]: type mismatch resolving `[u8; 3] <: <[u8] as Index<Range<usize>>>::Output`
-  --> $DIR/slice-match-byte-lit.rs:6:9
-   |
-LL |     match &s[0..3] {
-   |           -------- this expression has type `&<[u8] as Index<std::ops::Range<usize>>>::Output`
-LL |         b"uwu" => {}
-   |         ^^^^^^ types differ
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0271`.
diff --git a/tests/ui/traits/new-solver/tait-eq-proj-2.rs b/tests/ui/traits/new-solver/tait-eq-proj-2.rs
index 99a3d02bd1aea..77ea8bc246e64 100644
--- a/tests/ui/traits/new-solver/tait-eq-proj-2.rs
+++ b/tests/ui/traits/new-solver/tait-eq-proj-2.rs
@@ -8,9 +8,11 @@
 
 type Tait = impl Iterator<Item = impl Sized>;
 
-fn mk<T>() -> T { todo!() }
+fn mk<T>() -> T {
+    todo!()
+}
 
-fn a() {
+fn a(_: Tait) {
     let x: Tait = mk();
     let mut array = mk();
     let mut z = IntoIterator::into_iter(array);
diff --git a/tests/ui/traits/new-solver/tait-eq-proj.rs b/tests/ui/traits/new-solver/tait-eq-proj.rs
index 01141b2819a8d..01ef2ec953aeb 100644
--- a/tests/ui/traits/new-solver/tait-eq-proj.rs
+++ b/tests/ui/traits/new-solver/tait-eq-proj.rs
@@ -28,7 +28,7 @@ goals together. Essentially:
 
 */
 
-fn a() {
+fn a(_: Tait) {
     let _: Tait = IntoIterator::into_iter([0i32; 32]);
 }
 
diff --git a/tests/ui/traits/new-solver/tait-eq-tait.rs b/tests/ui/traits/new-solver/tait-eq-tait.rs
index 532c4c39bd499..70d9dc0eaa8ae 100644
--- a/tests/ui/traits/new-solver/tait-eq-tait.rs
+++ b/tests/ui/traits/new-solver/tait-eq-tait.rs
@@ -6,12 +6,13 @@
 
 #![feature(type_alias_impl_trait)]
 
-type Tait = impl Sized;
-type Tait2 = impl Sized;
-
-fn mk<T>() -> T { todo!() }
+fn mk<T>() -> T {
+    todo!()
+}
 
 fn main() {
+    type Tait = impl Sized;
+    type Tait2 = impl Sized;
     let x: Tait = 1u32;
     let y: Tait2 = x;
 }
diff --git a/tests/ui/treat-err-as-bug/delay_span_bug.rs b/tests/ui/treat-err-as-bug/delay_span_bug.rs
index 832afddf89147..a646092d16bac 100644
--- a/tests/ui/treat-err-as-bug/delay_span_bug.rs
+++ b/tests/ui/treat-err-as-bug/delay_span_bug.rs
@@ -1,4 +1,5 @@
 // compile-flags: -Ztreat-err-as-bug
+// rustc-env:RUSTC_ICE=0
 // failure-status: 101
 // error-pattern: aborting due to `-Z treat-err-as-bug=1`
 // error-pattern: [trigger_delay_span_bug] triggering a delay span bug
diff --git a/tests/ui/treat-err-as-bug/delay_span_bug.stderr b/tests/ui/treat-err-as-bug/delay_span_bug.stderr
index 22c6175048a63..bc48a6720a90b 100644
--- a/tests/ui/treat-err-as-bug/delay_span_bug.stderr
+++ b/tests/ui/treat-err-as-bug/delay_span_bug.stderr
@@ -1,5 +1,5 @@
 error: internal compiler error: delayed span bug triggered by #[rustc_error(delay_span_bug_from_inside_query)]
-  --> $DIR/delay_span_bug.rs:12:1
+  --> $DIR/delay_span_bug.rs:13:1
    |
 LL | fn main() {}
    | ^^^^^^^^^
diff --git a/tests/ui/type-alias-impl-trait/bound_reduction2.rs b/tests/ui/type-alias-impl-trait/bound_reduction2.rs
index 0bcc9e002ca04..4e9f65d88a129 100644
--- a/tests/ui/type-alias-impl-trait/bound_reduction2.rs
+++ b/tests/ui/type-alias-impl-trait/bound_reduction2.rs
@@ -13,6 +13,7 @@ trait Trait<U> {}
 impl<W> Trait<W> for () {}
 
 fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
+    //~^ ERROR non-defining opaque type use
     ()
     //~^ ERROR expected generic type parameter, found `<T as TraitWithAssoc>::Assoc`
 }
diff --git a/tests/ui/type-alias-impl-trait/bound_reduction2.stderr b/tests/ui/type-alias-impl-trait/bound_reduction2.stderr
index 3c259bd9e97cc..14f9dbbdb4e93 100644
--- a/tests/ui/type-alias-impl-trait/bound_reduction2.stderr
+++ b/tests/ui/type-alias-impl-trait/bound_reduction2.stderr
@@ -1,5 +1,17 @@
+error[E0792]: non-defining opaque type use in defining scope
+  --> $DIR/bound_reduction2.rs:15:46
+   |
+LL | fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
+   |                                              ^^^^^^^^^^^^^ argument `<T as TraitWithAssoc>::Assoc` is not a generic parameter
+   |
+note: for this opaque type
+  --> $DIR/bound_reduction2.rs:9:15
+   |
+LL | type Foo<V> = impl Trait<V>;
+   |               ^^^^^^^^^^^^^
+
 error[E0792]: expected generic type parameter, found `<T as TraitWithAssoc>::Assoc`
-  --> $DIR/bound_reduction2.rs:16:5
+  --> $DIR/bound_reduction2.rs:17:5
    |
 LL | type Foo<V> = impl Trait<V>;
    |          - this generic parameter must be used with a generic type parameter
@@ -7,6 +19,6 @@ LL | type Foo<V> = impl Trait<V>;
 LL |     ()
    |     ^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0792`.
diff --git a/tests/ui/type-alias-impl-trait/closure_args.rs b/tests/ui/type-alias-impl-trait/closure_args.rs
index c5e7af81d3dd0..243f9cd6d4f4c 100644
--- a/tests/ui/type-alias-impl-trait/closure_args.rs
+++ b/tests/ui/type-alias-impl-trait/closure_args.rs
@@ -11,6 +11,13 @@ fn run<F: FnOnce(Input) -> ()>(f: F, i: Input) {
     f(i);
 }
 
-fn main() {
-    run(|x: u32| {println!("{x}");}, 0);
+fn bop(_: Input) {
+    run(
+        |x: u32| {
+            println!("{x}");
+        },
+        0,
+    );
 }
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/closure_args2.rs b/tests/ui/type-alias-impl-trait/closure_args2.rs
index 82386c280a8e3..1dd5c3e40cda6 100644
--- a/tests/ui/type-alias-impl-trait/closure_args2.rs
+++ b/tests/ui/type-alias-impl-trait/closure_args2.rs
@@ -1,10 +1,12 @@
-// run-pass
+// check-pass
 
 #![feature(type_alias_impl_trait)]
 
 trait Foo {
     // This was reachable in https://github.com/rust-lang/rust/issues/100800
-    fn foo(&self) { unreachable!() }
+    fn foo(&self) {
+        unreachable!()
+    }
 }
 impl<T> Foo for T {}
 
@@ -14,10 +16,17 @@ impl B {
 }
 
 type Input = impl Foo;
-fn run1<F: FnOnce(Input)>(f: F, i: Input) {f(i)}
-fn run2<F: FnOnce(B)>(f: F, i: B) {f(i)}
+fn run1<F: FnOnce(Input)>(f: F, i: Input) {
+    f(i)
+}
+fn run2<F: FnOnce(B)>(f: F, i: B) {
+    f(i)
+}
 
-fn main() {
-    run1(|x: B| {x.foo()}, B);
-    run2(|x: B| {x.foo()}, B);
+fn bop() -> Input {
+    run1(|x: B| x.foo(), B);
+    run2(|x: B| x.foo(), B);
+    panic!()
 }
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.stderr b/tests/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.stderr
index fbfa0ccf1e8d9..d60f1ffbccc2d 100644
--- a/tests/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.stderr
+++ b/tests/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.stderr
@@ -19,6 +19,11 @@ LL |     ""
    |
    = note: expected opaque type `Boo`
                 found reference `&'static str`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/declared_but_not_defined_in_scope.rs:10:4
+   |
+LL | fn bomp() -> boo::Boo {
+   |    ^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-2.rs b/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-2.rs
index e5bfbfdae91fd..b2842df150a3f 100644
--- a/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-2.rs
+++ b/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-2.rs
@@ -2,7 +2,7 @@
 
 type Tait<'a> = impl Sized + 'a;
 
-fn foo<'a, 'b>() {
+fn foo<'a, 'b>() -> Tait<'a> {
     if false {
         if { return } {
             let y: Tait<'b> = 1i32;
@@ -10,6 +10,7 @@ fn foo<'a, 'b>() {
         }
     }
     let x: Tait<'a> = ();
+    x
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-2.stderr b/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-2.stderr
index f2eb7bc4dc79b..b138f9d5c45ab 100644
--- a/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-2.stderr
+++ b/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-2.stderr
@@ -5,10 +5,10 @@ LL |             let y: Tait<'b> = 1i32;
    |                               ^^^^ expected `()`, got `i32`
    |
 note: previous use here
-  --> $DIR/different_defining_uses_never_type-2.rs:12:23
+  --> $DIR/different_defining_uses_never_type-2.rs:7:14
    |
-LL |     let x: Tait<'a> = ();
-   |                       ^^
+LL |         if { return } {
+   |              ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-3.rs b/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-3.rs
index 2b30a9cd57cf6..a4ac27378e1d8 100644
--- a/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-3.rs
+++ b/tests/ui/type-alias-impl-trait/different_defining_uses_never_type-3.rs
@@ -2,7 +2,7 @@
 
 type Tait<T> = impl Sized;
 
-fn foo<T, U>() {
+fn foo<T, U>() -> Tait<T> {
     if false {
         if { return } {
             let y: Tait<U> = 1i32;
@@ -10,6 +10,7 @@ fn foo<T, U>() {
         }
     }
     let x: Tait<T> = ();
+    x
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/generic_duplicate_lifetime_param.rs b/tests/ui/type-alias-impl-trait/generic_duplicate_lifetime_param.rs
index 9d938a61600f5..14ced3418542a 100644
--- a/tests/ui/type-alias-impl-trait/generic_duplicate_lifetime_param.rs
+++ b/tests/ui/type-alias-impl-trait/generic_duplicate_lifetime_param.rs
@@ -9,6 +9,7 @@ impl<'a, T: ?Sized> Captures<'a> for T {}
 type Two<'a, 'b> = impl std::fmt::Debug + Captures<'a> + Captures<'b>;
 
 fn one<'a>(t: &'a ()) -> Two<'a, 'a> {
+    //~^ ERROR non-defining opaque type use
     t
     //~^ ERROR non-defining opaque type use
 }
diff --git a/tests/ui/type-alias-impl-trait/generic_duplicate_lifetime_param.stderr b/tests/ui/type-alias-impl-trait/generic_duplicate_lifetime_param.stderr
index 72e1ef4b4923b..4da69a705c07c 100644
--- a/tests/ui/type-alias-impl-trait/generic_duplicate_lifetime_param.stderr
+++ b/tests/ui/type-alias-impl-trait/generic_duplicate_lifetime_param.stderr
@@ -1,5 +1,17 @@
 error: non-defining opaque type use in defining scope
-  --> $DIR/generic_duplicate_lifetime_param.rs:12:5
+  --> $DIR/generic_duplicate_lifetime_param.rs:11:26
+   |
+LL | fn one<'a>(t: &'a ()) -> Two<'a, 'a> {
+   |                          ^^^^^^^^^^^ generic argument `'a` used twice
+   |
+note: for this opaque type
+  --> $DIR/generic_duplicate_lifetime_param.rs:9:20
+   |
+LL | type Two<'a, 'b> = impl std::fmt::Debug + Captures<'a> + Captures<'b>;
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: non-defining opaque type use in defining scope
+  --> $DIR/generic_duplicate_lifetime_param.rs:13:5
    |
 LL |     t
    |     ^
@@ -10,5 +22,5 @@ note: lifetime used multiple times
 LL | type Two<'a, 'b> = impl std::fmt::Debug + Captures<'a> + Captures<'b>;
    |          ^^  ^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
diff --git a/tests/ui/type-alias-impl-trait/generic_duplicate_param_use.rs b/tests/ui/type-alias-impl-trait/generic_duplicate_param_use.rs
index 80462f8ac046c..1e391b55a4fac 100644
--- a/tests/ui/type-alias-impl-trait/generic_duplicate_param_use.rs
+++ b/tests/ui/type-alias-impl-trait/generic_duplicate_param_use.rs
@@ -1,5 +1,12 @@
 #![feature(type_alias_impl_trait)]
 
+//! This test checks various cases where we are using the same
+//! generic parameter twice in the parameter list of a TAIT.
+//! Within defining scopes that is not legal, because the hidden type
+//! is not fully defined then. This could cause us to have a TAIT
+//! that doesn't have a hidden type for all possible combinations of generic
+//! parameters passed to it.
+
 use std::fmt::Debug;
 
 fn main() {}
@@ -7,7 +14,6 @@ fn main() {}
 // test that unused generic parameters are ok
 type TwoTys<T, U> = impl Debug;
 
-
 pub trait Captures<'a> {}
 
 impl<'a, T: ?Sized> Captures<'a> for T {}
@@ -16,18 +22,20 @@ type TwoLifetimes<'a, 'b> = impl Debug + Captures<'a> + Captures<'b>;
 
 type TwoConsts<const X: usize, const Y: usize> = impl Debug;
 
-
 fn one_ty<T: Debug>(t: T) -> TwoTys<T, T> {
+    //~^ ERROR non-defining opaque type use in defining scope
     t
     //~^ ERROR non-defining opaque type use in defining scope
 }
 
 fn one_lifetime<'a>(t: &'a u32) -> TwoLifetimes<'a, 'a> {
+    //~^ ERROR non-defining opaque type use in defining scope
     t
     //~^ ERROR non-defining opaque type use in defining scope
 }
 
 fn one_const<const N: usize>(t: *mut [u8; N]) -> TwoConsts<N, N> {
+    //~^ ERROR non-defining opaque type use in defining scope
     t
     //~^ ERROR non-defining opaque type use in defining scope
 }
diff --git a/tests/ui/type-alias-impl-trait/generic_duplicate_param_use.stderr b/tests/ui/type-alias-impl-trait/generic_duplicate_param_use.stderr
index 98e4bfea10d63..d8330771d301d 100644
--- a/tests/ui/type-alias-impl-trait/generic_duplicate_param_use.stderr
+++ b/tests/ui/type-alias-impl-trait/generic_duplicate_param_use.stderr
@@ -1,38 +1,74 @@
 error: non-defining opaque type use in defining scope
-  --> $DIR/generic_duplicate_param_use.rs:21:5
+  --> $DIR/generic_duplicate_param_use.rs:25:30
+   |
+LL | fn one_ty<T: Debug>(t: T) -> TwoTys<T, T> {
+   |                              ^^^^^^^^^^^^ generic argument `T` used twice
+   |
+note: for this opaque type
+  --> $DIR/generic_duplicate_param_use.rs:15:21
+   |
+LL | type TwoTys<T, U> = impl Debug;
+   |                     ^^^^^^^^^^
+
+error: non-defining opaque type use in defining scope
+  --> $DIR/generic_duplicate_param_use.rs:27:5
    |
 LL |     t
    |     ^
    |
 note: type used multiple times
-  --> $DIR/generic_duplicate_param_use.rs:8:13
+  --> $DIR/generic_duplicate_param_use.rs:15:13
    |
 LL | type TwoTys<T, U> = impl Debug;
    |             ^  ^
 
 error: non-defining opaque type use in defining scope
-  --> $DIR/generic_duplicate_param_use.rs:26:5
+  --> $DIR/generic_duplicate_param_use.rs:31:36
+   |
+LL | fn one_lifetime<'a>(t: &'a u32) -> TwoLifetimes<'a, 'a> {
+   |                                    ^^^^^^^^^^^^^^^^^^^^ generic argument `'a` used twice
+   |
+note: for this opaque type
+  --> $DIR/generic_duplicate_param_use.rs:21:29
+   |
+LL | type TwoLifetimes<'a, 'b> = impl Debug + Captures<'a> + Captures<'b>;
+   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: non-defining opaque type use in defining scope
+  --> $DIR/generic_duplicate_param_use.rs:33:5
    |
 LL |     t
    |     ^
    |
 note: lifetime used multiple times
-  --> $DIR/generic_duplicate_param_use.rs:15:19
+  --> $DIR/generic_duplicate_param_use.rs:21:19
    |
 LL | type TwoLifetimes<'a, 'b> = impl Debug + Captures<'a> + Captures<'b>;
    |                   ^^  ^^
 
 error: non-defining opaque type use in defining scope
-  --> $DIR/generic_duplicate_param_use.rs:31:5
+  --> $DIR/generic_duplicate_param_use.rs:37:50
+   |
+LL | fn one_const<const N: usize>(t: *mut [u8; N]) -> TwoConsts<N, N> {
+   |                                                  ^^^^^^^^^^^^^^^ generic argument `N` used twice
+   |
+note: for this opaque type
+  --> $DIR/generic_duplicate_param_use.rs:23:50
+   |
+LL | type TwoConsts<const X: usize, const Y: usize> = impl Debug;
+   |                                                  ^^^^^^^^^^
+
+error: non-defining opaque type use in defining scope
+  --> $DIR/generic_duplicate_param_use.rs:39:5
    |
 LL |     t
    |     ^
    |
 note: constant used multiple times
-  --> $DIR/generic_duplicate_param_use.rs:17:16
+  --> $DIR/generic_duplicate_param_use.rs:23:16
    |
 LL | type TwoConsts<const X: usize, const Y: usize> = impl Debug;
    |                ^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 6 previous errors
 
diff --git a/tests/ui/type-alias-impl-trait/generic_nondefining_use.rs b/tests/ui/type-alias-impl-trait/generic_nondefining_use.rs
index e7b8567b9a217..68f4c6923ae18 100644
--- a/tests/ui/type-alias-impl-trait/generic_nondefining_use.rs
+++ b/tests/ui/type-alias-impl-trait/generic_nondefining_use.rs
@@ -13,16 +13,19 @@ type OneConst<const X: usize> = impl Debug;
 // Not defining uses, because they doesn't define *all* possible generics.
 
 fn concrete_ty() -> OneTy<u32> {
+    //~^ ERROR: non-defining opaque type use in defining scope
     5u32
-    //~^ ERROR expected generic type parameter, found `u32`
+    //~^ ERROR: expected generic type parameter, found `u32`
 }
 
 fn concrete_lifetime() -> OneLifetime<'static> {
+    //~^ ERROR: non-defining opaque type use in defining scope
     6u32
-    //~^ ERROR expected generic lifetime parameter, found `'static`
+    //~^ ERROR: expected generic lifetime parameter, found `'static`
 }
 
 fn concrete_const() -> OneConst<{ 123 }> {
+    //~^ ERROR: non-defining opaque type use in defining scope
     7u32
-    //~^ ERROR expected generic constant parameter, found `123`
+    //~^ ERROR: expected generic constant parameter, found `123`
 }
diff --git a/tests/ui/type-alias-impl-trait/generic_nondefining_use.stderr b/tests/ui/type-alias-impl-trait/generic_nondefining_use.stderr
index 966fe823f024d..e3b7b1a76b09d 100644
--- a/tests/ui/type-alias-impl-trait/generic_nondefining_use.stderr
+++ b/tests/ui/type-alias-impl-trait/generic_nondefining_use.stderr
@@ -1,5 +1,17 @@
+error[E0792]: non-defining opaque type use in defining scope
+  --> $DIR/generic_nondefining_use.rs:15:21
+   |
+LL | fn concrete_ty() -> OneTy<u32> {
+   |                     ^^^^^^^^^^ argument `u32` is not a generic parameter
+   |
+note: for this opaque type
+  --> $DIR/generic_nondefining_use.rs:7:17
+   |
+LL | type OneTy<T> = impl Debug;
+   |                 ^^^^^^^^^^
+
 error[E0792]: expected generic type parameter, found `u32`
-  --> $DIR/generic_nondefining_use.rs:16:5
+  --> $DIR/generic_nondefining_use.rs:17:5
    |
 LL | type OneTy<T> = impl Debug;
    |            - this generic parameter must be used with a generic type parameter
@@ -7,8 +19,20 @@ LL | type OneTy<T> = impl Debug;
 LL |     5u32
    |     ^^^^
 
+error[E0792]: non-defining opaque type use in defining scope
+  --> $DIR/generic_nondefining_use.rs:21:27
+   |
+LL | fn concrete_lifetime() -> OneLifetime<'static> {
+   |                           ^^^^^^^^^^^^^^^^^^^^ argument `'static` is not a generic parameter
+   |
+note: for this opaque type
+  --> $DIR/generic_nondefining_use.rs:9:24
+   |
+LL | type OneLifetime<'a> = impl Debug;
+   |                        ^^^^^^^^^^
+
 error[E0792]: expected generic lifetime parameter, found `'static`
-  --> $DIR/generic_nondefining_use.rs:21:5
+  --> $DIR/generic_nondefining_use.rs:23:5
    |
 LL | type OneLifetime<'a> = impl Debug;
    |                  -- cannot use static lifetime; use a bound lifetime instead or remove the lifetime parameter from the opaque type
@@ -16,8 +40,20 @@ LL | type OneLifetime<'a> = impl Debug;
 LL |     6u32
    |     ^^^^
 
+error[E0792]: non-defining opaque type use in defining scope
+  --> $DIR/generic_nondefining_use.rs:27:24
+   |
+LL | fn concrete_const() -> OneConst<{ 123 }> {
+   |                        ^^^^^^^^^^^^^^^^^ argument `123` is not a generic parameter
+   |
+note: for this opaque type
+  --> $DIR/generic_nondefining_use.rs:11:33
+   |
+LL | type OneConst<const X: usize> = impl Debug;
+   |                                 ^^^^^^^^^^
+
 error[E0792]: expected generic constant parameter, found `123`
-  --> $DIR/generic_nondefining_use.rs:26:5
+  --> $DIR/generic_nondefining_use.rs:29:5
    |
 LL | type OneConst<const X: usize> = impl Debug;
    |               -------------- this generic parameter must be used with a generic constant parameter
@@ -25,6 +61,6 @@ LL | type OneConst<const X: usize> = impl Debug;
 LL |     7u32
    |     ^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0792`.
diff --git a/tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.rs b/tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.rs
index cdd8f6f1976a5..c60f5c11cd18c 100644
--- a/tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.rs
+++ b/tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.rs
@@ -5,12 +5,12 @@ fn main() {
     let x = wrong_generic(&y);
     let z: i32 = x;
     //~^ ERROR expected generic type parameter, found `&i32`
-}
 
-type WrongGeneric<T> = impl 'static;
-//~^ ERROR: at least one trait must be specified
+    type WrongGeneric<T> = impl 'static;
+    //~^ ERROR: at least one trait must be specified
 
-fn wrong_generic<T>(t: T) -> WrongGeneric<T> {
-    t
-    //~^ ERROR the parameter type `T` may not live long enough
+    fn wrong_generic<T>(t: T) -> WrongGeneric<T> {
+        t
+        //~^ ERROR the parameter type `T` may not live long enough
+    }
 }
diff --git a/tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.stderr b/tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.stderr
index fa79e51e9f79f..8c3a25dbfe7de 100644
--- a/tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.stderr
+++ b/tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.stderr
@@ -1,8 +1,8 @@
 error: at least one trait must be specified
-  --> $DIR/generic_type_does_not_live_long_enough.rs:10:24
+  --> $DIR/generic_type_does_not_live_long_enough.rs:9:28
    |
-LL | type WrongGeneric<T> = impl 'static;
-   |                        ^^^^^^^^^^^^
+LL |     type WrongGeneric<T> = impl 'static;
+   |                            ^^^^^^^^^^^^
 
 error[E0792]: expected generic type parameter, found `&i32`
   --> $DIR/generic_type_does_not_live_long_enough.rs:6:18
@@ -10,19 +10,19 @@ error[E0792]: expected generic type parameter, found `&i32`
 LL |     let z: i32 = x;
    |                  ^
 ...
-LL | type WrongGeneric<T> = impl 'static;
-   |                   - this generic parameter must be used with a generic type parameter
+LL |     type WrongGeneric<T> = impl 'static;
+   |                       - this generic parameter must be used with a generic type parameter
 
 error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/generic_type_does_not_live_long_enough.rs:14:5
+  --> $DIR/generic_type_does_not_live_long_enough.rs:13:9
    |
-LL |     t
-   |     ^ ...so that the type `T` will meet its required lifetime bounds
+LL |         t
+   |         ^ ...so that the type `T` will meet its required lifetime bounds
    |
 help: consider adding an explicit lifetime bound...
    |
-LL | fn wrong_generic<T: 'static>(t: T) -> WrongGeneric<T> {
-   |                   +++++++++
+LL |     fn wrong_generic<T: 'static>(t: T) -> WrongGeneric<T> {
+   |                       +++++++++
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/type-alias-impl-trait/higher_kinded_params.rs b/tests/ui/type-alias-impl-trait/higher_kinded_params.rs
new file mode 100644
index 0000000000000..db1a3a1c7a9d0
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/higher_kinded_params.rs
@@ -0,0 +1,28 @@
+//! This test checks that walking into binders
+//! during opaque type collection does not ICE or raise errors.
+
+// edition: 2021
+
+// check-pass
+
+#![feature(type_alias_impl_trait)]
+
+trait B {
+    type C;
+}
+
+struct A;
+
+impl<'a> B for &'a A {
+    type C = ();
+}
+
+struct Terminator;
+
+type Successors<'a> = impl std::fmt::Debug + 'a;
+
+impl Terminator {
+    fn successors(&self, _: for<'x> fn(&'x ()) -> <&'x A as B>::C) -> Successors<'_> {}
+}
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/higher_kinded_params2.rs b/tests/ui/type-alias-impl-trait/higher_kinded_params2.rs
new file mode 100644
index 0000000000000..f011e5b214813
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/higher_kinded_params2.rs
@@ -0,0 +1,35 @@
+//! This test checks the behaviour of walking into binders
+//! and normalizing something behind them actually works.
+
+// edition: 2021
+
+#![feature(type_alias_impl_trait)]
+
+trait B {
+    type C;
+}
+
+struct A;
+
+impl<'a> B for &'a A {
+    type C = Tait;
+}
+
+type Tait = impl std::fmt::Debug;
+
+struct Terminator;
+
+type Successors<'a> = impl std::fmt::Debug + 'a;
+
+impl Terminator {
+    fn successors(&self, mut f: for<'x> fn(&'x ()) -> <&'x A as B>::C) -> Successors<'_> {
+        f = g;
+        //~^ ERROR item constrains opaque type that is not in its signature
+    }
+}
+
+fn g(_: &()) -> String {
+    String::new()
+}
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/higher_kinded_params2.stderr b/tests/ui/type-alias-impl-trait/higher_kinded_params2.stderr
new file mode 100644
index 0000000000000..39f584dd49ca3
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/higher_kinded_params2.stderr
@@ -0,0 +1,15 @@
+error: item constrains opaque type that is not in its signature
+  --> $DIR/higher_kinded_params2.rs:26:13
+   |
+LL |         f = g;
+   |             ^
+   |
+   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
+note: this item must mention the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/higher_kinded_params2.rs:25:8
+   |
+LL |     fn successors(&self, mut f: for<'x> fn(&'x ()) -> <&'x A as B>::C) -> Successors<'_> {
+   |        ^^^^^^^^^^
+
+error: aborting due to previous error
+
diff --git a/tests/ui/type-alias-impl-trait/higher_kinded_params3.rs b/tests/ui/type-alias-impl-trait/higher_kinded_params3.rs
index 839a611cb71a9..6edfccaf7d179 100644
--- a/tests/ui/type-alias-impl-trait/higher_kinded_params3.rs
+++ b/tests/ui/type-alias-impl-trait/higher_kinded_params3.rs
@@ -24,7 +24,8 @@ type Successors<'a> = impl std::fmt::Debug + 'a;
 impl Terminator {
     fn successors(&self, mut f: for<'x> fn(&'x ()) -> <&'x A as B>::C) -> Successors<'_> {
         f = g;
-        //~^ ERROR: mismatched types
+        //~^ ERROR mismatched types
+        //~| ERROR item constrains opaque type that is not in its signature
     }
 }
 
diff --git a/tests/ui/type-alias-impl-trait/higher_kinded_params3.stderr b/tests/ui/type-alias-impl-trait/higher_kinded_params3.stderr
index aaba9ad5ca704..14372d8f3e64d 100644
--- a/tests/ui/type-alias-impl-trait/higher_kinded_params3.stderr
+++ b/tests/ui/type-alias-impl-trait/higher_kinded_params3.stderr
@@ -1,3 +1,16 @@
+error: item constrains opaque type that is not in its signature
+  --> $DIR/higher_kinded_params3.rs:26:13
+   |
+LL |         f = g;
+   |             ^
+   |
+   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
+note: this item must mention the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/higher_kinded_params3.rs:25:8
+   |
+LL |     fn successors(&self, mut f: for<'x> fn(&'x ()) -> <&'x A as B>::C) -> Successors<'_> {
+   |        ^^^^^^^^^^
+
 error[E0308]: mismatched types
   --> $DIR/higher_kinded_params3.rs:26:9
    |
@@ -10,6 +23,6 @@ LL |         f = g;
    = note: expected fn pointer `for<'x> fn(&'x ()) -> Tait<'x>`
               found fn pointer `for<'a> fn(&'a ()) -> &'a ()`
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/type-alias-impl-trait/inference-cycle.rs b/tests/ui/type-alias-impl-trait/inference-cycle.rs
index 093afc25249a7..20175a4feca00 100644
--- a/tests/ui/type-alias-impl-trait/inference-cycle.rs
+++ b/tests/ui/type-alias-impl-trait/inference-cycle.rs
@@ -17,8 +17,8 @@ mod m {
         //~^ ERROR: cannot check whether the hidden type of `inference_cycle[4ecc]::m::Foo::{opaque#0}` satisfies auto traits
     }
 
-    fn baz() {
-        let f: Foo = ();
+    fn baz() -> Foo {
+        ()
     }
 
     fn is_send<T: Send>(_: T) {}
diff --git a/tests/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.rs b/tests/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.rs
index a3f126d56cf20..a213dbba4ea01 100644
--- a/tests/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.rs
+++ b/tests/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.rs
@@ -1,19 +1,22 @@
 #![feature(generators, generator_trait, rustc_attrs)]
 #![feature(type_alias_impl_trait)]
 
-use std::ops::Generator;
+// check-pass
 
-type GenOnce<Y, R> = impl Generator<Yield = Y, Return = R>;
+mod gen {
+    use std::ops::Generator;
 
-const fn const_generator<Y, R>(yielding: Y, returning: R) -> GenOnce<Y, R> {
-    move || {
-        yield yielding;
+    pub type GenOnce<Y, R> = impl Generator<Yield = Y, Return = R>;
 
-        return returning;
+    pub const fn const_generator<Y, R>(yielding: Y, returning: R) -> GenOnce<Y, R> {
+        move || {
+            yield yielding;
+
+            return returning;
+        }
     }
 }
 
-const FOO: GenOnce<usize, usize> = const_generator(10, 100);
+const FOO: gen::GenOnce<usize, usize> = gen::const_generator(10, 100);
 
-#[rustc_error]
-fn main() {} //~ ERROR
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.stderr b/tests/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.stderr
deleted file mode 100644
index eb1c9603a60d6..0000000000000
--- a/tests/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.stderr
+++ /dev/null
@@ -1,8 +0,0 @@
-error: fatal error triggered by #[rustc_error]
-  --> $DIR/issue-53678-generator-and-const-fn.rs:19:1
-   |
-LL | fn main() {}
-   | ^^^^^^^^^
-
-error: aborting due to previous error
-
diff --git a/tests/ui/type-alias-impl-trait/issue-57961.rs b/tests/ui/type-alias-impl-trait/issue-57961.rs
index 4aa5966ff25d4..61af7a0f62500 100644
--- a/tests/ui/type-alias-impl-trait/issue-57961.rs
+++ b/tests/ui/type-alias-impl-trait/issue-57961.rs
@@ -11,8 +11,8 @@ impl Foo for () {
     //~^ ERROR expected `IntoIter<u32>` to be an iterator that yields `X`, but it yields `u32`
 }
 
-fn incoherent() {
-    let f: X = 22_i32;
+fn incoherent() -> X {
+    22_i32
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/issue-60564.rs b/tests/ui/type-alias-impl-trait/issue-60564.rs
index c2f4c37080746..48bd70bcca950 100644
--- a/tests/ui/type-alias-impl-trait/issue-60564.rs
+++ b/tests/ui/type-alias-impl-trait/issue-60564.rs
@@ -17,6 +17,7 @@ where
 {
     type BitsIter = IterBitsIter<T, E, u8>;
     fn iter_bits(self, n: u8) -> Self::BitsIter {
+        //~^ ERROR non-defining opaque type use
         (0u8..n).rev().map(move |shift| ((self >> T::from(shift)) & T::from(1)).try_into().unwrap())
         //~^ ERROR expected generic type parameter, found `u8`
     }
diff --git a/tests/ui/type-alias-impl-trait/issue-60564.stderr b/tests/ui/type-alias-impl-trait/issue-60564.stderr
index f8fdb004d0989..d42495e934d33 100644
--- a/tests/ui/type-alias-impl-trait/issue-60564.stderr
+++ b/tests/ui/type-alias-impl-trait/issue-60564.stderr
@@ -1,5 +1,17 @@
+error[E0792]: non-defining opaque type use in defining scope
+  --> $DIR/issue-60564.rs:19:34
+   |
+LL |     fn iter_bits(self, n: u8) -> Self::BitsIter {
+   |                                  ^^^^^^^^^^^^^^ argument `u8` is not a generic parameter
+   |
+note: for this opaque type
+  --> $DIR/issue-60564.rs:8:30
+   |
+LL | type IterBitsIter<T, E, I> = impl std::iter::Iterator<Item = I>;
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0792]: expected generic type parameter, found `u8`
-  --> $DIR/issue-60564.rs:20:9
+  --> $DIR/issue-60564.rs:21:9
    |
 LL | type IterBitsIter<T, E, I> = impl std::iter::Iterator<Item = I>;
    |                         - this generic parameter must be used with a generic type parameter
@@ -7,6 +19,6 @@ LL | type IterBitsIter<T, E, I> = impl std::iter::Iterator<Item = I>;
 LL |         (0u8..n).rev().map(move |shift| ((self >> T::from(shift)) & T::from(1)).try_into().unwrap())
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0792`.
diff --git a/tests/ui/type-alias-impl-trait/issue-63263-closure-return.rs b/tests/ui/type-alias-impl-trait/issue-63263-closure-return.rs
index 7414611a74893..ddea7aeb6cda7 100644
--- a/tests/ui/type-alias-impl-trait/issue-63263-closure-return.rs
+++ b/tests/ui/type-alias-impl-trait/issue-63263-closure-return.rs
@@ -8,6 +8,9 @@
 
 pub type Closure = impl FnOnce();
 
-fn main() {
+fn bop() -> Closure {
     || -> Closure { || () };
+    panic!()
 }
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/issue-65679-inst-opaque-ty-from-val-twice.rs b/tests/ui/type-alias-impl-trait/issue-65679-inst-opaque-ty-from-val-twice.rs
index b91cbce3727f6..7b3e9e12405c7 100644
--- a/tests/ui/type-alias-impl-trait/issue-65679-inst-opaque-ty-from-val-twice.rs
+++ b/tests/ui/type-alias-impl-trait/issue-65679-inst-opaque-ty-from-val-twice.rs
@@ -11,7 +11,9 @@ type T = impl Sized;
 
 fn take(_: fn() -> T) {}
 
-fn main() {
+fn bop(_: T) {
     take(|| {});
     take(|| {});
 }
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.rs b/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.rs
index 5e0a82a72868a..9dcdb578568aa 100644
--- a/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.rs
+++ b/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.rs
@@ -7,7 +7,8 @@ trait Trait<T> {}
 type Alias<'a, U> = impl Trait<U>;
 
 fn f<'a>() -> Alias<'a, ()> {}
-//~^ ERROR expected generic type parameter, found `()`
+//~^ ERROR non-defining opaque type use
+//~| ERROR expected generic type parameter, found `()`
 
 fn main() {}
 
diff --git a/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.stderr b/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.stderr
index 271743a4010c8..085bffe907b4b 100644
--- a/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.stderr
+++ b/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.stderr
@@ -1,3 +1,15 @@
+error[E0792]: non-defining opaque type use in defining scope
+  --> $DIR/issue-68368-non-defining-use-2.rs:9:15
+   |
+LL | fn f<'a>() -> Alias<'a, ()> {}
+   |               ^^^^^^^^^^^^^ argument `()` is not a generic parameter
+   |
+note: for this opaque type
+  --> $DIR/issue-68368-non-defining-use-2.rs:7:21
+   |
+LL | type Alias<'a, U> = impl Trait<U>;
+   |                     ^^^^^^^^^^^^^
+
 error[E0792]: expected generic type parameter, found `()`
   --> $DIR/issue-68368-non-defining-use-2.rs:9:29
    |
@@ -7,6 +19,6 @@ LL |
 LL | fn f<'a>() -> Alias<'a, ()> {}
    |                             ^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0792`.
diff --git a/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use.rs b/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use.rs
index 3b32260c96fe1..dfe2ee8204c75 100644
--- a/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use.rs
+++ b/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use.rs
@@ -8,6 +8,7 @@ type Alias<'a, U> = impl Trait<U>;
 
 fn f<'a>() -> Alias<'a, ()> {}
 //~^ ERROR expected generic type parameter, found `()`
+//~| ERROR non-defining opaque type use
 
 fn main() {}
 
diff --git a/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use.stderr b/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use.stderr
index 4d9a8d6eef915..ea704ffff97ab 100644
--- a/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use.stderr
+++ b/tests/ui/type-alias-impl-trait/issue-68368-non-defining-use.stderr
@@ -1,3 +1,15 @@
+error[E0792]: non-defining opaque type use in defining scope
+  --> $DIR/issue-68368-non-defining-use.rs:9:15
+   |
+LL | fn f<'a>() -> Alias<'a, ()> {}
+   |               ^^^^^^^^^^^^^ argument `()` is not a generic parameter
+   |
+note: for this opaque type
+  --> $DIR/issue-68368-non-defining-use.rs:7:21
+   |
+LL | type Alias<'a, U> = impl Trait<U>;
+   |                     ^^^^^^^^^^^^^
+
 error[E0792]: expected generic type parameter, found `()`
   --> $DIR/issue-68368-non-defining-use.rs:9:29
    |
@@ -7,6 +19,6 @@ LL |
 LL | fn f<'a>() -> Alias<'a, ()> {}
    |                             ^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0792`.
diff --git a/tests/ui/type-alias-impl-trait/issue-69136-inner-lifetime-resolve-error.rs b/tests/ui/type-alias-impl-trait/issue-69136-inner-lifetime-resolve-error.rs
index 7657fe2fb1aee..a0f8e48e268c9 100644
--- a/tests/ui/type-alias-impl-trait/issue-69136-inner-lifetime-resolve-error.rs
+++ b/tests/ui/type-alias-impl-trait/issue-69136-inner-lifetime-resolve-error.rs
@@ -1,4 +1,6 @@
-// Regression test for #69136
+//! Regression test for #69136
+//! This test checks that the unknown lifetime `'a` doesn't cause
+//! ICEs after emitting the error.
 
 #![feature(type_alias_impl_trait)]
 
@@ -17,7 +19,6 @@ impl<T> WithAssoc<T> for () {
 type Return<A> = impl WithAssoc<A, AssocType = impl SomeTrait + 'a>;
 //~^ ERROR use of undeclared lifetime name `'a`
 
-fn my_fun() -> Return<()> {}
-//~^ ERROR expected generic type parameter, found `()`
+fn my_fun<T>() -> Return<T> {}
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/issue-69136-inner-lifetime-resolve-error.stderr b/tests/ui/type-alias-impl-trait/issue-69136-inner-lifetime-resolve-error.stderr
index d1250786d938c..b7af3f06d0d9a 100644
--- a/tests/ui/type-alias-impl-trait/issue-69136-inner-lifetime-resolve-error.stderr
+++ b/tests/ui/type-alias-impl-trait/issue-69136-inner-lifetime-resolve-error.stderr
@@ -1,5 +1,5 @@
 error[E0261]: use of undeclared lifetime name `'a`
-  --> $DIR/issue-69136-inner-lifetime-resolve-error.rs:17:65
+  --> $DIR/issue-69136-inner-lifetime-resolve-error.rs:19:65
    |
 LL | type Return<A> = impl WithAssoc<A, AssocType = impl SomeTrait + 'a>;
    |                                                                 ^^ undeclared lifetime
@@ -14,16 +14,6 @@ help: consider introducing lifetime `'a` here
 LL | type Return<'a, A> = impl WithAssoc<A, AssocType = impl SomeTrait + 'a>;
    |             +++
 
-error[E0792]: expected generic type parameter, found `()`
-  --> $DIR/issue-69136-inner-lifetime-resolve-error.rs:20:27
-   |
-LL | type Return<A> = impl WithAssoc<A, AssocType = impl SomeTrait + 'a>;
-   |             - this generic parameter must be used with a generic type parameter
-...
-LL | fn my_fun() -> Return<()> {}
-   |                           ^^
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors have detailed explanations: E0261, E0792.
-For more information about an error, try `rustc --explain E0261`.
+For more information about this error, try `rustc --explain E0261`.
diff --git a/tests/ui/type-alias-impl-trait/issue-70121.rs b/tests/ui/type-alias-impl-trait/issue-70121.rs
index dff0d89d465dd..bfd8d8872e37f 100644
--- a/tests/ui/type-alias-impl-trait/issue-70121.rs
+++ b/tests/ui/type-alias-impl-trait/issue-70121.rs
@@ -1,5 +1,3 @@
-// check-pass
-
 #![feature(type_alias_impl_trait)]
 
 pub type Successors<'a> = impl Iterator<Item = &'a ()>;
@@ -17,6 +15,7 @@ impl<'a> Tr for &'a () {
 }
 
 pub fn kazusa<'a>() -> <&'a () as Tr>::Item {
+    //~^ ERROR item constrains opaque type that is not in its signature
     None.into_iter()
 }
 
diff --git a/tests/ui/type-alias-impl-trait/issue-70121.stderr b/tests/ui/type-alias-impl-trait/issue-70121.stderr
new file mode 100644
index 0000000000000..30c3ddd8659d1
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/issue-70121.stderr
@@ -0,0 +1,15 @@
+error: item constrains opaque type that is not in its signature
+  --> $DIR/issue-70121.rs:17:24
+   |
+LL | pub fn kazusa<'a>() -> <&'a () as Tr>::Item {
+   |                        ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
+note: this item must mention the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/issue-70121.rs:17:8
+   |
+LL | pub fn kazusa<'a>() -> <&'a () as Tr>::Item {
+   |        ^^^^^^
+
+error: aborting due to previous error
+
diff --git a/tests/ui/type-alias-impl-trait/issue-77179.rs b/tests/ui/type-alias-impl-trait/issue-77179.rs
index 8d818d4a387a6..e7b04a4897559 100644
--- a/tests/ui/type-alias-impl-trait/issue-77179.rs
+++ b/tests/ui/type-alias-impl-trait/issue-77179.rs
@@ -2,7 +2,7 @@
 
 #![feature(type_alias_impl_trait)]
 
-type Pointer<T> = impl std::ops::Deref<Target=T>;
+type Pointer<T> = impl std::ops::Deref<Target = T>;
 
 fn test() -> Pointer<_> {
     //~^ ERROR: the placeholder `_` is not allowed within types
diff --git a/tests/ui/type-alias-impl-trait/nested_in_closure.rs b/tests/ui/type-alias-impl-trait/nested_in_closure.rs
new file mode 100644
index 0000000000000..362f3d53e88bf
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/nested_in_closure.rs
@@ -0,0 +1,17 @@
+#![feature(type_alias_impl_trait)]
+// check-pass
+
+fn main() {
+    let x = || {
+        type Tait = impl Sized;
+        let y: Tait = ();
+    };
+
+    let y = || {
+        type Tait = impl std::fmt::Debug;
+        let y: Tait = ();
+        y
+    };
+    let mut z = y();
+    z = ();
+}
diff --git a/tests/ui/type-alias-impl-trait/nested_type_alias_impl_trait.rs b/tests/ui/type-alias-impl-trait/nested_type_alias_impl_trait.rs
index 60b6e1aac6281..07607516cc4bc 100644
--- a/tests/ui/type-alias-impl-trait/nested_type_alias_impl_trait.rs
+++ b/tests/ui/type-alias-impl-trait/nested_type_alias_impl_trait.rs
@@ -10,11 +10,11 @@ mod my_mod {
         5i32
     }
 
-    pub fn get_foot() -> Foot {
+    pub fn get_foot(_: Foo) -> Foot {
         get_foo() //~ ERROR opaque type's hidden type cannot be another opaque type
     }
 }
 
 fn main() {
-    let _: my_mod::Foot = my_mod::get_foot();
+    let _: my_mod::Foot = my_mod::get_foot(my_mod::get_foo());
 }
diff --git a/tests/ui/type-alias-impl-trait/no_revealing_outside_defining_module.stderr b/tests/ui/type-alias-impl-trait/no_revealing_outside_defining_module.stderr
index ae03a5b3e37bf..863282a0ff94d 100644
--- a/tests/ui/type-alias-impl-trait/no_revealing_outside_defining_module.stderr
+++ b/tests/ui/type-alias-impl-trait/no_revealing_outside_defining_module.stderr
@@ -11,6 +11,11 @@ LL |     let _: &str = bomp();
    |
    = note: expected reference `&str`
             found opaque type `Boo`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/no_revealing_outside_defining_module.rs:14:4
+   |
+LL | fn bomp2() {
+   |    ^^^^^
 
 error[E0308]: mismatched types
   --> $DIR/no_revealing_outside_defining_module.rs:19:5
@@ -25,6 +30,11 @@ LL |     ""
    |
    = note: expected opaque type `Boo`
                 found reference `&'static str`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/no_revealing_outside_defining_module.rs:18:4
+   |
+LL | fn bomp() -> boo::Boo {
+   |    ^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/type-alias-impl-trait/reveal_local.rs b/tests/ui/type-alias-impl-trait/reveal_local.rs
index 75015e41c3da7..7943bb240f15b 100644
--- a/tests/ui/type-alias-impl-trait/reveal_local.rs
+++ b/tests/ui/type-alias-impl-trait/reveal_local.rs
@@ -16,7 +16,7 @@ fn not_good() {
     //~^ ERROR: cannot check whether the hidden type of `reveal_local[9507]::Foo::{opaque#0}` satisfies auto traits
 }
 
-fn not_gooder() {
+fn not_gooder() -> Foo {
     // Constrain `Foo = u32`
     let x: Foo = 22_u32;
 
@@ -24,6 +24,8 @@ fn not_gooder() {
     // need extra roundabout logic to support it.
     is_send::<Foo>();
     //~^ ERROR: cannot check whether the hidden type of `reveal_local[9507]::Foo::{opaque#0}` satisfies auto traits
+
+    x
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/reveal_local.stderr b/tests/ui/type-alias-impl-trait/reveal_local.stderr
index 202a87ecbb773..0c5ef4a6fb418 100644
--- a/tests/ui/type-alias-impl-trait/reveal_local.stderr
+++ b/tests/ui/type-alias-impl-trait/reveal_local.stderr
@@ -78,8 +78,8 @@ LL | type Foo = impl Debug;
 note: ...which requires type-checking `not_gooder`...
   --> $DIR/reveal_local.rs:19:1
    |
-LL | fn not_gooder() {
-   | ^^^^^^^^^^^^^^^
+LL | fn not_gooder() -> Foo {
+   | ^^^^^^^^^^^^^^^^^^^^^^
    = note: ...which again requires computing type of `Foo::{opaque#0}`, completing the cycle
 note: cycle used when checking item types in top-level module
   --> $DIR/reveal_local.rs:1:1
@@ -107,7 +107,7 @@ LL | type Foo = impl Debug;
 note: this item depends on auto traits of the hidden type, but may also be registering the hidden type. This is not supported right now. You can try moving the opaque type and the item that actually registers a hidden type into a new submodule
   --> $DIR/reveal_local.rs:19:4
    |
-LL | fn not_gooder() {
+LL | fn not_gooder() -> Foo {
    |    ^^^^^^^^^^
 note: required by a bound in `is_send`
   --> $DIR/reveal_local.rs:10:15
diff --git a/tests/ui/type-alias-impl-trait/type_of_a_let.rs b/tests/ui/type-alias-impl-trait/type_of_a_let.rs
index 4e9d1788b94d8..36161171555ca 100644
--- a/tests/ui/type-alias-impl-trait/type_of_a_let.rs
+++ b/tests/ui/type-alias-impl-trait/type_of_a_let.rs
@@ -5,16 +5,16 @@ use std::fmt::Debug;
 
 type Foo = impl Debug;
 
-fn foo1() -> u32 {
+fn foo1() -> (u32, Foo) {
     let x: Foo = 22_u32;
-    x
+    (x, todo!())
 }
 
-fn foo2() -> u32 {
+fn foo2() -> (u32, Foo) {
     let x: Foo = 22_u32;
     let y: Foo = x;
     same_type((x, y)); //~ ERROR use of moved value
-    y //~ ERROR use of moved value
+    (y, todo!()) //~ ERROR use of moved value
 }
 
 fn same_type<T>(x: (T, T)) {}
diff --git a/tests/ui/type-alias-impl-trait/type_of_a_let.stderr b/tests/ui/type-alias-impl-trait/type_of_a_let.stderr
index 1dabe4586c5b9..7d7cad874faec 100644
--- a/tests/ui/type-alias-impl-trait/type_of_a_let.stderr
+++ b/tests/ui/type-alias-impl-trait/type_of_a_let.stderr
@@ -9,14 +9,14 @@ LL |     same_type((x, y));
    |                ^ value used here after move
 
 error[E0382]: use of moved value: `y`
-  --> $DIR/type_of_a_let.rs:17:5
+  --> $DIR/type_of_a_let.rs:17:6
    |
 LL |     let y: Foo = x;
    |         - move occurs because `y` has type `Foo`, which does not implement the `Copy` trait
 LL |     same_type((x, y));
    |                   - value moved here
-LL |     y
-   |     ^ value used here after move
+LL |     (y, todo!())
+   |      ^ value used here after move
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/typeck/issue-103899.rs b/tests/ui/typeck/issue-103899.rs
index ac9e4c716962f..e33be0950dac2 100644
--- a/tests/ui/typeck/issue-103899.rs
+++ b/tests/ui/typeck/issue-103899.rs
@@ -2,6 +2,7 @@
 // failure-status: 101
 // dont-check-compiler-stderr
 // known-bug: #103899
+// rustc-env:RUSTC_ICE=0
 
 trait BaseWithAssoc {
     type Assoc;