Merging upstream version 1.72.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

75 files changed, 2845 insertions, 2818 deletions

diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index a149a61ec..5a320865c 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -27,6 +27,11 @@ macro_rules! arena_types {
                     rustc_middle::mir::Promoted,
                     rustc_middle::mir::Body<'tcx>
                 >,
+            [decode] closure_debuginfo:
+                rustc_index::IndexVec<
+                    rustc_target::abi::FieldIdx,
+                    rustc_span::symbol::Symbol,
+                >,
             [decode] typeck_results: rustc_middle::ty::TypeckResults<'tcx>,
             [decode] borrowck_result:
                 rustc_middle::mir::BorrowCheckResult<'tcx>,
@@ -78,9 +83,9 @@ macro_rules! arena_types {
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx, rustc_middle::ty::FnSig<'tcx>>
                 >,
-            [] type_op_normalize_predicate:
+            [] type_op_normalize_clause:
                 rustc_middle::infer::canonical::Canonical<'tcx,
-                    rustc_middle::infer::canonical::QueryResponse<'tcx, rustc_middle::ty::Predicate<'tcx>>
+                    rustc_middle::infer::canonical::QueryResponse<'tcx, rustc_middle::ty::Clause<'tcx>>
                 >,
             [] type_op_normalize_ty:
                 rustc_middle::infer::canonical::Canonical<'tcx,
@@ -124,6 +129,7 @@ macro_rules! arena_types {
             [] predefined_opaques_in_body: rustc_middle::traits::solve::PredefinedOpaquesData<'tcx>,
             [decode] doc_link_resolutions: rustc_hir::def::DocLinkResMap,
             [] closure_kind_origin: (rustc_span::Span, rustc_middle::hir::place::Place<'tcx>),
+            [] stripped_cfg_items: rustc_ast::expand::StrippedCfgItem,
             [] mod_child: rustc_middle::metadata::ModChild,
         ]);
     )
diff --git a/compiler/rustc_middle/src/error.rs b/compiler/rustc_middle/src/error.rs
index 046186d27..57b2de84b 100644
--- a/compiler/rustc_middle/src/error.rs
+++ b/compiler/rustc_middle/src/error.rs
@@ -1,3 +1,7 @@
+use std::borrow::Cow;
+use std::fmt;
+
+use rustc_errors::{DiagnosticArgValue, DiagnosticMessage};
 use rustc_macros::Diagnostic;
 use rustc_span::{Span, Symbol};
 
@@ -88,3 +92,54 @@ pub(super) struct ConstNotUsedTraitAlias {
     #[primary_span]
     pub span: Span,
 }
+
+pub struct CustomSubdiagnostic<'a> {
+    pub msg: fn() -> DiagnosticMessage,
+    pub add_args:
+        Box<dyn FnOnce(&mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue<'static>)) + 'a>,
+}
+
+impl<'a> CustomSubdiagnostic<'a> {
+    pub fn label(x: fn() -> DiagnosticMessage) -> Self {
+        Self::label_and_then(x, |_| {})
+    }
+    pub fn label_and_then<
+        F: FnOnce(&mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue<'static>)) + 'a,
+    >(
+        msg: fn() -> DiagnosticMessage,
+        f: F,
+    ) -> Self {
+        Self { msg, add_args: Box::new(move |x| f(x)) }
+    }
+}
+
+impl fmt::Debug for CustomSubdiagnostic<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("CustomSubdiagnostic").finish_non_exhaustive()
+    }
+}
+
+#[derive(Diagnostic)]
+pub enum LayoutError<'tcx> {
+    #[diag(middle_unknown_layout)]
+    Unknown { ty: Ty<'tcx> },
+
+    #[diag(middle_values_too_big)]
+    Overflow { ty: Ty<'tcx> },
+
+    #[diag(middle_cannot_be_normalized)]
+    NormalizationFailure { ty: Ty<'tcx>, failure_ty: String },
+
+    #[diag(middle_cycle)]
+    Cycle,
+}
+
+#[derive(Diagnostic)]
+#[diag(middle_adjust_for_foreign_abi_error)]
+pub struct UnsupportedFnAbi {
+    pub arch: Symbol,
+    pub abi: &'static str,
+}
+
+/// Used by `rustc_const_eval`
+pub use crate::fluent_generated::middle_adjust_for_foreign_abi_error;
diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index d1ddc8fc1..5f2eb890c 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -44,6 +44,7 @@ pub fn associated_body(node: Node<'_>) -> Option<(LocalDefId, BodyId)> {
         }
 
         Node::AnonConst(constant) => Some((constant.def_id, constant.body)),
+        Node::ConstBlock(constant) => Some((constant.def_id, constant.body)),
 
         _ => None,
     }
@@ -240,15 +241,8 @@ impl<'hir> Map<'hir> {
                     None => bug!("constructor node without a constructor"),
                 }
             }
-            Node::AnonConst(_) => {
-                let inline = match self.find_parent(hir_id) {
-                    Some(Node::Expr(&Expr {
-                        kind: ExprKind::ConstBlock(ref anon_const), ..
-                    })) if anon_const.hir_id == hir_id => true,
-                    _ => false,
-                };
-                if inline { DefKind::InlineConst } else { DefKind::AnonConst }
-            }
+            Node::AnonConst(_) => DefKind::AnonConst,
+            Node::ConstBlock(_) => DefKind::InlineConst,
             Node::Field(_) => DefKind::Field,
             Node::Expr(expr) => match expr.kind {
                 ExprKind::Closure(Closure { movability: None, .. }) => DefKind::Closure,
@@ -1060,6 +1054,7 @@ impl<'hir> Map<'hir> {
             Node::Variant(variant) => variant.span,
             Node::Field(field) => field.span,
             Node::AnonConst(constant) => self.body(constant.body).value.span,
+            Node::ConstBlock(constant) => self.body(constant.body).value.span,
             Node::Expr(expr) => expr.span,
             Node::ExprField(field) => field.span,
             Node::Stmt(stmt) => stmt.span,
@@ -1289,6 +1284,7 @@ fn hir_id_to_string(map: Map<'_>, id: HirId) -> String {
             format!("{id} (field `{}` in {})", field.ident, path_str(field.def_id))
         }
         Some(Node::AnonConst(_)) => node_str("const"),
+        Some(Node::ConstBlock(_)) => node_str("const"),
         Some(Node::Expr(_)) => node_str("expr"),
         Some(Node::ExprField(_)) => node_str("expr field"),
         Some(Node::Stmt(_)) => node_str("stmt"),
@@ -1434,6 +1430,11 @@ impl<'hir> Visitor<'hir> for ItemCollector<'hir> {
         intravisit::walk_anon_const(self, c)
     }
 
+    fn visit_inline_const(&mut self, c: &'hir ConstBlock) {
+        self.body_owners.push(c.def_id);
+        intravisit::walk_inline_const(self, c)
+    }
+
     fn visit_expr(&mut self, ex: &'hir Expr<'hir>) {
         if let ExprKind::Closure(closure) = ex.kind {
             self.body_owners.push(closure.def_id);
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index 561713149..d5e8330b3 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -82,15 +82,40 @@ impl CanonicalVarValues<'_> {
     }
 
     pub fn is_identity_modulo_regions(&self) -> bool {
-        self.var_values.iter().enumerate().all(|(bv, arg)| match arg.unpack() {
-            ty::GenericArgKind::Lifetime(_) => true,
-            ty::GenericArgKind::Type(ty) => {
-                matches!(*ty.kind(), ty::Bound(ty::INNERMOST, bt) if bt.var.as_usize() == bv)
-            }
-            ty::GenericArgKind::Const(ct) => {
-                matches!(ct.kind(), ty::ConstKind::Bound(ty::INNERMOST, bc) if bc.as_usize() == bv)
+        let mut var = ty::BoundVar::from_u32(0);
+        for arg in self.var_values {
+            match arg.unpack() {
+                ty::GenericArgKind::Lifetime(r) => {
+                    if let ty::ReLateBound(ty::INNERMOST, br) = *r
+                        && var == br.var
+                    {
+                        var = var + 1;
+                    } else {
+                        // It's ok if this region var isn't unique
+                    }
+                },
+                ty::GenericArgKind::Type(ty) => {
+                    if let ty::Bound(ty::INNERMOST, bt) = *ty.kind()
+                        && var == bt.var
+                    {
+                        var = var + 1;
+                    } else {
+                        return false;
+                    }
+                }
+                ty::GenericArgKind::Const(ct) => {
+                    if let ty::ConstKind::Bound(ty::INNERMOST, bc) = ct.kind()
+                        && var == bc
+                    {
+                        var = var + 1;
+                    } else {
+                        return false;
+                    }
+                }
             }
-        })
+        }
+
+        true
     }
 }
 
@@ -408,22 +433,24 @@ impl<'tcx> CanonicalVarValues<'tcx> {
                 |(i, info)| -> ty::GenericArg<'tcx> {
                     match info.kind {
                         CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
-                            tcx.mk_bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into()).into()
+                            Ty::new_bound(tcx, ty::INNERMOST, ty::BoundVar::from_usize(i).into())
+                                .into()
                         }
                         CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
                             let br = ty::BoundRegion {
                                 var: ty::BoundVar::from_usize(i),
                                 kind: ty::BrAnon(None),
                             };
-                            tcx.mk_re_late_bound(ty::INNERMOST, br).into()
+                            ty::Region::new_late_bound(tcx, ty::INNERMOST, br).into()
                         }
                         CanonicalVarKind::Const(_, ty)
-                        | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
-                            .mk_const(
-                                ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)),
-                                ty,
-                            )
-                            .into(),
+                        | CanonicalVarKind::PlaceholderConst(_, ty) => ty::Const::new_bound(
+                            tcx,
+                            ty::INNERMOST,
+                            ty::BoundVar::from_usize(i),
+                            ty,
+                        )
+                        .into(),
                     }
                 },
             )),
diff --git a/compiler/rustc_middle/src/infer/unify_key.rs b/compiler/rustc_middle/src/infer/unify_key.rs
index a873854f0..85fb9214d 100644
--- a/compiler/rustc_middle/src/infer/unify_key.rs
+++ b/compiler/rustc_middle/src/infer/unify_key.rs
@@ -90,15 +90,15 @@ impl<'tcx> UnifyValue for UnifiedRegion<'tcx> {
 impl ToType for ty::IntVarValue {
     fn to_type<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
         match *self {
-            ty::IntType(i) => tcx.mk_mach_int(i),
-            ty::UintType(i) => tcx.mk_mach_uint(i),
+            ty::IntType(i) => Ty::new_int(tcx, i),
+            ty::UintType(i) => Ty::new_uint(tcx, i),
         }
     }
 }
 
 impl ToType for ty::FloatVarValue {
     fn to_type<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
-        tcx.mk_mach_float(self.0)
+        Ty::new_float(tcx, self.0)
     }
 }
 
@@ -116,7 +116,6 @@ pub enum ConstVariableOriginKind {
     MiscVariable,
     ConstInference,
     ConstParameterDefinition(Symbol, DefId),
-    SubstitutionPlaceholder,
 }
 
 #[derive(Copy, Clone, Debug)]
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index 22ee2a8c5..1b125e8e2 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -48,12 +48,13 @@
 #![feature(associated_type_bounds)]
 #![feature(rustc_attrs)]
 #![feature(control_flow_enum)]
+#![feature(trait_upcasting)]
 #![feature(trusted_step)]
 #![feature(try_blocks)]
 #![feature(try_reserve_kind)]
 #![feature(nonzero_ops)]
 #![feature(decl_macro)]
-#![feature(drain_filter)]
+#![feature(extract_if)]
 #![feature(intra_doc_pointers)]
 #![feature(yeet_expr)]
 #![feature(result_option_inspect)]
@@ -86,7 +87,7 @@ mod macros;
 
 #[macro_use]
 pub mod arena;
-pub(crate) mod error;
+pub mod error;
 pub mod hir;
 pub mod infer;
 pub mod lint;
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 14343ac11..81c1ae4f6 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -251,7 +251,7 @@ pub fn explain_lint_level_source(
         }
         LintLevelSource::Node { name: lint_attr_name, span, reason, .. } => {
             if let Some(rationale) = reason {
-                err.note(rationale.as_str());
+                err.note(rationale.to_string());
             }
             err.span_note_once(span, "the lint level is defined here");
             if lint_attr_name.as_str() != name {
@@ -388,10 +388,11 @@ pub fn struct_lint_level(
             // it'll become a hard error, so we have to emit *something*. Also,
             // if this lint occurs in the expansion of a macro from an external crate,
             // allow individual lints to opt-out from being reported.
-            let not_future_incompatible =
-                future_incompatible.map(|f| f.reason.edition().is_some()).unwrap_or(true);
-            if not_future_incompatible && !lint.report_in_external_macro {
+            let incompatible = future_incompatible.is_some_and(|f| f.reason.edition().is_none());
+
+            if !incompatible && !lint.report_in_external_macro {
                 err.cancel();
+
                 // Don't continue further, since we don't want to have
                 // `diag_span_note_once` called for a diagnostic that isn't emitted.
                 return;
diff --git a/compiler/rustc_middle/src/middle/limits.rs b/compiler/rustc_middle/src/middle/limits.rs
index bd859d4d6..d4f023958 100644
--- a/compiler/rustc_middle/src/middle/limits.rs
+++ b/compiler/rustc_middle/src/middle/limits.rs
@@ -1,8 +1,7 @@
 //! Registering limits:
 //! * recursion_limit,
-//! * move_size_limit,
-//! * type_length_limit, and
-//! * const_eval_limit
+//! * move_size_limit, and
+//! * type_length_limit
 //!
 //! There are various parts of the compiler that must impose arbitrary limits
 //! on how deeply they recurse to prevent stack overflow. Users can override
@@ -34,12 +33,6 @@ pub fn provide(providers: &mut Providers) {
             sym::type_length_limit,
             1048576,
         ),
-        const_eval_limit: get_limit(
-            tcx.hir().krate_attrs(),
-            tcx.sess,
-            sym::const_eval_limit,
-            2_000_000,
-        ),
     }
 }
 
diff --git a/compiler/rustc_middle/src/middle/privacy.rs b/compiler/rustc_middle/src/middle/privacy.rs
index f45cf788d..5baeb1ee0 100644
--- a/compiler/rustc_middle/src/middle/privacy.rs
+++ b/compiler/rustc_middle/src/middle/privacy.rs
@@ -4,6 +4,7 @@
 use crate::ty::{TyCtxt, Visibility};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_hir::def::DefKind;
 use rustc_macros::HashStable;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_span::def_id::{LocalDefId, CRATE_DEF_ID};
@@ -148,13 +149,12 @@ impl EffectiveVisibilities {
         };
     }
 
-    pub fn check_invariants(&self, tcx: TyCtxt<'_>, early: bool) {
+    pub fn check_invariants(&self, tcx: TyCtxt<'_>) {
         if !cfg!(debug_assertions) {
             return;
         }
         for (&def_id, ev) in &self.map {
             // More direct visibility levels can never go farther than less direct ones,
-            // neither of effective visibilities can go farther than nominal visibility,
             // and all effective visibilities are larger or equal than private visibility.
             let private_vis = Visibility::Restricted(tcx.parent_module_from_def_id(def_id));
             let span = tcx.def_span(def_id.to_def_id());
@@ -175,17 +175,20 @@ impl EffectiveVisibilities {
                     ev.reachable_through_impl_trait
                 );
             }
-            let nominal_vis = tcx.visibility(def_id);
-            // FIXME: `rustc_privacy` is not yet updated for the new logic and can set
-            // effective visibilities that are larger than the nominal one.
-            if !nominal_vis.is_at_least(ev.reachable_through_impl_trait, tcx) && early {
-                span_bug!(
-                    span,
-                    "{:?}: reachable_through_impl_trait {:?} > nominal {:?}",
-                    def_id,
-                    ev.reachable_through_impl_trait,
-                    nominal_vis
-                );
+            // All effective visibilities except `reachable_through_impl_trait` are limited to
+            // nominal visibility. For some items nominal visibility doesn't make sense so we
+            // don't check this condition for them.
+            if !matches!(tcx.def_kind(def_id), DefKind::Impl { .. }) {
+                let nominal_vis = tcx.visibility(def_id);
+                if !nominal_vis.is_at_least(ev.reachable, tcx) {
+                    span_bug!(
+                        span,
+                        "{:?}: reachable {:?} > nominal {:?}",
+                        def_id,
+                        ev.reachable,
+                        nominal_vis
+                    );
+                }
             }
         }
     }
@@ -212,7 +215,7 @@ impl<Id: Eq + Hash> EffectiveVisibilities<Id> {
     pub fn update(
         &mut self,
         id: Id,
-        nominal_vis: Option<Visibility>,
+        max_vis: Option<Visibility>,
         lazy_private_vis: impl FnOnce() -> Visibility,
         inherited_effective_vis: EffectiveVisibility,
         level: Level,
@@ -236,8 +239,8 @@ impl<Id: Eq + Hash> EffectiveVisibilities<Id> {
                 if !(inherited_effective_vis_at_prev_level == inherited_effective_vis_at_level
                     && level != l)
                 {
-                    calculated_effective_vis = if let Some(nominal_vis) = nominal_vis && !nominal_vis.is_at_least(inherited_effective_vis_at_level, tcx) {
-                        nominal_vis
+                    calculated_effective_vis = if let Some(max_vis) = max_vis && !max_vis.is_at_least(inherited_effective_vis_at_level, tcx) {
+                        max_vis
                     } else {
                         inherited_effective_vis_at_level
                     }
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 6354c0aab..60844c17e 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -104,7 +104,7 @@ pub fn report_unstable(
     suggestion: Option<(Span, String, String, Applicability)>,
     is_soft: bool,
     span: Span,
-    soft_handler: impl FnOnce(&'static Lint, Span, &str),
+    soft_handler: impl FnOnce(&'static Lint, Span, String),
 ) {
     let msg = match reason {
         Some(r) => format!("use of unstable library feature '{}': {}", feature, r),
@@ -112,7 +112,7 @@ pub fn report_unstable(
     };
 
     if is_soft {
-        soft_handler(SOFT_UNSTABLE, span, &msg)
+        soft_handler(SOFT_UNSTABLE, span, msg)
     } else {
         let mut err =
             feature_err_issue(&sess.parse_sess, feature, span, GateIssue::Library(issue), msg);
@@ -225,7 +225,7 @@ pub fn deprecation_message_and_lint(
 
 pub fn early_report_deprecation(
     lint_buffer: &mut LintBuffer,
-    message: &str,
+    message: String,
     suggestion: Option<Symbol>,
     lint: &'static Lint,
     span: Span,
@@ -241,7 +241,7 @@ pub fn early_report_deprecation(
 
 fn late_report_deprecation(
     tcx: TyCtxt<'_>,
-    message: &str,
+    message: String,
     suggestion: Option<Symbol>,
     lint: &'static Lint,
     span: Span,
@@ -396,7 +396,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
                         late_report_deprecation(
                             self,
-                            &deprecation_message(
+                            deprecation_message(
                                 is_in_effect,
                                 depr_attr.since,
                                 depr_attr.note,
@@ -619,7 +619,7 @@ impl<'tcx> TyCtxt<'tcx> {
         allow_unstable: AllowUnstable,
         unmarked: impl FnOnce(Span, DefId),
     ) -> bool {
-        let soft_handler = |lint, span, msg: &_| {
+        let soft_handler = |lint, span, msg: String| {
             self.struct_span_lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, msg, |lint| lint)
         };
         let eval_result =
diff --git a/compiler/rustc_middle/src/mir/basic_blocks.rs b/compiler/rustc_middle/src/mir/basic_blocks.rs
index 9d70dbfa0..7722e7b47 100644
--- a/compiler/rustc_middle/src/mir/basic_blocks.rs
+++ b/compiler/rustc_middle/src/mir/basic_blocks.rs
@@ -26,7 +26,7 @@ struct Cache {
     predecessors: OnceCell<Predecessors>,
     switch_sources: OnceCell<SwitchSources>,
     is_cyclic: OnceCell<bool>,
-    postorder: OnceCell<Vec<BasicBlock>>,
+    reverse_postorder: OnceCell<Vec<BasicBlock>>,
     dominators: OnceCell<Dominators<BasicBlock>>,
 }
 
@@ -62,11 +62,14 @@ impl<'tcx> BasicBlocks<'tcx> {
         })
     }
 
-    /// Returns basic blocks in a postorder.
+    /// Returns basic blocks in a reverse postorder.
     #[inline]
-    pub fn postorder(&self) -> &[BasicBlock] {
-        self.cache.postorder.get_or_init(|| {
-            Postorder::new(&self.basic_blocks, START_BLOCK).map(|(bb, _)| bb).collect()
+    pub fn reverse_postorder(&self) -> &[BasicBlock] {
+        self.cache.reverse_postorder.get_or_init(|| {
+            let mut rpo: Vec<_> =
+                Postorder::new(&self.basic_blocks, START_BLOCK).map(|(bb, _)| bb).collect();
+            rpo.reverse();
+            rpo
         })
     }
 
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 1a8e48264..b8030d9db 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -296,25 +296,13 @@ impl<Prov: Provenance, Bytes: AllocBytes> Allocation<Prov, (), Bytes> {
         Allocation::from_bytes(slice, Align::ONE, Mutability::Not)
     }
 
-    /// Try to create an Allocation of `size` bytes, failing if there is not enough memory
-    /// available to the compiler to do so.
-    ///
-    /// If `panic_on_fail` is true, this will never return `Err`.
-    pub fn uninit<'tcx>(size: Size, align: Align, panic_on_fail: bool) -> InterpResult<'tcx, Self> {
-        let bytes = Bytes::zeroed(size, align).ok_or_else(|| {
-            // This results in an error that can happen non-deterministically, since the memory
-            // available to the compiler can change between runs. Normally queries are always
-            // deterministic. However, we can be non-deterministic here because all uses of const
-            // evaluation (including ConstProp!) will make compilation fail (via hard error
-            // or ICE) upon encountering a `MemoryExhausted` error.
-            if panic_on_fail {
-                panic!("Allocation::uninit called with panic_on_fail had allocation failure")
-            }
-            ty::tls::with(|tcx| {
-                tcx.sess.delay_span_bug(DUMMY_SP, "exhausted memory during interpretation")
-            });
-            InterpError::ResourceExhaustion(ResourceExhaustionInfo::MemoryExhausted)
-        })?;
+    fn uninit_inner<R>(size: Size, align: Align, fail: impl FnOnce() -> R) -> Result<Self, R> {
+        // This results in an error that can happen non-deterministically, since the memory
+        // available to the compiler can change between runs. Normally queries are always
+        // deterministic. However, we can be non-deterministic here because all uses of const
+        // evaluation (including ConstProp!) will make compilation fail (via hard error
+        // or ICE) upon encountering a `MemoryExhausted` error.
+        let bytes = Bytes::zeroed(size, align).ok_or_else(fail)?;
 
         Ok(Allocation {
             bytes,
@@ -325,6 +313,28 @@ impl<Prov: Provenance, Bytes: AllocBytes> Allocation<Prov, (), Bytes> {
             extra: (),
         })
     }
+
+    /// Try to create an Allocation of `size` bytes, failing if there is not enough memory
+    /// available to the compiler to do so.
+    pub fn try_uninit<'tcx>(size: Size, align: Align) -> InterpResult<'tcx, Self> {
+        Self::uninit_inner(size, align, || {
+            ty::tls::with(|tcx| {
+                tcx.sess.delay_span_bug(DUMMY_SP, "exhausted memory during interpretation")
+            });
+            InterpError::ResourceExhaustion(ResourceExhaustionInfo::MemoryExhausted).into()
+        })
+    }
+
+    /// Try to create an Allocation of `size` bytes, panics if there is not enough memory
+    /// available to the compiler to do so.
+    pub fn uninit(size: Size, align: Align) -> Self {
+        match Self::uninit_inner(size, align, || {
+            panic!("Allocation::uninit called with panic_on_fail had allocation failure");
+        }) {
+            Ok(x) => x,
+            Err(x) => x,
+        }
+    }
 }
 
 impl<Bytes: AllocBytes> Allocation<AllocId, (), Bytes> {
diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index 055d8e9a3..2435bc59e 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -5,11 +5,15 @@ use crate::query::TyCtxtAt;
 use crate::ty::{layout, tls, Ty, ValTree};
 
 use rustc_data_structures::sync::Lock;
-use rustc_errors::{pluralize, struct_span_err, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{
+    struct_span_err, DiagnosticArgValue, DiagnosticBuilder, DiagnosticMessage, ErrorGuaranteed,
+    IntoDiagnosticArg,
+};
 use rustc_macros::HashStable;
 use rustc_session::CtfeBacktrace;
 use rustc_span::def_id::DefId;
-use rustc_target::abi::{call, Align, Size};
+use rustc_target::abi::{call, Align, Size, WrappingRange};
+use std::borrow::Cow;
 use std::{any::Any, backtrace::Backtrace, fmt};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
@@ -91,21 +95,54 @@ pub struct InterpErrorInfo<'tcx>(Box<InterpErrorInfoInner<'tcx>>);
 #[derive(Debug)]
 struct InterpErrorInfoInner<'tcx> {
     kind: InterpError<'tcx>,
+    backtrace: InterpErrorBacktrace,
+}
+
+#[derive(Debug)]
+pub struct InterpErrorBacktrace {
     backtrace: Option<Box<Backtrace>>,
 }
 
-impl fmt::Display for InterpErrorInfo<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.0.kind)
+impl InterpErrorBacktrace {
+    pub fn new() -> InterpErrorBacktrace {
+        let capture_backtrace = tls::with_opt(|tcx| {
+            if let Some(tcx) = tcx {
+                *Lock::borrow(&tcx.sess.ctfe_backtrace)
+            } else {
+                CtfeBacktrace::Disabled
+            }
+        });
+
+        let backtrace = match capture_backtrace {
+            CtfeBacktrace::Disabled => None,
+            CtfeBacktrace::Capture => Some(Box::new(Backtrace::force_capture())),
+            CtfeBacktrace::Immediate => {
+                // Print it now.
+                let backtrace = Backtrace::force_capture();
+                print_backtrace(&backtrace);
+                None
+            }
+        };
+
+        InterpErrorBacktrace { backtrace }
     }
-}
 
-impl<'tcx> InterpErrorInfo<'tcx> {
     pub fn print_backtrace(&self) {
-        if let Some(backtrace) = self.0.backtrace.as_ref() {
+        if let Some(backtrace) = self.backtrace.as_ref() {
             print_backtrace(backtrace);
         }
     }
+}
+
+impl<'tcx> InterpErrorInfo<'tcx> {
+    pub fn from_parts(kind: InterpError<'tcx>, backtrace: InterpErrorBacktrace) -> Self {
+        Self(Box::new(InterpErrorInfoInner { kind, backtrace }))
+    }
+
+    pub fn into_parts(self) -> (InterpError<'tcx>, InterpErrorBacktrace) {
+        let InterpErrorInfo(box InterpErrorInfoInner { kind, backtrace }) = self;
+        (kind, backtrace)
+    }
 
     pub fn into_kind(self) -> InterpError<'tcx> {
         let InterpErrorInfo(box InterpErrorInfoInner { kind, .. }) = self;
@@ -130,32 +167,17 @@ impl From<ErrorGuaranteed> for InterpErrorInfo<'_> {
 
 impl<'tcx> From<InterpError<'tcx>> for InterpErrorInfo<'tcx> {
     fn from(kind: InterpError<'tcx>) -> Self {
-        let capture_backtrace = tls::with_opt(|tcx| {
-            if let Some(tcx) = tcx {
-                *Lock::borrow(&tcx.sess.ctfe_backtrace)
-            } else {
-                CtfeBacktrace::Disabled
-            }
-        });
-
-        let backtrace = match capture_backtrace {
-            CtfeBacktrace::Disabled => None,
-            CtfeBacktrace::Capture => Some(Box::new(Backtrace::force_capture())),
-            CtfeBacktrace::Immediate => {
-                // Print it now.
-                let backtrace = Backtrace::force_capture();
-                print_backtrace(&backtrace);
-                None
-            }
-        };
-
-        InterpErrorInfo(Box::new(InterpErrorInfoInner { kind, backtrace }))
+        InterpErrorInfo(Box::new(InterpErrorInfoInner {
+            kind,
+            backtrace: InterpErrorBacktrace::new(),
+        }))
     }
 }
 
 /// Error information for when the program we executed turned out not to actually be a valid
 /// program. This cannot happen in stand-alone Miri, but it can happen during CTFE/ConstProp
 /// where we work on generic code or execution does not have all information available.
+#[derive(Debug)]
 pub enum InvalidProgramInfo<'tcx> {
     /// Resolution can fail if we are in a too generic context.
     TooGeneric,
@@ -174,25 +196,6 @@ pub enum InvalidProgramInfo<'tcx> {
     UninitUnsizedLocal,
 }
 
-impl fmt::Display for InvalidProgramInfo<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        use InvalidProgramInfo::*;
-        match self {
-            TooGeneric => write!(f, "encountered overly generic constant"),
-            AlreadyReported(_) => {
-                write!(
-                    f,
-                    "an error has already been reported elsewhere (this should not usually be printed)"
-                )
-            }
-            Layout(ref err) => write!(f, "{err}"),
-            FnAbiAdjustForForeignAbi(ref err) => write!(f, "{err}"),
-            SizeOfUnsizedType(ty) => write!(f, "size_of called on unsized type `{ty}`"),
-            UninitUnsizedLocal => write!(f, "unsized local is used while uninitialized"),
-        }
-    }
-}
-
 /// Details of why a pointer had to be in-bounds.
 #[derive(Debug, Copy, Clone, TyEncodable, TyDecodable, HashStable)]
 pub enum CheckInAllocMsg {
@@ -208,26 +211,25 @@ pub enum CheckInAllocMsg {
     InboundsTest,
 }
 
-impl fmt::Display for CheckInAllocMsg {
-    /// When this is printed as an error the context looks like this:
-    /// "{msg}{pointer} is a dangling pointer".
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "{}",
-            match *self {
-                CheckInAllocMsg::DerefTest => "dereferencing pointer failed: ",
-                CheckInAllocMsg::MemoryAccessTest => "memory access failed: ",
-                CheckInAllocMsg::PointerArithmeticTest => "out-of-bounds pointer arithmetic: ",
-                CheckInAllocMsg::OffsetFromTest => "out-of-bounds offset_from: ",
-                CheckInAllocMsg::InboundsTest => "out-of-bounds pointer use: ",
-            }
-        )
+#[derive(Debug, Copy, Clone, TyEncodable, TyDecodable, HashStable)]
+pub enum InvalidMetaKind {
+    /// Size of a `[T]` is too big
+    SliceTooBig,
+    /// Size of a DST is too big
+    TooBig,
+}
+
+impl IntoDiagnosticArg for InvalidMetaKind {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Borrowed(match self {
+            InvalidMetaKind::SliceTooBig => "slice_too_big",
+            InvalidMetaKind::TooBig => "too_big",
+        }))
     }
 }
 
 /// Details of an access to uninitialized bytes where it is not allowed.
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy)]
 pub struct UninitBytesAccess {
     /// Range of the original memory access.
     pub access: AllocRange,
@@ -242,17 +244,32 @@ pub struct ScalarSizeMismatch {
     pub data_size: u64,
 }
 
+macro_rules! impl_into_diagnostic_arg_through_debug {
+    ($($ty:ty),*$(,)?) => {$(
+        impl IntoDiagnosticArg for $ty {
+            fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+                DiagnosticArgValue::Str(Cow::Owned(format!("{self:?}")))
+            }
+        }
+    )*}
+}
+
+// These types have nice `Debug` output so we can just use them in diagnostics.
+impl_into_diagnostic_arg_through_debug! {
+    AllocId,
+    Pointer,
+    AllocRange,
+}
+
 /// Error information for when the program caused Undefined Behavior.
-pub enum UndefinedBehaviorInfo {
-    /// Free-form case. Only for errors that are never caught!
+#[derive(Debug)]
+pub enum UndefinedBehaviorInfo<'a> {
+    /// Free-form case. Only for errors that are never caught! Used by miri
     Ub(String),
     /// Unreachable code was executed.
     Unreachable,
     /// A slice/array index projection went out-of-bounds.
-    BoundsCheckFailed {
-        len: u64,
-        index: u64,
-    },
+    BoundsCheckFailed { len: u64, index: u64 },
     /// Something was divided by 0 (x / 0).
     DivisionByZero,
     /// Something was "remainded" by 0 (x % 0).
@@ -263,8 +280,8 @@ pub enum UndefinedBehaviorInfo {
     RemainderOverflow,
     /// Overflowing inbounds pointer arithmetic.
     PointerArithOverflow,
-    /// Invalid metadata in a wide pointer (using `str` to avoid allocations).
-    InvalidMeta(&'static str),
+    /// Invalid metadata in a wide pointer
+    InvalidMeta(InvalidMetaKind),
     /// Reading a C string that does not end within its allocation.
     UnterminatedCString(Pointer),
     /// Dereferencing a dangling pointer after it got freed.
@@ -281,25 +298,13 @@ pub enum UndefinedBehaviorInfo {
     /// Using an integer as a pointer in the wrong way.
     DanglingIntPointer(u64, CheckInAllocMsg),
     /// Used a pointer with bad alignment.
-    AlignmentCheckFailed {
-        required: Align,
-        has: Align,
-    },
+    AlignmentCheckFailed { required: Align, has: Align },
     /// Writing to read-only memory.
     WriteToReadOnly(AllocId),
-    // Trying to access the data behind a function pointer.
+    /// Trying to access the data behind a function pointer.
     DerefFunctionPointer(AllocId),
-    // Trying to access the data behind a vtable pointer.
+    /// Trying to access the data behind a vtable pointer.
     DerefVTablePointer(AllocId),
-    /// The value validity check found a problem.
-    /// Should only be thrown by `validity.rs` and always point out which part of the value
-    /// is the problem.
-    ValidationFailure {
-        /// The "path" to the value in question, e.g. `.0[5].field` for a struct
-        /// field in the 6th element of an array that is the first element of a tuple.
-        path: Option<String>,
-        msg: String,
-    },
     /// Using a non-boolean `u8` as bool.
     InvalidBool(u8),
     /// Using a non-character `u32` as character.
@@ -320,110 +325,100 @@ pub enum UndefinedBehaviorInfo {
     ScalarSizeMismatch(ScalarSizeMismatch),
     /// A discriminant of an uninhabited enum variant is written.
     UninhabitedEnumVariantWritten,
+    /// Validation error.
+    Validation(ValidationErrorInfo<'a>),
+    // FIXME(fee1-dead) these should all be actual variants of the enum instead of dynamically
+    // dispatched
+    /// A custom (free-form) error, created by `err_ub_custom!`.
+    Custom(crate::error::CustomSubdiagnostic<'a>),
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum PointerKind {
+    Ref,
+    Box,
+}
+
+impl IntoDiagnosticArg for PointerKind {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(
+            match self {
+                Self::Ref => "ref",
+                Self::Box => "box",
+            }
+            .into(),
+        )
+    }
 }
 
-impl fmt::Display for UndefinedBehaviorInfo {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        use UndefinedBehaviorInfo::*;
-        match self {
-            Ub(msg) => write!(f, "{msg}"),
-            Unreachable => write!(f, "entering unreachable code"),
-            BoundsCheckFailed { ref len, ref index } => {
-                write!(f, "indexing out of bounds: the len is {len} but the index is {index}")
-            }
-            DivisionByZero => write!(f, "dividing by zero"),
-            RemainderByZero => write!(f, "calculating the remainder with a divisor of zero"),
-            DivisionOverflow => write!(f, "overflow in signed division (dividing MIN by -1)"),
-            RemainderOverflow => write!(f, "overflow in signed remainder (dividing MIN by -1)"),
-            PointerArithOverflow => write!(f, "overflowing in-bounds pointer arithmetic"),
-            InvalidMeta(msg) => write!(f, "invalid metadata in wide pointer: {msg}"),
-            UnterminatedCString(p) => write!(
-                f,
-                "reading a null-terminated string starting at {p:?} with no null found before end of allocation",
-            ),
-            PointerUseAfterFree(a) => {
-                write!(f, "pointer to {a:?} was dereferenced after this allocation got freed")
-            }
-            PointerOutOfBounds { alloc_id, alloc_size, ptr_offset, ptr_size: Size::ZERO, msg } => {
-                write!(
-                    f,
-                    "{msg}{alloc_id:?} has size {alloc_size}, so pointer at offset {ptr_offset} is out-of-bounds",
-                    alloc_size = alloc_size.bytes(),
-                )
-            }
-            PointerOutOfBounds { alloc_id, alloc_size, ptr_offset, ptr_size, msg } => write!(
-                f,
-                "{msg}{alloc_id:?} has size {alloc_size}, so pointer to {ptr_size} byte{ptr_size_p} starting at offset {ptr_offset} is out-of-bounds",
-                alloc_size = alloc_size.bytes(),
-                ptr_size = ptr_size.bytes(),
-                ptr_size_p = pluralize!(ptr_size.bytes()),
-            ),
-            DanglingIntPointer(i, msg) => {
-                write!(
-                    f,
-                    "{msg}{pointer} is a dangling pointer (it has no provenance)",
-                    pointer = Pointer::<Option<AllocId>>::from_addr_invalid(*i),
-                )
-            }
-            AlignmentCheckFailed { required, has } => write!(
-                f,
-                "accessing memory with alignment {has}, but alignment {required} is required",
-                has = has.bytes(),
-                required = required.bytes()
-            ),
-            WriteToReadOnly(a) => write!(f, "writing to {a:?} which is read-only"),
-            DerefFunctionPointer(a) => write!(f, "accessing {a:?} which contains a function"),
-            DerefVTablePointer(a) => write!(f, "accessing {a:?} which contains a vtable"),
-            ValidationFailure { path: None, msg } => {
-                write!(f, "constructing invalid value: {msg}")
-            }
-            ValidationFailure { path: Some(path), msg } => {
-                write!(f, "constructing invalid value at {path}: {msg}")
-            }
-            InvalidBool(b) => {
-                write!(f, "interpreting an invalid 8-bit value as a bool: 0x{b:02x}")
-            }
-            InvalidChar(c) => {
-                write!(f, "interpreting an invalid 32-bit value as a char: 0x{c:08x}")
-            }
-            InvalidTag(val) => write!(f, "enum value has invalid tag: {val:x}"),
-            InvalidFunctionPointer(p) => {
-                write!(f, "using {p:?} as function pointer but it does not point to a function")
-            }
-            InvalidVTablePointer(p) => {
-                write!(f, "using {p:?} as vtable pointer but it does not point to a vtable")
-            }
-            InvalidStr(err) => write!(f, "this string is not valid UTF-8: {err}"),
-            InvalidUninitBytes(Some((alloc, info))) => write!(
-                f,
-                "reading memory at {alloc:?}{access:?}, \
-                 but memory is uninitialized at {uninit:?}, \
-                 and this operation requires initialized memory",
-                access = info.access,
-                uninit = info.uninit,
-            ),
-            InvalidUninitBytes(None) => write!(
-                f,
-                "using uninitialized data, but this operation requires initialized memory"
-            ),
-            DeadLocal => write!(f, "accessing a dead local variable"),
-            ScalarSizeMismatch(self::ScalarSizeMismatch { target_size, data_size }) => write!(
-                f,
-                "scalar size mismatch: expected {target_size} bytes but got {data_size} bytes instead",
-            ),
-            UninhabitedEnumVariantWritten => {
-                write!(f, "writing discriminant of an uninhabited enum")
-            }
+#[derive(Debug)]
+pub struct ValidationErrorInfo<'tcx> {
+    pub path: Option<String>,
+    pub kind: ValidationErrorKind<'tcx>,
+}
+
+#[derive(Debug)]
+pub enum ExpectedKind {
+    Reference,
+    Box,
+    RawPtr,
+    InitScalar,
+    Bool,
+    Char,
+    Float,
+    Int,
+    FnPtr,
+}
+
+impl From<PointerKind> for ExpectedKind {
+    fn from(x: PointerKind) -> ExpectedKind {
+        match x {
+            PointerKind::Box => ExpectedKind::Box,
+            PointerKind::Ref => ExpectedKind::Reference,
         }
     }
 }
 
+#[derive(Debug)]
+pub enum ValidationErrorKind<'tcx> {
+    PtrToUninhabited { ptr_kind: PointerKind, ty: Ty<'tcx> },
+    PtrToStatic { ptr_kind: PointerKind },
+    PtrToMut { ptr_kind: PointerKind },
+    ExpectedNonPtr { value: String },
+    MutableRefInConst,
+    NullFnPtr,
+    NeverVal,
+    NullablePtrOutOfRange { range: WrappingRange, max_value: u128 },
+    PtrOutOfRange { range: WrappingRange, max_value: u128 },
+    OutOfRange { value: String, range: WrappingRange, max_value: u128 },
+    UnsafeCell,
+    UninhabitedVal { ty: Ty<'tcx> },
+    InvalidEnumTag { value: String },
+    UninitEnumTag,
+    UninitStr,
+    Uninit { expected: ExpectedKind },
+    UninitVal,
+    InvalidVTablePtr { value: String },
+    InvalidMetaSliceTooLarge { ptr_kind: PointerKind },
+    InvalidMetaTooLarge { ptr_kind: PointerKind },
+    UnalignedPtr { ptr_kind: PointerKind, required_bytes: u64, found_bytes: u64 },
+    NullPtr { ptr_kind: PointerKind },
+    DanglingPtrNoProvenance { ptr_kind: PointerKind, pointer: String },
+    DanglingPtrOutOfBounds { ptr_kind: PointerKind },
+    DanglingPtrUseAfterFree { ptr_kind: PointerKind },
+    InvalidBool { value: String },
+    InvalidChar { value: String },
+    InvalidFnPtr { value: String },
+}
+
 /// Error information for when the program did something that might (or might not) be correct
 /// to do according to the Rust spec, but due to limitations in the interpreter, the
 /// operation could not be carried out. These limitations can differ between CTFE and the
 /// Miri engine, e.g., CTFE does not support dereferencing pointers at integral addresses.
+#[derive(Debug)]
 pub enum UnsupportedOpInfo {
     /// Free-form case. Only for errors that are never caught!
+    // FIXME still use translatable diagnostics
     Unsupported(String),
     //
     // The variants below are only reachable from CTFE/const prop, miri will never emit them.
@@ -442,83 +437,42 @@ pub enum UnsupportedOpInfo {
     ReadExternStatic(DefId),
 }
 
-impl fmt::Display for UnsupportedOpInfo {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        use UnsupportedOpInfo::*;
-        match self {
-            Unsupported(ref msg) => write!(f, "{msg}"),
-            PartialPointerOverwrite(ptr) => {
-                write!(f, "unable to overwrite parts of a pointer in memory at {ptr:?}")
-            }
-            PartialPointerCopy(ptr) => {
-                write!(f, "unable to copy parts of a pointer from memory at {ptr:?}")
-            }
-            ReadPointerAsBytes => write!(f, "unable to turn pointer into raw bytes"),
-            ThreadLocalStatic(did) => write!(f, "cannot access thread local static ({did:?})"),
-            ReadExternStatic(did) => write!(f, "cannot read from extern static ({did:?})"),
-        }
-    }
-}
-
 /// Error information for when the program exhausted the resources granted to it
 /// by the interpreter.
+#[derive(Debug)]
 pub enum ResourceExhaustionInfo {
     /// The stack grew too big.
     StackFrameLimitReached,
-    /// The program ran for too long.
-    ///
-    /// The exact limit is set by the `const_eval_limit` attribute.
-    StepLimitReached,
     /// There is not enough memory (on the host) to perform an allocation.
     MemoryExhausted,
     /// The address space (of the target) is full.
     AddressSpaceFull,
 }
 
-impl fmt::Display for ResourceExhaustionInfo {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        use ResourceExhaustionInfo::*;
-        match self {
-            StackFrameLimitReached => {
-                write!(f, "reached the configured maximum number of stack frames")
-            }
-            StepLimitReached => {
-                write!(f, "exceeded interpreter step limit (see `#[const_eval_limit]`)")
-            }
-            MemoryExhausted => {
-                write!(f, "tried to allocate more memory than available to compiler")
-            }
-            AddressSpaceFull => {
-                write!(f, "there are no more free addresses in the address space")
-            }
-        }
-    }
-}
-
-/// A trait to work around not having trait object upcasting.
-pub trait AsAny: Any {
-    fn as_any(&self) -> &dyn Any;
-}
-impl<T: Any> AsAny for T {
-    #[inline(always)]
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-}
-
 /// A trait for machine-specific errors (or other "machine stop" conditions).
-pub trait MachineStopType: AsAny + fmt::Display + Send {}
+pub trait MachineStopType: Any + fmt::Debug + Send {
+    /// The diagnostic message for this error
+    fn diagnostic_message(&self) -> DiagnosticMessage;
+    /// Add diagnostic arguments by passing name and value pairs to `adder`, which are passed to
+    /// fluent for formatting the translated diagnostic message.
+    fn add_args(
+        self: Box<Self>,
+        adder: &mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue<'static>),
+    );
+}
 
 impl dyn MachineStopType {
     #[inline(always)]
     pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
-        self.as_any().downcast_ref()
+        let x: &dyn Any = self;
+        x.downcast_ref()
     }
 }
 
+#[derive(Debug)]
 pub enum InterpError<'tcx> {
     /// The program caused undefined behavior.
-    UndefinedBehavior(UndefinedBehaviorInfo),
+    UndefinedBehavior(UndefinedBehaviorInfo<'tcx>),
     /// The program did something the interpreter does not support (some of these *might* be UB
     /// but the interpreter is not sure).
     Unsupported(UnsupportedOpInfo),
@@ -534,26 +488,6 @@ pub enum InterpError<'tcx> {
 
 pub type InterpResult<'tcx, T = ()> = Result<T, InterpErrorInfo<'tcx>>;
 
-impl fmt::Display for InterpError<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        use InterpError::*;
-        match *self {
-            Unsupported(ref msg) => write!(f, "{msg}"),
-            InvalidProgram(ref msg) => write!(f, "{msg}"),
-            UndefinedBehavior(ref msg) => write!(f, "{msg}"),
-            ResourceExhaustion(ref msg) => write!(f, "{msg}"),
-            MachineStop(ref msg) => write!(f, "{msg}"),
-        }
-    }
-}
-
-// Forward `Debug` to `Display`, so it does not look awful.
-impl fmt::Debug for InterpError<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(self, f)
-    }
-}
-
 impl InterpError<'_> {
     /// Some errors do string formatting even if the error is never printed.
     /// To avoid performance issues, there are places where we want to be sure to never raise these formatting errors,
@@ -562,7 +496,7 @@ impl InterpError<'_> {
         matches!(
             self,
             InterpError::Unsupported(UnsupportedOpInfo::Unsupported(_))
-                | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::ValidationFailure { .. })
+                | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::Validation { .. })
                 | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::Ub(_))
         )
     }
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index 3620385fa..2d2cfee1b 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -89,6 +89,30 @@ macro_rules! throw_machine_stop {
     ($($tt:tt)*) => { do yeet err_machine_stop!($($tt)*) };
 }
 
+#[macro_export]
+macro_rules! err_ub_custom {
+    ($msg:expr $(, $($name:ident = $value:expr),* $(,)?)?) => {{
+        $(
+            let ($($name,)*) = ($($value,)*);
+        )?
+        err_ub!(Custom(
+            rustc_middle::error::CustomSubdiagnostic {
+                msg: || $msg,
+                add_args: Box::new(move |mut set_arg| {
+                    $($(
+                        set_arg(stringify!($name).into(), rustc_errors::IntoDiagnosticArg::into_diagnostic_arg($name));
+                    )*)?
+                })
+            }
+        ))
+    }};
+}
+
+#[macro_export]
+macro_rules! throw_ub_custom {
+    ($($tt:tt)*) => { do yeet err_ub_custom!($($tt)*) };
+}
+
 mod allocation;
 mod error;
 mod pointer;
@@ -119,9 +143,10 @@ use crate::ty::{self, Instance, Ty, TyCtxt};
 
 pub use self::error::{
     struct_error, CheckInAllocMsg, ErrorHandled, EvalToAllocationRawResult, EvalToConstValueResult,
-    EvalToValTreeResult, InterpError, InterpErrorInfo, InterpResult, InvalidProgramInfo,
-    MachineStopType, ReportedErrorInfo, ResourceExhaustionInfo, ScalarSizeMismatch,
-    UndefinedBehaviorInfo, UninitBytesAccess, UnsupportedOpInfo,
+    EvalToValTreeResult, ExpectedKind, InterpError, InterpErrorInfo, InterpResult, InvalidMetaKind,
+    InvalidProgramInfo, MachineStopType, PointerKind, ReportedErrorInfo, ResourceExhaustionInfo,
+    ScalarSizeMismatch, UndefinedBehaviorInfo, UninitBytesAccess, UnsupportedOpInfo,
+    ValidationErrorInfo, ValidationErrorKind,
 };
 
 pub use self::value::{get_slice_bytes, ConstAlloc, ConstValue, Scalar};
diff --git a/compiler/rustc_middle/src/mir/interpret/queries.rs b/compiler/rustc_middle/src/mir/interpret/queries.rs
index f53dc8cb0..9c97431f3 100644
--- a/compiler/rustc_middle/src/mir/interpret/queries.rs
+++ b/compiler/rustc_middle/src/mir/interpret/queries.rs
@@ -95,8 +95,15 @@ impl<'tcx> TyCtxt<'tcx> {
                     // used generic parameters is a bug of evaluation, so checking for it
                     // here does feel somewhat sensible.
                     if !self.features().generic_const_exprs && ct.substs.has_non_region_param() {
-                        assert!(matches!(self.def_kind(ct.def), DefKind::AnonConst));
-                        let mir_body = self.mir_for_ctfe(ct.def);
+                        let def_kind = self.def_kind(instance.def_id());
+                        assert!(
+                            matches!(
+                                def_kind,
+                                DefKind::InlineConst | DefKind::AnonConst | DefKind::AssocConst
+                            ),
+                            "{cid:?} is {def_kind:?}",
+                        );
+                        let mir_body = self.mir_for_ctfe(instance.def_id());
                         if mir_body.is_polymorphic {
                             let Some(local_def_id) = ct.def.as_local() else { return };
                             self.struct_span_lint_hir(
@@ -236,15 +243,3 @@ impl<'tcx> TyCtxtEnsure<'tcx> {
         self.eval_to_allocation_raw(param_env.and(gid))
     }
 }
-
-impl<'tcx> TyCtxt<'tcx> {
-    /// Destructure a mir constant ADT or array into its variant index and its field values.
-    /// Panics if the destructuring fails, use `try_destructure_mir_constant` for fallible version.
-    pub fn destructure_mir_constant(
-        self,
-        param_env: ty::ParamEnv<'tcx>,
-        constant: mir::ConstantKind<'tcx>,
-    ) -> mir::DestructuredConstant<'tcx> {
-        self.try_destructure_mir_constant(param_env.and(constant)).unwrap()
-    }
-}
diff --git a/compiler/rustc_middle/src/mir/interpret/value.rs b/compiler/rustc_middle/src/mir/interpret/value.rs
index 36dbbe4bf..0416411df 100644
--- a/compiler/rustc_middle/src/mir/interpret/value.rs
+++ b/compiler/rustc_middle/src/mir/interpret/value.rs
@@ -97,6 +97,10 @@ impl<'tcx> ConstValue<'tcx> {
         ConstValue::Scalar(Scalar::from_u64(i))
     }
 
+    pub fn from_u128(i: u128) -> Self {
+        ConstValue::Scalar(Scalar::from_u128(i))
+    }
+
     pub fn from_target_usize(i: u64, cx: &impl HasDataLayout) -> Self {
         ConstValue::Scalar(Scalar::from_target_usize(i, cx))
     }
@@ -241,6 +245,11 @@ impl<Prov> Scalar<Prov> {
     }
 
     #[inline]
+    pub fn from_u128(i: u128) -> Self {
+        Scalar::Int(i.into())
+    }
+
+    #[inline]
     pub fn from_target_usize(i: u64, cx: &impl HasDataLayout) -> Self {
         Self::from_uint(i, cx.data_layout().pointer_size)
     }
@@ -375,7 +384,8 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
     #[inline(always)]
     #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
     pub fn assert_bits(self, target_size: Size) -> u128 {
-        self.to_bits(target_size).unwrap()
+        self.to_bits(target_size)
+            .unwrap_or_else(|_| panic!("assertion failed: {self:?} fits {target_size:?}"))
     }
 
     pub fn to_bool(self) -> InterpResult<'tcx, bool> {
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 5c71910a9..28c505878 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -3,7 +3,7 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/mir/index.html
 
 use crate::mir::interpret::{
-    AllocRange, ConstAllocation, ConstValue, ErrorHandled, GlobalAlloc, LitToConstInput, Scalar,
+    AllocRange, ConstAllocation, ConstValue, ErrorHandled, GlobalAlloc, Scalar,
 };
 use crate::mir::visit::MirVisitable;
 use crate::ty::codec::{TyDecoder, TyEncoder};
@@ -15,7 +15,7 @@ use crate::ty::{AdtDef, InstanceDef, ScalarInt, UserTypeAnnotationIndex};
 use crate::ty::{GenericArg, InternalSubsts, SubstsRef};
 
 use rustc_data_structures::captures::Captures;
-use rustc_errors::ErrorGuaranteed;
+use rustc_errors::{DiagnosticArgValue, DiagnosticMessage, ErrorGuaranteed, IntoDiagnosticArg};
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_hir::{self, GeneratorKind, ImplicitSelfKind};
@@ -145,7 +145,7 @@ impl MirPhase {
             }
             "analysis" => Self::Analysis(AnalysisPhase::parse(phase)),
             "runtime" => Self::Runtime(RuntimePhase::parse(phase)),
-            _ => panic!("Unknown MIR dialect {}", dialect),
+            _ => bug!("Unknown MIR dialect: '{}'", dialect),
         }
     }
 }
@@ -159,7 +159,7 @@ impl AnalysisPhase {
         match &*phase.to_ascii_lowercase() {
             "initial" => Self::Initial,
             "post_cleanup" | "post-cleanup" | "postcleanup" => Self::PostCleanup,
-            _ => panic!("Unknown analysis phase {}", phase),
+            _ => bug!("Unknown analysis phase: '{}'", phase),
         }
     }
 }
@@ -174,7 +174,7 @@ impl RuntimePhase {
             "initial" => Self::Initial,
             "post_cleanup" | "post-cleanup" | "postcleanup" => Self::PostCleanup,
             "optimized" => Self::Optimized,
-            _ => panic!("Unknown runtime phase {}", phase),
+            _ => bug!("Unknown runtime phase: '{}'", phase),
         }
     }
 }
@@ -476,7 +476,7 @@ impl<'tcx> Body<'tcx> {
     /// Returns the return type; it always return first element from `local_decls` array.
     #[inline]
     pub fn bound_return_ty(&self) -> ty::EarlyBinder<Ty<'tcx>> {
-        ty::EarlyBinder(self.local_decls[RETURN_PLACE].ty)
+        ty::EarlyBinder::bind(self.local_decls[RETURN_PLACE].ty)
     }
 
     /// Gets the location of the terminator for the given block.
@@ -1371,55 +1371,61 @@ impl<O> AssertKind<O> {
             _ => write!(f, "\"{}\"", self.description()),
         }
     }
-}
 
-impl<O: fmt::Debug> fmt::Debug for AssertKind<O> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    pub fn diagnostic_message(&self) -> DiagnosticMessage {
+        use crate::fluent_generated::*;
         use AssertKind::*;
+
         match self {
-            BoundsCheck { ref len, ref index } => write!(
-                f,
-                "index out of bounds: the length is {:?} but the index is {:?}",
-                len, index
-            ),
-            OverflowNeg(op) => write!(f, "attempt to negate `{:#?}`, which would overflow", op),
-            DivisionByZero(op) => write!(f, "attempt to divide `{:#?}` by zero", op),
-            RemainderByZero(op) => write!(
-                f,
-                "attempt to calculate the remainder of `{:#?}` with a divisor of zero",
-                op
-            ),
-            Overflow(BinOp::Add, l, r) => {
-                write!(f, "attempt to compute `{:#?} + {:#?}`, which would overflow", l, r)
-            }
-            Overflow(BinOp::Sub, l, r) => {
-                write!(f, "attempt to compute `{:#?} - {:#?}`, which would overflow", l, r)
-            }
-            Overflow(BinOp::Mul, l, r) => {
-                write!(f, "attempt to compute `{:#?} * {:#?}`, which would overflow", l, r)
-            }
-            Overflow(BinOp::Div, l, r) => {
-                write!(f, "attempt to compute `{:#?} / {:#?}`, which would overflow", l, r)
+            BoundsCheck { .. } => middle_bounds_check,
+            Overflow(BinOp::Shl, _, _) => middle_assert_shl_overflow,
+            Overflow(BinOp::Shr, _, _) => middle_assert_shr_overflow,
+            Overflow(_, _, _) => middle_assert_op_overflow,
+            OverflowNeg(_) => middle_assert_overflow_neg,
+            DivisionByZero(_) => middle_assert_divide_by_zero,
+            RemainderByZero(_) => middle_assert_remainder_by_zero,
+            ResumedAfterReturn(GeneratorKind::Async(_)) => middle_assert_async_resume_after_return,
+            ResumedAfterReturn(GeneratorKind::Gen) => middle_assert_generator_resume_after_return,
+            ResumedAfterPanic(GeneratorKind::Async(_)) => middle_assert_async_resume_after_panic,
+            ResumedAfterPanic(GeneratorKind::Gen) => middle_assert_generator_resume_after_panic,
+
+            MisalignedPointerDereference { .. } => middle_assert_misaligned_ptr_deref,
+        }
+    }
+
+    pub fn add_args(self, adder: &mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue<'static>))
+    where
+        O: fmt::Debug,
+    {
+        use AssertKind::*;
+
+        macro_rules! add {
+            ($name: expr, $value: expr) => {
+                adder($name.into(), $value.into_diagnostic_arg());
+            };
+        }
+
+        match self {
+            BoundsCheck { len, index } => {
+                add!("len", format!("{len:?}"));
+                add!("index", format!("{index:?}"));
             }
-            Overflow(BinOp::Rem, l, r) => write!(
-                f,
-                "attempt to compute the remainder of `{:#?} % {:#?}`, which would overflow",
-                l, r
-            ),
-            Overflow(BinOp::Shr, _, r) => {
-                write!(f, "attempt to shift right by `{:#?}`, which would overflow", r)
+            Overflow(BinOp::Shl | BinOp::Shr, _, val)
+            | DivisionByZero(val)
+            | RemainderByZero(val)
+            | OverflowNeg(val) => {
+                add!("val", format!("{val:#?}"));
             }
-            Overflow(BinOp::Shl, _, r) => {
-                write!(f, "attempt to shift left by `{:#?}`, which would overflow", r)
+            Overflow(binop, left, right) => {
+                add!("op", binop.to_hir_binop().as_str());
+                add!("left", format!("{left:#?}"));
+                add!("right", format!("{right:#?}"));
             }
+            ResumedAfterReturn(_) | ResumedAfterPanic(_) => {}
             MisalignedPointerDereference { required, found } => {
-                write!(
-                    f,
-                    "misaligned pointer dereference: address must be a multiple of {:?} but is {:?}",
-                    required, found
-                )
+                add!("required", format!("{required:#?}"));
+                add!("found", format!("{found:#?}"));
             }
-            _ => write!(f, "{}", self.description()),
         }
     }
 }
@@ -1907,7 +1913,7 @@ impl<'tcx> Operand<'tcx> {
         substs: impl IntoIterator<Item = GenericArg<'tcx>>,
         span: Span,
     ) -> Self {
-        let ty = tcx.mk_fn_def(def_id, substs);
+        let ty = Ty::new_fn_def(tcx, def_id, substs);
         Operand::Constant(Box::new(Constant {
             span,
             user_ty: None,
@@ -2008,7 +2014,7 @@ impl<'tcx> Rvalue<'tcx> {
                 | CastKind::IntToFloat
                 | CastKind::FnPtrToPtr
                 | CastKind::PtrToPtr
-                | CastKind::Pointer(_)
+                | CastKind::PointerCoercion(_)
                 | CastKind::PointerFromExposedAddress
                 | CastKind::DynStar
                 | CastKind::Transmute,
@@ -2029,23 +2035,19 @@ impl<'tcx> Rvalue<'tcx> {
 impl BorrowKind {
     pub fn mutability(&self) -> Mutability {
         match *self {
-            BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => Mutability::Not,
+            BorrowKind::Shared | BorrowKind::Shallow => Mutability::Not,
             BorrowKind::Mut { .. } => Mutability::Mut,
         }
     }
 
     pub fn allows_two_phase_borrow(&self) -> bool {
         match *self {
-            BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => false,
-            BorrowKind::Mut { allow_two_phase_borrow } => allow_two_phase_borrow,
-        }
-    }
-
-    // FIXME: won't be used after diagnostic migration
-    pub fn describe_mutability(&self) -> &str {
-        match *self {
-            BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => "immutable",
-            BorrowKind::Mut { .. } => "mutable",
+            BorrowKind::Shared
+            | BorrowKind::Shallow
+            | BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::ClosureCapture } => {
+                false
+            }
+            BorrowKind::Mut { kind: MutBorrowKind::TwoPhaseBorrow } => true,
         }
     }
 }
@@ -2084,7 +2086,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                 let kind_str = match borrow_kind {
                     BorrowKind::Shared => "",
                     BorrowKind::Shallow => "shallow ",
-                    BorrowKind::Mut { .. } | BorrowKind::Unique => "mut ",
+                    BorrowKind::Mut { .. } => "mut ",
                 };
 
                 // When printing regions, add trailing space if necessary.
@@ -2327,10 +2329,10 @@ impl<'tcx> ConstantKind<'tcx> {
     pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self {
         match self {
             Self::Ty(c) => {
-                if let Some(val) = c.kind().try_eval_for_mir(tcx, param_env) {
+                if let Some(val) = c.try_eval_for_mir(tcx, param_env) {
                     match val {
                         Ok(val) => Self::Val(val, c.ty()),
-                        Err(guar) => Self::Ty(tcx.const_error(self.ty(), guar)),
+                        Err(guar) => Self::Ty(ty::Const::new_error(tcx, guar, self.ty())),
                     }
                 } else {
                     self
@@ -2342,7 +2344,9 @@ impl<'tcx> ConstantKind<'tcx> {
                 match tcx.const_eval_resolve(param_env, uneval, None) {
                     Ok(val) => Self::Val(val, ty),
                     Err(ErrorHandled::TooGeneric) => self,
-                    Err(ErrorHandled::Reported(guar)) => Self::Ty(tcx.const_error(ty, guar.into())),
+                    Err(ErrorHandled::Reported(guar)) => {
+                        Self::Ty(ty::Const::new_error(tcx, guar.into(), ty))
+                    }
                 }
             }
         }
@@ -2461,51 +2465,6 @@ impl<'tcx> ConstantKind<'tcx> {
         Self::Val(val, ty)
     }
 
-    #[instrument(skip(tcx), level = "debug", ret)]
-    pub fn from_inline_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self {
-        let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
-        let body_id = match tcx.hir().get(hir_id) {
-            hir::Node::AnonConst(ac) => ac.body,
-            _ => span_bug!(
-                tcx.def_span(def_id.to_def_id()),
-                "from_inline_const can only process anonymous constants"
-            ),
-        };
-        let expr = &tcx.hir().body(body_id).value;
-        let ty = tcx.typeck(def_id).node_type(hir_id);
-
-        let lit_input = match expr.kind {
-            hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
-            hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => match expr.kind {
-                hir::ExprKind::Lit(ref lit) => {
-                    Some(LitToConstInput { lit: &lit.node, ty, neg: true })
-                }
-                _ => None,
-            },
-            _ => None,
-        };
-        if let Some(lit_input) = lit_input {
-            // If an error occurred, ignore that it's a literal and leave reporting the error up to
-            // mir.
-            match tcx.at(expr.span).lit_to_mir_constant(lit_input) {
-                Ok(c) => return c,
-                Err(_) => {}
-            }
-        }
-
-        let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id());
-        let parent_substs =
-            tcx.erase_regions(InternalSubsts::identity_for_item(tcx, typeck_root_def_id));
-        let substs =
-            ty::InlineConstSubsts::new(tcx, ty::InlineConstSubstsParts { parent_substs, ty })
-                .substs;
-
-        let uneval = UnevaluatedConst { def: def_id.to_def_id(), substs, promoted: None };
-        debug_assert!(!uneval.has_free_regions());
-
-        Self::Unevaluated(uneval, ty)
-    }
-
     /// Literals are converted to `ConstantKindVal`, const generic parameters are eagerly
     /// converted to a constant, everything else becomes `Unevaluated`.
     #[instrument(skip(tcx), level = "debug", ret)]
@@ -2553,7 +2512,7 @@ impl<'tcx> ConstantKind<'tcx> {
                 let generics = tcx.generics_of(item_def_id);
                 let index = generics.param_def_id_to_index[&def_id];
                 let name = tcx.item_name(def_id);
-                let ty_const = tcx.mk_const(ty::ParamConst::new(index, name), ty);
+                let ty_const = ty::Const::new_param(tcx, ty::ParamConst::new(index, name), ty);
                 debug!(?ty_const);
 
                 return Self::Ty(ty_const);
@@ -2624,10 +2583,9 @@ pub struct UnevaluatedConst<'tcx> {
 }
 
 impl<'tcx> UnevaluatedConst<'tcx> {
-    // FIXME: probably should get rid of this method. It's also wrong to
-    // shrink and then later expand a promoted.
     #[inline]
     pub fn shrink(self) -> ty::UnevaluatedConst<'tcx> {
+        assert_eq!(self.promoted, None);
         ty::UnevaluatedConst { def: self.def, substs: self.substs }
     }
 }
@@ -2818,7 +2776,7 @@ impl<'tcx> Display for ConstantKind<'tcx> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
         match *self {
             ConstantKind::Ty(c) => pretty_print_const(c, fmt, true),
-            ConstantKind::Val(val, ty) => pretty_print_const_value(val, ty, fmt, true),
+            ConstantKind::Val(val, ty) => pretty_print_const_value(val, ty, fmt),
             // FIXME(valtrees): Correctly print mir constants.
             ConstantKind::Unevaluated(..) => {
                 fmt.write_str("_")?;
@@ -2848,13 +2806,16 @@ fn pretty_print_byte_str(fmt: &mut Formatter<'_>, byte_str: &[u8]) -> fmt::Resul
     write!(fmt, "b\"{}\"", byte_str.escape_ascii())
 }
 
-fn comma_sep<'tcx>(fmt: &mut Formatter<'_>, elems: Vec<ConstantKind<'tcx>>) -> fmt::Result {
+fn comma_sep<'tcx>(
+    fmt: &mut Formatter<'_>,
+    elems: Vec<(ConstValue<'tcx>, Ty<'tcx>)>,
+) -> fmt::Result {
     let mut first = true;
-    for elem in elems {
+    for (ct, ty) in elems {
         if !first {
             fmt.write_str(", ")?;
         }
-        fmt.write_str(&format!("{}", elem))?;
+        pretty_print_const_value(ct, ty, fmt)?;
         first = false;
     }
     Ok(())
@@ -2865,7 +2826,6 @@ fn pretty_print_const_value<'tcx>(
     ct: ConstValue<'tcx>,
     ty: Ty<'tcx>,
     fmt: &mut Formatter<'_>,
-    print_ty: bool,
 ) -> fmt::Result {
     use crate::ty::print::PrettyPrinter;
 
@@ -2909,7 +2869,7 @@ fn pretty_print_const_value<'tcx>(
                 }
             }
             (ConstValue::ByRef { alloc, offset }, ty::Array(t, n)) if *t == u8_type => {
-                let n = n.kind().try_to_bits(tcx.data_layout.pointer_size).unwrap();
+                let n = n.try_to_bits(tcx.data_layout.pointer_size).unwrap();
                 // cast is ok because we already checked for pointer size (32 or 64 bit) above
                 let range = AllocRange { start: offset, size: Size::from_bytes(n) };
                 let byte_str = alloc.inner().get_bytes_strip_provenance(&tcx, range).unwrap();
@@ -2924,16 +2884,11 @@ fn pretty_print_const_value<'tcx>(
             // introducing ICEs (e.g. via `layout_of`) from missing bounds.
             // E.g. `transmute([0usize; 2]): (u8, *mut T)` needs to know `T: Sized`
             // to be able to destructure the tuple into `(0u8, *mut T)`
-            //
-            // FIXME(eddyb) for `--emit=mir`/`-Z dump-mir`, we should provide the
-            // correct `ty::ParamEnv` to allow printing *all* constant values.
             (_, ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) if !ty.has_non_region_param() => {
                 let ct = tcx.lift(ct).unwrap();
                 let ty = tcx.lift(ty).unwrap();
-                if let Some(contents) = tcx.try_destructure_mir_constant(
-                    ty::ParamEnv::reveal_all().and(ConstantKind::Val(ct, ty)),
-                ) {
-                    let fields = contents.fields.to_vec();
+                if let Some(contents) = tcx.try_destructure_mir_constant_for_diagnostics((ct, ty)) {
+                    let fields: Vec<(ConstValue<'_>, Ty<'_>)> = contents.fields.to_vec();
                     match *ty.kind() {
                         ty::Array(..) => {
                             fmt.write_str("[")?;
@@ -2972,12 +2927,14 @@ fn pretty_print_const_value<'tcx>(
                                 None => {
                                     fmt.write_str(" {{ ")?;
                                     let mut first = true;
-                                    for (field_def, field) in iter::zip(&variant_def.fields, fields)
+                                    for (field_def, (ct, ty)) in
+                                        iter::zip(&variant_def.fields, fields)
                                     {
                                         if !first {
                                             fmt.write_str(", ")?;
                                         }
-                                        fmt.write_str(&format!("{}: {}", field_def.name, field))?;
+                                        write!(fmt, "{}: ", field_def.name)?;
+                                        pretty_print_const_value(ct, ty, fmt)?;
                                         first = false;
                                     }
                                     fmt.write_str(" }}")?;
@@ -2987,20 +2944,13 @@ fn pretty_print_const_value<'tcx>(
                         _ => unreachable!(),
                     }
                     return Ok(());
-                } else {
-                    // Fall back to debug pretty printing for invalid constants.
-                    fmt.write_str(&format!("{:?}", ct))?;
-                    if print_ty {
-                        fmt.write_str(&format!(": {}", ty))?;
-                    }
-                    return Ok(());
-                };
+                }
             }
             (ConstValue::Scalar(scalar), _) => {
                 let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
                 cx.print_alloc_ids = true;
                 let ty = tcx.lift(ty).unwrap();
-                cx = cx.pretty_print_const_scalar(scalar, ty, print_ty)?;
+                cx = cx.pretty_print_const_scalar(scalar, ty)?;
                 fmt.write_str(&cx.into_buffer())?;
                 return Ok(());
             }
@@ -3015,12 +2965,8 @@ fn pretty_print_const_value<'tcx>(
             // their fields instead of just dumping the memory.
             _ => {}
         }
-        // fallback
-        fmt.write_str(&format!("{:?}", ct))?;
-        if print_ty {
-            fmt.write_str(&format!(": {}", ty))?;
-        }
-        Ok(())
+        // Fall back to debug pretty printing for invalid constants.
+        write!(fmt, "{ct:?}: {ty}")
     })
 }
 
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index f31b343c9..ca735d523 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -231,7 +231,7 @@ pub struct CodegenUnit<'tcx> {
     /// as well as the crate name and disambiguator.
     name: Symbol,
     items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
-    size_estimate: Option<usize>,
+    size_estimate: usize,
     primary: bool,
     /// True if this is CGU is used to hold code coverage information for dead code,
     /// false otherwise.
@@ -269,7 +269,7 @@ impl<'tcx> CodegenUnit<'tcx> {
         CodegenUnit {
             name,
             items: Default::default(),
-            size_estimate: None,
+            size_estimate: 0,
             primary: false,
             is_code_coverage_dead_code_cgu: false,
         }
@@ -291,10 +291,12 @@ impl<'tcx> CodegenUnit<'tcx> {
         self.primary = true;
     }
 
+    /// The order of these items is non-determinstic.
     pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
         &self.items
     }
 
+    /// The order of these items is non-determinstic.
     pub fn items_mut(&mut self) -> &mut FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
         &mut self.items
     }
@@ -318,23 +320,21 @@ impl<'tcx> CodegenUnit<'tcx> {
         base_n::encode(hash, base_n::CASE_INSENSITIVE)
     }
 
-    pub fn create_size_estimate(&mut self, tcx: TyCtxt<'tcx>) {
+    pub fn compute_size_estimate(&mut self, tcx: TyCtxt<'tcx>) {
         // Estimate the size of a codegen unit as (approximately) the number of MIR
         // statements it corresponds to.
-        self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum());
+        self.size_estimate = self.items.keys().map(|mi| mi.size_estimate(tcx)).sum();
     }
 
     #[inline]
-    /// Should only be called if [`create_size_estimate`] has previously been called.
+    /// Should only be called if [`compute_size_estimate`] has previously been called.
     ///
-    /// [`create_size_estimate`]: Self::create_size_estimate
+    /// [`compute_size_estimate`]: Self::compute_size_estimate
     pub fn size_estimate(&self) -> usize {
+        // Items are never zero-sized, so if we have items the estimate must be
+        // non-zero, unless we forgot to call `compute_size_estimate` first.
+        assert!(self.items.is_empty() || self.size_estimate != 0);
         self.size_estimate
-            .expect("create_size_estimate must be called before getting a size_estimate")
-    }
-
-    pub fn modify_size_estimate(&mut self, delta: usize) {
-        *self.size_estimate.as_mut().unwrap() += delta;
     }
 
     pub fn contains_item(&self, item: &MonoItem<'tcx>) -> bool {
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index 62c3d8cf2..ffa7a5400 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -353,14 +353,22 @@ where
     for statement in &data.statements {
         extra_data(PassWhere::BeforeLocation(current_location), w)?;
         let indented_body = format!("{0}{0}{1:?};", INDENT, statement);
-        writeln!(
-            w,
-            "{:A$} // {}{}",
-            indented_body,
-            if tcx.sess.verbose() { format!("{:?}: ", current_location) } else { String::new() },
-            comment(tcx, statement.source_info, body.span),
-            A = ALIGN,
-        )?;
+        if tcx.sess.opts.unstable_opts.mir_include_spans {
+            writeln!(
+                w,
+                "{:A$} // {}{}",
+                indented_body,
+                if tcx.sess.verbose() {
+                    format!("{:?}: ", current_location)
+                } else {
+                    String::new()
+                },
+                comment(tcx, statement.source_info),
+                A = ALIGN,
+            )?;
+        } else {
+            writeln!(w, "{}", indented_body)?;
+        }
 
         write_extra(tcx, w, |visitor| {
             visitor.visit_statement(statement, current_location);
@@ -374,14 +382,18 @@ where
     // Terminator at the bottom.
     extra_data(PassWhere::BeforeLocation(current_location), w)?;
     let indented_terminator = format!("{0}{0}{1:?};", INDENT, data.terminator().kind);
-    writeln!(
-        w,
-        "{:A$} // {}{}",
-        indented_terminator,
-        if tcx.sess.verbose() { format!("{:?}: ", current_location) } else { String::new() },
-        comment(tcx, data.terminator().source_info, body.span),
-        A = ALIGN,
-    )?;
+    if tcx.sess.opts.unstable_opts.mir_include_spans {
+        writeln!(
+            w,
+            "{:A$} // {}{}",
+            indented_terminator,
+            if tcx.sess.verbose() { format!("{:?}: ", current_location) } else { String::new() },
+            comment(tcx, data.terminator().source_info),
+            A = ALIGN,
+        )?;
+    } else {
+        writeln!(w, "{}", indented_terminator)?;
+    }
 
     write_extra(tcx, w, |visitor| {
         visitor.visit_terminator(data.terminator(), current_location);
@@ -400,10 +412,12 @@ fn write_extra<'tcx, F>(tcx: TyCtxt<'tcx>, write: &mut dyn Write, mut visit_op:
 where
     F: FnMut(&mut ExtraComments<'tcx>),
 {
-    let mut extra_comments = ExtraComments { tcx, comments: vec![] };
-    visit_op(&mut extra_comments);
-    for comment in extra_comments.comments {
-        writeln!(write, "{:A$} // {}", "", comment, A = ALIGN)?;
+    if tcx.sess.opts.unstable_opts.mir_include_spans {
+        let mut extra_comments = ExtraComments { tcx, comments: vec![] };
+        visit_op(&mut extra_comments);
+        for comment in extra_comments.comments {
+            writeln!(write, "{:A$} // {}", "", comment, A = ALIGN)?;
+        }
     }
     Ok(())
 }
@@ -522,13 +536,8 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
     }
 }
 
-fn comment(tcx: TyCtxt<'_>, SourceInfo { span, scope }: SourceInfo, function_span: Span) -> String {
-    let location = if tcx.sess.opts.unstable_opts.mir_pretty_relative_line_numbers {
-        tcx.sess.source_map().span_to_relative_line_string(span, function_span)
-    } else {
-        tcx.sess.source_map().span_to_embeddable_string(span)
-    };
-
+fn comment(tcx: TyCtxt<'_>, SourceInfo { span, scope }: SourceInfo) -> String {
+    let location = tcx.sess.source_map().span_to_embeddable_string(span);
     format!("scope {} at {}", scope.index(), location,)
 }
 
@@ -560,13 +569,17 @@ fn write_scope_tree(
             var_debug_info.value,
         );
 
-        writeln!(
-            w,
-            "{0:1$} // in {2}",
-            indented_debug_info,
-            ALIGN,
-            comment(tcx, var_debug_info.source_info, body.span),
-        )?;
+        if tcx.sess.opts.unstable_opts.mir_include_spans {
+            writeln!(
+                w,
+                "{0:1$} // in {2}",
+                indented_debug_info,
+                ALIGN,
+                comment(tcx, var_debug_info.source_info),
+            )?;
+        } else {
+            writeln!(w, "{}", indented_debug_info)?;
+        }
     }
 
     // Local variable types.
@@ -594,14 +607,18 @@ fn write_scope_tree(
 
         let local_name = if local == RETURN_PLACE { " return place" } else { "" };
 
-        writeln!(
-            w,
-            "{0:1$} //{2} in {3}",
-            indented_decl,
-            ALIGN,
-            local_name,
-            comment(tcx, local_decl.source_info, body.span),
-        )?;
+        if tcx.sess.opts.unstable_opts.mir_include_spans {
+            writeln!(
+                w,
+                "{0:1$} //{2} in {3}",
+                indented_decl,
+                ALIGN,
+                local_name,
+                comment(tcx, local_decl.source_info),
+            )?;
+        } else {
+            writeln!(w, "{}", indented_decl,)?;
+        }
     }
 
     let Some(children) = scope_tree.get(&parent) else {
@@ -627,14 +644,18 @@ fn write_scope_tree(
 
         let indented_header = format!("{0:1$}scope {2}{3} {{", "", indent, child.index(), special);
 
-        if let Some(span) = span {
-            writeln!(
-                w,
-                "{0:1$} // at {2}",
-                indented_header,
-                ALIGN,
-                tcx.sess.source_map().span_to_embeddable_string(span),
-            )?;
+        if tcx.sess.opts.unstable_opts.mir_include_spans {
+            if let Some(span) = span {
+                writeln!(
+                    w,
+                    "{0:1$} // at {2}",
+                    indented_header,
+                    ALIGN,
+                    tcx.sess.source_map().span_to_embeddable_string(span),
+                )?;
+            } else {
+                writeln!(w, "{}", indented_header)?;
+            }
         } else {
             writeln!(w, "{}", indented_header)?;
         }
@@ -846,7 +867,7 @@ fn write_allocation_newline(
 /// The `prefix` argument allows callers to add an arbitrary prefix before each line (even if there
 /// is only one line). Note that your prefix should contain a trailing space as the lines are
 /// printed directly after it.
-fn write_allocation_bytes<'tcx, Prov: Provenance, Extra, Bytes: AllocBytes>(
+pub fn write_allocation_bytes<'tcx, Prov: Provenance, Extra, Bytes: AllocBytes>(
     tcx: TyCtxt<'tcx>,
     alloc: &Allocation<Prov, Extra, Bytes>,
     w: &mut dyn std::fmt::Write,
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 53fd2dd23..613b132ff 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -1,6 +1,6 @@
 //! Values computed by queries that use MIR.
 
-use crate::mir::ConstantKind;
+use crate::mir::interpret::ConstValue;
 use crate::ty::{self, OpaqueHiddenType, Ty, TyCtxt};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::unord::UnordSet;
@@ -9,6 +9,7 @@ use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_index::bit_set::BitMatrix;
 use rustc_index::{Idx, IndexVec};
+use rustc_span::symbol::Symbol;
 use rustc_span::Span;
 use rustc_target::abi::{FieldIdx, VariantIdx};
 use smallvec::SmallVec;
@@ -150,6 +151,9 @@ pub struct GeneratorLayout<'tcx> {
     /// The type of every local stored inside the generator.
     pub field_tys: IndexVec<GeneratorSavedLocal, GeneratorSavedTy<'tcx>>,
 
+    /// The name for debuginfo.
+    pub field_names: IndexVec<GeneratorSavedLocal, Option<Symbol>>,
+
     /// Which of the above fields are in each variant. Note that one field may
     /// be stored in multiple variants.
     pub variant_fields: IndexVec<VariantIdx, IndexVec<FieldIdx, GeneratorSavedLocal>>,
@@ -413,7 +417,7 @@ impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
             ty::ReVar(vid) => {
                 let br =
                     ty::BoundRegion { var: ty::BoundVar::new(vid.index()), kind: ty::BrAnon(None) };
-                tcx.mk_re_late_bound(depth, br)
+                ty::Region::new_late_bound(tcx, depth, br)
             }
             _ => bug!("unexpected region in ClosureOutlivesSubjectTy: {r:?}"),
         });
@@ -440,7 +444,7 @@ impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
 #[derive(Copy, Clone, Debug, HashStable)]
 pub struct DestructuredConstant<'tcx> {
     pub variant: Option<VariantIdx>,
-    pub fields: &'tcx [ConstantKind<'tcx>],
+    pub fields: &'tcx [(ConstValue<'tcx>, Ty<'tcx>)],
 }
 
 /// Coverage information summarized from a MIR if instrumented for source code coverage (see
diff --git a/compiler/rustc_middle/src/mir/spanview.rs b/compiler/rustc_middle/src/mir/spanview.rs
index 2165403da..730c55157 100644
--- a/compiler/rustc_middle/src/mir/spanview.rs
+++ b/compiler/rustc_middle/src/mir/spanview.rs
@@ -3,7 +3,7 @@ use rustc_middle::hir;
 use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::MirSpanview;
-use rustc_span::{BytePos, Pos, Span, SyntaxContext};
+use rustc_span::{BytePos, Pos, Span};
 
 use std::cmp;
 use std::io::{self, Write};
@@ -15,8 +15,9 @@ const ANNOTATION_LEFT_BRACKET: char = '\u{298a}'; // Unicode `Z NOTATION RIGHT B
 const ANNOTATION_RIGHT_BRACKET: char = '\u{2989}'; // Unicode `Z NOTATION LEFT BINDING BRACKET`
 const NEW_LINE_SPAN: &str = "</span>\n<span class=\"line\">";
 const HEADER: &str = r#"<!DOCTYPE html>
-<html>
-<head>"#;
+<html lang="en">
+<head>
+<meta charset="utf-8">"#;
 const START_BODY: &str = r#"</head>
 <body>"#;
 const FOOTER: &str = r#"</body>
@@ -327,7 +328,7 @@ fn compute_block_span(data: &BasicBlockData<'_>, body_span: Span) -> Span {
     let mut span = data.terminator().source_info.span;
     for statement_span in data.statements.iter().map(|statement| statement.source_info.span) {
         // Only combine Spans from the root context, and within the function's body_span.
-        if statement_span.ctxt() == SyntaxContext::root() && body_span.contains(statement_span) {
+        if statement_span.ctxt().is_root() && body_span.contains(statement_span) {
             span = span.to(statement_span);
         }
     }
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 3e474c1d3..7f1d38203 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -7,7 +7,7 @@ use super::{BasicBlock, Constant, Local, SwitchTargets, UserTypeProjection};
 
 use crate::mir::coverage::{CodeRegion, CoverageKind};
 use crate::traits::Reveal;
-use crate::ty::adjustment::PointerCast;
+use crate::ty::adjustment::PointerCoercion;
 use crate::ty::subst::SubstsRef;
 use crate::ty::{self, List, Ty};
 use crate::ty::{Region, UserTypeAnnotationIndex};
@@ -182,6 +182,16 @@ pub enum BorrowKind {
     /// We can also report errors with this kind of borrow differently.
     Shallow,
 
+    /// Data is mutable and not aliasable.
+    Mut { kind: MutBorrowKind },
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, TyEncodable, TyDecodable)]
+#[derive(Hash, HashStable)]
+pub enum MutBorrowKind {
+    Default,
+    /// This borrow arose from method-call auto-ref. (i.e., `adjustment::Adjust::Borrow`)
+    TwoPhaseBorrow,
     /// Data must be immutable but not aliasable. This kind of borrow
     /// cannot currently be expressed by the user and is used only in
     /// implicit closure bindings. It is needed when the closure is
@@ -216,23 +226,14 @@ pub enum BorrowKind {
     /// user code, if awkward, but extra weird for closures, since the
     /// borrow is hidden.
     ///
-    /// So we introduce a "unique imm" borrow -- the referent is
-    /// immutable, but not aliasable. This solves the problem. For
-    /// simplicity, we don't give users the way to express this
-    /// borrow, it's just used when translating closures.
+    /// So we introduce a `ClosureCapture` borrow -- user will not have to mark the variable
+    /// containing the mutable reference as `mut`, as they didn't ever
+    /// intend to mutate the mutable reference itself. We still mutable capture it in order to
+    /// mutate the pointed value through it (but not mutating the reference itself).
     ///
-    // FIXME(#112072): This is wrong. Unique borrows are mutable borrows except
-    // that they do not require their pointee to be marked as a mutable.
-    // They should still be treated as mutable borrows in every other way,
-    // e.g. for variance or overlap checking.
-    Unique,
-
-    /// Data is mutable and not aliasable.
-    Mut {
-        /// `true` if this borrow arose from method-call auto-ref
-        /// (i.e., `adjustment::Adjust::Borrow`).
-        allow_two_phase_borrow: bool,
-    },
+    /// This solves the problem. For simplicity, we don't give users the way to express this
+    /// borrow, it's just used when translating closures.
+    ClosureCapture,
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -512,6 +513,31 @@ pub struct CopyNonOverlapping<'tcx> {
     pub count: Operand<'tcx>,
 }
 
+/// Represents how a `TerminatorKind::Call` was constructed, used for diagnostics
+#[derive(Clone, Copy, TyEncodable, TyDecodable, Debug, PartialEq, Hash, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
+pub enum CallSource {
+    /// This came from something such as `a > b` or `a + b`. In THIR, if `from_hir_call`
+    /// is false then this is the desugaring.
+    OverloadedOperator,
+    /// This was from comparison generated by a match, used by const-eval for better errors
+    /// when the comparison cannot be done in compile time.
+    ///
+    /// (see <https://github.com/rust-lang/rust/issues/90237>)
+    MatchCmp,
+    /// Other types of desugaring that did not come from the HIR, but we don't care about
+    /// for diagnostics (yet).
+    Misc,
+    /// Normal function call, no special source
+    Normal,
+}
+
+impl CallSource {
+    pub fn from_hir_call(self) -> bool {
+        matches!(self, CallSource::Normal)
+    }
+}
+
 ///////////////////////////////////////////////////////////////////////////
 // Terminators
 
@@ -638,11 +664,10 @@ pub enum TerminatorKind<'tcx> {
         target: Option<BasicBlock>,
         /// Action to be taken if the call unwinds.
         unwind: UnwindAction,
-        /// `true` if this is from a call in HIR rather than from an overloaded
-        /// operator. True for overloaded function call.
-        from_hir_call: bool,
+        /// Where this call came from in HIR/THIR.
+        call_source: CallSource,
         /// This `Span` is the span of the function, without the dot and receiver
-        /// (e.g. `foo(a, b)` in `x.foo(a, b)`
+        /// e.g. `foo(a, b)` in `x.foo(a, b)`
         fn_span: Span,
     },
 
@@ -801,7 +826,8 @@ pub enum UnwindAction {
 }
 
 /// Information about an assertion failure.
-#[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, TypeFoldable, TypeVisitable)]
+#[derive(Clone, Hash, HashStable, PartialEq, Debug)]
+#[derive(TyEncodable, TyDecodable, TypeFoldable, TypeVisitable)]
 pub enum AssertKind<O> {
     BoundsCheck { len: O, index: O },
     Overflow(BinOp, O, O),
@@ -1204,9 +1230,9 @@ pub enum CastKind {
     /// An address-to-pointer cast that picks up an exposed provenance.
     /// See the docs on `from_exposed_addr` for more details.
     PointerFromExposedAddress,
-    /// All sorts of pointer-to-pointer casts. Note that reference-to-raw-ptr casts are
+    /// Pointer related casts that are done by coercions. Note that reference-to-raw-ptr casts are
     /// translated into `&raw mut/const *r`, i.e., they are not actually casts.
-    Pointer(PointerCast),
+    PointerCoercion(PointerCoercion),
     /// Cast into a dyn* object.
     DynStar,
     IntToInt,
@@ -1266,19 +1292,30 @@ pub enum UnOp {
 pub enum BinOp {
     /// The `+` operator (addition)
     Add,
+    /// Like `Add`, but with UB on overflow.  (Integers only.)
+    AddUnchecked,
     /// The `-` operator (subtraction)
     Sub,
+    /// Like `Sub`, but with UB on overflow.  (Integers only.)
+    SubUnchecked,
     /// The `*` operator (multiplication)
     Mul,
+    /// Like `Mul`, but with UB on overflow.  (Integers only.)
+    MulUnchecked,
     /// The `/` operator (division)
     ///
-    /// Division by zero is UB, because the compiler should have inserted checks
-    /// prior to this.
+    /// For integer types, division by zero is UB, as is `MIN / -1` for signed.
+    /// The compiler should have inserted checks prior to this.
+    ///
+    /// Floating-point division by zero is safe, and does not need guards.
     Div,
     /// The `%` operator (modulus)
     ///
-    /// Using zero as the modulus (second operand) is UB, because the compiler
-    /// should have inserted checks prior to this.
+    /// For integer types, using zero as the modulus (second operand) is UB,
+    /// as is `MIN % -1` for signed.
+    /// The compiler should have inserted checks prior to this.
+    ///
+    /// Floating-point remainder by zero is safe, and does not need guards.
     Rem,
     /// The `^` operator (bitwise xor)
     BitXor,
@@ -1290,10 +1327,17 @@ pub enum BinOp {
     ///
     /// The offset is truncated to the size of the first operand before shifting.
     Shl,
+    /// Like `Shl`, but is UB if the RHS >= LHS::BITS
+    ShlUnchecked,
     /// The `>>` operator (shift right)
     ///
     /// The offset is truncated to the size of the first operand before shifting.
+    ///
+    /// This is an arithmetic shift if the LHS is signed
+    /// and a logical shift if the LHS is unsigned.
     Shr,
+    /// Like `Shl`, but is UB if the RHS >= LHS::BITS
+    ShrUnchecked,
     /// The `==` operator (equality)
     Eq,
     /// The `<` operator (less than)
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index 5ca824134..8618a5315 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -95,11 +95,13 @@ impl<'tcx> PlaceTy<'tcx> {
             ProjectionElem::Subslice { from, to, from_end } => {
                 PlaceTy::from_ty(match self.ty.kind() {
                     ty::Slice(..) => self.ty,
-                    ty::Array(inner, _) if !from_end => tcx.mk_array(*inner, (to - from) as u64),
+                    ty::Array(inner, _) if !from_end => {
+                        Ty::new_array(tcx, *inner, (to - from) as u64)
+                    }
                     ty::Array(inner, size) if from_end => {
                         let size = size.eval_target_usize(tcx, param_env);
                         let len = size - from - to;
-                        tcx.mk_array(*inner, len)
+                        Ty::new_array(tcx, *inner, len)
                     }
                     _ => bug!("cannot subslice non-array type: `{:?}`", self),
                 })
@@ -162,16 +164,16 @@ impl<'tcx> Rvalue<'tcx> {
         match *self {
             Rvalue::Use(ref operand) => operand.ty(local_decls, tcx),
             Rvalue::Repeat(ref operand, count) => {
-                tcx.mk_array_with_const_len(operand.ty(local_decls, tcx), count)
+                Ty::new_array_with_const_len(tcx, operand.ty(local_decls, tcx), count)
             }
             Rvalue::ThreadLocalRef(did) => tcx.thread_local_ptr_ty(did),
             Rvalue::Ref(reg, bk, ref place) => {
                 let place_ty = place.ty(local_decls, tcx).ty;
-                tcx.mk_ref(reg, ty::TypeAndMut { ty: place_ty, mutbl: bk.to_mutbl_lossy() })
+                Ty::new_ref(tcx, reg, ty::TypeAndMut { ty: place_ty, mutbl: bk.to_mutbl_lossy() })
             }
             Rvalue::AddressOf(mutability, ref place) => {
                 let place_ty = place.ty(local_decls, tcx).ty;
-                tcx.mk_ptr(ty::TypeAndMut { ty: place_ty, mutbl: mutability })
+                Ty::new_ptr(tcx, ty::TypeAndMut { ty: place_ty, mutbl: mutability })
             }
             Rvalue::Len(..) => tcx.types.usize,
             Rvalue::Cast(.., ty) => ty,
@@ -184,7 +186,7 @@ impl<'tcx> Rvalue<'tcx> {
                 let lhs_ty = lhs.ty(local_decls, tcx);
                 let rhs_ty = rhs.ty(local_decls, tcx);
                 let ty = op.ty(tcx, lhs_ty, rhs_ty);
-                tcx.mk_tup(&[ty, tcx.types.bool])
+                Ty::new_tup(tcx, &[ty, tcx.types.bool])
             }
             Rvalue::UnaryOp(UnOp::Not | UnOp::Neg, ref operand) => operand.ty(local_decls, tcx),
             Rvalue::Discriminant(ref place) => place.ty(local_decls, tcx).ty.discriminant_ty(tcx),
@@ -192,17 +194,17 @@ impl<'tcx> Rvalue<'tcx> {
                 tcx.types.usize
             }
             Rvalue::Aggregate(ref ak, ref ops) => match **ak {
-                AggregateKind::Array(ty) => tcx.mk_array(ty, ops.len() as u64),
+                AggregateKind::Array(ty) => Ty::new_array(tcx, ty, ops.len() as u64),
                 AggregateKind::Tuple => {
-                    tcx.mk_tup_from_iter(ops.iter().map(|op| op.ty(local_decls, tcx)))
+                    Ty::new_tup_from_iter(tcx, ops.iter().map(|op| op.ty(local_decls, tcx)))
                 }
                 AggregateKind::Adt(did, _, substs, _, _) => tcx.type_of(did).subst(tcx, substs),
-                AggregateKind::Closure(did, substs) => tcx.mk_closure(did, substs),
+                AggregateKind::Closure(did, substs) => Ty::new_closure(tcx, did, substs),
                 AggregateKind::Generator(did, substs, movability) => {
-                    tcx.mk_generator(did, substs, movability)
+                    Ty::new_generator(tcx, did, substs, movability)
                 }
             },
-            Rvalue::ShallowInitBox(_, ty) => tcx.mk_box(ty),
+            Rvalue::ShallowInitBox(_, ty) => Ty::new_box(tcx, ty),
             Rvalue::CopyForDeref(ref place) => place.ty(local_decls, tcx).ty,
         }
     }
@@ -235,8 +237,11 @@ impl<'tcx> BinOp {
         // FIXME: handle SIMD correctly
         match self {
             &BinOp::Add
+            | &BinOp::AddUnchecked
             | &BinOp::Sub
+            | &BinOp::SubUnchecked
             | &BinOp::Mul
+            | &BinOp::MulUnchecked
             | &BinOp::Div
             | &BinOp::Rem
             | &BinOp::BitXor
@@ -246,7 +251,11 @@ impl<'tcx> BinOp {
                 assert_eq!(lhs_ty, rhs_ty);
                 lhs_ty
             }
-            &BinOp::Shl | &BinOp::Shr | &BinOp::Offset => {
+            &BinOp::Shl
+            | &BinOp::ShlUnchecked
+            | &BinOp::Shr
+            | &BinOp::ShrUnchecked
+            | &BinOp::Offset => {
                 lhs_ty // lhs_ty can be != rhs_ty
             }
             &BinOp::Eq | &BinOp::Lt | &BinOp::Le | &BinOp::Ne | &BinOp::Ge | &BinOp::Gt => {
@@ -262,11 +271,6 @@ impl BorrowKind {
             BorrowKind::Mut { .. } => hir::Mutability::Mut,
             BorrowKind::Shared => hir::Mutability::Not,
 
-            // We have no type corresponding to a unique imm borrow, so
-            // use `&mut`. It gives all the capabilities of a `&uniq`
-            // and hence is a safe "over approximation".
-            BorrowKind::Unique => hir::Mutability::Mut,
-
             // We have no type corresponding to a shallow borrow, so use
             // `&` as an approximation.
             BorrowKind::Shallow => hir::Mutability::Not,
@@ -293,7 +297,14 @@ impl BinOp {
             BinOp::Gt => hir::BinOpKind::Gt,
             BinOp::Le => hir::BinOpKind::Le,
             BinOp::Ge => hir::BinOpKind::Ge,
-            BinOp::Offset => unreachable!(),
+            BinOp::AddUnchecked
+            | BinOp::SubUnchecked
+            | BinOp::MulUnchecked
+            | BinOp::ShlUnchecked
+            | BinOp::ShrUnchecked
+            | BinOp::Offset => {
+                unreachable!()
+            }
         }
     }
 }
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index 2c6126cdd..1b9c1438f 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -105,7 +105,7 @@ pub struct Terminator<'tcx> {
     pub kind: TerminatorKind<'tcx>,
 }
 
-pub type Successors<'a> = impl Iterator<Item = BasicBlock> + 'a;
+pub type Successors<'a> = impl DoubleEndedIterator<Item = BasicBlock> + 'a;
 pub type SuccessorsMut<'a> =
     iter::Chain<std::option::IntoIter<&'a mut BasicBlock>, slice::IterMut<'a, BasicBlock>>;
 
@@ -272,7 +272,8 @@ impl<'tcx> Debug for TerminatorKind<'tcx> {
 
         let unwind = match self.unwind() {
             // Not needed or included in successors
-            None | Some(UnwindAction::Continue) | Some(UnwindAction::Cleanup(_)) => None,
+            None | Some(UnwindAction::Cleanup(_)) => None,
+            Some(UnwindAction::Continue) => Some("unwind continue"),
             Some(UnwindAction::Unreachable) => Some("unwind unreachable"),
             Some(UnwindAction::Terminate) => Some("unwind terminate"),
         };
diff --git a/compiler/rustc_middle/src/mir/traversal.rs b/compiler/rustc_middle/src/mir/traversal.rs
index 7d247eeb6..ec16a8470 100644
--- a/compiler/rustc_middle/src/mir/traversal.rs
+++ b/compiler/rustc_middle/src/mir/traversal.rs
@@ -149,7 +149,7 @@ impl<'a, 'tcx> Postorder<'a, 'tcx> {
         //      B     C
         //      |     |
         //      |     |
-        //      D     |
+        //      |     D
         //       \   /
         //        \ /
         //         E
@@ -159,26 +159,26 @@ impl<'a, 'tcx> Postorder<'a, 'tcx> {
         //
         // When the first call to `traverse_successor` happens, the following happens:
         //
-        //     [(B, [D]),  // `B` taken from the successors of `A`, pushed to the
-        //                 // top of the stack along with the successors of `B`
-        //      (A, [C])]
+        //     [(C, [D]),  // `C` taken from the successors of `A`, pushed to the
+        //                 // top of the stack along with the successors of `C`
+        //      (A, [B])]
         //
-        //     [(D, [E]),  // `D` taken from successors of `B`, pushed to stack
-        //      (B, []),
-        //      (A, [C])]
+        //     [(D, [E]),  // `D` taken from successors of `C`, pushed to stack
+        //      (C, []),
+        //      (A, [B])]
         //
         //     [(E, []),   // `E` taken from successors of `D`, pushed to stack
         //      (D, []),
-        //      (B, []),
-        //      (A, [C])]
+        //      (C, []),
+        //      (A, [B])]
         //
         // Now that the top of the stack has no successors we can traverse, each item will
-        // be popped off during iteration until we get back to `A`. This yields [E, D, B].
+        // be popped off during iteration until we get back to `A`. This yields [E, D, C].
         //
-        // When we yield `B` and call `traverse_successor`, we push `C` to the stack, but
+        // When we yield `C` and call `traverse_successor`, we push `B` to the stack, but
         // since we've already visited `E`, that child isn't added to the stack. The last
-        // two iterations yield `C` and finally `A` for a final traversal of [E, D, B, C, A]
-        while let Some(&mut (_, ref mut iter)) = self.visit_stack.last_mut() && let Some(bb) = iter.next() {
+        // two iterations yield `B` and finally `A` for a final traversal of [E, D, C, B, A]
+        while let Some(&mut (_, ref mut iter)) = self.visit_stack.last_mut() && let Some(bb) = iter.next_back() {
             if self.visited.insert(bb) {
                 if let Some(term) = &self.basic_blocks[bb].terminator {
                     self.visit_stack.push((bb, term.successors()));
@@ -188,10 +188,6 @@ impl<'a, 'tcx> Postorder<'a, 'tcx> {
     }
 }
 
-pub fn postorder<'a, 'tcx>(body: &'a Body<'tcx>) -> Postorder<'a, 'tcx> {
-    Postorder::new(&body.basic_blocks, START_BLOCK)
-}
-
 impl<'a, 'tcx> Iterator for Postorder<'a, 'tcx> {
     type Item = (BasicBlock, &'a BasicBlockData<'tcx>);
 
@@ -219,6 +215,17 @@ impl<'a, 'tcx> Iterator for Postorder<'a, 'tcx> {
     }
 }
 
+/// Creates an iterator over the `Body`'s basic blocks, that:
+/// - returns basic blocks in a postorder,
+/// - traverses the `BasicBlocks` CFG cache's reverse postorder backwards, and does not cache the
+///   postorder itself.
+pub fn postorder<'a, 'tcx>(
+    body: &'a Body<'tcx>,
+) -> impl Iterator<Item = (BasicBlock, &'a BasicBlockData<'tcx>)> + ExactSizeIterator + DoubleEndedIterator
+{
+    reverse_postorder(body).rev()
+}
+
 /// Reverse postorder traversal of a graph
 ///
 /// Reverse postorder is the reverse order of a postorder traversal.
@@ -295,34 +302,12 @@ pub fn reachable_as_bitset(body: &Body<'_>) -> BitSet<BasicBlock> {
     iter.visited
 }
 
-#[derive(Clone)]
-pub struct ReversePostorderIter<'a, 'tcx> {
+/// Creates an iterator over the `Body`'s basic blocks, that:
+/// - returns basic blocks in a reverse postorder,
+/// - makes use of the `BasicBlocks` CFG cache's reverse postorder.
+pub fn reverse_postorder<'a, 'tcx>(
     body: &'a Body<'tcx>,
-    blocks: &'a [BasicBlock],
-    idx: usize,
-}
-
-impl<'a, 'tcx> Iterator for ReversePostorderIter<'a, 'tcx> {
-    type Item = (BasicBlock, &'a BasicBlockData<'tcx>);
-
-    fn next(&mut self) -> Option<(BasicBlock, &'a BasicBlockData<'tcx>)> {
-        if self.idx == 0 {
-            return None;
-        }
-        self.idx -= 1;
-
-        self.blocks.get(self.idx).map(|&bb| (bb, &self.body[bb]))
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        (self.idx, Some(self.idx))
-    }
-}
-
-impl<'a, 'tcx> ExactSizeIterator for ReversePostorderIter<'a, 'tcx> {}
-
-pub fn reverse_postorder<'a, 'tcx>(body: &'a Body<'tcx>) -> ReversePostorderIter<'a, 'tcx> {
-    let blocks = body.basic_blocks.postorder();
-    let len = blocks.len();
-    ReversePostorderIter { body, blocks, idx: len }
+) -> impl Iterator<Item = (BasicBlock, &'a BasicBlockData<'tcx>)> + ExactSizeIterator + DoubleEndedIterator
+{
+    body.basic_blocks.reverse_postorder().iter().map(|&bb| (bb, &body.basic_blocks[bb]))
 }
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 8d44e929a..205dc9ec7 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -519,7 +519,7 @@ macro_rules! make_mir_visitor {
                         destination,
                         target: _,
                         unwind: _,
-                        from_hir_call: _,
+                        call_source: _,
                         fn_span: _
                     } => {
                         self.visit_operand(func, location);
@@ -650,9 +650,6 @@ macro_rules! make_mir_visitor {
                             BorrowKind::Shallow => PlaceContext::NonMutatingUse(
                                 NonMutatingUseContext::ShallowBorrow
                             ),
-                            BorrowKind::Unique => PlaceContext::MutatingUse(
-                                MutatingUseContext::Borrow
-                            ),
                             BorrowKind::Mut { .. } =>
                                 PlaceContext::MutatingUse(MutatingUseContext::Borrow),
                         };
@@ -1136,13 +1133,12 @@ macro_rules! visit_place_fns {
 
         fn visit_projection_elem(
             &mut self,
-            local: Local,
-            proj_base: &[PlaceElem<'tcx>],
+            place_ref: PlaceRef<'tcx>,
             elem: PlaceElem<'tcx>,
             context: PlaceContext,
             location: Location,
         ) {
-            self.super_projection_elem(local, proj_base, elem, context, location);
+            self.super_projection_elem(place_ref, elem, context, location);
         }
 
         fn super_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
@@ -1171,15 +1167,13 @@ macro_rules! visit_place_fns {
             location: Location,
         ) {
             for (base, elem) in place_ref.iter_projections().rev() {
-                let base_proj = base.projection;
-                self.visit_projection_elem(place_ref.local, base_proj, elem, context, location);
+                self.visit_projection_elem(base, elem, context, location);
             }
         }
 
         fn super_projection_elem(
             &mut self,
-            _local: Local,
-            _proj_base: &[PlaceElem<'tcx>],
+            _place_ref: PlaceRef<'tcx>,
             elem: PlaceElem<'tcx>,
             _context: PlaceContext,
             location: Location,
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index fd02a1613..2c481745d 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -55,6 +55,10 @@ impl<T> EraseType for &'_ ty::List<T> {
     type Result = [u8; size_of::<*const ()>()];
 }
 
+impl<I: rustc_index::Idx, T> EraseType for &'_ rustc_index::IndexSlice<I, T> {
+    type Result = [u8; size_of::<&'static rustc_index::IndexSlice<u32, ()>>()];
+}
+
 impl<T> EraseType for Result<&'_ T, traits::query::NoSolution> {
     type Result = [u8; size_of::<Result<&'static (), traits::query::NoSolution>>()];
 }
@@ -67,8 +71,8 @@ impl<T> EraseType for Result<&'_ T, traits::CodegenObligationError> {
     type Result = [u8; size_of::<Result<&'static (), traits::CodegenObligationError>>()];
 }
 
-impl<T> EraseType for Result<&'_ T, ty::layout::FnAbiError<'_>> {
-    type Result = [u8; size_of::<Result<&'static (), ty::layout::FnAbiError<'static>>>()];
+impl<T> EraseType for Result<&'_ T, &'_ ty::layout::FnAbiError<'_>> {
+    type Result = [u8; size_of::<Result<&'static (), &'static ty::layout::FnAbiError<'static>>>()];
 }
 
 impl<T> EraseType for Result<(&'_ T, rustc_middle::thir::ExprId), rustc_errors::ErrorGuaranteed> {
@@ -92,15 +96,17 @@ impl EraseType for Result<ty::GenericArg<'_>, traits::query::NoSolution> {
     type Result = [u8; size_of::<Result<ty::GenericArg<'static>, traits::query::NoSolution>>()];
 }
 
-impl EraseType for Result<bool, ty::layout::LayoutError<'_>> {
-    type Result = [u8; size_of::<Result<bool, ty::layout::LayoutError<'static>>>()];
+impl EraseType for Result<bool, &ty::layout::LayoutError<'_>> {
+    type Result = [u8; size_of::<Result<bool, &'static ty::layout::LayoutError<'static>>>()];
 }
 
-impl EraseType for Result<rustc_target::abi::TyAndLayout<'_, Ty<'_>>, ty::layout::LayoutError<'_>> {
+impl EraseType
+    for Result<rustc_target::abi::TyAndLayout<'_, Ty<'_>>, &ty::layout::LayoutError<'_>>
+{
     type Result = [u8; size_of::<
         Result<
             rustc_target::abi::TyAndLayout<'static, Ty<'static>>,
-            ty::layout::LayoutError<'static>,
+            &'static ty::layout::LayoutError<'static>,
         >,
     >()];
 }
@@ -309,7 +315,6 @@ tcx_lifetime! {
     rustc_middle::mir::interpret::ConstValue,
     rustc_middle::mir::interpret::GlobalId,
     rustc_middle::mir::interpret::LitToConstInput,
-    rustc_middle::traits::ChalkEnvironmentAndGoal,
     rustc_middle::traits::query::MethodAutoderefStepsResult,
     rustc_middle::traits::query::type_op::AscribeUserType,
     rustc_middle::traits::query::type_op::Eq,
@@ -317,7 +322,7 @@ tcx_lifetime! {
     rustc_middle::traits::query::type_op::Subtype,
     rustc_middle::ty::AdtDef,
     rustc_middle::ty::AliasTy,
-    rustc_middle::ty::Clause,
+    rustc_middle::ty::ClauseKind,
     rustc_middle::ty::ClosureTypeInfo,
     rustc_middle::ty::Const,
     rustc_middle::ty::DestructuredConst,
diff --git a/compiler/rustc_middle/src/query/keys.rs b/compiler/rustc_middle/src/query/keys.rs
index fa62b7f32..28e699cd2 100644
--- a/compiler/rustc_middle/src/query/keys.rs
+++ b/compiler/rustc_middle/src/query/keys.rs
@@ -2,6 +2,7 @@
 
 use crate::infer::canonical::Canonical;
 use crate::mir;
+use crate::mir::interpret::ConstValue;
 use crate::traits;
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::layout::{TyAndLayout, ValidityRequirement};
@@ -317,11 +318,11 @@ impl<'tcx> Key for (LocalDefId, DefId, SubstsRef<'tcx>) {
     }
 }
 
-impl<'tcx> Key for (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>) {
+impl<'tcx> Key for (ty::ParamEnv<'tcx>, ty::TraitRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
-        tcx.def_span(self.1.def_id())
+        tcx.def_span(self.1.def_id)
     }
 }
 
@@ -333,6 +334,14 @@ impl<'tcx> Key for (ty::Const<'tcx>, FieldIdx) {
     }
 }
 
+impl<'tcx> Key for (ConstValue<'tcx>, Ty<'tcx>) {
+    type CacheSelector = DefaultCacheSelector<Self>;
+
+    fn default_span(&self, _: TyCtxt<'_>) -> Span {
+        DUMMY_SP
+    }
+}
+
 impl<'tcx> Key for mir::interpret::ConstAlloc<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
@@ -420,7 +429,7 @@ impl<'tcx> Key for (Ty<'tcx>, Ty<'tcx>) {
     }
 }
 
-impl<'tcx> Key for &'tcx ty::List<ty::Predicate<'tcx>> {
+impl<'tcx> Key for &'tcx ty::List<ty::Clause<'tcx>> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 1528be42f..a059590e6 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -39,8 +39,8 @@ use crate::traits::query::{
 };
 use crate::traits::specialization_graph;
 use crate::traits::{
-    CanonicalChalkEnvironmentAndGoal, CodegenObligationError, EvaluationResult, ImplSource,
-    ObjectSafetyViolation, ObligationCause, OverflowError, WellFormedLoc,
+    CodegenObligationError, EvaluationResult, ImplSource, ObjectSafetyViolation, ObligationCause,
+    OverflowError, WellFormedLoc,
 };
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::layout::ValidityRequirement;
@@ -54,7 +54,7 @@ use crate::ty::{
 };
 use rustc_arena::TypedArena;
 use rustc_ast as ast;
-use rustc_ast::expand::allocator::AllocatorKind;
+use rustc_ast::expand::{allocator::AllocatorKind, StrippedCfgItem};
 use rustc_attr as attr;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
@@ -346,7 +346,7 @@ rustc_queries! {
     /// `key` is the `DefId` of the associated type or opaque type.
     ///
     /// Bounds from the parent (e.g. with nested impl trait) are not included.
-    query explicit_item_bounds(key: DefId) -> ty::EarlyBinder<&'tcx [(ty::Predicate<'tcx>, Span)]> {
+    query explicit_item_bounds(key: DefId) -> ty::EarlyBinder<&'tcx [(ty::Clause<'tcx>, Span)]> {
         desc { |tcx| "finding item bounds for `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
@@ -373,7 +373,7 @@ rustc_queries! {
     /// ```
     ///
     /// Bounds from the parent (e.g. with nested impl trait) are not included.
-    query item_bounds(key: DefId) -> ty::EarlyBinder<&'tcx ty::List<ty::Predicate<'tcx>>> {
+    query item_bounds(key: DefId) -> ty::EarlyBinder<&'tcx ty::List<ty::Clause<'tcx>>> {
         desc { |tcx| "elaborating item bounds for `{}`", tcx.def_path_str(key) }
     }
 
@@ -531,6 +531,19 @@ rustc_queries! {
         }
     }
 
+    /// Returns names of captured upvars for closures and generators.
+    ///
+    /// Here are some examples:
+    ///  - `name__field1__field2` when the upvar is captured by value.
+    ///  - `_ref__name__field` when the upvar is captured by reference.
+    ///
+    /// For generators this only contains upvars that are shared by all states.
+    query closure_saved_names_of_captured_variables(def_id: DefId) -> &'tcx IndexVec<abi::FieldIdx, Symbol> {
+        arena_cache
+        desc { |tcx| "computing debuginfo for closure `{}`", tcx.def_path_str(def_id) }
+        separate_provide_extern
+    }
+
     query mir_generator_witnesses(key: DefId) -> &'tcx Option<mir::GeneratorLayout<'tcx>> {
         arena_cache
         desc { |tcx| "generator witness types for `{}`", tcx.def_path_str(key) }
@@ -868,7 +881,7 @@ rustc_queries! {
     ///
     /// Note that we've liberated the late bound regions of function signatures, so
     /// this can not be used to check whether these types are well formed.
-    query assumed_wf_types(key: DefId) -> &'tcx ty::List<Ty<'tcx>> {
+    query assumed_wf_types(key: LocalDefId) -> &'tcx [(Ty<'tcx>, Span)] {
         desc { |tcx| "computing the implied bounds of `{}`", tcx.def_path_str(key) }
     }
 
@@ -1074,19 +1087,13 @@ rustc_queries! {
     }
 
     /// Tries to destructure an `mir::ConstantKind` ADT or array into its variant index
-    /// and its field values.
-    query try_destructure_mir_constant(
-        key: ty::ParamEnvAnd<'tcx, mir::ConstantKind<'tcx>>
+    /// and its field values. This should only be used for pretty printing.
+    query try_destructure_mir_constant_for_diagnostics(
+        key: (ConstValue<'tcx>, Ty<'tcx>)
     ) -> Option<mir::DestructuredConstant<'tcx>> {
         desc { "destructuring MIR constant"}
-    }
-
-    /// Dereference a constant reference or raw pointer and turn the result into a constant
-    /// again.
-    query deref_mir_constant(
-        key: ty::ParamEnvAnd<'tcx, mir::ConstantKind<'tcx>>
-    ) -> mir::ConstantKind<'tcx> {
-        desc { "dereferencing MIR constant" }
+        no_hash
+        eval_always
     }
 
     query const_caller_location(key: (rustc_span::Symbol, u32, u32)) -> ConstValue<'tcx> {
@@ -1100,10 +1107,6 @@ rustc_queries! {
         desc { "converting literal to const" }
     }
 
-    query lit_to_mir_constant(key: LitToConstInput<'tcx>) -> Result<mir::ConstantKind<'tcx>, LitToConstError> {
-        desc { "converting literal to mir constant" }
-    }
-
     query check_match(key: LocalDefId) -> Result<(), rustc_errors::ErrorGuaranteed> {
         desc { |tcx| "match-checking `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { true }
@@ -1275,7 +1278,7 @@ rustc_queries! {
     }
 
     query codegen_select_candidate(
-        key: (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>)
+        key: (ty::ParamEnv<'tcx>, ty::TraitRef<'tcx>)
     ) -> Result<&'tcx ImplSource<'tcx, ()>, CodegenObligationError> {
         cache_on_disk_if { true }
         desc { |tcx| "computing candidate for `{}`", key.1 }
@@ -1382,7 +1385,7 @@ rustc_queries! {
     /// executes in "reveal all" mode, and will normalize the input type.
     query layout_of(
         key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>
-    ) -> Result<ty::layout::TyAndLayout<'tcx>, ty::layout::LayoutError<'tcx>> {
+    ) -> Result<ty::layout::TyAndLayout<'tcx>, &'tcx ty::layout::LayoutError<'tcx>> {
         depth_limit
         desc { "computing layout of `{}`", key.value }
     }
@@ -1393,7 +1396,7 @@ rustc_queries! {
     /// instead, where the instance is an `InstanceDef::Virtual`.
     query fn_abi_of_fn_ptr(
         key: ty::ParamEnvAnd<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>
-    ) -> Result<&'tcx abi::call::FnAbi<'tcx, Ty<'tcx>>, ty::layout::FnAbiError<'tcx>> {
+    ) -> Result<&'tcx abi::call::FnAbi<'tcx, Ty<'tcx>>, &'tcx ty::layout::FnAbiError<'tcx>> {
         desc { "computing call ABI of `{}` function pointers", key.value.0 }
     }
 
@@ -1404,7 +1407,7 @@ rustc_queries! {
     /// to an `InstanceDef::Virtual` instance (of `<dyn Trait as Trait>::fn`).
     query fn_abi_of_instance(
         key: ty::ParamEnvAnd<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>
-    ) -> Result<&'tcx abi::call::FnAbi<'tcx, Ty<'tcx>>, ty::layout::FnAbiError<'tcx>> {
+    ) -> Result<&'tcx abi::call::FnAbi<'tcx, Ty<'tcx>>, &'tcx ty::layout::FnAbiError<'tcx>> {
         desc { "computing call ABI of `{}`", key.value.0 }
     }
 
@@ -1487,8 +1490,9 @@ rustc_queries! {
         desc { "getting traits in scope at a block" }
     }
 
-    query impl_defaultness(def_id: DefId) -> hir::Defaultness {
-        desc { |tcx| "looking up whether `{}` is a default impl", tcx.def_path_str(def_id) }
+    /// Returns whether the impl or associated function has the `default` keyword.
+    query defaultness(def_id: DefId) -> hir::Defaultness {
+        desc { |tcx| "looking up whether `{}` has `default`", tcx.def_path_str(def_id) }
         separate_provide_extern
         feedable
     }
@@ -1915,6 +1919,16 @@ rustc_queries! {
     }
 
     /// Do not call this query directly: invoke `normalize` instead.
+    query normalize_weak_ty(
+        goal: CanonicalProjectionGoal<'tcx>
+    ) -> Result<
+        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, NormalizationResult<'tcx>>>,
+        NoSolution,
+    > {
+        desc { "normalizing `{}`", goal.value.value }
+    }
+
+    /// Do not call this query directly: invoke `normalize` instead.
     query normalize_inherent_projection_ty(
         goal: CanonicalProjectionGoal<'tcx>
     ) -> Result<
@@ -1959,15 +1973,6 @@ rustc_queries! {
         desc { "evaluating trait selection obligation `{}`", goal.value.value }
     }
 
-    query evaluate_goal(
-        goal: CanonicalChalkEnvironmentAndGoal<'tcx>
-    ) -> Result<
-        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ()>>,
-        NoSolution
-    > {
-        desc { "evaluating trait selection obligation `{}`", goal.value }
-    }
-
     /// Do not call this query directly: part of the `Eq` type-op
     query type_op_ascribe_user_type(
         goal: CanonicalTypeOpAscribeUserTypeGoal<'tcx>
@@ -2019,10 +2024,10 @@ rustc_queries! {
     }
 
     /// Do not call this query directly: part of the `Normalize` type-op
-    query type_op_normalize_predicate(
-        goal: CanonicalTypeOpNormalizeGoal<'tcx, ty::Predicate<'tcx>>
+    query type_op_normalize_clause(
+        goal: CanonicalTypeOpNormalizeGoal<'tcx, ty::Clause<'tcx>>
     ) -> Result<
-        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ty::Predicate<'tcx>>>,
+        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ty::Clause<'tcx>>>,
         NoSolution,
     > {
         desc { "normalizing `{:?}`", goal.value.value.value }
@@ -2113,7 +2118,7 @@ rustc_queries! {
         desc { "resolving instance `{}`", ty::Instance::new(key.value.0, key.value.1) }
     }
 
-    query reveal_opaque_types_in_bounds(key: &'tcx ty::List<ty::Predicate<'tcx>>) -> &'tcx ty::List<ty::Predicate<'tcx>> {
+    query reveal_opaque_types_in_bounds(key: &'tcx ty::List<ty::Clause<'tcx>>) -> &'tcx ty::List<ty::Clause<'tcx>> {
         desc { "revealing opaque types in `{:?}`", key }
     }
 
@@ -2152,7 +2157,7 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query check_validity_requirement(key: (ValidityRequirement, ty::ParamEnvAnd<'tcx, Ty<'tcx>>)) -> Result<bool, ty::layout::LayoutError<'tcx>> {
+    query check_validity_requirement(key: (ValidityRequirement, ty::ParamEnvAnd<'tcx, Ty<'tcx>>)) -> Result<bool, &'tcx ty::layout::LayoutError<'tcx>> {
         desc { "checking validity requirement for `{}`: {}", key.1.value, key.0 }
     }
 
@@ -2185,6 +2190,19 @@ rustc_queries! {
     query check_tys_might_be_eq(arg: Canonical<'tcx, (ty::ParamEnv<'tcx>, Ty<'tcx>, Ty<'tcx>)>) -> Result<(), NoSolution> {
         desc { "check whether two const param are definitely not equal to eachother"}
     }
+
+    /// Get all item paths that were stripped by a `#[cfg]` in a particular crate.
+    /// Should not be called for the local crate before the resolver outputs are created, as it
+    /// is only fed there.
+    query stripped_cfg_items(cnum: CrateNum) -> &'tcx [StrippedCfgItem] {
+        feedable
+        desc { "getting cfg-ed out item names" }
+        separate_provide_extern
+    }
+
+    query generics_require_sized_self(def_id: DefId) -> bool {
+        desc { "check whether the item has a `where Self: Sized` bound" }
+    }
 }
 
 rustc_query_append! { define_callbacks! }
diff --git a/compiler/rustc_middle/src/query/on_disk_cache.rs b/compiler/rustc_middle/src/query/on_disk_cache.rs
index 220118ae5..8751d3b78 100644
--- a/compiler/rustc_middle/src/query/on_disk_cache.rs
+++ b/compiler/rustc_middle/src/query/on_disk_cache.rs
@@ -791,13 +791,6 @@ impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>>
     }
 }
 
-impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for &'tcx [(ty::Predicate<'tcx>, Span)] {
-    #[inline]
-    fn decode(d: &mut CacheDecoder<'a, 'tcx>) -> Self {
-        RefDecodable::decode(d)
-    }
-}
-
 impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for &'tcx [(ty::Clause<'tcx>, Span)] {
     #[inline]
     fn decode(d: &mut CacheDecoder<'a, 'tcx>) -> Self {
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 813e109c4..e9af5070e 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -18,7 +18,7 @@ use rustc_index::IndexVec;
 use rustc_middle::middle::region;
 use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Mutability, UnOp};
-use rustc_middle::ty::adjustment::PointerCast;
+use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, AdtDef, FnSig, List, Ty, UpvarSubsts};
 use rustc_middle::ty::{CanonicalUserType, CanonicalUserTypeAnnotation};
@@ -329,9 +329,10 @@ pub enum ExprKind<'tcx> {
     NeverToAny {
         source: ExprId,
     },
-    /// A pointer cast. More information can be found in [`PointerCast`].
-    Pointer {
-        cast: PointerCast,
+    /// A pointer coercion. More information can be found in [`PointerCoercion`].
+    /// Pointer casts that cannot be done by coercions are represented by [`ExprKind::Cast`].
+    PointerCoercion {
+        cast: PointerCoercion,
         source: ExprId,
     },
     /// A `loop` expression.
@@ -410,6 +411,10 @@ pub enum ExprKind<'tcx> {
     Return {
         value: Option<ExprId>,
     },
+    /// A `become` expression.
+    Become {
+        value: ExprId,
+    },
     /// An inline `const` block, e.g. `const {}`.
     ConstBlock {
         did: DefId,
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index 5c7ec31cf..14bc1ac0c 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -65,7 +65,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
         Cast { source } => visitor.visit_expr(&visitor.thir()[source]),
         Use { source } => visitor.visit_expr(&visitor.thir()[source]),
         NeverToAny { source } => visitor.visit_expr(&visitor.thir()[source]),
-        Pointer { source, cast: _ } => visitor.visit_expr(&visitor.thir()[source]),
+        PointerCoercion { source, cast: _ } => visitor.visit_expr(&visitor.thir()[source]),
         Let { expr, .. } => {
             visitor.visit_expr(&visitor.thir()[expr]);
         }
@@ -100,6 +100,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
                 visitor.visit_expr(&visitor.thir()[value])
             }
         }
+        Become { value } => visitor.visit_expr(&visitor.thir()[value]),
         ConstBlock { did: _, substs: _ } => {}
         Repeat { value, count: _ } => {
             visitor.visit_expr(&visitor.thir()[value]);
diff --git a/compiler/rustc_middle/src/traits/chalk.rs b/compiler/rustc_middle/src/traits/chalk.rs
deleted file mode 100644
index fcc8f457a..000000000
--- a/compiler/rustc_middle/src/traits/chalk.rs
+++ /dev/null
@@ -1,396 +0,0 @@
-//! Types required for Chalk-related queries
-//!
-//! The primary purpose of this file is defining an implementation for the
-//! `chalk_ir::interner::Interner` trait. The primary purpose of this trait, as
-//! its name suggest, is to provide an abstraction boundary for creating
-//! interned Chalk types.
-
-use rustc_middle::ty::{self, AdtDef, TyCtxt};
-
-use rustc_hir::def_id::DefId;
-use rustc_target::spec::abi::Abi;
-
-use std::cmp::Ordering;
-use std::fmt;
-use std::hash::{Hash, Hasher};
-
-#[derive(Copy, Clone)]
-pub struct RustInterner<'tcx> {
-    pub tcx: TyCtxt<'tcx>,
-}
-
-/// We don't ever actually need this. It's only required for derives.
-impl<'tcx> Hash for RustInterner<'tcx> {
-    fn hash<H: Hasher>(&self, _state: &mut H) {}
-}
-
-/// We don't ever actually need this. It's only required for derives.
-impl<'tcx> Ord for RustInterner<'tcx> {
-    fn cmp(&self, _other: &Self) -> Ordering {
-        Ordering::Equal
-    }
-}
-
-/// We don't ever actually need this. It's only required for derives.
-impl<'tcx> PartialOrd for RustInterner<'tcx> {
-    fn partial_cmp(&self, _other: &Self) -> Option<Ordering> {
-        None
-    }
-}
-
-/// We don't ever actually need this. It's only required for derives.
-impl<'tcx> PartialEq for RustInterner<'tcx> {
-    fn eq(&self, _other: &Self) -> bool {
-        false
-    }
-}
-
-/// We don't ever actually need this. It's only required for derives.
-impl<'tcx> Eq for RustInterner<'tcx> {}
-
-impl fmt::Debug for RustInterner<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "RustInterner")
-    }
-}
-
-// Right now, there is no interning at all. I was running into problems with
-// adding interning in `ty/context.rs` for Chalk types with
-// `parallel-compiler = true`. -jackh726
-impl<'tcx> chalk_ir::interner::Interner for RustInterner<'tcx> {
-    type InternedType = Box<chalk_ir::TyData<Self>>;
-    type InternedLifetime = Box<chalk_ir::LifetimeData<Self>>;
-    type InternedConst = Box<chalk_ir::ConstData<Self>>;
-    type InternedConcreteConst = ty::ValTree<'tcx>;
-    type InternedGenericArg = Box<chalk_ir::GenericArgData<Self>>;
-    type InternedGoal = Box<chalk_ir::GoalData<Self>>;
-    type InternedGoals = Vec<chalk_ir::Goal<Self>>;
-    type InternedSubstitution = Vec<chalk_ir::GenericArg<Self>>;
-    type InternedProgramClause = Box<chalk_ir::ProgramClauseData<Self>>;
-    type InternedProgramClauses = Vec<chalk_ir::ProgramClause<Self>>;
-    type InternedQuantifiedWhereClauses = Vec<chalk_ir::QuantifiedWhereClause<Self>>;
-    type InternedVariableKinds = Vec<chalk_ir::VariableKind<Self>>;
-    type InternedCanonicalVarKinds = Vec<chalk_ir::CanonicalVarKind<Self>>;
-    type InternedVariances = Vec<chalk_ir::Variance>;
-    type InternedConstraints = Vec<chalk_ir::InEnvironment<chalk_ir::Constraint<Self>>>;
-    type DefId = DefId;
-    type InternedAdtId = AdtDef<'tcx>;
-    type Identifier = ();
-    type FnAbi = Abi;
-
-    fn debug_program_clause_implication(
-        pci: &chalk_ir::ProgramClauseImplication<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        let mut write = || {
-            write!(fmt, "{:?}", pci.consequence)?;
-
-            let conditions = pci.conditions.interned();
-            let constraints = pci.constraints.interned();
-
-            let conds = conditions.len();
-            let consts = constraints.len();
-            if conds == 0 && consts == 0 {
-                return Ok(());
-            }
-
-            write!(fmt, " :- ")?;
-
-            if conds != 0 {
-                for cond in &conditions[..conds - 1] {
-                    write!(fmt, "{:?}, ", cond)?;
-                }
-                write!(fmt, "{:?}", conditions[conds - 1])?;
-            }
-
-            if conds != 0 && consts != 0 {
-                write!(fmt, " ; ")?;
-            }
-
-            if consts != 0 {
-                for constraint in &constraints[..consts - 1] {
-                    write!(fmt, "{:?}, ", constraint)?;
-                }
-                write!(fmt, "{:?}", constraints[consts - 1])?;
-            }
-
-            Ok(())
-        };
-        Some(write())
-    }
-
-    fn debug_substitution(
-        substitution: &chalk_ir::Substitution<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        Some(write!(fmt, "{:?}", substitution.interned()))
-    }
-
-    fn debug_separator_trait_ref(
-        separator_trait_ref: &chalk_ir::SeparatorTraitRef<'_, Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        let substitution = &separator_trait_ref.trait_ref.substitution;
-        let parameters = substitution.interned();
-        Some(write!(
-            fmt,
-            "{:?}{}{:?}{:?}",
-            parameters[0],
-            separator_trait_ref.separator,
-            separator_trait_ref.trait_ref.trait_id,
-            chalk_ir::debug::Angle(&parameters[1..])
-        ))
-    }
-
-    fn debug_quantified_where_clauses(
-        clauses: &chalk_ir::QuantifiedWhereClauses<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        Some(write!(fmt, "{:?}", clauses.interned()))
-    }
-
-    fn debug_ty(ty: &chalk_ir::Ty<Self>, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
-        match &ty.interned().kind {
-            chalk_ir::TyKind::Ref(chalk_ir::Mutability::Not, lifetime, ty) => {
-                Some(write!(fmt, "(&{:?} {:?})", lifetime, ty))
-            }
-            chalk_ir::TyKind::Ref(chalk_ir::Mutability::Mut, lifetime, ty) => {
-                Some(write!(fmt, "(&{:?} mut {:?})", lifetime, ty))
-            }
-            chalk_ir::TyKind::Array(ty, len) => Some(write!(fmt, "[{:?}; {:?}]", ty, len)),
-            chalk_ir::TyKind::Slice(ty) => Some(write!(fmt, "[{:?}]", ty)),
-            chalk_ir::TyKind::Tuple(len, substs) => Some(
-                try {
-                    write!(fmt, "(")?;
-                    for (idx, substitution) in substs.interned().iter().enumerate() {
-                        if idx == *len && *len != 1 {
-                            // Don't add a trailing comma if the tuple has more than one element
-                            write!(fmt, "{:?}", substitution)?;
-                        } else {
-                            write!(fmt, "{:?},", substitution)?;
-                        }
-                    }
-                    write!(fmt, ")")?;
-                },
-            ),
-            _ => None,
-        }
-    }
-
-    fn debug_alias(
-        alias_ty: &chalk_ir::AliasTy<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        match alias_ty {
-            chalk_ir::AliasTy::Projection(projection_ty) => {
-                Self::debug_projection_ty(projection_ty, fmt)
-            }
-            chalk_ir::AliasTy::Opaque(opaque_ty) => Self::debug_opaque_ty(opaque_ty, fmt),
-        }
-    }
-
-    fn debug_projection_ty(
-        projection_ty: &chalk_ir::ProjectionTy<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        Some(write!(
-            fmt,
-            "projection: {:?} {:?}",
-            projection_ty.associated_ty_id, projection_ty.substitution,
-        ))
-    }
-
-    fn debug_opaque_ty(
-        opaque_ty: &chalk_ir::OpaqueTy<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        Some(write!(fmt, "{:?}", opaque_ty.opaque_ty_id))
-    }
-
-    fn intern_ty(self, ty: chalk_ir::TyKind<Self>) -> Self::InternedType {
-        let flags = ty.compute_flags(self);
-        Box::new(chalk_ir::TyData { kind: ty, flags: flags })
-    }
-
-    fn ty_data(self, ty: &Self::InternedType) -> &chalk_ir::TyData<Self> {
-        ty
-    }
-
-    fn intern_lifetime(self, lifetime: chalk_ir::LifetimeData<Self>) -> Self::InternedLifetime {
-        Box::new(lifetime)
-    }
-
-    fn lifetime_data(self, lifetime: &Self::InternedLifetime) -> &chalk_ir::LifetimeData<Self> {
-        &lifetime
-    }
-
-    fn intern_const(self, constant: chalk_ir::ConstData<Self>) -> Self::InternedConst {
-        Box::new(constant)
-    }
-
-    fn const_data(self, constant: &Self::InternedConst) -> &chalk_ir::ConstData<Self> {
-        &constant
-    }
-
-    fn const_eq(
-        self,
-        _ty: &Self::InternedType,
-        c1: &Self::InternedConcreteConst,
-        c2: &Self::InternedConcreteConst,
-    ) -> bool {
-        c1 == c2
-    }
-
-    fn intern_generic_arg(self, data: chalk_ir::GenericArgData<Self>) -> Self::InternedGenericArg {
-        Box::new(data)
-    }
-
-    fn generic_arg_data(self, data: &Self::InternedGenericArg) -> &chalk_ir::GenericArgData<Self> {
-        &data
-    }
-
-    fn intern_goal(self, goal: chalk_ir::GoalData<Self>) -> Self::InternedGoal {
-        Box::new(goal)
-    }
-
-    fn goal_data(self, goal: &Self::InternedGoal) -> &chalk_ir::GoalData<Self> {
-        &goal
-    }
-
-    fn intern_goals<E>(
-        self,
-        data: impl IntoIterator<Item = Result<chalk_ir::Goal<Self>, E>>,
-    ) -> Result<Self::InternedGoals, E> {
-        data.into_iter().collect::<Result<Vec<_>, _>>()
-    }
-
-    fn goals_data(self, goals: &Self::InternedGoals) -> &[chalk_ir::Goal<Self>] {
-        goals
-    }
-
-    fn intern_substitution<E>(
-        self,
-        data: impl IntoIterator<Item = Result<chalk_ir::GenericArg<Self>, E>>,
-    ) -> Result<Self::InternedSubstitution, E> {
-        data.into_iter().collect::<Result<Vec<_>, _>>()
-    }
-
-    fn substitution_data(
-        self,
-        substitution: &Self::InternedSubstitution,
-    ) -> &[chalk_ir::GenericArg<Self>] {
-        substitution
-    }
-
-    fn intern_program_clause(
-        self,
-        data: chalk_ir::ProgramClauseData<Self>,
-    ) -> Self::InternedProgramClause {
-        Box::new(data)
-    }
-
-    fn program_clause_data(
-        self,
-        clause: &Self::InternedProgramClause,
-    ) -> &chalk_ir::ProgramClauseData<Self> {
-        &clause
-    }
-
-    fn intern_program_clauses<E>(
-        self,
-        data: impl IntoIterator<Item = Result<chalk_ir::ProgramClause<Self>, E>>,
-    ) -> Result<Self::InternedProgramClauses, E> {
-        data.into_iter().collect::<Result<Vec<_>, _>>()
-    }
-
-    fn program_clauses_data(
-        self,
-        clauses: &Self::InternedProgramClauses,
-    ) -> &[chalk_ir::ProgramClause<Self>] {
-        clauses
-    }
-
-    fn intern_quantified_where_clauses<E>(
-        self,
-        data: impl IntoIterator<Item = Result<chalk_ir::QuantifiedWhereClause<Self>, E>>,
-    ) -> Result<Self::InternedQuantifiedWhereClauses, E> {
-        data.into_iter().collect::<Result<Vec<_>, _>>()
-    }
-
-    fn quantified_where_clauses_data(
-        self,
-        clauses: &Self::InternedQuantifiedWhereClauses,
-    ) -> &[chalk_ir::QuantifiedWhereClause<Self>] {
-        clauses
-    }
-
-    fn intern_generic_arg_kinds<E>(
-        self,
-        data: impl IntoIterator<Item = Result<chalk_ir::VariableKind<Self>, E>>,
-    ) -> Result<Self::InternedVariableKinds, E> {
-        data.into_iter().collect::<Result<Vec<_>, _>>()
-    }
-
-    fn variable_kinds_data(
-        self,
-        parameter_kinds: &Self::InternedVariableKinds,
-    ) -> &[chalk_ir::VariableKind<Self>] {
-        parameter_kinds
-    }
-
-    fn intern_canonical_var_kinds<E>(
-        self,
-        data: impl IntoIterator<Item = Result<chalk_ir::CanonicalVarKind<Self>, E>>,
-    ) -> Result<Self::InternedCanonicalVarKinds, E> {
-        data.into_iter().collect::<Result<Vec<_>, _>>()
-    }
-
-    fn canonical_var_kinds_data(
-        self,
-        canonical_var_kinds: &Self::InternedCanonicalVarKinds,
-    ) -> &[chalk_ir::CanonicalVarKind<Self>] {
-        canonical_var_kinds
-    }
-
-    fn intern_constraints<E>(
-        self,
-        data: impl IntoIterator<Item = Result<chalk_ir::InEnvironment<chalk_ir::Constraint<Self>>, E>>,
-    ) -> Result<Self::InternedConstraints, E> {
-        data.into_iter().collect::<Result<Vec<_>, _>>()
-    }
-
-    fn constraints_data(
-        self,
-        constraints: &Self::InternedConstraints,
-    ) -> &[chalk_ir::InEnvironment<chalk_ir::Constraint<Self>>] {
-        constraints
-    }
-
-    fn intern_variances<E>(
-        self,
-        data: impl IntoIterator<Item = Result<chalk_ir::Variance, E>>,
-    ) -> Result<Self::InternedVariances, E> {
-        data.into_iter().collect::<Result<Vec<_>, _>>()
-    }
-
-    fn variances_data(self, variances: &Self::InternedVariances) -> &[chalk_ir::Variance] {
-        variances
-    }
-}
-
-impl<'tcx> chalk_ir::interner::HasInterner for RustInterner<'tcx> {
-    type Interner = Self;
-}
-
-/// A chalk environment and goal.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable, TypeVisitable)]
-pub struct ChalkEnvironmentAndGoal<'tcx> {
-    pub environment: &'tcx ty::List<ty::Predicate<'tcx>>,
-    pub goal: ty::Predicate<'tcx>,
-}
-
-impl<'tcx> fmt::Display for ChalkEnvironmentAndGoal<'tcx> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "environment: {:?}, goal: {}", self.environment, self.goal)
-    }
-}
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 0a903a769..c7d2e4c22 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -2,7 +2,6 @@
 //!
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/resolution.html
 
-mod chalk;
 pub mod query;
 pub mod select;
 pub mod solve;
@@ -30,12 +29,8 @@ use std::hash::{Hash, Hasher};
 
 pub use self::select::{EvaluationCache, EvaluationResult, OverflowError, SelectionCache};
 
-pub type CanonicalChalkEnvironmentAndGoal<'tcx> = Canonical<'tcx, ChalkEnvironmentAndGoal<'tcx>>;
-
 pub use self::ObligationCauseCode::*;
 
-pub use self::chalk::{ChalkEnvironmentAndGoal, RustInterner as ChalkRustInterner};
-
 /// Depending on the stage of compilation, we want projection to be
 /// more or less conservative.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable, Encodable, Decodable)]
@@ -445,6 +440,12 @@ pub enum ObligationCauseCode<'tcx> {
     /// Obligations to prove that a `std::ops::Drop` impl is not stronger than
     /// the ADT it's being implemented for.
     DropImpl,
+
+    /// Requirement for a `const N: Ty` to implement `Ty: ConstParamTy`
+    ConstParam(Ty<'tcx>),
+
+    /// Obligations emitted during the normalization of a weak type alias.
+    TypeAlias(InternedObligationCauseCode<'tcx>, Span, DefId),
 }
 
 /// The 'location' at which we try to perform HIR-based wf checking.
@@ -587,6 +588,10 @@ pub enum SelectionError<'tcx> {
     /// Signaling that an error has already been emitted, to avoid
     /// multiple errors being shown.
     ErrorReporting,
+    /// Computing an opaque type's hidden type caused an error (e.g. a cycle error).
+    /// We can thus not know whether the hidden type implements an auto trait, so
+    /// we should not presume anything about it.
+    OpaqueTypeAutoTraitLeakageUnknown(DefId),
 }
 
 #[derive(Clone, Debug, TypeVisitable, Lift)]
@@ -640,12 +645,6 @@ pub enum ImplSource<'tcx, N> {
     /// ImplSource identifying a particular impl.
     UserDefined(ImplSourceUserDefinedData<'tcx, N>),
 
-    /// ImplSource for auto trait implementations.
-    /// This carries the information and nested obligations with regards
-    /// to an auto implementation for a trait `Trait`. The nested obligations
-    /// ensure the trait implementation holds for all the constituent types.
-    AutoImpl(ImplSourceAutoImplData<N>),
-
     /// Successful resolution to an obligation provided by the caller
     /// for some type parameter. The `Vec<N>` represents the
     /// obligations incurred from normalizing the where-clause (if
@@ -653,84 +652,40 @@ pub enum ImplSource<'tcx, N> {
     Param(Vec<N>, ty::BoundConstness),
 
     /// Virtual calls through an object.
-    Object(ImplSourceObjectData<'tcx, N>),
+    Object(ImplSourceObjectData<N>),
 
     /// Successful resolution for a builtin trait.
-    Builtin(ImplSourceBuiltinData<N>),
+    Builtin(Vec<N>),
 
     /// ImplSource for trait upcasting coercion
-    TraitUpcasting(ImplSourceTraitUpcastingData<'tcx, N>),
-
-    /// ImplSource automatically generated for a closure. The `DefId` is the ID
-    /// of the closure expression. This is an `ImplSource::UserDefined` in spirit, but the
-    /// impl is generated by the compiler and does not appear in the source.
-    Closure(ImplSourceClosureData<'tcx, N>),
-
-    /// Same as above, but for a function pointer type with the given signature.
-    FnPointer(ImplSourceFnPointerData<'tcx, N>),
-
-    /// ImplSource automatically generated for a generator.
-    Generator(ImplSourceGeneratorData<'tcx, N>),
-
-    /// ImplSource automatically generated for a generator backing an async future.
-    Future(ImplSourceFutureData<'tcx, N>),
-
-    /// ImplSource for a trait alias.
-    TraitAlias(ImplSourceTraitAliasData<'tcx, N>),
-
-    /// ImplSource for a `const Drop` implementation.
-    ConstDestruct(ImplSourceConstDestructData<N>),
+    TraitUpcasting(ImplSourceTraitUpcastingData<N>),
 }
 
 impl<'tcx, N> ImplSource<'tcx, N> {
     pub fn nested_obligations(self) -> Vec<N> {
         match self {
             ImplSource::UserDefined(i) => i.nested,
-            ImplSource::Param(n, _) => n,
-            ImplSource::Builtin(i) => i.nested,
-            ImplSource::AutoImpl(d) => d.nested,
-            ImplSource::Closure(c) => c.nested,
-            ImplSource::Generator(c) => c.nested,
-            ImplSource::Future(c) => c.nested,
+            ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
             ImplSource::Object(d) => d.nested,
-            ImplSource::FnPointer(d) => d.nested,
-            ImplSource::TraitAlias(d) => d.nested,
             ImplSource::TraitUpcasting(d) => d.nested,
-            ImplSource::ConstDestruct(i) => i.nested,
         }
     }
 
     pub fn borrow_nested_obligations(&self) -> &[N] {
         match self {
             ImplSource::UserDefined(i) => &i.nested,
-            ImplSource::Param(n, _) => n,
-            ImplSource::Builtin(i) => &i.nested,
-            ImplSource::AutoImpl(d) => &d.nested,
-            ImplSource::Closure(c) => &c.nested,
-            ImplSource::Generator(c) => &c.nested,
-            ImplSource::Future(c) => &c.nested,
+            ImplSource::Param(n, _) | ImplSource::Builtin(n) => &n,
             ImplSource::Object(d) => &d.nested,
-            ImplSource::FnPointer(d) => &d.nested,
-            ImplSource::TraitAlias(d) => &d.nested,
             ImplSource::TraitUpcasting(d) => &d.nested,
-            ImplSource::ConstDestruct(i) => &i.nested,
         }
     }
 
     pub fn borrow_nested_obligations_mut(&mut self) -> &mut [N] {
         match self {
             ImplSource::UserDefined(i) => &mut i.nested,
-            ImplSource::Param(n, _) => n,
-            ImplSource::Builtin(i) => &mut i.nested,
-            ImplSource::AutoImpl(d) => &mut d.nested,
-            ImplSource::Closure(c) => &mut c.nested,
-            ImplSource::Generator(c) => &mut c.nested,
-            ImplSource::Future(c) => &mut c.nested,
+            ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
             ImplSource::Object(d) => &mut d.nested,
-            ImplSource::FnPointer(d) => &mut d.nested,
-            ImplSource::TraitAlias(d) => &mut d.nested,
             ImplSource::TraitUpcasting(d) => &mut d.nested,
-            ImplSource::ConstDestruct(i) => &mut i.nested,
         }
     }
 
@@ -745,54 +700,17 @@ impl<'tcx, N> ImplSource<'tcx, N> {
                 nested: i.nested.into_iter().map(f).collect(),
             }),
             ImplSource::Param(n, ct) => ImplSource::Param(n.into_iter().map(f).collect(), ct),
-            ImplSource::Builtin(i) => ImplSource::Builtin(ImplSourceBuiltinData {
-                nested: i.nested.into_iter().map(f).collect(),
-            }),
+            ImplSource::Builtin(n) => ImplSource::Builtin(n.into_iter().map(f).collect()),
             ImplSource::Object(o) => ImplSource::Object(ImplSourceObjectData {
-                upcast_trait_ref: o.upcast_trait_ref,
                 vtable_base: o.vtable_base,
                 nested: o.nested.into_iter().map(f).collect(),
             }),
-            ImplSource::AutoImpl(d) => ImplSource::AutoImpl(ImplSourceAutoImplData {
-                trait_def_id: d.trait_def_id,
-                nested: d.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::Closure(c) => ImplSource::Closure(ImplSourceClosureData {
-                closure_def_id: c.closure_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::Generator(c) => ImplSource::Generator(ImplSourceGeneratorData {
-                generator_def_id: c.generator_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::Future(c) => ImplSource::Future(ImplSourceFutureData {
-                generator_def_id: c.generator_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::FnPointer(p) => ImplSource::FnPointer(ImplSourceFnPointerData {
-                fn_ty: p.fn_ty,
-                nested: p.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::TraitAlias(d) => ImplSource::TraitAlias(ImplSourceTraitAliasData {
-                alias_def_id: d.alias_def_id,
-                substs: d.substs,
-                nested: d.nested.into_iter().map(f).collect(),
-            }),
             ImplSource::TraitUpcasting(d) => {
                 ImplSource::TraitUpcasting(ImplSourceTraitUpcastingData {
-                    upcast_trait_ref: d.upcast_trait_ref,
                     vtable_vptr_slot: d.vtable_vptr_slot,
                     nested: d.nested.into_iter().map(f).collect(),
                 })
             }
-            ImplSource::ConstDestruct(i) => {
-                ImplSource::ConstDestruct(ImplSourceConstDestructData {
-                    nested: i.nested.into_iter().map(f).collect(),
-                })
-            }
         }
     }
 }
@@ -817,47 +735,7 @@ pub struct ImplSourceUserDefinedData<'tcx, N> {
 
 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceGeneratorData<'tcx, N> {
-    pub generator_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the generator
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceFutureData<'tcx, N> {
-    pub generator_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the generator
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceClosureData<'tcx, N> {
-    pub closure_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the closure
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceAutoImplData<N> {
-    pub trait_def_id: DefId,
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceTraitUpcastingData<'tcx, N> {
-    /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
-    pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
-
+pub struct ImplSourceTraitUpcastingData<N> {
     /// The vtable is formed by concatenating together the method lists of
     /// the base object trait and all supertraits, pointers to supertrait vtable will
     /// be provided when necessary; this is the position of `upcast_trait_ref`'s vtable
@@ -867,18 +745,9 @@ pub struct ImplSourceTraitUpcastingData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceBuiltinData<N> {
-    pub nested: Vec<N>,
-}
-
 #[derive(PartialEq, Eq, Clone, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceObjectData<'tcx, N> {
-    /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
-    pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
-
+pub struct ImplSourceObjectData<N> {
     /// The vtable is formed by concatenating together the method lists of
     /// the base object trait and all supertraits, pointers to supertrait vtable will
     /// be provided when necessary; this is the start of `upcast_trait_ref`'s methods
@@ -888,27 +757,6 @@ pub struct ImplSourceObjectData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceFnPointerData<'tcx, N> {
-    pub fn_ty: Ty<'tcx>,
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceConstDestructData<N> {
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceTraitAliasData<'tcx, N> {
-    pub alias_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    pub nested: Vec<N>,
-}
-
 #[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable, PartialOrd, Ord)]
 pub enum ObjectSafetyViolation {
     /// `Self: Sized` declared on the trait.
@@ -1109,7 +957,7 @@ pub enum CodegenObligationError {
     FulfillmentError,
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub enum DefiningAnchor {
     /// `DefId` of the item.
     Bind(LocalDefId),
diff --git a/compiler/rustc_middle/src/traits/query.rs b/compiler/rustc_middle/src/traits/query.rs
index eae5a280e..60a38747f 100644
--- a/compiler/rustc_middle/src/traits/query.rs
+++ b/compiler/rustc_middle/src/traits/query.rs
@@ -92,7 +92,7 @@ pub type CanonicalTypeOpProvePredicateGoal<'tcx> =
 pub type CanonicalTypeOpNormalizeGoal<'tcx, T> =
     Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::Normalize<T>>>;
 
-#[derive(Copy, Clone, Debug, HashStable, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, Hash, HashStable, PartialEq, Eq)]
 pub struct NoSolution;
 
 impl<'tcx> From<TypeError<'tcx>> for NoSolution {
diff --git a/compiler/rustc_middle/src/traits/solve.rs b/compiler/rustc_middle/src/traits/solve.rs
index 2c5b64a59..73b332fd8 100644
--- a/compiler/rustc_middle/src/traits/solve.rs
+++ b/compiler/rustc_middle/src/traits/solve.rs
@@ -11,6 +11,8 @@ use crate::ty::{
     TypeVisitor,
 };
 
+pub mod inspect;
+
 pub type EvaluationCache<'tcx> = Cache<CanonicalInput<'tcx>, QueryResult<'tcx>>;
 
 /// A goal is a statement, i.e. `predicate`, we want to prove
@@ -18,7 +20,7 @@ pub type EvaluationCache<'tcx> = Cache<CanonicalInput<'tcx>, QueryResult<'tcx>>;
 ///
 /// Most of the time the `param_env` contains the `where`-bounds of the function
 /// we're currently typechecking while the `predicate` is some trait bound.
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Goal<'tcx, P> {
     pub predicate: P,
     pub param_env: ty::ParamEnv<'tcx>,
@@ -39,7 +41,7 @@ impl<'tcx, P> Goal<'tcx, P> {
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Response<'tcx> {
     pub certainty: Certainty,
     pub var_values: CanonicalVarValues<'tcx>,
@@ -47,7 +49,7 @@ pub struct Response<'tcx> {
     pub external_constraints: ExternalConstraints<'tcx>,
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub enum Certainty {
     Yes,
     Maybe(MaybeCause),
@@ -86,7 +88,7 @@ impl Certainty {
 }
 
 /// Why we failed to evaluate a goal.
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub enum MaybeCause {
     /// We failed due to ambiguity. This ambiguity can either
     /// be a true ambiguity, i.e. there are multiple different answers,
@@ -96,7 +98,7 @@ pub enum MaybeCause {
     Overflow,
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct QueryInput<'tcx, T> {
     pub goal: Goal<'tcx, T>,
     pub anchor: DefiningAnchor,
@@ -104,12 +106,12 @@ pub struct QueryInput<'tcx, T> {
 }
 
 /// Additional constraints returned on success.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, Default)]
+#[derive(Debug, PartialEq, Eq, Clone, Hash, HashStable, Default)]
 pub struct PredefinedOpaquesData<'tcx> {
     pub opaque_types: Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>,
 }
 
-#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
+#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash, HashStable)]
 pub struct PredefinedOpaques<'tcx>(pub(crate) Interned<'tcx, PredefinedOpaquesData<'tcx>>);
 
 impl<'tcx> std::ops::Deref for PredefinedOpaques<'tcx> {
@@ -132,7 +134,7 @@ pub type CanonicalResponse<'tcx> = Canonical<'tcx, Response<'tcx>>;
 /// solver, merge the two responses again.
 pub type QueryResult<'tcx> = Result<CanonicalResponse<'tcx>, NoSolution>;
 
-#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
+#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash, HashStable)]
 pub struct ExternalConstraints<'tcx>(pub(crate) Interned<'tcx, ExternalConstraintsData<'tcx>>);
 
 impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
@@ -144,7 +146,7 @@ impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
 }
 
 /// Additional constraints returned on success.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, Default)]
+#[derive(Debug, PartialEq, Eq, Clone, Hash, HashStable, Default)]
 pub struct ExternalConstraintsData<'tcx> {
     // FIXME: implement this.
     pub region_constraints: QueryRegionConstraints<'tcx>,
@@ -226,3 +228,9 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for PredefinedOpaques<'tcx> {
         self.opaque_types.visit_with(visitor)
     }
 }
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable)]
+pub enum IsNormalizesToHack {
+    Yes,
+    No,
+}
diff --git a/compiler/rustc_middle/src/traits/solve/inspect.rs b/compiler/rustc_middle/src/traits/solve/inspect.rs
new file mode 100644
index 000000000..527afa005
--- /dev/null
+++ b/compiler/rustc_middle/src/traits/solve/inspect.rs
@@ -0,0 +1,83 @@
+use super::{
+    CanonicalInput, Certainty, Goal, IsNormalizesToHack, NoSolution, QueryInput, QueryResult,
+};
+use crate::ty;
+use format::ProofTreeFormatter;
+use std::fmt::{Debug, Write};
+
+mod format;
+
+#[derive(Eq, PartialEq, Debug, Hash, HashStable)]
+pub enum CacheHit {
+    Provisional,
+    Global,
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub struct GoalEvaluation<'tcx> {
+    pub uncanonicalized_goal: Goal<'tcx, ty::Predicate<'tcx>>,
+    pub canonicalized_goal: CanonicalInput<'tcx>,
+
+    pub kind: GoalEvaluationKind<'tcx>,
+    pub is_normalizes_to_hack: IsNormalizesToHack,
+    pub returned_goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
+
+    pub result: QueryResult<'tcx>,
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub enum GoalEvaluationKind<'tcx> {
+    CacheHit(CacheHit),
+    Uncached { revisions: Vec<GoalEvaluationStep<'tcx>> },
+}
+impl Debug for GoalEvaluation<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ProofTreeFormatter { f, on_newline: true }.format_goal_evaluation(self)
+    }
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub struct AddedGoalsEvaluation<'tcx> {
+    pub evaluations: Vec<Vec<GoalEvaluation<'tcx>>>,
+    pub result: Result<Certainty, NoSolution>,
+}
+impl Debug for AddedGoalsEvaluation<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ProofTreeFormatter { f, on_newline: true }.format_nested_goal_evaluation(self)
+    }
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub struct GoalEvaluationStep<'tcx> {
+    pub instantiated_goal: QueryInput<'tcx, ty::Predicate<'tcx>>,
+
+    pub nested_goal_evaluations: Vec<AddedGoalsEvaluation<'tcx>>,
+    pub candidates: Vec<GoalCandidate<'tcx>>,
+
+    pub result: QueryResult<'tcx>,
+}
+impl Debug for GoalEvaluationStep<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ProofTreeFormatter { f, on_newline: true }.format_evaluation_step(self)
+    }
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub struct GoalCandidate<'tcx> {
+    pub nested_goal_evaluations: Vec<AddedGoalsEvaluation<'tcx>>,
+    pub candidates: Vec<GoalCandidate<'tcx>>,
+    pub kind: CandidateKind<'tcx>,
+}
+
+#[derive(Eq, PartialEq, Debug, Hash, HashStable)]
+pub enum CandidateKind<'tcx> {
+    /// Probe entered when normalizing the self ty during candidate assembly
+    NormalizedSelfTyAssembly,
+    /// A normal candidate for proving a goal
+    Candidate { name: String, result: QueryResult<'tcx> },
+}
+impl Debug for GoalCandidate<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ProofTreeFormatter { f, on_newline: true }.format_candidate(self)
+    }
+}
diff --git a/compiler/rustc_middle/src/traits/solve/inspect/format.rs b/compiler/rustc_middle/src/traits/solve/inspect/format.rs
new file mode 100644
index 000000000..2ee625674
--- /dev/null
+++ b/compiler/rustc_middle/src/traits/solve/inspect/format.rs
@@ -0,0 +1,131 @@
+use super::*;
+
+pub(super) struct ProofTreeFormatter<'a, 'b> {
+    pub(super) f: &'a mut (dyn Write + 'b),
+    pub(super) on_newline: bool,
+}
+
+impl Write for ProofTreeFormatter<'_, '_> {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        for line in s.split_inclusive("\n") {
+            if self.on_newline {
+                self.f.write_str("    ")?;
+            }
+            self.on_newline = line.ends_with("\n");
+            self.f.write_str(line)?;
+        }
+
+        Ok(())
+    }
+}
+
+impl ProofTreeFormatter<'_, '_> {
+    fn nested(&mut self) -> ProofTreeFormatter<'_, '_> {
+        ProofTreeFormatter { f: self, on_newline: true }
+    }
+
+    pub(super) fn format_goal_evaluation(&mut self, goal: &GoalEvaluation<'_>) -> std::fmt::Result {
+        let f = &mut *self.f;
+
+        let goal_text = match goal.is_normalizes_to_hack {
+            IsNormalizesToHack::Yes => "NORMALIZES-TO HACK GOAL",
+            IsNormalizesToHack::No => "GOAL",
+        };
+
+        writeln!(f, "{}: {:?}", goal_text, goal.uncanonicalized_goal,)?;
+        writeln!(f, "CANONICALIZED: {:?}", goal.canonicalized_goal)?;
+
+        match &goal.kind {
+            GoalEvaluationKind::CacheHit(CacheHit::Global) => {
+                writeln!(f, "GLOBAL CACHE HIT: {:?}", goal.result)
+            }
+            GoalEvaluationKind::CacheHit(CacheHit::Provisional) => {
+                writeln!(f, "PROVISIONAL CACHE HIT: {:?}", goal.result)
+            }
+            GoalEvaluationKind::Uncached { revisions } => {
+                for (n, step) in revisions.iter().enumerate() {
+                    let f = &mut *self.f;
+                    writeln!(f, "REVISION {n}: {:?}", step.result)?;
+                    let mut f = self.nested();
+                    f.format_evaluation_step(step)?;
+                }
+
+                let f = &mut *self.f;
+                writeln!(f, "RESULT: {:?}", goal.result)
+            }
+        }?;
+
+        if goal.returned_goals.len() > 0 {
+            let f = &mut *self.f;
+            writeln!(f, "NESTED GOALS ADDED TO CALLER: [")?;
+            let mut f = self.nested();
+            for goal in goal.returned_goals.iter() {
+                writeln!(f, "ADDED GOAL: {:?},", goal)?;
+            }
+            writeln!(self.f, "]")?;
+        }
+
+        Ok(())
+    }
+
+    pub(super) fn format_evaluation_step(
+        &mut self,
+        evaluation_step: &GoalEvaluationStep<'_>,
+    ) -> std::fmt::Result {
+        let f = &mut *self.f;
+        writeln!(f, "INSTANTIATED: {:?}", evaluation_step.instantiated_goal)?;
+
+        for candidate in &evaluation_step.candidates {
+            let mut f = self.nested();
+            f.format_candidate(candidate)?;
+        }
+        for nested_goal_evaluation in &evaluation_step.nested_goal_evaluations {
+            let mut f = self.nested();
+            f.format_nested_goal_evaluation(nested_goal_evaluation)?;
+        }
+
+        Ok(())
+    }
+
+    pub(super) fn format_candidate(&mut self, candidate: &GoalCandidate<'_>) -> std::fmt::Result {
+        let f = &mut *self.f;
+
+        match &candidate.kind {
+            CandidateKind::NormalizedSelfTyAssembly => {
+                writeln!(f, "NORMALIZING SELF TY FOR ASSEMBLY:")
+            }
+            CandidateKind::Candidate { name, result } => {
+                writeln!(f, "CANDIDATE {}: {:?}", name, result)
+            }
+        }?;
+
+        let mut f = self.nested();
+        for candidate in &candidate.candidates {
+            f.format_candidate(candidate)?;
+        }
+        for nested_evaluations in &candidate.nested_goal_evaluations {
+            f.format_nested_goal_evaluation(nested_evaluations)?;
+        }
+
+        Ok(())
+    }
+
+    pub(super) fn format_nested_goal_evaluation(
+        &mut self,
+        nested_goal_evaluation: &AddedGoalsEvaluation<'_>,
+    ) -> std::fmt::Result {
+        let f = &mut *self.f;
+        writeln!(f, "TRY_EVALUATE_ADDED_GOALS: {:?}", nested_goal_evaluation.result)?;
+
+        for (n, revision) in nested_goal_evaluation.evaluations.iter().enumerate() {
+            let f = &mut *self.f;
+            writeln!(f, "REVISION {n}")?;
+            let mut f = self.nested();
+            for goal_evaluation in revision {
+                f.format_goal_evaluation(goal_evaluation)?;
+            }
+        }
+
+        Ok(())
+    }
+}
diff --git a/compiler/rustc_middle/src/traits/specialization_graph.rs b/compiler/rustc_middle/src/traits/specialization_graph.rs
index c016f7227..dc2cd2035 100644
--- a/compiler/rustc_middle/src/traits/specialization_graph.rs
+++ b/compiler/rustc_middle/src/traits/specialization_graph.rs
@@ -228,7 +228,7 @@ impl<'tcx> Ancestors<'tcx> {
             if let Some(item) = node.item(tcx, trait_item_def_id) {
                 if finalizing_node.is_none() {
                     let is_specializable = item.defaultness(tcx).is_default()
-                        || tcx.impl_defaultness(node.def_id()).is_default();
+                        || tcx.defaultness(node.def_id()).is_default();
 
                     if !is_specializable {
                         finalizing_node = Some(node);
diff --git a/compiler/rustc_middle/src/traits/structural_impls.rs b/compiler/rustc_middle/src/traits/structural_impls.rs
index 6acb7745d..a703e3c95 100644
--- a/compiler/rustc_middle/src/traits/structural_impls.rs
+++ b/compiler/rustc_middle/src/traits/structural_impls.rs
@@ -9,15 +9,7 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSource<'tcx, N> {
         match *self {
             super::ImplSource::UserDefined(ref v) => write!(f, "{:?}", v),
 
-            super::ImplSource::AutoImpl(ref t) => write!(f, "{:?}", t),
-
-            super::ImplSource::Closure(ref d) => write!(f, "{:?}", d),
-
-            super::ImplSource::Generator(ref d) => write!(f, "{:?}", d),
-
-            super::ImplSource::Future(ref d) => write!(f, "{:?}", d),
-
-            super::ImplSource::FnPointer(ref d) => write!(f, "({:?})", d),
+            super::ImplSource::Builtin(ref d) => write!(f, "{:?}", d),
 
             super::ImplSource::Object(ref d) => write!(f, "{:?}", d),
 
@@ -25,13 +17,7 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSource<'tcx, N> {
                 write!(f, "ImplSourceParamData({:?}, {:?})", n, ct)
             }
 
-            super::ImplSource::Builtin(ref d) => write!(f, "{:?}", d),
-
-            super::ImplSource::TraitAlias(ref d) => write!(f, "{:?}", d),
-
             super::ImplSource::TraitUpcasting(ref d) => write!(f, "{:?}", d),
-
-            super::ImplSource::ConstDestruct(ref d) => write!(f, "{:?}", d),
         }
     }
 }
@@ -46,90 +32,22 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceUserDefinedData<'tcx,
     }
 }
 
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceGeneratorData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceGeneratorData(generator_def_id={:?}, substs={:?}, nested={:?})",
-            self.generator_def_id, self.substs, self.nested
-        )
-    }
-}
-
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceFutureData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceFutureData(generator_def_id={:?}, substs={:?}, nested={:?})",
-            self.generator_def_id, self.substs, self.nested
-        )
-    }
-}
-
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceClosureData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceClosureData(closure_def_id={:?}, substs={:?}, nested={:?})",
-            self.closure_def_id, self.substs, self.nested
-        )
-    }
-}
-
-impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceBuiltinData<N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "ImplSourceBuiltinData(nested={:?})", self.nested)
-    }
-}
-
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceTraitUpcastingData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceTraitUpcastingData(upcast={:?}, vtable_vptr_slot={:?}, nested={:?})",
-            self.upcast_trait_ref, self.vtable_vptr_slot, self.nested
-        )
-    }
-}
-
-impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceAutoImplData<N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceAutoImplData(trait_def_id={:?}, nested={:?})",
-            self.trait_def_id, self.nested
-        )
-    }
-}
-
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceObjectData<'tcx, N> {
+impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceTraitUpcastingData<N> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            "ImplSourceObjectData(upcast={:?}, vtable_base={}, nested={:?})",
-            self.upcast_trait_ref, self.vtable_base, self.nested
+            "ImplSourceTraitUpcastingData(vtable_vptr_slot={:?}, nested={:?})",
+            self.vtable_vptr_slot, self.nested
         )
     }
 }
 
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceFnPointerData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "ImplSourceFnPointerData(fn_ty={:?}, nested={:?})", self.fn_ty, self.nested)
-    }
-}
-
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceTraitAliasData<'tcx, N> {
+impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceObjectData<N> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            "ImplSourceTraitAliasData(alias_def_id={:?}, substs={:?}, nested={:?})",
-            self.alias_def_id, self.substs, self.nested
+            "ImplSourceObjectData(vtable_base={}, nested={:?})",
+            self.vtable_base, self.nested
         )
     }
 }
-
-impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceConstDestructData<N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "ImplSourceConstDestructData(nested={:?})", self.nested)
-    }
-}
diff --git a/compiler/rustc_middle/src/traits/util.rs b/compiler/rustc_middle/src/traits/util.rs
index d54b8c599..05c06efaf 100644
--- a/compiler/rustc_middle/src/traits/util.rs
+++ b/compiler/rustc_middle/src/traits/util.rs
@@ -25,9 +25,7 @@ impl<'tcx> Elaborator<'tcx> {
             .super_predicates_of(trait_ref.def_id())
             .predicates
             .into_iter()
-            .flat_map(|(pred, _)| {
-                pred.subst_supertrait(self.tcx, &trait_ref).to_opt_poly_trait_pred()
-            })
+            .flat_map(|(pred, _)| pred.subst_supertrait(self.tcx, &trait_ref).as_trait_clause())
             .map(|t| t.map_bound(|pred| pred.trait_ref))
             .filter(|supertrait_ref| self.visited.insert(*supertrait_ref));
 
diff --git a/compiler/rustc_middle/src/ty/_match.rs b/compiler/rustc_middle/src/ty/_match.rs
index cbc68fde9..09517200b 100644
--- a/compiler/rustc_middle/src/ty/_match.rs
+++ b/compiler/rustc_middle/src/ty/_match.rs
@@ -81,7 +81,7 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> {
                 Err(TypeError::Sorts(relate::expected_found(self, a, b)))
             }
 
-            (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(self.tcx().ty_error(guar)),
+            (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(Ty::new_error(self.tcx(), guar)),
 
             _ => relate::structurally_relate_tys(self, a, b),
         }
diff --git a/compiler/rustc_middle/src/ty/abstract_const.rs b/compiler/rustc_middle/src/ty/abstract_const.rs
index a39631da9..ffee7ba28 100644
--- a/compiler/rustc_middle/src/ty/abstract_const.rs
+++ b/compiler/rustc_middle/src/ty/abstract_const.rs
@@ -53,7 +53,7 @@ impl<'tcx> TyCtxt<'tcx> {
             fn fold_const(&mut self, c: Const<'tcx>) -> Const<'tcx> {
                 let ct = match c.kind() {
                     ty::ConstKind::Unevaluated(uv) => match self.tcx.thir_abstract_const(uv.def) {
-                        Err(e) => self.tcx.const_error(c.ty(), e),
+                        Err(e) => ty::Const::new_error(self.tcx, e, c.ty()),
                         Ok(Some(bac)) => {
                             let substs = self.tcx.erase_regions(uv.substs);
                             let bac = bac.subst(self.tcx, substs);
diff --git a/compiler/rustc_middle/src/ty/adjustment.rs b/compiler/rustc_middle/src/ty/adjustment.rs
index cd0f7e8da..76931ceaa 100644
--- a/compiler/rustc_middle/src/ty/adjustment.rs
+++ b/compiler/rustc_middle/src/ty/adjustment.rs
@@ -6,7 +6,7 @@ use rustc_span::Span;
 use rustc_target::abi::FieldIdx;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
-pub enum PointerCast {
+pub enum PointerCoercion {
     /// Go from a fn-item type to a fn-pointer type.
     ReifyFnPointer,
 
@@ -99,7 +99,7 @@ pub enum Adjust<'tcx> {
     /// Take the address and produce either a `&` or `*` pointer.
     Borrow(AutoBorrow<'tcx>),
 
-    Pointer(PointerCast),
+    Pointer(PointerCoercion),
 
     /// Cast into a dyn* object.
     DynStar,
@@ -132,7 +132,7 @@ impl<'tcx> OverloadedDeref<'tcx> {
             .find(|m| m.kind == ty::AssocKind::Fn)
             .unwrap()
             .def_id;
-        tcx.mk_fn_def(method_def_id, [source])
+        Ty::new_fn_def(tcx, method_def_id, [source])
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/adt.rs b/compiler/rustc_middle/src/ty/adt.rs
index 7c5c030c2..e067d2a98 100644
--- a/compiler/rustc_middle/src/ty/adt.rs
+++ b/compiler/rustc_middle/src/ty/adt.rs
@@ -573,7 +573,7 @@ impl<'tcx> AdtDef<'tcx> {
     /// Due to normalization being eager, this applies even if
     /// the associated type is behind a pointer (e.g., issue #31299).
     pub fn sized_constraint(self, tcx: TyCtxt<'tcx>) -> ty::EarlyBinder<&'tcx [Ty<'tcx>]> {
-        ty::EarlyBinder(tcx.adt_sized_constraint(self.did()))
+        ty::EarlyBinder::bind(tcx.adt_sized_constraint(self.did()))
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index 090b76932..cce609c26 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -48,7 +48,7 @@ impl AssocItem {
     ///
     /// [`type_of`]: crate::ty::TyCtxt::type_of
     pub fn defaultness(&self, tcx: TyCtxt<'_>) -> hir::Defaultness {
-        tcx.impl_defaultness(self.def_id)
+        tcx.defaultness(self.def_id)
     }
 
     #[inline]
diff --git a/compiler/rustc_middle/src/ty/closure.rs b/compiler/rustc_middle/src/ty/closure.rs
index be7b2b7ec..bc9273745 100644
--- a/compiler/rustc_middle/src/ty/closure.rs
+++ b/compiler/rustc_middle/src/ty/closure.rs
@@ -427,6 +427,8 @@ pub enum BorrowKind {
     /// immutable, but not aliasable. This solves the problem. For
     /// simplicity, we don't give users the way to express this
     /// borrow, it's just used when translating closures.
+    ///
+    /// FIXME: Rename this to indicate the borrow is actually not immutable.
     UniqueImmBorrow,
 
     /// Data is mutable and not aliasable.
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 7fc75674d..6adbb44a1 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -128,6 +128,12 @@ impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Predicate<'tcx>
     }
 }
 
+impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Clause<'tcx> {
+    fn encode(&self, e: &mut E) {
+        self.as_predicate().encode(e);
+    }
+}
+
 impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Region<'tcx> {
     fn encode(&self, e: &mut E) {
         self.kind().encode(e);
@@ -241,6 +247,13 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Predicate<'tcx>
     }
 }
 
+impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Clause<'tcx> {
+    fn decode(decoder: &mut D) -> ty::Clause<'tcx> {
+        let pred: ty::Predicate<'tcx> = Decodable::decode(decoder);
+        pred.expect_clause()
+    }
+}
+
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for SubstsRef<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let len = decoder.read_usize();
@@ -264,7 +277,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for mir::Place<'tcx> {
 
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Region<'tcx> {
     fn decode(decoder: &mut D) -> Self {
-        decoder.interner().mk_region_from_kind(Decodable::decode(decoder))
+        ty::Region::new_from_kind(decoder.interner(), Decodable::decode(decoder))
     }
 }
 
@@ -331,7 +344,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Const<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let consts: ty::ConstData<'tcx> = Decodable::decode(decoder);
-        decoder.interner().mk_const(consts.kind, consts.ty)
+        decoder.interner().mk_ct_from_kind(consts.kind, consts.ty)
     }
 }
 
@@ -355,16 +368,6 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for AdtDef<'tcx> {
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
-    for [(ty::Predicate<'tcx>, Span)]
-{
-    fn decode(decoder: &mut D) -> &'tcx Self {
-        decoder.interner().arena.alloc_from_iter(
-            (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
-        )
-    }
-}
-
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [(ty::Clause<'tcx>, Span)] {
     fn decode(decoder: &mut D) -> &'tcx Self {
         decoder.interner().arena.alloc_from_iter(
@@ -393,11 +396,11 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<ty
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<ty::Predicate<'tcx>> {
+impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<ty::Clause<'tcx>> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
-        decoder.interner().mk_predicates_from_iter(
-            (0..len).map::<ty::Predicate<'tcx>, _>(|_| Decodable::decode(decoder)),
+        decoder.interner().mk_clauses_from_iter(
+            (0..len).map::<ty::Clause<'tcx>, _>(|_| Decodable::decode(decoder)),
         )
     }
 }
@@ -421,7 +424,7 @@ impl_decodable_via_ref! {
     &'tcx mir::BorrowCheckResult<'tcx>,
     &'tcx mir::coverage::CodeRegion,
     &'tcx ty::List<ty::BoundVariableKind>,
-    &'tcx ty::List<ty::Predicate<'tcx>>,
+    &'tcx ty::List<ty::Clause<'tcx>>,
     &'tcx ty::List<FieldIdx>,
 }
 
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index 1a4bd1481..1cbfe99f8 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -1,7 +1,8 @@
 use crate::middle::resolve_bound_vars as rbv;
-use crate::mir::interpret::LitToConstInput;
-use crate::ty::{self, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt};
+use crate::mir::interpret::{AllocId, ConstValue, LitToConstInput, Scalar};
+use crate::ty::{self, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt, TypeVisitableExt};
 use rustc_data_structures::intern::Interned;
+use rustc_error_messages::MultiSpan;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::LocalDefId;
@@ -13,8 +14,13 @@ mod valtree;
 
 pub use int::*;
 pub use kind::*;
+use rustc_span::ErrorGuaranteed;
+use rustc_span::DUMMY_SP;
+use rustc_target::abi::Size;
 pub use valtree::*;
 
+use super::sty::ConstKind;
+
 /// Use this rather than `ConstData`, whenever possible.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
 #[rustc_pass_by_value]
@@ -30,6 +36,16 @@ pub struct ConstData<'tcx> {
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 static_assert_size!(ConstData<'_>, 40);
 
+enum EvalMode {
+    Typeck,
+    Mir,
+}
+
+enum EvalResult<'tcx> {
+    ValTree(ty::ValTree<'tcx>),
+    ConstVal(ConstValue<'tcx>),
+}
+
 impl<'tcx> Const<'tcx> {
     #[inline]
     pub fn ty(self) -> Ty<'tcx> {
@@ -38,7 +54,98 @@ impl<'tcx> Const<'tcx> {
 
     #[inline]
     pub fn kind(self) -> ConstKind<'tcx> {
-        self.0.kind
+        self.0.kind.clone()
+    }
+
+    #[inline]
+    pub fn new(tcx: TyCtxt<'tcx>, kind: ty::ConstKind<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> {
+        tcx.mk_ct_from_kind(kind, ty)
+    }
+
+    #[inline]
+    pub fn new_param(tcx: TyCtxt<'tcx>, param: ty::ParamConst, ty: Ty<'tcx>) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Param(param), ty)
+    }
+
+    #[inline]
+    pub fn new_var(tcx: TyCtxt<'tcx>, infer: ty::ConstVid<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Infer(ty::InferConst::Var(infer)), ty)
+    }
+
+    #[inline]
+    pub fn new_fresh(tcx: TyCtxt<'tcx>, fresh: u32, ty: Ty<'tcx>) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Infer(ty::InferConst::Fresh(fresh)), ty)
+    }
+
+    #[inline]
+    pub fn new_infer(tcx: TyCtxt<'tcx>, infer: ty::InferConst<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Infer(infer), ty)
+    }
+
+    #[inline]
+    pub fn new_bound(
+        tcx: TyCtxt<'tcx>,
+        debruijn: ty::DebruijnIndex,
+        var: ty::BoundVar,
+        ty: Ty<'tcx>,
+    ) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Bound(debruijn, var), ty)
+    }
+
+    #[inline]
+    pub fn new_placeholder(
+        tcx: TyCtxt<'tcx>,
+        placeholder: ty::PlaceholderConst<'tcx>,
+        ty: Ty<'tcx>,
+    ) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Placeholder(placeholder), ty)
+    }
+
+    #[inline]
+    pub fn new_unevaluated(
+        tcx: TyCtxt<'tcx>,
+        uv: ty::UnevaluatedConst<'tcx>,
+        ty: Ty<'tcx>,
+    ) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Unevaluated(uv), ty)
+    }
+
+    #[inline]
+    pub fn new_value(tcx: TyCtxt<'tcx>, val: ty::ValTree<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Value(val), ty)
+    }
+
+    #[inline]
+    pub fn new_expr(tcx: TyCtxt<'tcx>, expr: ty::Expr<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Expr(expr), ty)
+    }
+
+    #[inline]
+    pub fn new_error(tcx: TyCtxt<'tcx>, e: ty::ErrorGuaranteed, ty: Ty<'tcx>) -> Const<'tcx> {
+        Const::new(tcx, ty::ConstKind::Error(e), ty)
+    }
+
+    /// Like [Ty::new_error] but for constants.
+    #[track_caller]
+    pub fn new_misc_error(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> {
+        Const::new_error_with_message(
+            tcx,
+            ty,
+            DUMMY_SP,
+            "ty::ConstKind::Error constructed but no error reported",
+        )
+    }
+
+    /// Like [Ty::new_error_with_message] but for constants.
+    #[track_caller]
+    pub fn new_error_with_message<S: Into<MultiSpan>>(
+        tcx: TyCtxt<'tcx>,
+        ty: Ty<'tcx>,
+        span: S,
+        msg: &'static str,
+    ) -> Const<'tcx> {
+        let reported = tcx.sess.delay_span_bug(span, msg);
+        Const::new_error(tcx, reported, ty)
     }
 
     /// Literals and const generic parameters are eagerly converted to a constant, everything else
@@ -60,7 +167,8 @@ impl<'tcx> Const<'tcx> {
 
         match Self::try_eval_lit_or_param(tcx, ty, expr) {
             Some(v) => v,
-            None => tcx.mk_const(
+            None => ty::Const::new_unevaluated(
+                tcx,
                 ty::UnevaluatedConst {
                     def: def.to_def_id(),
                     substs: InternalSubsts::identity_for_item(tcx, def.to_def_id()),
@@ -126,13 +234,19 @@ impl<'tcx> Const<'tcx> {
                         let generics = tcx.generics_of(item_def_id);
                         let index = generics.param_def_id_to_index[&def_id];
                         let name = tcx.item_name(def_id);
-                        Some(tcx.mk_const(ty::ParamConst::new(index, name), param_ty))
+                        Some(ty::Const::new_param(tcx, ty::ParamConst::new(index, name), param_ty))
+                    }
+                    Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
+                        Some(ty::Const::new_bound(
+                            tcx,
+                            debruijn,
+                            ty::BoundVar::from_u32(index),
+                            param_ty,
+                        ))
+                    }
+                    Some(rbv::ResolvedArg::Error(guar)) => {
+                        Some(ty::Const::new_error(tcx, guar, param_ty))
                     }
-                    Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => Some(tcx.mk_const(
-                        ty::ConstKind::Bound(debruijn, ty::BoundVar::from_u32(index)),
-                        param_ty,
-                    )),
-                    Some(rbv::ResolvedArg::Error(guar)) => Some(tcx.const_error(param_ty, guar)),
                     arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", expr.hir_id),
                 }
             }
@@ -155,7 +269,8 @@ impl<'tcx> Const<'tcx> {
             .layout_of(ty)
             .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e))
             .size;
-        tcx.mk_const(
+        ty::Const::new_value(
+            tcx,
             ty::ValTree::from_scalar_int(ScalarInt::try_from_uint(bits, size).unwrap()),
             ty.value,
         )
@@ -164,7 +279,7 @@ impl<'tcx> Const<'tcx> {
     #[inline]
     /// Creates an interned zst constant.
     pub fn zero_sized(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self {
-        tcx.mk_const(ty::ValTree::zst(), ty)
+        ty::Const::new_value(tcx, ty::ValTree::zst(), ty)
     }
 
     #[inline]
@@ -192,12 +307,12 @@ impl<'tcx> Const<'tcx> {
         assert_eq!(self.ty(), ty);
         let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
         // if `ty` does not depend on generic parameters, use an empty param_env
-        self.kind().eval(tcx, param_env).try_to_bits(size)
+        self.eval(tcx, param_env).try_to_bits(size)
     }
 
     #[inline]
     pub fn try_eval_bool(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> {
-        self.kind().eval(tcx, param_env).try_to_bool()
+        self.eval(tcx, param_env).try_to_bool()
     }
 
     #[inline]
@@ -206,17 +321,17 @@ impl<'tcx> Const<'tcx> {
         tcx: TyCtxt<'tcx>,
         param_env: ParamEnv<'tcx>,
     ) -> Option<u64> {
-        self.kind().eval(tcx, param_env).try_to_target_usize(tcx)
+        self.eval(tcx, param_env).try_to_target_usize(tcx)
     }
 
     #[inline]
     /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the
     /// unevaluated constant.
     pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Const<'tcx> {
-        if let Some(val) = self.kind().try_eval_for_typeck(tcx, param_env) {
+        if let Some(val) = self.try_eval_for_typeck(tcx, param_env) {
             match val {
-                Ok(val) => tcx.mk_const(val, self.ty()),
-                Err(guar) => tcx.const_error(self.ty(), guar),
+                Ok(val) => ty::Const::new_value(tcx, val, self.ty()),
+                Err(guar) => ty::Const::new_error(tcx, guar, self.ty()),
             }
         } else {
             // Either the constant isn't evaluatable or ValTree creation failed.
@@ -238,6 +353,138 @@ impl<'tcx> Const<'tcx> {
             .unwrap_or_else(|| bug!("expected usize, got {:#?}", self))
     }
 
+    #[inline]
+    /// Tries to evaluate the constant if it is `Unevaluated`. If that isn't possible or necessary
+    /// return `None`.
+    // FIXME(@lcnr): Completely rework the evaluation/normalization system for `ty::Const` once valtrees are merged.
+    pub fn try_eval_for_mir(
+        self,
+        tcx: TyCtxt<'tcx>,
+        param_env: ParamEnv<'tcx>,
+    ) -> Option<Result<ConstValue<'tcx>, ErrorGuaranteed>> {
+        match self.try_eval_inner(tcx, param_env, EvalMode::Mir) {
+            Some(Ok(EvalResult::ValTree(_))) => unreachable!(),
+            Some(Ok(EvalResult::ConstVal(v))) => Some(Ok(v)),
+            Some(Err(e)) => Some(Err(e)),
+            None => None,
+        }
+    }
+
+    #[inline]
+    /// Tries to evaluate the constant if it is `Unevaluated`. If that isn't possible or necessary
+    /// return `None`.
+    // FIXME(@lcnr): Completely rework the evaluation/normalization system for `ty::Const` once valtrees are merged.
+    pub fn try_eval_for_typeck(
+        self,
+        tcx: TyCtxt<'tcx>,
+        param_env: ParamEnv<'tcx>,
+    ) -> Option<Result<ty::ValTree<'tcx>, ErrorGuaranteed>> {
+        match self.try_eval_inner(tcx, param_env, EvalMode::Typeck) {
+            Some(Ok(EvalResult::ValTree(v))) => Some(Ok(v)),
+            Some(Ok(EvalResult::ConstVal(_))) => unreachable!(),
+            Some(Err(e)) => Some(Err(e)),
+            None => None,
+        }
+    }
+
+    #[inline]
+    fn try_eval_inner(
+        self,
+        tcx: TyCtxt<'tcx>,
+        param_env: ParamEnv<'tcx>,
+        eval_mode: EvalMode,
+    ) -> Option<Result<EvalResult<'tcx>, ErrorGuaranteed>> {
+        assert!(!self.has_escaping_bound_vars(), "escaping vars in {self:?}");
+        if let ConstKind::Unevaluated(unevaluated) = self.kind() {
+            use crate::mir::interpret::ErrorHandled;
+
+            // HACK(eddyb) this erases lifetimes even though `const_eval_resolve`
+            // also does later, but we want to do it before checking for
+            // inference variables.
+            // Note that we erase regions *before* calling `with_reveal_all_normalized`,
+            // so that we don't try to invoke this query with
+            // any region variables.
+
+            // HACK(eddyb) when the query key would contain inference variables,
+            // attempt using identity substs and `ParamEnv` instead, that will succeed
+            // when the expression doesn't depend on any parameters.
+            // FIXME(eddyb, skinny121) pass `InferCtxt` into here when it's available, so that
+            // we can call `infcx.const_eval_resolve` which handles inference variables.
+            let param_env_and = if (param_env, unevaluated).has_non_region_infer() {
+                tcx.param_env(unevaluated.def).and(ty::UnevaluatedConst {
+                    def: unevaluated.def,
+                    substs: InternalSubsts::identity_for_item(tcx, unevaluated.def),
+                })
+            } else {
+                tcx.erase_regions(param_env)
+                    .with_reveal_all_normalized(tcx)
+                    .and(tcx.erase_regions(unevaluated))
+            };
+
+            // FIXME(eddyb) maybe the `const_eval_*` methods should take
+            // `ty::ParamEnvAnd` instead of having them separate.
+            let (param_env, unevaluated) = param_env_and.into_parts();
+            // try to resolve e.g. associated constants to their definition on an impl, and then
+            // evaluate the const.
+            match eval_mode {
+                EvalMode::Typeck => {
+                    match tcx.const_eval_resolve_for_typeck(param_env, unevaluated, None) {
+                        // NOTE(eddyb) `val` contains no lifetimes/types/consts,
+                        // and we use the original type, so nothing from `substs`
+                        // (which may be identity substs, see above),
+                        // can leak through `val` into the const we return.
+                        Ok(val) => Some(Ok(EvalResult::ValTree(val?))),
+                        Err(ErrorHandled::TooGeneric) => None,
+                        Err(ErrorHandled::Reported(e)) => Some(Err(e.into())),
+                    }
+                }
+                EvalMode::Mir => {
+                    match tcx.const_eval_resolve(param_env, unevaluated.expand(), None) {
+                        // NOTE(eddyb) `val` contains no lifetimes/types/consts,
+                        // and we use the original type, so nothing from `substs`
+                        // (which may be identity substs, see above),
+                        // can leak through `val` into the const we return.
+                        Ok(val) => Some(Ok(EvalResult::ConstVal(val))),
+                        Err(ErrorHandled::TooGeneric) => None,
+                        Err(ErrorHandled::Reported(e)) => Some(Err(e.into())),
+                    }
+                }
+            }
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    pub fn try_to_value(self) -> Option<ty::ValTree<'tcx>> {
+        if let ConstKind::Value(val) = self.kind() { Some(val) } else { None }
+    }
+
+    #[inline]
+    pub fn try_to_scalar(self) -> Option<Scalar<AllocId>> {
+        self.try_to_value()?.try_to_scalar()
+    }
+
+    #[inline]
+    pub fn try_to_scalar_int(self) -> Option<ScalarInt> {
+        self.try_to_value()?.try_to_scalar_int()
+    }
+
+    #[inline]
+    pub fn try_to_bits(self, size: Size) -> Option<u128> {
+        self.try_to_scalar_int()?.to_bits(size).ok()
+    }
+
+    #[inline]
+    pub fn try_to_bool(self) -> Option<bool> {
+        self.try_to_scalar_int()?.try_into().ok()
+    }
+
+    #[inline]
+    pub fn try_to_target_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> {
+        self.try_to_value()?.try_to_target_usize(tcx)
+    }
+
     pub fn is_ct_infer(self) -> bool {
         matches!(self.kind(), ty::ConstKind::Infer(_))
     }
@@ -254,5 +501,5 @@ pub fn const_param_default(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBind
             "`const_param_default` expected a generic parameter with a constant"
         ),
     };
-    ty::EarlyBinder(Const::from_anon_const(tcx, default_def_id))
+    ty::EarlyBinder::bind(Const::from_anon_const(tcx, default_def_id))
 }
diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index d1dbc531e..1e43fab45 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -1,5 +1,6 @@
 use rustc_apfloat::ieee::{Double, Single};
 use rustc_apfloat::Float;
+use rustc_errors::{DiagnosticArgValue, IntoDiagnosticArg};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_target::abi::Size;
 use std::fmt;
@@ -113,6 +114,14 @@ impl std::fmt::Debug for ConstInt {
     }
 }
 
+impl IntoDiagnosticArg for ConstInt {
+    // FIXME this simply uses the Debug impl, but we could probably do better by converting both
+    // to an inherent method that returns `Cow`.
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(format!("{self:?}").into())
+    }
+}
+
 /// The raw bytes of a simple value.
 ///
 /// This is a packed struct in order to allow this type to be optimally embedded in enums
diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs
index 1dd4f8a24..a6bf74911 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -1,17 +1,11 @@
 use super::Const;
 use crate::mir;
-use crate::mir::interpret::{AllocId, ConstValue, Scalar};
 use crate::ty::abstract_const::CastKind;
-use crate::ty::subst::{InternalSubsts, SubstsRef};
-use crate::ty::ParamEnv;
-use crate::ty::{self, List, Ty, TyCtxt, TypeVisitableExt};
+use crate::ty::subst::SubstsRef;
+use crate::ty::{self, List, Ty};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
-use rustc_target::abi::Size;
-
-use super::ScalarInt;
 
 /// An unevaluated (potentially generic) constant used in the type-system.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Lift)]
@@ -41,45 +35,6 @@ impl<'tcx> UnevaluatedConst<'tcx> {
     }
 }
 
-/// Represents a constant in Rust.
-#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable)]
-#[derive(Hash, HashStable, TypeFoldable, TypeVisitable)]
-#[derive(derive_more::From)]
-pub enum ConstKind<'tcx> {
-    /// A const generic parameter.
-    Param(ty::ParamConst),
-
-    /// Infer the value of the const.
-    Infer(InferConst<'tcx>),
-
-    /// Bound const variable, used only when preparing a trait query.
-    Bound(ty::DebruijnIndex, ty::BoundVar),
-
-    /// A placeholder const - universally quantified higher-ranked const.
-    Placeholder(ty::PlaceholderConst<'tcx>),
-
-    /// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other
-    /// variants when the code is monomorphic enough for that.
-    Unevaluated(UnevaluatedConst<'tcx>),
-
-    /// Used to hold computed value.
-    Value(ty::ValTree<'tcx>),
-
-    /// A placeholder for a const which could not be computed; this is
-    /// propagated to avoid useless error messages.
-    #[from(ignore)]
-    Error(ErrorGuaranteed),
-
-    /// Expr which contains an expression which has partially evaluated items.
-    Expr(Expr<'tcx>),
-}
-
-impl<'tcx> From<ty::ConstVid<'tcx>> for ConstKind<'tcx> {
-    fn from(const_vid: ty::ConstVid<'tcx>) -> Self {
-        InferConst::Var(const_vid).into()
-    }
-}
-
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 #[derive(HashStable, TyEncodable, TyDecodable, TypeVisitable, TypeFoldable)]
 pub enum Expr<'tcx> {
@@ -93,39 +48,7 @@ pub enum Expr<'tcx> {
 static_assert_size!(Expr<'_>, 24);
 
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-static_assert_size!(ConstKind<'_>, 32);
-
-impl<'tcx> ConstKind<'tcx> {
-    #[inline]
-    pub fn try_to_value(self) -> Option<ty::ValTree<'tcx>> {
-        if let ConstKind::Value(val) = self { Some(val) } else { None }
-    }
-
-    #[inline]
-    pub fn try_to_scalar(self) -> Option<Scalar<AllocId>> {
-        self.try_to_value()?.try_to_scalar()
-    }
-
-    #[inline]
-    pub fn try_to_scalar_int(self) -> Option<ScalarInt> {
-        self.try_to_value()?.try_to_scalar_int()
-    }
-
-    #[inline]
-    pub fn try_to_bits(self, size: Size) -> Option<u128> {
-        self.try_to_scalar_int()?.to_bits(size).ok()
-    }
-
-    #[inline]
-    pub fn try_to_bool(self) -> Option<bool> {
-        self.try_to_scalar_int()?.try_into().ok()
-    }
-
-    #[inline]
-    pub fn try_to_target_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> {
-        self.try_to_value()?.try_to_target_usize(tcx)
-    }
-}
+static_assert_size!(super::ConstKind<'_>, 32);
 
 /// An inference variable for a const, for use in const generics.
 #[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Hash)]
@@ -144,124 +67,3 @@ impl<CTX> HashStable<CTX> for InferConst<'_> {
         }
     }
 }
-
-enum EvalMode {
-    Typeck,
-    Mir,
-}
-
-enum EvalResult<'tcx> {
-    ValTree(ty::ValTree<'tcx>),
-    ConstVal(ConstValue<'tcx>),
-}
-
-impl<'tcx> ConstKind<'tcx> {
-    #[inline]
-    /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the
-    /// unevaluated constant.
-    pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Self {
-        self.try_eval_for_typeck(tcx, param_env).and_then(Result::ok).map_or(self, ConstKind::Value)
-    }
-
-    #[inline]
-    /// Tries to evaluate the constant if it is `Unevaluated`. If that isn't possible or necessary
-    /// return `None`.
-    // FIXME(@lcnr): Completely rework the evaluation/normalization system for `ty::Const` once valtrees are merged.
-    pub fn try_eval_for_mir(
-        self,
-        tcx: TyCtxt<'tcx>,
-        param_env: ParamEnv<'tcx>,
-    ) -> Option<Result<ConstValue<'tcx>, ErrorGuaranteed>> {
-        match self.try_eval_inner(tcx, param_env, EvalMode::Mir) {
-            Some(Ok(EvalResult::ValTree(_))) => unreachable!(),
-            Some(Ok(EvalResult::ConstVal(v))) => Some(Ok(v)),
-            Some(Err(e)) => Some(Err(e)),
-            None => None,
-        }
-    }
-
-    #[inline]
-    /// Tries to evaluate the constant if it is `Unevaluated`. If that isn't possible or necessary
-    /// return `None`.
-    // FIXME(@lcnr): Completely rework the evaluation/normalization system for `ty::Const` once valtrees are merged.
-    pub fn try_eval_for_typeck(
-        self,
-        tcx: TyCtxt<'tcx>,
-        param_env: ParamEnv<'tcx>,
-    ) -> Option<Result<ty::ValTree<'tcx>, ErrorGuaranteed>> {
-        match self.try_eval_inner(tcx, param_env, EvalMode::Typeck) {
-            Some(Ok(EvalResult::ValTree(v))) => Some(Ok(v)),
-            Some(Ok(EvalResult::ConstVal(_))) => unreachable!(),
-            Some(Err(e)) => Some(Err(e)),
-            None => None,
-        }
-    }
-
-    #[inline]
-    fn try_eval_inner(
-        self,
-        tcx: TyCtxt<'tcx>,
-        param_env: ParamEnv<'tcx>,
-        eval_mode: EvalMode,
-    ) -> Option<Result<EvalResult<'tcx>, ErrorGuaranteed>> {
-        assert!(!self.has_escaping_bound_vars(), "escaping vars in {self:?}");
-        if let ConstKind::Unevaluated(unevaluated) = self {
-            use crate::mir::interpret::ErrorHandled;
-
-            // HACK(eddyb) this erases lifetimes even though `const_eval_resolve`
-            // also does later, but we want to do it before checking for
-            // inference variables.
-            // Note that we erase regions *before* calling `with_reveal_all_normalized`,
-            // so that we don't try to invoke this query with
-            // any region variables.
-
-            // HACK(eddyb) when the query key would contain inference variables,
-            // attempt using identity substs and `ParamEnv` instead, that will succeed
-            // when the expression doesn't depend on any parameters.
-            // FIXME(eddyb, skinny121) pass `InferCtxt` into here when it's available, so that
-            // we can call `infcx.const_eval_resolve` which handles inference variables.
-            let param_env_and = if (param_env, unevaluated).has_non_region_infer() {
-                tcx.param_env(unevaluated.def).and(ty::UnevaluatedConst {
-                    def: unevaluated.def,
-                    substs: InternalSubsts::identity_for_item(tcx, unevaluated.def),
-                })
-            } else {
-                tcx.erase_regions(param_env)
-                    .with_reveal_all_normalized(tcx)
-                    .and(tcx.erase_regions(unevaluated))
-            };
-
-            // FIXME(eddyb) maybe the `const_eval_*` methods should take
-            // `ty::ParamEnvAnd` instead of having them separate.
-            let (param_env, unevaluated) = param_env_and.into_parts();
-            // try to resolve e.g. associated constants to their definition on an impl, and then
-            // evaluate the const.
-            match eval_mode {
-                EvalMode::Typeck => {
-                    match tcx.const_eval_resolve_for_typeck(param_env, unevaluated, None) {
-                        // NOTE(eddyb) `val` contains no lifetimes/types/consts,
-                        // and we use the original type, so nothing from `substs`
-                        // (which may be identity substs, see above),
-                        // can leak through `val` into the const we return.
-                        Ok(val) => Some(Ok(EvalResult::ValTree(val?))),
-                        Err(ErrorHandled::TooGeneric) => None,
-                        Err(ErrorHandled::Reported(e)) => Some(Err(e.into())),
-                    }
-                }
-                EvalMode::Mir => {
-                    match tcx.const_eval_resolve(param_env, unevaluated.expand(), None) {
-                        // NOTE(eddyb) `val` contains no lifetimes/types/consts,
-                        // and we use the original type, so nothing from `substs`
-                        // (which may be identity substs, see above),
-                        // can leak through `val` into the const we return.
-                        Ok(val) => Some(Ok(EvalResult::ConstVal(val))),
-                        Err(ErrorHandled::TooGeneric) => None,
-                        Err(ErrorHandled::Reported(e)) => Some(Err(e.into())),
-                    }
-                }
-            }
-        } else {
-            None
-        }
-    }
-}
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 2bde55bc4..035e978f6 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -25,10 +25,10 @@ use crate::traits::solve::{
     ExternalConstraints, ExternalConstraintsData, PredefinedOpaques, PredefinedOpaquesData,
 };
 use crate::ty::{
-    self, AdtDef, AdtDefData, AdtKind, Binder, Const, ConstData, FloatTy, FloatVar, FloatVid,
-    GenericParamDefKind, ImplPolarity, InferTy, IntTy, IntVar, IntVid, List, ParamConst, ParamTy,
-    PolyExistentialPredicate, PolyFnSig, Predicate, PredicateKind, Region, RegionKind, ReprOptions,
-    TraitObjectVisitor, Ty, TyKind, TyVar, TyVid, TypeAndMut, UintTy, Visibility,
+    self, AdtDef, AdtDefData, AdtKind, Binder, Clause, Const, ConstData, GenericParamDefKind,
+    ImplPolarity, InferTy, List, ParamConst, ParamTy, PolyExistentialPredicate, PolyFnSig,
+    Predicate, PredicateKind, Region, RegionKind, ReprOptions, TraitObjectVisitor, Ty, TyKind,
+    TyVid, TypeAndMut, Visibility,
 };
 use crate::ty::{GenericArg, InternalSubsts, SubstsRef};
 use rustc_ast::{self as ast, attr};
@@ -70,10 +70,9 @@ use rustc_target::abi::{FieldIdx, Layout, LayoutS, TargetDataLayout, VariantIdx}
 use rustc_target::spec::abi;
 use rustc_type_ir::sty::TyKind::*;
 use rustc_type_ir::WithCachedTypeInfo;
-use rustc_type_ir::{CollectAndApply, DynKind, Interner, TypeFlags};
+use rustc_type_ir::{CollectAndApply, Interner, TypeFlags};
 
 use std::any::Any;
-use std::assert_matches::debug_assert_matches;
 use std::borrow::Borrow;
 use std::cmp::Ordering;
 use std::fmt;
@@ -82,8 +81,6 @@ use std::iter;
 use std::mem;
 use std::ops::{Bound, Deref};
 
-const TINY_CONST_EVAL_LIMIT: Limit = Limit(20);
-
 #[allow(rustc::usage_of_ty_tykind)]
 impl<'tcx> Interner for TyCtxt<'tcx> {
     type AdtDef = ty::AdtDef<'tcx>;
@@ -110,11 +107,29 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     type PredicateKind = ty::PredicateKind<'tcx>;
     type AllocId = crate::mir::interpret::AllocId;
 
+    type InferConst = ty::InferConst<'tcx>;
+    type AliasConst = ty::UnevaluatedConst<'tcx>;
+    type ParamConst = ty::ParamConst;
+    type BoundConst = ty::BoundVar;
+    type PlaceholderConst = ty::PlaceholderConst<'tcx>;
+    type ValueConst = ty::ValTree<'tcx>;
+    type ExprConst = ty::Expr<'tcx>;
+
     type EarlyBoundRegion = ty::EarlyBoundRegion;
     type BoundRegion = ty::BoundRegion;
     type FreeRegion = ty::FreeRegion;
     type RegionVid = ty::RegionVid;
     type PlaceholderRegion = ty::PlaceholderRegion;
+
+    fn ty_and_mut_to_parts(
+        TypeAndMut { ty, mutbl }: TypeAndMut<'tcx>,
+    ) -> (Self::Ty, Self::Mutability) {
+        (ty, mutbl)
+    }
+
+    fn mutability_is_mut(mutbl: Self::Mutability) -> bool {
+        mutbl.is_mut()
+    }
 }
 
 type InternedSet<'tcx, T> = ShardedHashMap<InternedInSet<'tcx, T>, ()>;
@@ -133,7 +148,7 @@ pub struct CtxtInterners<'tcx> {
     region: InternedSet<'tcx, RegionKind<'tcx>>,
     poly_existential_predicates: InternedSet<'tcx, List<PolyExistentialPredicate<'tcx>>>,
     predicate: InternedSet<'tcx, WithCachedTypeInfo<ty::Binder<'tcx, PredicateKind<'tcx>>>>,
-    predicates: InternedSet<'tcx, List<Predicate<'tcx>>>,
+    clauses: InternedSet<'tcx, List<Clause<'tcx>>>,
     projs: InternedSet<'tcx, List<ProjectionKind>>,
     place_elems: InternedSet<'tcx, List<PlaceElem<'tcx>>>,
     const_: InternedSet<'tcx, ConstData<'tcx>>,
@@ -158,7 +173,7 @@ impl<'tcx> CtxtInterners<'tcx> {
             poly_existential_predicates: Default::default(),
             canonical_var_infos: Default::default(),
             predicate: Default::default(),
-            predicates: Default::default(),
+            clauses: Default::default(),
             projs: Default::default(),
             place_elems: Default::default(),
             const_: Default::default(),
@@ -312,6 +327,8 @@ pub struct CommonLifetimes<'tcx> {
 
 pub struct CommonConsts<'tcx> {
     pub unit: Const<'tcx>,
+    pub true_: Const<'tcx>,
+    pub false_: Const<'tcx>,
 }
 
 impl<'tcx> CommonTypes<'tcx> {
@@ -409,6 +426,14 @@ impl<'tcx> CommonConsts<'tcx> {
                 kind: ty::ConstKind::Value(ty::ValTree::zst()),
                 ty: types.unit,
             }),
+            true_: mk_const(ty::ConstData {
+                kind: ty::ConstKind::Value(ty::ValTree::Leaf(ty::ScalarInt::TRUE)),
+                ty: types.bool,
+            }),
+            false_: mk_const(ty::ConstData {
+                kind: ty::ConstKind::Value(ty::ValTree::Leaf(ty::ScalarInt::FALSE)),
+                ty: types.bool,
+            }),
         }
     }
 }
@@ -470,6 +495,17 @@ impl<'tcx> TyCtxtFeed<'tcx, LocalDefId> {
 /// [rustc dev guide] for more details.
 ///
 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/ty.html
+///
+/// An implementation detail: `TyCtxt` is a wrapper type for [GlobalCtxt],
+/// which is the struct that actually holds all the data. `TyCtxt` derefs to
+/// `GlobalCtxt`, and in practice `TyCtxt` is passed around everywhere, and all
+/// operations are done via `TyCtxt`. A `TyCtxt` is obtained for a `GlobalCtxt`
+/// by calling `enter` with a closure `f`. That function creates both the
+/// `TyCtxt`, and an `ImplicitCtxt` around it that is put into TLS. Within `f`:
+/// - The `ImplicitCtxt` is available implicitly via TLS.
+/// - The `TyCtxt` is available explicitly via the `tcx` parameter, and also
+///   implicitly within the `ImplicitCtxt`. Explicit access is preferred when
+///   possible.
 #[derive(Copy, Clone)]
 #[rustc_diagnostic_item = "TyCtxt"]
 #[rustc_pass_by_value]
@@ -485,6 +521,7 @@ impl<'tcx> Deref for TyCtxt<'tcx> {
     }
 }
 
+/// See [TyCtxt] for details about this type.
 pub struct GlobalCtxt<'tcx> {
     pub arena: &'tcx WorkerLocal<Arena<'tcx>>,
     pub hir_arena: &'tcx WorkerLocal<hir::Arena<'tcx>>,
@@ -689,82 +726,6 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    /// Constructs a `TyKind::Error` type with current `ErrorGuaranteed`
-    #[track_caller]
-    pub fn ty_error(self, reported: ErrorGuaranteed) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Error(reported))
-    }
-
-    /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` to ensure it gets used.
-    #[track_caller]
-    pub fn ty_error_misc(self) -> Ty<'tcx> {
-        self.ty_error_with_message(DUMMY_SP, "TyKind::Error constructed but no error reported")
-    }
-
-    /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` with the given `msg` to
-    /// ensure it gets used.
-    #[track_caller]
-    pub fn ty_error_with_message<S: Into<MultiSpan>>(
-        self,
-        span: S,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> Ty<'tcx> {
-        let reported = self.sess.delay_span_bug(span, msg);
-        self.mk_ty_from_kind(Error(reported))
-    }
-
-    /// Constructs a `RegionKind::ReError` lifetime.
-    #[track_caller]
-    pub fn mk_re_error(self, reported: ErrorGuaranteed) -> Region<'tcx> {
-        self.intern_region(ty::ReError(reported))
-    }
-
-    /// Constructs a `RegionKind::ReError` lifetime and registers a `delay_span_bug` to ensure it
-    /// gets used.
-    #[track_caller]
-    pub fn mk_re_error_misc(self) -> Region<'tcx> {
-        self.mk_re_error_with_message(
-            DUMMY_SP,
-            "RegionKind::ReError constructed but no error reported",
-        )
-    }
-
-    /// Constructs a `RegionKind::ReError` lifetime and registers a `delay_span_bug` with the given
-    /// `msg` to ensure it gets used.
-    #[track_caller]
-    pub fn mk_re_error_with_message<S: Into<MultiSpan>>(self, span: S, msg: &str) -> Region<'tcx> {
-        let reported = self.sess.delay_span_bug(span, msg);
-        self.mk_re_error(reported)
-    }
-
-    /// Like [TyCtxt::ty_error] but for constants, with current `ErrorGuaranteed`
-    #[track_caller]
-    pub fn const_error(self, ty: Ty<'tcx>, reported: ErrorGuaranteed) -> Const<'tcx> {
-        self.mk_const(ty::ConstKind::Error(reported), ty)
-    }
-
-    /// Like [TyCtxt::ty_error] but for constants.
-    #[track_caller]
-    pub fn const_error_misc(self, ty: Ty<'tcx>) -> Const<'tcx> {
-        self.const_error_with_message(
-            ty,
-            DUMMY_SP,
-            "ty::ConstKind::Error constructed but no error reported",
-        )
-    }
-
-    /// Like [TyCtxt::ty_error_with_message] but for constants.
-    #[track_caller]
-    pub fn const_error_with_message<S: Into<MultiSpan>>(
-        self,
-        ty: Ty<'tcx>,
-        span: S,
-        msg: &str,
-    ) -> Const<'tcx> {
-        let reported = self.sess.delay_span_bug(span, msg);
-        self.mk_const(ty::ConstKind::Error(reported), ty)
-    }
-
     pub fn consider_optimizing<T: Fn() -> String>(self, msg: T) -> bool {
         self.sess.consider_optimizing(|| self.crate_name(LOCAL_CRATE), msg)
     }
@@ -1019,15 +980,6 @@ impl<'tcx> TyCtxt<'tcx> {
         self.query_system.on_disk_cache.as_ref().map_or(Ok(0), |c| c.serialize(self, encoder))
     }
 
-    /// If `true`, we should use lazy normalization for constants, otherwise
-    /// we still evaluate them eagerly.
-    #[inline]
-    pub fn lazy_normalization(self) -> bool {
-        let features = self.features();
-        // Note: We only use lazy normalization for generic const expressions.
-        features.generic_const_exprs
-    }
-
     #[inline]
     pub fn local_crate_exports_generics(self) -> bool {
         debug_assert!(self.sess.opts.share_generics());
@@ -1167,7 +1119,8 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Returns `&'static core::panic::Location<'static>`.
     pub fn caller_location_ty(self) -> Ty<'tcx> {
-        self.mk_imm_ref(
+        Ty::new_imm_ref(
+            self,
             self.lifetimes.re_static,
             self.type_of(self.require_lang_item(LangItem::PanicLocation, None))
                 .subst(self, self.mk_substs(&[self.lifetimes.re_static.into()])),
@@ -1192,14 +1145,6 @@ impl<'tcx> TyCtxt<'tcx> {
         self.limits(()).move_size_limit
     }
 
-    pub fn const_eval_limit(self) -> Limit {
-        if self.sess.opts.unstable_opts.tiny_const_eval_limit {
-            TINY_CONST_EVAL_LIMIT
-        } else {
-            self.limits(()).const_eval_limit
-        }
-    }
-
     pub fn all_traits(self) -> impl Iterator<Item = DefId> + 'tcx {
         iter::once(LOCAL_CRATE)
             .chain(self.crates(()).iter().copied())
@@ -1210,6 +1155,12 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn local_visibility(self, def_id: LocalDefId) -> Visibility {
         self.visibility(def_id).expect_local()
     }
+
+    /// Returns the origin of the opaque type `def_id`.
+    #[instrument(skip(self), level = "trace", ret)]
+    pub fn opaque_type_origin(self, def_id: LocalDefId) -> hir::OpaqueTyOrigin {
+        self.hir().expect_item(def_id).expect_opaque_ty().origin
+    }
 }
 
 /// A trait implemented for all `X<'a>` types that can be safely and
@@ -1272,10 +1223,11 @@ nop_lift! {region; Region<'a> => Region<'tcx>}
 nop_lift! {const_; Const<'a> => Const<'tcx>}
 nop_lift! {const_allocation; ConstAllocation<'a> => ConstAllocation<'tcx>}
 nop_lift! {predicate; Predicate<'a> => Predicate<'tcx>}
+nop_lift! {predicate; Clause<'a> => Clause<'tcx>}
 
 nop_list_lift! {type_lists; Ty<'a> => Ty<'tcx>}
 nop_list_lift! {poly_existential_predicates; PolyExistentialPredicate<'a> => PolyExistentialPredicate<'tcx>}
-nop_list_lift! {predicates; Predicate<'a> => Predicate<'tcx>}
+nop_list_lift! {clauses; Clause<'a> => Clause<'tcx>}
 nop_list_lift! {canonical_var_infos; CanonicalVarInfo<'a> => CanonicalVarInfo<'tcx>}
 nop_list_lift! {projs; ProjectionKind => ProjectionKind}
 nop_list_lift! {bound_variable_kinds; ty::BoundVariableKind => ty::BoundVariableKind}
@@ -1515,9 +1467,9 @@ macro_rules! direct_interners {
 
 // Functions with a `mk_` prefix are intended for use outside this file and
 // crate. Functions with an `intern_` prefix are intended for use within this
-// file only, and have a corresponding `mk_` function.
+// crate only, and have a corresponding `mk_` function.
 direct_interners! {
-    region: intern_region(RegionKind<'tcx>): Region -> Region<'tcx>,
+    region: pub(crate) intern_region(RegionKind<'tcx>): Region -> Region<'tcx>,
     const_: intern_const(ConstData<'tcx>): Const -> Const<'tcx>,
     const_allocation: pub mk_const_alloc(Allocation): ConstAllocation -> ConstAllocation<'tcx>,
     layout: pub mk_layout(LayoutS): Layout -> Layout<'tcx>,
@@ -1553,7 +1505,7 @@ slice_interners!(
     type_lists: pub mk_type_list(Ty<'tcx>),
     canonical_var_infos: pub mk_canonical_var_infos(CanonicalVarInfo<'tcx>),
     poly_existential_predicates: intern_poly_existential_predicates(PolyExistentialPredicate<'tcx>),
-    predicates: intern_predicates(Predicate<'tcx>),
+    clauses: intern_clauses(Clause<'tcx>),
     projs: pub mk_projs(ProjectionKind),
     place_elems: pub mk_place_elems(PlaceElem<'tcx>),
     bound_variable_kinds: pub mk_bound_variable_kinds(ty::BoundVariableKind),
@@ -1566,7 +1518,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// unsafe.
     pub fn safe_to_unsafe_fn_ty(self, sig: PolyFnSig<'tcx>) -> Ty<'tcx> {
         assert_eq!(sig.unsafety(), hir::Unsafety::Normal);
-        self.mk_fn_ptr(sig.map_bound(|sig| ty::FnSig { unsafety: hir::Unsafety::Unsafe, ..sig }))
+        Ty::new_fn_ptr(
+            self,
+            sig.map_bound(|sig| ty::FnSig { unsafety: hir::Unsafety::Unsafe, ..sig }),
+        )
     }
 
     /// Given the def_id of a Trait `trait_def_id` and the name of an associated item `assoc_name`
@@ -1585,7 +1540,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let future_trait = self.require_lang_item(LangItem::Future, None);
 
         self.explicit_item_bounds(def_id).skip_binder().iter().any(|&(predicate, _)| {
-            let ty::PredicateKind::Clause(ty::Clause::Trait(trait_predicate)) = predicate.kind().skip_binder() else {
+            let ty::ClauseKind::Trait(trait_predicate) = predicate.kind().skip_binder() else {
                 return false;
             };
             trait_predicate.trait_ref.def_id == future_trait
@@ -1608,9 +1563,7 @@ impl<'tcx> TyCtxt<'tcx> {
             let generic_predicates = self.super_predicates_of(trait_did);
 
             for (predicate, _) in generic_predicates.predicates {
-                if let ty::PredicateKind::Clause(ty::Clause::Trait(data)) =
-                    predicate.kind().skip_binder()
-                {
+                if let ty::ClauseKind::Trait(data) = predicate.kind().skip_binder() {
                     if set.insert(data.def_id()) {
                         stack.push(data.def_id());
                     }
@@ -1642,18 +1595,6 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    // Avoid this in favour of more specific `mk_*` methods, where possible.
-    #[allow(rustc::usage_of_ty_tykind)]
-    #[inline]
-    pub fn mk_ty_from_kind(self, st: TyKind<'tcx>) -> Ty<'tcx> {
-        self.interners.intern_ty(
-            st,
-            self.sess,
-            // This is only used to create a stable hashing context.
-            &self.untracked,
-        )
-    }
-
     #[inline]
     pub fn mk_predicate(self, binder: Binder<'tcx, PredicateKind<'tcx>>) -> Predicate<'tcx> {
         self.interners.intern_predicate(
@@ -1673,174 +1614,6 @@ impl<'tcx> TyCtxt<'tcx> {
         if pred.kind() != binder { self.mk_predicate(binder) } else { pred }
     }
 
-    pub fn mk_mach_int(self, tm: IntTy) -> Ty<'tcx> {
-        match tm {
-            IntTy::Isize => self.types.isize,
-            IntTy::I8 => self.types.i8,
-            IntTy::I16 => self.types.i16,
-            IntTy::I32 => self.types.i32,
-            IntTy::I64 => self.types.i64,
-            IntTy::I128 => self.types.i128,
-        }
-    }
-
-    pub fn mk_mach_uint(self, tm: UintTy) -> Ty<'tcx> {
-        match tm {
-            UintTy::Usize => self.types.usize,
-            UintTy::U8 => self.types.u8,
-            UintTy::U16 => self.types.u16,
-            UintTy::U32 => self.types.u32,
-            UintTy::U64 => self.types.u64,
-            UintTy::U128 => self.types.u128,
-        }
-    }
-
-    pub fn mk_mach_float(self, tm: FloatTy) -> Ty<'tcx> {
-        match tm {
-            FloatTy::F32 => self.types.f32,
-            FloatTy::F64 => self.types.f64,
-        }
-    }
-
-    #[inline]
-    pub fn mk_static_str(self) -> Ty<'tcx> {
-        self.mk_imm_ref(self.lifetimes.re_static, self.types.str_)
-    }
-
-    #[inline]
-    pub fn mk_adt(self, def: AdtDef<'tcx>, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        // Take a copy of substs so that we own the vectors inside.
-        self.mk_ty_from_kind(Adt(def, substs))
-    }
-
-    #[inline]
-    pub fn mk_foreign(self, def_id: DefId) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Foreign(def_id))
-    }
-
-    fn mk_generic_adt(self, wrapper_def_id: DefId, ty_param: Ty<'tcx>) -> Ty<'tcx> {
-        let adt_def = self.adt_def(wrapper_def_id);
-        let substs =
-            InternalSubsts::for_item(self, wrapper_def_id, |param, substs| match param.kind {
-                GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => bug!(),
-                GenericParamDefKind::Type { has_default, .. } => {
-                    if param.index == 0 {
-                        ty_param.into()
-                    } else {
-                        assert!(has_default);
-                        self.type_of(param.def_id).subst(self, substs).into()
-                    }
-                }
-            });
-        self.mk_ty_from_kind(Adt(adt_def, substs))
-    }
-
-    #[inline]
-    pub fn mk_box(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let def_id = self.require_lang_item(LangItem::OwnedBox, None);
-        self.mk_generic_adt(def_id, ty)
-    }
-
-    #[inline]
-    pub fn mk_lang_item(self, ty: Ty<'tcx>, item: LangItem) -> Option<Ty<'tcx>> {
-        let def_id = self.lang_items().get(item)?;
-        Some(self.mk_generic_adt(def_id, ty))
-    }
-
-    #[inline]
-    pub fn mk_diagnostic_item(self, ty: Ty<'tcx>, name: Symbol) -> Option<Ty<'tcx>> {
-        let def_id = self.get_diagnostic_item(name)?;
-        Some(self.mk_generic_adt(def_id, ty))
-    }
-
-    #[inline]
-    pub fn mk_maybe_uninit(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let def_id = self.require_lang_item(LangItem::MaybeUninit, None);
-        self.mk_generic_adt(def_id, ty)
-    }
-
-    #[inline]
-    pub fn mk_ptr(self, tm: TypeAndMut<'tcx>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(RawPtr(tm))
-    }
-
-    #[inline]
-    pub fn mk_ref(self, r: Region<'tcx>, tm: TypeAndMut<'tcx>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Ref(r, tm.ty, tm.mutbl))
-    }
-
-    #[inline]
-    pub fn mk_mut_ref(self, r: Region<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ref(r, TypeAndMut { ty, mutbl: hir::Mutability::Mut })
-    }
-
-    #[inline]
-    pub fn mk_imm_ref(self, r: Region<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ref(r, TypeAndMut { ty, mutbl: hir::Mutability::Not })
-    }
-
-    #[inline]
-    pub fn mk_mut_ptr(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ptr(TypeAndMut { ty, mutbl: hir::Mutability::Mut })
-    }
-
-    #[inline]
-    pub fn mk_imm_ptr(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ptr(TypeAndMut { ty, mutbl: hir::Mutability::Not })
-    }
-
-    #[inline]
-    pub fn mk_array(self, ty: Ty<'tcx>, n: u64) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Array(ty, ty::Const::from_target_usize(self, n)))
-    }
-
-    #[inline]
-    pub fn mk_array_with_const_len(self, ty: Ty<'tcx>, ct: Const<'tcx>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Array(ty, ct))
-    }
-
-    #[inline]
-    pub fn mk_slice(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Slice(ty))
-    }
-
-    #[inline]
-    pub fn mk_tup(self, ts: &[Ty<'tcx>]) -> Ty<'tcx> {
-        if ts.is_empty() {
-            self.types.unit
-        } else {
-            self.mk_ty_from_kind(Tuple(self.mk_type_list(&ts)))
-        }
-    }
-
-    pub fn mk_tup_from_iter<I, T>(self, iter: I) -> T::Output
-    where
-        I: Iterator<Item = T>,
-        T: CollectAndApply<Ty<'tcx>, Ty<'tcx>>,
-    {
-        T::collect_and_apply(iter, |ts| self.mk_tup(ts))
-    }
-
-    #[inline]
-    pub fn mk_unit(self) -> Ty<'tcx> {
-        self.types.unit
-    }
-
-    #[inline]
-    pub fn mk_diverging_default(self) -> Ty<'tcx> {
-        if self.features().never_type_fallback { self.types.never } else { self.types.unit }
-    }
-
-    #[inline]
-    pub fn mk_fn_def(
-        self,
-        def_id: DefId,
-        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
-    ) -> Ty<'tcx> {
-        let substs = self.check_and_mk_substs(def_id, substs);
-        self.mk_ty_from_kind(FnDef(def_id, substs))
-    }
-
     #[inline(always)]
     pub(crate) fn check_and_mk_substs(
         self,
@@ -1872,222 +1645,36 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     #[inline]
-    pub fn mk_fn_ptr(self, fty: PolyFnSig<'tcx>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(FnPtr(fty))
-    }
-
-    #[inline]
-    pub fn mk_dynamic(
-        self,
-        obj: &'tcx List<PolyExistentialPredicate<'tcx>>,
-        reg: ty::Region<'tcx>,
-        repr: DynKind,
-    ) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Dynamic(obj, reg, repr))
-    }
-
-    #[inline]
-    pub fn mk_projection(
-        self,
-        item_def_id: DefId,
-        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
-    ) -> Ty<'tcx> {
-        self.mk_alias(ty::Projection, self.mk_alias_ty(item_def_id, substs))
-    }
-
-    #[inline]
-    pub fn mk_closure(self, closure_id: DefId, closure_substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Closure(closure_id, closure_substs))
-    }
-
-    #[inline]
-    pub fn mk_generator(
-        self,
-        id: DefId,
-        generator_substs: SubstsRef<'tcx>,
-        movability: hir::Movability,
-    ) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Generator(id, generator_substs, movability))
-    }
-
-    #[inline]
-    pub fn mk_generator_witness(self, types: ty::Binder<'tcx, &'tcx List<Ty<'tcx>>>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(GeneratorWitness(types))
-    }
-
-    /// Creates a `&mut Context<'_>` [`Ty`] with erased lifetimes.
-    pub fn mk_task_context(self) -> Ty<'tcx> {
-        let context_did = self.require_lang_item(LangItem::Context, None);
-        let context_adt_ref = self.adt_def(context_did);
-        let context_substs = self.mk_substs(&[self.lifetimes.re_erased.into()]);
-        let context_ty = self.mk_adt(context_adt_ref, context_substs);
-        self.mk_mut_ref(self.lifetimes.re_erased, context_ty)
-    }
-
-    #[inline]
-    pub fn mk_generator_witness_mir(self, id: DefId, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(GeneratorWitnessMIR(id, substs))
-    }
-
-    #[inline]
-    pub fn mk_const(self, kind: impl Into<ty::ConstKind<'tcx>>, ty: Ty<'tcx>) -> Const<'tcx> {
-        self.intern_const(ty::ConstData { kind: kind.into(), ty })
-    }
-
-    #[inline]
-    pub fn mk_ty_var(self, v: TyVid) -> Ty<'tcx> {
-        // Use a pre-interned one when possible.
-        self.types
-            .ty_vars
-            .get(v.as_usize())
-            .copied()
-            .unwrap_or_else(|| self.mk_ty_from_kind(Infer(TyVar(v))))
-    }
-
-    #[inline]
-    pub fn mk_int_var(self, v: IntVid) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Infer(IntVar(v)))
-    }
-
-    #[inline]
-    pub fn mk_float_var(self, v: FloatVid) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Infer(FloatVar(v)))
-    }
-
-    #[inline]
-    pub fn mk_fresh_ty(self, n: u32) -> Ty<'tcx> {
-        // Use a pre-interned one when possible.
-        self.types
-            .fresh_tys
-            .get(n as usize)
-            .copied()
-            .unwrap_or_else(|| self.mk_ty_from_kind(Infer(ty::FreshTy(n))))
-    }
-
-    #[inline]
-    pub fn mk_fresh_int_ty(self, n: u32) -> Ty<'tcx> {
-        // Use a pre-interned one when possible.
-        self.types
-            .fresh_int_tys
-            .get(n as usize)
-            .copied()
-            .unwrap_or_else(|| self.mk_ty_from_kind(Infer(ty::FreshIntTy(n))))
-    }
-
-    #[inline]
-    pub fn mk_fresh_float_ty(self, n: u32) -> Ty<'tcx> {
-        // Use a pre-interned one when possible.
-        self.types
-            .fresh_float_tys
-            .get(n as usize)
-            .copied()
-            .unwrap_or_else(|| self.mk_ty_from_kind(Infer(ty::FreshFloatTy(n))))
+    pub fn mk_ct_from_kind(self, kind: ty::ConstKind<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> {
+        self.intern_const(ty::ConstData { kind, ty })
     }
 
+    // Avoid this in favour of more specific `Ty::new_*` methods, where possible.
+    #[allow(rustc::usage_of_ty_tykind)]
     #[inline]
-    pub fn mk_ty_param(self, index: u32, name: Symbol) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Param(ParamTy { index, name }))
+    pub fn mk_ty_from_kind(self, st: TyKind<'tcx>) -> Ty<'tcx> {
+        self.interners.intern_ty(
+            st,
+            self.sess,
+            // This is only used to create a stable hashing context.
+            &self.untracked,
+        )
     }
 
     pub fn mk_param_from_def(self, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
         match param.kind {
             GenericParamDefKind::Lifetime => {
-                self.mk_re_early_bound(param.to_early_bound_region_data()).into()
-            }
-            GenericParamDefKind::Type { .. } => self.mk_ty_param(param.index, param.name).into(),
-            GenericParamDefKind::Const { .. } => self
-                .mk_const(
-                    ParamConst { index: param.index, name: param.name },
-                    self.type_of(param.def_id)
-                        .no_bound_vars()
-                        .expect("const parameter types cannot be generic"),
-                )
-                .into(),
-        }
-    }
-
-    #[inline]
-    pub fn mk_bound(self, index: ty::DebruijnIndex, bound_ty: ty::BoundTy) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Bound(index, bound_ty))
-    }
-
-    #[inline]
-    pub fn mk_placeholder(self, placeholder: ty::PlaceholderType) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Placeholder(placeholder))
-    }
-
-    #[inline]
-    pub fn mk_alias(self, kind: ty::AliasKind, alias_ty: ty::AliasTy<'tcx>) -> Ty<'tcx> {
-        debug_assert_matches!(
-            (kind, self.def_kind(alias_ty.def_id)),
-            (ty::Opaque, DefKind::OpaqueTy)
-                | (ty::Projection | ty::Inherent, DefKind::AssocTy)
-                | (ty::Opaque | ty::Projection, DefKind::ImplTraitPlaceholder)
-        );
-        self.mk_ty_from_kind(Alias(kind, alias_ty))
-    }
-
-    #[inline]
-    pub fn mk_opaque(self, def_id: DefId, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        self.mk_alias(ty::Opaque, self.mk_alias_ty(def_id, substs))
-    }
-
-    #[inline]
-    pub fn mk_re_early_bound(self, early_bound_region: ty::EarlyBoundRegion) -> Region<'tcx> {
-        self.intern_region(ty::ReEarlyBound(early_bound_region))
-    }
-
-    #[inline]
-    pub fn mk_re_late_bound(
-        self,
-        debruijn: ty::DebruijnIndex,
-        bound_region: ty::BoundRegion,
-    ) -> Region<'tcx> {
-        // Use a pre-interned one when possible.
-        if let ty::BoundRegion { var, kind: ty::BrAnon(None) } = bound_region
-            && let Some(inner) = self.lifetimes.re_late_bounds.get(debruijn.as_usize())
-            && let Some(re) = inner.get(var.as_usize()).copied()
-        {
-            re
-        } else {
-            self.intern_region(ty::ReLateBound(debruijn, bound_region))
-        }
-    }
-
-    #[inline]
-    pub fn mk_re_free(self, scope: DefId, bound_region: ty::BoundRegionKind) -> Region<'tcx> {
-        self.intern_region(ty::ReFree(ty::FreeRegion { scope, bound_region }))
-    }
-
-    #[inline]
-    pub fn mk_re_var(self, v: ty::RegionVid) -> Region<'tcx> {
-        // Use a pre-interned one when possible.
-        self.lifetimes
-            .re_vars
-            .get(v.as_usize())
-            .copied()
-            .unwrap_or_else(|| self.intern_region(ty::ReVar(v)))
-    }
-
-    #[inline]
-    pub fn mk_re_placeholder(self, placeholder: ty::PlaceholderRegion) -> Region<'tcx> {
-        self.intern_region(ty::RePlaceholder(placeholder))
-    }
-
-    // Avoid this in favour of more specific `mk_re_*` methods, where possible,
-    // to avoid the cost of the `match`.
-    pub fn mk_region_from_kind(self, kind: ty::RegionKind<'tcx>) -> Region<'tcx> {
-        match kind {
-            ty::ReEarlyBound(region) => self.mk_re_early_bound(region),
-            ty::ReLateBound(debruijn, region) => self.mk_re_late_bound(debruijn, region),
-            ty::ReFree(ty::FreeRegion { scope, bound_region }) => {
-                self.mk_re_free(scope, bound_region)
+                ty::Region::new_early_bound(self, param.to_early_bound_region_data()).into()
             }
-            ty::ReStatic => self.lifetimes.re_static,
-            ty::ReVar(vid) => self.mk_re_var(vid),
-            ty::RePlaceholder(region) => self.mk_re_placeholder(region),
-            ty::ReErased => self.lifetimes.re_erased,
-            ty::ReError(reported) => self.mk_re_error(reported),
+            GenericParamDefKind::Type { .. } => Ty::new_param(self, param.index, param.name).into(),
+            GenericParamDefKind::Const { .. } => ty::Const::new_param(
+                self,
+                ParamConst { index: param.index, name: param.name },
+                self.type_of(param.def_id)
+                    .no_bound_vars()
+                    .expect("const parameter types cannot be generic"),
+            )
+            .into(),
         }
     }
 
@@ -2146,11 +1733,11 @@ impl<'tcx> TyCtxt<'tcx> {
         self.intern_poly_existential_predicates(eps)
     }
 
-    pub fn mk_predicates(self, preds: &[Predicate<'tcx>]) -> &'tcx List<Predicate<'tcx>> {
+    pub fn mk_clauses(self, clauses: &[Clause<'tcx>]) -> &'tcx List<Clause<'tcx>> {
         // FIXME consider asking the input slice to be sorted to avoid
         // re-interning permutations, in which case that would be asserted
         // here.
-        self.intern_predicates(preds)
+        self.intern_clauses(clauses)
     }
 
     pub fn mk_const_list_from_iter<I, T>(self, iter: I) -> T::Output
@@ -2196,12 +1783,12 @@ impl<'tcx> TyCtxt<'tcx> {
         T::collect_and_apply(iter, |xs| self.mk_poly_existential_predicates(xs))
     }
 
-    pub fn mk_predicates_from_iter<I, T>(self, iter: I) -> T::Output
+    pub fn mk_clauses_from_iter<I, T>(self, iter: I) -> T::Output
     where
         I: Iterator<Item = T>,
-        T: CollectAndApply<Predicate<'tcx>, &'tcx List<Predicate<'tcx>>>,
+        T: CollectAndApply<Clause<'tcx>, &'tcx List<Clause<'tcx>>>,
     {
-        T::collect_and_apply(iter, |xs| self.mk_predicates(xs))
+        T::collect_and_apply(iter, |xs| self.mk_clauses(xs))
     }
 
     pub fn mk_type_list_from_iter<I, T>(self, iter: I) -> T::Output
@@ -2403,10 +1990,18 @@ impl<'tcx> TyCtxt<'tcx> {
         self.opt_local_def_id_to_hir_id(local_def_id).unwrap()
     }
 
-    pub fn trait_solver_next(self) -> bool {
+    pub fn next_trait_solver_globally(self) -> bool {
         self.sess.opts.unstable_opts.trait_solver == rustc_session::config::TraitSolver::Next
     }
 
+    pub fn next_trait_solver_in_coherence(self) -> bool {
+        matches!(
+            self.sess.opts.unstable_opts.trait_solver,
+            rustc_session::config::TraitSolver::Next
+                | rustc_session::config::TraitSolver::NextCoherence
+        )
+    }
+
     pub fn lower_impl_trait_in_trait_to_assoc_ty(self) -> bool {
         self.sess.opts.unstable_opts.lower_impl_trait_in_trait_to_assoc_ty
     }
@@ -2433,21 +2028,6 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 }
 
-impl<'tcx> TyCtxtAt<'tcx> {
-    /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` to ensure it gets used.
-    #[track_caller]
-    pub fn ty_error_misc(self) -> Ty<'tcx> {
-        self.tcx.ty_error_with_message(self.span, "TyKind::Error constructed but no error reported")
-    }
-
-    /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` with the given `msg` to
-    /// ensure it gets used.
-    #[track_caller]
-    pub fn ty_error_with_message(self, msg: impl Into<DiagnosticMessage>) -> Ty<'tcx> {
-        self.tcx.ty_error_with_message(self.span, msg)
-    }
-}
-
 /// Parameter attributes that can only be determined by examining the body of a function instead
 /// of just its signature.
 ///
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index 6a29063b8..a0b17c374 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -1,5 +1,6 @@
 //! Diagnostics related methods for `Ty`.
 
+use std::borrow::Cow;
 use std::ops::ControlFlow;
 
 use crate::ty::{
@@ -13,8 +14,8 @@ use rustc_errors::{Applicability, Diagnostic, DiagnosticArgValue, IntoDiagnostic
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
-use rustc_hir::WherePredicate;
-use rustc_span::Span;
+use rustc_hir::{PredicateOrigin, WherePredicate};
+use rustc_span::{BytePos, Span};
 use rustc_type_ir::sty::TyKind::*;
 
 impl<'tcx> IntoDiagnosticArg for Ty<'tcx> {
@@ -155,10 +156,11 @@ enum SuggestChangingConstraintsMessage<'a> {
     RestrictBoundFurther,
     RestrictType { ty: &'a str },
     RestrictTypeFurther { ty: &'a str },
-    RemovingQSized,
+    RemoveMaybeUnsized,
+    ReplaceMaybeUnsizedWithSized,
 }
 
-fn suggest_removing_unsized_bound(
+fn suggest_changing_unsized_bound(
     generics: &hir::Generics<'_>,
     suggestions: &mut Vec<(Span, String, SuggestChangingConstraintsMessage<'_>)>,
     param: &hir::GenericParam<'_>,
@@ -182,12 +184,25 @@ fn suggest_removing_unsized_bound(
             if poly.trait_ref.trait_def_id() != def_id {
                 continue;
             }
-            let sp = generics.span_for_bound_removal(where_pos, pos);
-            suggestions.push((
-                sp,
-                String::new(),
-                SuggestChangingConstraintsMessage::RemovingQSized,
-            ));
+            if predicate.origin == PredicateOrigin::ImplTrait && predicate.bounds.len() == 1 {
+                // For `impl ?Sized` with no other bounds, suggest `impl Sized` instead.
+                let bound_span = bound.span();
+                if bound_span.can_be_used_for_suggestions() {
+                    let question_span = bound_span.with_hi(bound_span.lo() + BytePos(1));
+                    suggestions.push((
+                        question_span,
+                        String::new(),
+                        SuggestChangingConstraintsMessage::ReplaceMaybeUnsizedWithSized,
+                    ));
+                }
+            } else {
+                let sp = generics.span_for_bound_removal(where_pos, pos);
+                suggestions.push((
+                    sp,
+                    String::new(),
+                    SuggestChangingConstraintsMessage::RemoveMaybeUnsized,
+                ));
+            }
         }
     }
 }
@@ -236,15 +251,12 @@ pub fn suggest_constraining_type_params<'a>(
 
         {
             let mut sized_constraints =
-                constraints.drain_filter(|(_, def_id)| *def_id == tcx.lang_items().sized_trait());
-            if let Some((constraint, def_id)) = sized_constraints.next() {
+                constraints.extract_if(|(_, def_id)| *def_id == tcx.lang_items().sized_trait());
+            if let Some((_, def_id)) = sized_constraints.next() {
                 applicability = Applicability::MaybeIncorrect;
 
-                err.span_label(
-                    param.span,
-                    format!("this type parameter needs to be `{}`", constraint),
-                );
-                suggest_removing_unsized_bound(generics, &mut suggestions, param, def_id);
+                err.span_label(param.span, "this type parameter needs to be `Sized`");
+                suggest_changing_unsized_bound(generics, &mut suggestions, param, def_id);
             }
         }
 
@@ -384,22 +396,21 @@ pub fn suggest_constraining_type_params<'a>(
 
     if suggestions.len() == 1 {
         let (span, suggestion, msg) = suggestions.pop().unwrap();
-
-        let s;
         let msg = match msg {
             SuggestChangingConstraintsMessage::RestrictBoundFurther => {
-                "consider further restricting this bound"
+                Cow::from("consider further restricting this bound")
             }
             SuggestChangingConstraintsMessage::RestrictType { ty } => {
-                s = format!("consider restricting type parameter `{}`", ty);
-                &s
+                Cow::from(format!("consider restricting type parameter `{}`", ty))
             }
             SuggestChangingConstraintsMessage::RestrictTypeFurther { ty } => {
-                s = format!("consider further restricting type parameter `{}`", ty);
-                &s
+                Cow::from(format!("consider further restricting type parameter `{}`", ty))
+            }
+            SuggestChangingConstraintsMessage::RemoveMaybeUnsized => {
+                Cow::from("consider removing the `?Sized` bound to make the type parameter `Sized`")
             }
-            SuggestChangingConstraintsMessage::RemovingQSized => {
-                "consider removing the `?Sized` bound to make the type parameter `Sized`"
+            SuggestChangingConstraintsMessage::ReplaceMaybeUnsizedWithSized => {
+                Cow::from("consider replacing `?Sized` with `Sized`")
             }
         };
 
@@ -548,7 +559,7 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for MakeSuggestableFolder<'tcx> {
             Infer(InferTy::TyVar(_)) if self.infer_suggestable => t,
 
             FnDef(def_id, substs) => {
-                self.tcx.mk_fn_ptr(self.tcx.fn_sig(def_id).subst(self.tcx, substs))
+                Ty::new_fn_ptr(self.tcx, self.tcx.fn_sig(def_id).subst(self.tcx, substs))
             }
 
             // FIXME(compiler-errors): We could replace these with infer, I guess.
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 49ab9b79e..c794c3fad 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -45,7 +45,6 @@ pub enum TypeError<'tcx> {
 
     RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>),
     RegionsInsufficientlyPolymorphic(BoundRegionKind, Region<'tcx>),
-    RegionsOverlyPolymorphic(BoundRegionKind, Region<'tcx>),
     RegionsPlaceholderMismatch,
 
     Sorts(ExpectedFound<Ty<'tcx>>),
@@ -74,7 +73,6 @@ impl TypeError<'_> {
         match self {
             TypeError::RegionsDoesNotOutlive(_, _)
             | TypeError::RegionsInsufficientlyPolymorphic(_, _)
-            | TypeError::RegionsOverlyPolymorphic(_, _)
             | TypeError::RegionsPlaceholderMismatch => true,
             _ => false,
         }
@@ -98,11 +96,6 @@ impl<'tcx> TypeError<'tcx> {
             }
         }
 
-        let br_string = |br: ty::BoundRegionKind| match br {
-            ty::BrNamed(_, name) => format!(" {}", name),
-            _ => String::new(),
-        };
-
         match self {
             CyclicTy(_) => "cyclic type of infinite size".into(),
             CyclicConst(_) => "encountered a self-referencing constant".into(),
@@ -144,11 +137,6 @@ impl<'tcx> TypeError<'tcx> {
             RegionsInsufficientlyPolymorphic(..) => {
                 "one type is more general than the other".into()
             }
-            RegionsOverlyPolymorphic(br, _) => format!(
-                "expected concrete lifetime, found bound lifetime parameter{}",
-                br_string(br)
-            )
-            .into(),
             RegionsPlaceholderMismatch => "one type is more general than the other".into(),
             ArgumentSorts(values, _) | Sorts(values) => {
                 let expected = values.expected.sort_string(tcx);
@@ -228,7 +216,6 @@ impl<'tcx> TypeError<'tcx> {
             | FieldMisMatch(..)
             | RegionsDoesNotOutlive(..)
             | RegionsInsufficientlyPolymorphic(..)
-            | RegionsOverlyPolymorphic(..)
             | RegionsPlaceholderMismatch
             | Traits(_)
             | ProjectionMismatched(_)
@@ -313,6 +300,7 @@ impl<'tcx> Ty<'tcx> {
             ty::Placeholder(..) => "higher-ranked type".into(),
             ty::Bound(..) => "bound type variable".into(),
             ty::Alias(ty::Projection | ty::Inherent, _) => "associated type".into(),
+            ty::Alias(ty::Weak, _) => "type alias".into(),
             ty::Param(_) => "type parameter".into(),
             ty::Alias(ty::Opaque, ..) => "opaque type".into(),
         }
diff --git a/compiler/rustc_middle/src/ty/flags.rs b/compiler/rustc_middle/src/ty/flags.rs
index d64875a9f..ff3917947 100644
--- a/compiler/rustc_middle/src/ty/flags.rs
+++ b/compiler/rustc_middle/src/ty/flags.rs
@@ -178,7 +178,7 @@ impl FlagComputation {
 
             &ty::Alias(kind, data) => {
                 self.add_flags(match kind {
-                    ty::Projection => TypeFlags::HAS_TY_PROJECTION,
+                    ty::Weak | ty::Projection => TypeFlags::HAS_TY_PROJECTION,
                     ty::Inherent => TypeFlags::HAS_TY_INHERENT,
                     ty::Opaque => TypeFlags::HAS_TY_OPAQUE,
                 });
@@ -237,21 +237,24 @@ impl FlagComputation {
 
     fn add_predicate_atom(&mut self, atom: ty::PredicateKind<'_>) {
         match atom {
-            ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred)) => {
+            ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_pred)) => {
                 self.add_substs(trait_pred.trait_ref.substs);
             }
-            ty::PredicateKind::Clause(ty::Clause::RegionOutlives(ty::OutlivesPredicate(a, b))) => {
+            ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(
+                a,
+                b,
+            ))) => {
                 self.add_region(a);
                 self.add_region(b);
             }
-            ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate(
+            ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(
                 ty,
                 region,
             ))) => {
                 self.add_ty(ty);
                 self.add_region(region);
             }
-            ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(ct, ty)) => {
+            ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
                 self.add_const(ct);
                 self.add_ty(ty);
             }
@@ -263,30 +266,27 @@ impl FlagComputation {
                 self.add_ty(a);
                 self.add_ty(b);
             }
-            ty::PredicateKind::Clause(ty::Clause::Projection(ty::ProjectionPredicate {
+            ty::PredicateKind::Clause(ty::ClauseKind::Projection(ty::ProjectionPredicate {
                 projection_ty,
                 term,
             })) => {
                 self.add_alias_ty(projection_ty);
                 self.add_term(term);
             }
-            ty::PredicateKind::WellFormed(arg) => {
+            ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) => {
                 self.add_substs(slice::from_ref(&arg));
             }
             ty::PredicateKind::ObjectSafe(_def_id) => {}
             ty::PredicateKind::ClosureKind(_def_id, substs, _kind) => {
                 self.add_substs(substs);
             }
-            ty::PredicateKind::ConstEvaluatable(uv) => {
+            ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(uv)) => {
                 self.add_const(uv);
             }
             ty::PredicateKind::ConstEquate(expected, found) => {
                 self.add_const(expected);
                 self.add_const(found);
             }
-            ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
-                self.add_ty(ty);
-            }
             ty::PredicateKind::Ambiguous => {}
             ty::PredicateKind::AliasRelate(t1, t2, _) => {
                 self.add_term(t1);
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 25890eb15..77cf6bee7 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -213,7 +213,7 @@ where
                     // debruijn index. Then we adjust it to the
                     // correct depth.
                     assert_eq!(debruijn1, ty::INNERMOST);
-                    self.tcx.mk_re_late_bound(debruijn, br)
+                    ty::Region::new_late_bound(self.tcx, debruijn, br)
                 } else {
                     region
                 }
@@ -328,7 +328,7 @@ impl<'tcx> TyCtxt<'tcx> {
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
         self.replace_late_bound_regions_uncached(value, |br| {
-            self.mk_re_free(all_outlive_scope, br.kind)
+            ty::Region::new_free(self, all_outlive_scope, br.kind)
         })
     }
 
@@ -341,16 +341,21 @@ impl<'tcx> TyCtxt<'tcx> {
             value,
             FnMutDelegate {
                 regions: &mut |r: ty::BoundRegion| {
-                    self.mk_re_late_bound(
+                    ty::Region::new_late_bound(
+                        self,
                         ty::INNERMOST,
                         ty::BoundRegion { var: shift_bv(r.var), kind: r.kind },
                     )
                 },
                 types: &mut |t: ty::BoundTy| {
-                    self.mk_bound(ty::INNERMOST, ty::BoundTy { var: shift_bv(t.var), kind: t.kind })
+                    Ty::new_bound(
+                        self,
+                        ty::INNERMOST,
+                        ty::BoundTy { var: shift_bv(t.var), kind: t.kind },
+                    )
                 },
                 consts: &mut |c, ty: Ty<'tcx>| {
-                    self.mk_const(ty::ConstKind::Bound(ty::INNERMOST, shift_bv(c)), ty)
+                    ty::Const::new_bound(self, ty::INNERMOST, shift_bv(c), ty)
                 },
             },
         )
@@ -383,7 +388,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     .or_insert_with(|| ty::BoundVariableKind::Region(ty::BrAnon(None)))
                     .expect_region();
                 let br = ty::BoundRegion { var, kind };
-                self.tcx.mk_re_late_bound(ty::INNERMOST, br)
+                ty::Region::new_late_bound(self.tcx, ty::INNERMOST, br)
             }
             fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> {
                 let entry = self.map.entry(bt.var);
@@ -392,14 +397,14 @@ impl<'tcx> TyCtxt<'tcx> {
                 let kind = entry
                     .or_insert_with(|| ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon))
                     .expect_ty();
-                self.tcx.mk_bound(ty::INNERMOST, BoundTy { var, kind })
+                Ty::new_bound(self.tcx, ty::INNERMOST, BoundTy { var, kind })
             }
             fn replace_const(&mut self, bv: ty::BoundVar, ty: Ty<'tcx>) -> ty::Const<'tcx> {
                 let entry = self.map.entry(bv);
                 let index = entry.index();
                 let var = ty::BoundVar::from_usize(index);
                 let () = entry.or_insert_with(|| ty::BoundVariableKind::Const).expect_const();
-                self.tcx.mk_const(ty::ConstKind::Bound(ty::INNERMOST, var), ty)
+                ty::Const::new_bound(self.tcx, ty::INNERMOST, var, ty)
             }
         }
 
@@ -451,7 +456,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Shifter<'tcx> {
         match *r {
             ty::ReLateBound(debruijn, br) if debruijn >= self.current_index => {
                 let debruijn = debruijn.shifted_in(self.amount);
-                self.tcx.mk_re_late_bound(debruijn, br)
+                ty::Region::new_late_bound(self.tcx, debruijn, br)
             }
             _ => r,
         }
@@ -461,7 +466,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Shifter<'tcx> {
         match *ty.kind() {
             ty::Bound(debruijn, bound_ty) if debruijn >= self.current_index => {
                 let debruijn = debruijn.shifted_in(self.amount);
-                self.tcx.mk_bound(debruijn, bound_ty)
+                Ty::new_bound(self.tcx, debruijn, bound_ty)
             }
 
             _ if ty.has_vars_bound_at_or_above(self.current_index) => ty.super_fold_with(self),
@@ -474,7 +479,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Shifter<'tcx> {
             && debruijn >= self.current_index
         {
             let debruijn = debruijn.shifted_in(self.amount);
-            self.tcx.mk_const(ty::ConstKind::Bound(debruijn, bound_ct), ct.ty())
+            ty::Const::new_bound(self.tcx, debruijn, bound_ct, ct.ty())
         } else {
             ct.super_fold_with(self)
         }
@@ -492,7 +497,7 @@ pub fn shift_region<'tcx>(
 ) -> ty::Region<'tcx> {
     match *region {
         ty::ReLateBound(debruijn, br) if amount > 0 => {
-            tcx.mk_re_late_bound(debruijn.shifted_in(amount), br)
+            ty::Region::new_late_bound(tcx, debruijn.shifted_in(amount), br)
         }
         _ => region,
     }
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index b0ffe7829..6c7125c4c 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -6,7 +6,7 @@ use rustc_hir::def_id::DefId;
 use rustc_span::symbol::{kw, Symbol};
 use rustc_span::Span;
 
-use super::{EarlyBoundRegion, InstantiatedPredicates, ParamConst, ParamTy, Predicate, TyCtxt};
+use super::{Clause, EarlyBoundRegion, InstantiatedPredicates, ParamConst, ParamTy, Ty, TyCtxt};
 
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub enum GenericParamDefKind {
@@ -100,11 +100,13 @@ impl GenericParamDef {
         preceding_substs: &[ty::GenericArg<'tcx>],
     ) -> ty::GenericArg<'tcx> {
         match &self.kind {
-            ty::GenericParamDefKind::Lifetime => tcx.mk_re_error_misc().into(),
-            ty::GenericParamDefKind::Type { .. } => tcx.ty_error_misc().into(),
-            ty::GenericParamDefKind::Const { .. } => {
-                tcx.const_error_misc(tcx.type_of(self.def_id).subst(tcx, preceding_substs)).into()
-            }
+            ty::GenericParamDefKind::Lifetime => ty::Region::new_error_misc(tcx).into(),
+            ty::GenericParamDefKind::Type { .. } => Ty::new_misc_error(tcx).into(),
+            ty::GenericParamDefKind::Const { .. } => ty::Const::new_misc_error(
+                tcx,
+                tcx.type_of(self.def_id).subst(tcx, preceding_substs),
+            )
+            .into(),
         }
     }
 }
@@ -133,6 +135,9 @@ pub struct Generics {
 
     pub has_self: bool,
     pub has_late_bound_regions: Option<Span>,
+
+    // The index of the host effect when substituted. (i.e. might be index to parent substs)
+    pub host_effect_index: Option<usize>,
 }
 
 impl<'tcx> Generics {
@@ -323,7 +328,7 @@ impl<'tcx> Generics {
 #[derive(Copy, Clone, Default, Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct GenericPredicates<'tcx> {
     pub parent: Option<DefId>,
-    pub predicates: &'tcx [(Predicate<'tcx>, Span)],
+    pub predicates: &'tcx [(Clause<'tcx>, Span)],
 }
 
 impl<'tcx> GenericPredicates<'tcx> {
@@ -341,9 +346,8 @@ impl<'tcx> GenericPredicates<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         substs: SubstsRef<'tcx>,
-    ) -> impl Iterator<Item = (Predicate<'tcx>, Span)> + DoubleEndedIterator + ExactSizeIterator
-    {
-        EarlyBinder(self.predicates).subst_iter_copied(tcx, substs)
+    ) -> impl Iterator<Item = (Clause<'tcx>, Span)> + DoubleEndedIterator + ExactSizeIterator {
+        EarlyBinder::bind(self.predicates).subst_iter_copied(tcx, substs)
     }
 
     #[instrument(level = "debug", skip(self, tcx))]
@@ -358,7 +362,7 @@ impl<'tcx> GenericPredicates<'tcx> {
         }
         instantiated
             .predicates
-            .extend(self.predicates.iter().map(|(p, _)| EarlyBinder(*p).subst(tcx, substs)));
+            .extend(self.predicates.iter().map(|(p, _)| EarlyBinder::bind(*p).subst(tcx, substs)));
         instantiated.spans.extend(self.predicates.iter().map(|(_, sp)| *sp));
     }
 
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
index ac42d6e05..295cb1464 100644
--- a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
+++ b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
@@ -62,7 +62,18 @@ impl<'tcx> InhabitedPredicate<'tcx> {
                 Some(1..) => Ok(false),
             },
             Self::NotInModule(id) => in_module(id).map(|in_mod| !in_mod),
-            Self::GenericType(_) => Ok(true),
+            // `t` may be a projection, for which `inhabited_predicate` returns a `GenericType`. As
+            // we have a param_env available, we can do better.
+            Self::GenericType(t) => {
+                let normalized_pred = tcx
+                    .try_normalize_erasing_regions(param_env, t)
+                    .map_or(self, |t| t.inhabited_predicate(tcx));
+                match normalized_pred {
+                    // We don't have more information than we started with, so consider inhabited.
+                    Self::GenericType(_) => Ok(true),
+                    pred => pred.apply_inner(tcx, param_env, in_module),
+                }
+            }
             Self::And([a, b]) => try_and(a, b, |x| x.apply_inner(tcx, param_env, in_module)),
             Self::Or([a, b]) => try_or(a, b, |x| x.apply_inner(tcx, param_env, in_module)),
         }
@@ -158,8 +169,8 @@ impl<'tcx> InhabitedPredicate<'tcx> {
     fn subst_opt(self, tcx: TyCtxt<'tcx>, substs: ty::SubstsRef<'tcx>) -> Option<Self> {
         match self {
             Self::ConstIsZero(c) => {
-                let c = ty::EarlyBinder(c).subst(tcx, substs);
-                let pred = match c.kind().try_to_target_usize(tcx) {
+                let c = ty::EarlyBinder::bind(c).subst(tcx, substs);
+                let pred = match c.try_to_target_usize(tcx) {
                     Some(0) => Self::True,
                     Some(1..) => Self::False,
                     None => Self::ConstIsZero(c),
@@ -167,7 +178,7 @@ impl<'tcx> InhabitedPredicate<'tcx> {
                 Some(pred)
             }
             Self::GenericType(t) => {
-                Some(ty::EarlyBinder(t).subst(tcx, substs).inhabited_predicate(tcx))
+                Some(ty::EarlyBinder::bind(t).subst(tcx, substs).inhabited_predicate(tcx))
             }
             Self::And(&[a, b]) => match a.subst_opt(tcx, substs) {
                 None => b.subst_opt(tcx, substs).map(|b| a.and(tcx, b)),
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/mod.rs b/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
index 422350284..b92d84152 100644
--- a/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
+++ b/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
@@ -197,7 +197,7 @@ fn inhabited_predicate_type<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> InhabitedP
 
         // If we can evaluate the array length before having a `ParamEnv`, then
         // we can simplify the predicate. This is an optimization.
-        Array(ty, len) => match len.kind().try_to_target_usize(tcx) {
+        Array(ty, len) => match len.try_to_target_usize(tcx) {
             Some(0) => InhabitedPredicate::True,
             Some(1..) => ty.inhabited_predicate(tcx),
             None => ty.inhabited_predicate(tcx).or(tcx, InhabitedPredicate::ConstIsZero(len)),
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index e641d1ef1..ae57e954f 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -410,8 +410,8 @@ impl<'tcx> Instance<'tcx> {
     ) -> Instance<'tcx> {
         match ty::Instance::resolve(tcx, param_env, def_id, substs) {
             Ok(Some(instance)) => instance,
-            _ => bug!(
-                "failed to resolve instance for {}",
+            instance => bug!(
+                "failed to resolve instance for {}: {instance:#?}",
                 tcx.def_path_str_with_substs(def_id, substs)
             ),
         }
@@ -552,7 +552,7 @@ impl<'tcx> Instance<'tcx> {
             tcx.codegen_fn_attrs(closure_did).flags.contains(CodegenFnAttrFlags::TRACK_CALLER);
         let def = ty::InstanceDef::ClosureOnceShim { call_once, track_caller };
 
-        let self_ty = tcx.mk_closure(closure_did, substs);
+        let self_ty = Ty::new_closure(tcx, closure_did, substs);
 
         let sig = substs.as_closure().sig();
         let sig =
@@ -586,7 +586,7 @@ impl<'tcx> Instance<'tcx> {
         if let Some(substs) = self.substs_for_mir_body() {
             v.subst(tcx, substs)
         } else {
-            v.skip_binder()
+            v.subst_identity()
         }
     }
 
@@ -680,7 +680,7 @@ fn polymorphize<'tcx>(
                     if substs == polymorphized_substs {
                         ty
                     } else {
-                        self.tcx.mk_closure(def_id, polymorphized_substs)
+                        Ty::new_closure(self.tcx, def_id, polymorphized_substs)
                     }
                 }
                 ty::Generator(def_id, substs, movability) => {
@@ -689,7 +689,7 @@ fn polymorphize<'tcx>(
                     if substs == polymorphized_substs {
                         ty
                     } else {
-                        self.tcx.mk_generator(def_id, polymorphized_substs, movability)
+                        Ty::new_generator(self.tcx, def_id, polymorphized_substs, movability)
                     }
                 }
                 _ => ty.super_fold_with(self),
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index b5a743cfe..d95b05ef7 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -1,8 +1,9 @@
-use crate::fluent_generated as fluent;
+use crate::error::UnsupportedFnAbi;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::query::TyCtxtAt;
 use crate::ty::normalize_erasing_regions::NormalizationError;
-use crate::ty::{self, ReprOptions, Ty, TyCtxt, TypeVisitableExt};
+use crate::ty::{self, ConstKind, ReprOptions, Ty, TyCtxt, TypeVisitableExt};
+use rustc_error_messages::DiagnosticMessage;
 use rustc_errors::{DiagnosticBuilder, Handler, IntoDiagnostic};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
@@ -14,7 +15,7 @@ use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::*;
 use rustc_target::spec::{abi::Abi as SpecAbi, HasTargetSpec, PanicStrategy, Target};
 
-use std::cmp::{self};
+use std::cmp;
 use std::fmt;
 use std::num::NonZeroUsize;
 use std::ops::Bound;
@@ -132,7 +133,7 @@ impl PrimitiveExt for Primitive {
             F32 => tcx.types.f32,
             F64 => tcx.types.f64,
             // FIXME(erikdesjardins): handle non-default addrspace ptr sizes
-            Pointer(_) => tcx.mk_mut_ptr(tcx.mk_unit()),
+            Pointer(_) => Ty::new_mut_ptr(tcx, Ty::new_unit(tcx)),
         }
     }
 
@@ -214,29 +215,29 @@ pub enum LayoutError<'tcx> {
     Cycle,
 }
 
-impl IntoDiagnostic<'_, !> for LayoutError<'_> {
-    fn into_diagnostic(self, handler: &Handler) -> DiagnosticBuilder<'_, !> {
-        let mut diag = handler.struct_fatal("");
+impl<'tcx> LayoutError<'tcx> {
+    pub fn diagnostic_message(&self) -> DiagnosticMessage {
+        use crate::fluent_generated::*;
+        use LayoutError::*;
+        match self {
+            Unknown(_) => middle_unknown_layout,
+            SizeOverflow(_) => middle_values_too_big,
+            NormalizationFailure(_, _) => middle_cannot_be_normalized,
+            Cycle => middle_cycle,
+        }
+    }
 
+    pub fn into_diagnostic(self) -> crate::error::LayoutError<'tcx> {
+        use crate::error::LayoutError as E;
+        use LayoutError::*;
         match self {
-            LayoutError::Unknown(ty) => {
-                diag.set_arg("ty", ty);
-                diag.set_primary_message(fluent::middle_unknown_layout);
-            }
-            LayoutError::SizeOverflow(ty) => {
-                diag.set_arg("ty", ty);
-                diag.set_primary_message(fluent::middle_values_too_big);
-            }
-            LayoutError::NormalizationFailure(ty, e) => {
-                diag.set_arg("ty", ty);
-                diag.set_arg("failure_ty", e.get_type_for_failure());
-                diag.set_primary_message(fluent::middle_cannot_be_normalized);
-            }
-            LayoutError::Cycle => {
-                diag.set_primary_message(fluent::middle_cycle);
+            Unknown(ty) => E::Unknown { ty },
+            SizeOverflow(ty) => E::Overflow { ty },
+            NormalizationFailure(ty, e) => {
+                E::NormalizationFailure { ty, failure_ty: e.get_type_for_failure() }
             }
+            Cycle => E::Cycle,
         }
-        diag
     }
 }
 
@@ -309,7 +310,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
         ty: Ty<'tcx>,
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-    ) -> Result<SizeSkeleton<'tcx>, LayoutError<'tcx>> {
+    ) -> Result<SizeSkeleton<'tcx>, &'tcx LayoutError<'tcx>> {
         debug_assert!(!ty.has_non_region_infer());
 
         // First try computing a static layout.
@@ -317,7 +318,13 @@ impl<'tcx> SizeSkeleton<'tcx> {
             Ok(layout) => {
                 return Ok(SizeSkeleton::Known(layout.size));
             }
-            Err(err) => err,
+            Err(err @ LayoutError::Unknown(_)) => err,
+            // We can't extract SizeSkeleton info from other layout errors
+            Err(
+                e @ LayoutError::Cycle
+                | e @ LayoutError::SizeOverflow(_)
+                | e @ LayoutError::NormalizationFailure(..),
+            ) => return Err(e),
         };
 
         match *ty.kind() {
@@ -330,11 +337,8 @@ impl<'tcx> SizeSkeleton<'tcx> {
                         Ok(SizeSkeleton::Pointer { non_zero, tail: tcx.erase_regions(tail) })
                     }
                     _ => bug!(
-                        "SizeSkeleton::compute({}): layout errored ({}), yet \
-                              tail `{}` is not a type parameter or a projection",
-                        ty,
-                        err,
-                        tail
+                        "SizeSkeleton::compute({ty}): layout errored ({err:?}), yet \
+                              tail `{tail}` is not a type parameter or a projection",
                     ),
                 }
             }
@@ -349,13 +353,13 @@ impl<'tcx> SizeSkeleton<'tcx> {
                             let size = s
                                 .bytes()
                                 .checked_mul(c)
-                                .ok_or_else(|| LayoutError::SizeOverflow(ty))?;
+                                .ok_or_else(|| &*tcx.arena.alloc(LayoutError::SizeOverflow(ty)))?;
                             return Ok(SizeSkeleton::Known(Size::from_bytes(size)));
                         }
                         let len = tcx.expand_abstract_consts(len);
                         let prev = ty::Const::from_target_usize(tcx, s.bytes());
                         let Some(gen_size) = mul_sorted_consts(tcx, param_env, len, prev) else {
-                            return Err(LayoutError::SizeOverflow(ty));
+                            return Err(tcx.arena.alloc(LayoutError::SizeOverflow(ty)));
                         };
                         Ok(SizeSkeleton::Generic(gen_size))
                     }
@@ -363,7 +367,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
                     SizeSkeleton::Generic(g) => {
                         let len = tcx.expand_abstract_consts(len);
                         let Some(gen_size) = mul_sorted_consts(tcx, param_env, len, g) else {
-                            return Err(LayoutError::SizeOverflow(ty));
+                            return Err(tcx.arena.alloc(LayoutError::SizeOverflow(ty)));
                         };
                         Ok(SizeSkeleton::Generic(gen_size))
                     }
@@ -476,13 +480,11 @@ fn mul_sorted_consts<'tcx>(
     b: ty::Const<'tcx>,
 ) -> Option<ty::Const<'tcx>> {
     use crate::mir::BinOp::Mul;
-    use ty::ConstKind::Expr;
-    use ty::Expr::Binop;
 
     let mut work = vec![a, b];
     let mut done = vec![];
     while let Some(n) = work.pop() {
-        if let Expr(Binop(Mul, l, r)) = n.kind() {
+        if let ConstKind::Expr(ty::Expr::Binop(Mul, l, r)) = n.kind() {
             work.push(l);
             work.push(r)
         } else {
@@ -513,7 +515,7 @@ fn mul_sorted_consts<'tcx>(
     done.sort_unstable();
 
     // create a single tree from the buffer
-    done.into_iter().reduce(|acc, n| tcx.mk_const(Expr(Binop(Mul, n, acc)), n.ty()))
+    done.into_iter().reduce(|acc, n| ty::Const::new_expr(tcx, ty::Expr::Binop(Mul, n, acc), n.ty()))
 }
 
 pub trait HasTyCtxt<'tcx>: HasDataLayout {
@@ -668,7 +670,7 @@ pub trait LayoutOf<'tcx>: LayoutOfHelpers<'tcx> {
 
         MaybeResult::from(
             tcx.layout_of(self.param_env().and(ty))
-                .map_err(|err| self.handle_layout_err(err, span, ty)),
+                .map_err(|err| self.handle_layout_err(*err, span, ty)),
         )
     }
 }
@@ -676,16 +678,21 @@ pub trait LayoutOf<'tcx>: LayoutOfHelpers<'tcx> {
 impl<'tcx, C: LayoutOfHelpers<'tcx>> LayoutOf<'tcx> for C {}
 
 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxt<'tcx>> {
-    type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
+    type LayoutOfResult = Result<TyAndLayout<'tcx>, &'tcx LayoutError<'tcx>>;
 
     #[inline]
-    fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
-        err
+    fn handle_layout_err(
+        &self,
+        err: LayoutError<'tcx>,
+        _: Span,
+        _: Ty<'tcx>,
+    ) -> &'tcx LayoutError<'tcx> {
+        self.tcx.arena.alloc(err)
     }
 }
 
 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxtAt<'tcx>> {
-    type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
+    type LayoutOfResult = Result<TyAndLayout<'tcx>, &'tcx LayoutError<'tcx>>;
 
     #[inline]
     fn layout_tcx_at_span(&self) -> Span {
@@ -693,8 +700,13 @@ impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxtAt<'tcx>> {
     }
 
     #[inline]
-    fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
-        err
+    fn handle_layout_err(
+        &self,
+        err: LayoutError<'tcx>,
+        _: Span,
+        _: Ty<'tcx>,
+    ) -> &'tcx LayoutError<'tcx> {
+        self.tcx.arena.alloc(err)
     }
 }
 
@@ -798,11 +810,11 @@ where
                     // (which may have no non-DST form), and will work as long
                     // as the `Abi` or `FieldsShape` is checked by users.
                     if i == 0 {
-                        let nil = tcx.mk_unit();
+                        let nil = Ty::new_unit(tcx);
                         let unit_ptr_ty = if this.ty.is_unsafe_ptr() {
-                            tcx.mk_mut_ptr(nil)
+                            Ty::new_mut_ptr(tcx, nil)
                         } else {
-                            tcx.mk_mut_ref(tcx.lifetimes.re_static, nil)
+                            Ty::new_mut_ref(tcx, tcx.lifetimes.re_static, nil)
                         };
 
                         // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing
@@ -815,7 +827,11 @@ where
                     }
 
                     let mk_dyn_vtable = || {
-                        tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.usize, 3))
+                        Ty::new_imm_ref(
+                            tcx,
+                            tcx.lifetimes.re_static,
+                            Ty::new_array(tcx, tcx.types.usize, 3),
+                        )
                         /* FIXME: use actual fn pointers
                         Warning: naively computing the number of entries in the
                         vtable by counting the methods on the trait + methods on
@@ -824,9 +840,9 @@ where
                         Increase this counter if you tried to implement this but
                         failed to do it without duplicating a lot of code from
                         other places in the compiler: 2
-                        tcx.mk_tup(&[
-                            tcx.mk_array(tcx.types.usize, 3),
-                            tcx.mk_array(Option<fn()>),
+                        Ty::new_tup(tcx,&[
+                            Ty::new_array(tcx,tcx.types.usize, 3),
+                            Ty::new_array(tcx,Option<fn()>),
                         ])
                         */
                     };
@@ -838,7 +854,7 @@ where
                     {
                         let metadata = tcx.normalize_erasing_regions(
                             cx.param_env(),
-                            tcx.mk_projection(metadata_def_id, [pointee]),
+                            Ty::new_projection(tcx,metadata_def_id, [pointee]),
                         );
 
                         // Map `Metadata = DynMetadata<dyn Trait>` back to a vtable, since it
@@ -913,15 +929,14 @@ where
 
                 ty::Dynamic(_, _, ty::DynStar) => {
                     if i == 0 {
-                        TyMaybeWithLayout::Ty(tcx.mk_mut_ptr(tcx.types.unit))
+                        TyMaybeWithLayout::Ty(Ty::new_mut_ptr(tcx, tcx.types.unit))
                     } else if i == 1 {
                         // FIXME(dyn-star) same FIXME as above applies here too
-                        TyMaybeWithLayout::Ty(
-                            tcx.mk_imm_ref(
-                                tcx.lifetimes.re_static,
-                                tcx.mk_array(tcx.types.usize, 3),
-                            ),
-                        )
+                        TyMaybeWithLayout::Ty(Ty::new_imm_ref(
+                            tcx,
+                            tcx.lifetimes.re_static,
+                            Ty::new_array(tcx, tcx.types.usize, 3),
+                        ))
                     } else {
                         bug!("no field {i} on dyn*")
                     }
@@ -940,12 +955,8 @@ where
             TyMaybeWithLayout::Ty(field_ty) => {
                 cx.tcx().layout_of(cx.param_env().and(field_ty)).unwrap_or_else(|e| {
                     bug!(
-                        "failed to get layout for `{}`: {},\n\
-                         despite it being a field (#{}) of an existing layout: {:#?}",
-                        field_ty,
-                        e,
-                        i,
-                        this
+                        "failed to get layout for `{field_ty}`: {e:?},\n\
+                         despite it being a field (#{i}) of an existing layout: {this:#?}",
                     )
                 })
             }
@@ -970,10 +981,8 @@ where
                 })
             }
             ty::FnPtr(fn_sig) if offset.bytes() == 0 => {
-                tcx.layout_of(param_env.and(tcx.mk_fn_ptr(fn_sig))).ok().map(|layout| PointeeInfo {
-                    size: layout.size,
-                    align: layout.align.abi,
-                    safe: None,
+                tcx.layout_of(param_env.and(Ty::new_fn_ptr(tcx, fn_sig))).ok().map(|layout| {
+                    PointeeInfo { size: layout.size, align: layout.align.abi, safe: None }
                 })
             }
             ty::Ref(_, ty, mt) if offset.bytes() == 0 => {
@@ -1101,12 +1110,11 @@ where
 ///
 /// This takes two primary parameters:
 ///
-/// * `codegen_fn_attr_flags` - these are flags calculated as part of the
-///   codegen attrs for a defined function. For function pointers this set of
-///   flags is the empty set. This is only applicable for Rust-defined
-///   functions, and generally isn't needed except for small optimizations where
-///   we try to say a function which otherwise might look like it could unwind
-///   doesn't actually unwind (such as for intrinsics and such).
+/// * `fn_def_id` - the `DefId` of the function. If this is provided then we can
+///   determine more precisely if the function can unwind. If this is not provided
+///   then we will only infer whether the function can unwind or not based on the
+///   ABI of the function. For example, a function marked with `#[rustc_nounwind]`
+///   is known to not unwind even if it's using Rust ABI.
 ///
 /// * `abi` - this is the ABI that the function is defined with. This is the
 ///   primary factor for determining whether a function can unwind or not.
@@ -1138,11 +1146,6 @@ where
 ///   aborts the process.
 /// * This affects whether functions have the LLVM `nounwind` attribute, which
 ///   affects various optimizations and codegen.
-///
-/// FIXME: this is actually buggy with respect to Rust functions. Rust functions
-/// compiled with `-Cpanic=unwind` and referenced from another crate compiled
-/// with `-Cpanic=abort` will look like they can't unwind when in fact they
-/// might (from a foreign exception or similar).
 #[inline]
 #[tracing::instrument(level = "debug", skip(tcx))]
 pub fn fn_can_unwind(tcx: TyCtxt<'_>, fn_def_id: Option<DefId>, abi: SpecAbi) -> bool {
@@ -1250,33 +1253,18 @@ pub enum FnAbiError<'tcx> {
     AdjustForForeignAbi(call::AdjustForForeignAbiError),
 }
 
-impl<'tcx> From<LayoutError<'tcx>> for FnAbiError<'tcx> {
-    fn from(err: LayoutError<'tcx>) -> Self {
-        Self::Layout(err)
-    }
-}
-
-impl From<call::AdjustForForeignAbiError> for FnAbiError<'_> {
-    fn from(err: call::AdjustForForeignAbiError) -> Self {
-        Self::AdjustForForeignAbi(err)
-    }
-}
-
-impl<'tcx> fmt::Display for FnAbiError<'tcx> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+impl<'a, 'b> IntoDiagnostic<'a, !> for FnAbiError<'b> {
+    fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, !> {
         match self {
-            Self::Layout(err) => err.fmt(f),
-            Self::AdjustForForeignAbi(err) => err.fmt(f),
+            Self::Layout(e) => e.into_diagnostic().into_diagnostic(handler),
+            Self::AdjustForForeignAbi(call::AdjustForForeignAbiError::Unsupported {
+                arch,
+                abi,
+            }) => UnsupportedFnAbi { arch, abi: abi.name() }.into_diagnostic(handler),
         }
     }
 }
 
-impl IntoDiagnostic<'_, !> for FnAbiError<'_> {
-    fn into_diagnostic(self, handler: &Handler) -> DiagnosticBuilder<'_, !> {
-        handler.struct_fatal(self.to_string())
-    }
-}
-
 // FIXME(eddyb) maybe use something like this for an unified `fn_abi_of`, not
 // just for error handling.
 #[derive(Debug)]
@@ -1324,7 +1312,7 @@ pub trait FnAbiOf<'tcx>: FnAbiOfHelpers<'tcx> {
         let tcx = self.tcx().at(span);
 
         MaybeResult::from(tcx.fn_abi_of_fn_ptr(self.param_env().and((sig, extra_args))).map_err(
-            |err| self.handle_fn_abi_err(err, span, FnAbiRequest::OfFnPtr { sig, extra_args }),
+            |err| self.handle_fn_abi_err(*err, span, FnAbiRequest::OfFnPtr { sig, extra_args }),
         ))
     }
 
@@ -1351,7 +1339,11 @@ pub trait FnAbiOf<'tcx>: FnAbiOfHelpers<'tcx> {
                 // However, we don't do this early in order to avoid calling
                 // `def_span` unconditionally (which may have a perf penalty).
                 let span = if !span.is_dummy() { span } else { tcx.def_span(instance.def_id()) };
-                self.handle_fn_abi_err(err, span, FnAbiRequest::OfInstance { instance, extra_args })
+                self.handle_fn_abi_err(
+                    *err,
+                    span,
+                    FnAbiRequest::OfInstance { instance, extra_args },
+                )
             }),
         )
     }
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index a8d0dca37..aa8bfd317 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -53,7 +53,6 @@ use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{ExpnId, ExpnKind, Span};
 use rustc_target::abi::{Align, FieldIdx, Integer, IntegerType, VariantIdx};
 pub use rustc_target::abi::{ReprFlags, ReprOptions};
-use rustc_type_ir::WithCachedTypeInfo;
 pub use subst::*;
 pub use vtable::*;
 
@@ -67,6 +66,10 @@ use std::{fmt, str};
 
 pub use crate::ty::diagnostics::*;
 pub use rustc_type_ir::AliasKind::*;
+pub use rustc_type_ir::ConstKind::{
+    Bound as BoundCt, Error as ErrorCt, Expr as ExprCt, Infer as InferCt, Param as ParamCt,
+    Placeholder as PlaceholderCt, Unevaluated, Value,
+};
 pub use rustc_type_ir::DynKind::*;
 pub use rustc_type_ir::InferTy::*;
 pub use rustc_type_ir::RegionKind::*;
@@ -82,7 +85,7 @@ pub use self::closure::{
     CAPTURE_STRUCT_LOCAL,
 };
 pub use self::consts::{
-    Const, ConstData, ConstInt, ConstKind, Expr, InferConst, ScalarInt, UnevaluatedConst, ValTree,
+    Const, ConstData, ConstInt, Expr, InferConst, ScalarInt, UnevaluatedConst, ValTree,
 };
 pub use self::context::{
     tls, CtxtInterners, DeducedParamAttrs, FreeRegionInfo, GlobalCtxt, Lift, TyCtxt, TyCtxtFeed,
@@ -94,7 +97,7 @@ pub use self::rvalue_scopes::RvalueScopes;
 pub use self::sty::BoundRegionKind::*;
 pub use self::sty::{
     AliasTy, Article, Binder, BoundRegion, BoundRegionKind, BoundTy, BoundTyKind, BoundVar,
-    BoundVariableKind, CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstVid,
+    BoundVariableKind, CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstKind, ConstVid,
     EarlyBoundRegion, ExistentialPredicate, ExistentialProjection, ExistentialTraitRef, FnSig,
     FreeRegion, GenSig, GeneratorSubsts, GeneratorSubstsParts, InlineConstSubsts,
     InlineConstSubstsParts, ParamConst, ParamTy, PolyExistentialPredicate,
@@ -145,6 +148,7 @@ mod opaque_types;
 mod parameterized;
 mod rvalue_scopes;
 mod structural_impls;
+#[cfg_attr(not(bootstrap), allow(hidden_glob_reexports))]
 mod sty;
 mod typeck_results;
 
@@ -456,6 +460,11 @@ impl ty::EarlyBoundRegion {
     }
 }
 
+/// A statement that can be proven by a trait solver. This includes things that may
+/// show up in where clauses, such as trait predicates and projection predicates,
+/// and also things that are emitted as part of type checking such as `ObjectSafe`
+/// predicate which is emitted when a type is coerced to a trait object.
+///
 /// Use this rather than `PredicateKind`, whenever possible.
 #[derive(Clone, Copy, PartialEq, Eq, Hash, HashStable)]
 #[rustc_pass_by_value]
@@ -487,11 +496,11 @@ impl<'tcx> Predicate<'tcx> {
         let kind = self
             .kind()
             .map_bound(|kind| match kind {
-                PredicateKind::Clause(Clause::Trait(TraitPredicate {
+                PredicateKind::Clause(ClauseKind::Trait(TraitPredicate {
                     trait_ref,
                     constness,
                     polarity,
-                })) => Some(PredicateKind::Clause(Clause::Trait(TraitPredicate {
+                })) => Some(PredicateKind::Clause(ClauseKind::Trait(TraitPredicate {
                     trait_ref,
                     constness,
                     polarity: polarity.flip()?,
@@ -505,10 +514,10 @@ impl<'tcx> Predicate<'tcx> {
     }
 
     pub fn without_const(mut self, tcx: TyCtxt<'tcx>) -> Self {
-        if let PredicateKind::Clause(Clause::Trait(TraitPredicate { trait_ref, constness, polarity })) = self.kind().skip_binder()
+        if let PredicateKind::Clause(ClauseKind::Trait(TraitPredicate { trait_ref, constness, polarity })) = self.kind().skip_binder()
             && constness != BoundConstness::NotConst
         {
-            self = tcx.mk_predicate(self.kind().rebind(PredicateKind::Clause(Clause::Trait(TraitPredicate {
+            self = tcx.mk_predicate(self.kind().rebind(PredicateKind::Clause(ClauseKind::Trait(TraitPredicate {
                 trait_ref,
                 constness: BoundConstness::NotConst,
                 polarity,
@@ -520,10 +529,10 @@ impl<'tcx> Predicate<'tcx> {
     #[instrument(level = "debug", skip(tcx), ret)]
     pub fn is_coinductive(self, tcx: TyCtxt<'tcx>) -> bool {
         match self.kind().skip_binder() {
-            ty::PredicateKind::Clause(ty::Clause::Trait(data)) => {
+            ty::PredicateKind::Clause(ty::ClauseKind::Trait(data)) => {
                 tcx.trait_is_coinductive(data.def_id())
             }
-            ty::PredicateKind::WellFormed(_) => true,
+            ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_)) => true,
             _ => false,
         }
     }
@@ -536,21 +545,20 @@ impl<'tcx> Predicate<'tcx> {
     #[inline]
     pub fn allow_normalization(self) -> bool {
         match self.kind().skip_binder() {
-            PredicateKind::WellFormed(_) => false,
-            PredicateKind::Clause(Clause::Trait(_))
-            | PredicateKind::Clause(Clause::RegionOutlives(_))
-            | PredicateKind::Clause(Clause::TypeOutlives(_))
-            | PredicateKind::Clause(Clause::Projection(_))
-            | PredicateKind::Clause(Clause::ConstArgHasType(..))
+            PredicateKind::Clause(ClauseKind::WellFormed(_)) => false,
+            PredicateKind::Clause(ClauseKind::Trait(_))
+            | PredicateKind::Clause(ClauseKind::RegionOutlives(_))
+            | PredicateKind::Clause(ClauseKind::TypeOutlives(_))
+            | PredicateKind::Clause(ClauseKind::Projection(_))
+            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
             | PredicateKind::AliasRelate(..)
             | PredicateKind::ObjectSafe(_)
             | PredicateKind::ClosureKind(_, _, _)
             | PredicateKind::Subtype(_)
             | PredicateKind::Coerce(_)
-            | PredicateKind::ConstEvaluatable(_)
+            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(_))
             | PredicateKind::ConstEquate(_, _)
-            | PredicateKind::Ambiguous
-            | PredicateKind::TypeWellFormedFromEnv(_) => true,
+            | PredicateKind::Ambiguous => true,
         }
     }
 }
@@ -561,11 +569,77 @@ impl rustc_errors::IntoDiagnosticArg for Predicate<'_> {
     }
 }
 
+impl rustc_errors::IntoDiagnosticArg for Clause<'_> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+        rustc_errors::DiagnosticArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
+    }
+}
+
+/// A subset of predicates which can be assumed by the trait solver. They show up in
+/// an item's where clauses, hence the name `Clause`, and may either be user-written
+/// (such as traits) or may be inserted during lowering.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, HashStable)]
+#[rustc_pass_by_value]
+pub struct Clause<'tcx>(Interned<'tcx, WithCachedTypeInfo<ty::Binder<'tcx, PredicateKind<'tcx>>>>);
+
+impl<'tcx> Clause<'tcx> {
+    pub fn as_predicate(self) -> Predicate<'tcx> {
+        Predicate(self.0)
+    }
+
+    pub fn kind(self) -> Binder<'tcx, ClauseKind<'tcx>> {
+        self.0.internee.map_bound(|kind| match kind {
+            PredicateKind::Clause(clause) => clause,
+            _ => unreachable!(),
+        })
+    }
+
+    pub fn as_trait_clause(self) -> Option<Binder<'tcx, TraitPredicate<'tcx>>> {
+        let clause = self.kind();
+        if let ty::ClauseKind::Trait(trait_clause) = clause.skip_binder() {
+            Some(clause.rebind(trait_clause))
+        } else {
+            None
+        }
+    }
+
+    pub fn as_projection_clause(self) -> Option<Binder<'tcx, ProjectionPredicate<'tcx>>> {
+        let clause = self.kind();
+        if let ty::ClauseKind::Projection(projection_clause) = clause.skip_binder() {
+            Some(clause.rebind(projection_clause))
+        } else {
+            None
+        }
+    }
+
+    pub fn as_type_outlives_clause(self) -> Option<Binder<'tcx, TypeOutlivesPredicate<'tcx>>> {
+        let clause = self.kind();
+        if let ty::ClauseKind::TypeOutlives(o) = clause.skip_binder() {
+            Some(clause.rebind(o))
+        } else {
+            None
+        }
+    }
+
+    pub fn as_region_outlives_clause(self) -> Option<Binder<'tcx, RegionOutlivesPredicate<'tcx>>> {
+        let clause = self.kind();
+        if let ty::ClauseKind::RegionOutlives(o) = clause.skip_binder() {
+            Some(clause.rebind(o))
+        } else {
+            None
+        }
+    }
+
+    pub fn without_const(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        self.as_predicate().without_const(tcx).expect_clause()
+    }
+}
+
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 /// A clause is something that can appear in where bounds or be inferred
 /// by implied bounds.
-pub enum Clause<'tcx> {
+pub enum ClauseKind<'tcx> {
     /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
     /// the `Self` type of the trait reference and `A`, `B`, and `C`
     /// would be the type parameters.
@@ -584,16 +658,19 @@ pub enum Clause<'tcx> {
     /// Ensures that a const generic argument to a parameter `const N: u8`
     /// is of type `u8`.
     ConstArgHasType(Const<'tcx>, Ty<'tcx>),
+
+    /// No syntax: `T` well-formed.
+    WellFormed(GenericArg<'tcx>),
+
+    /// Constant initializer must evaluate successfully.
+    ConstEvaluatable(ty::Const<'tcx>),
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub enum PredicateKind<'tcx> {
     /// Prove a clause
-    Clause(Clause<'tcx>),
-
-    /// No syntax: `T` well-formed.
-    WellFormed(GenericArg<'tcx>),
+    Clause(ClauseKind<'tcx>),
 
     /// Trait must be object-safe.
     ObjectSafe(DefId),
@@ -620,22 +697,14 @@ pub enum PredicateKind<'tcx> {
     /// logic.
     Coerce(CoercePredicate<'tcx>),
 
-    /// Constant initializer must evaluate successfully.
-    ConstEvaluatable(ty::Const<'tcx>),
-
     /// Constants must be equal. The first component is the const that is expected.
     ConstEquate(Const<'tcx>, Const<'tcx>),
 
-    /// Represents a type found in the environment that we can use for implied bounds.
-    ///
-    /// Only used for Chalk.
-    TypeWellFormedFromEnv(Ty<'tcx>),
-
     /// A marker predicate that is always ambiguous.
     /// Used for coherence to mark opaque types as possibly equal to each other but ambiguous.
     Ambiguous,
 
-    /// Separate from `Clause::Projection` which is used for normalization in new solver.
+    /// Separate from `ClauseKind::Projection` which is used for normalization in new solver.
     /// This predicate requires two terms to be equal to eachother.
     ///
     /// Only used for new solver
@@ -672,7 +741,7 @@ pub struct CratePredicatesMap<'tcx> {
     pub predicates: FxHashMap<DefId, &'tcx [(Clause<'tcx>, Span)]>,
 }
 
-impl<'tcx> Predicate<'tcx> {
+impl<'tcx> Clause<'tcx> {
     /// Performs a substitution suitable for going from a
     /// poly-trait-ref to supertraits that must hold if that
     /// poly-trait-ref holds. This is slightly different from a normal
@@ -682,7 +751,7 @@ impl<'tcx> Predicate<'tcx> {
         self,
         tcx: TyCtxt<'tcx>,
         trait_ref: &ty::PolyTraitRef<'tcx>,
-    ) -> Predicate<'tcx> {
+    ) -> Clause<'tcx> {
         // The interaction between HRTB and supertraits is not entirely
         // obvious. Let me walk you (and myself) through an example.
         //
@@ -764,11 +833,17 @@ impl<'tcx> Predicate<'tcx> {
         let shifted_pred =
             tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
         // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
-        let new = EarlyBinder(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
+        let new = EarlyBinder::bind(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
         // 3) ['x] + ['b] -> ['x, 'b]
         let bound_vars =
             tcx.mk_bound_variable_kinds_from_iter(trait_bound_vars.iter().chain(pred_bound_vars));
-        tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
+
+        // FIXME: Is it really perf sensitive to use reuse_or_mk_predicate here?
+        tcx.reuse_or_mk_predicate(
+            self.as_predicate(),
+            ty::Binder::bind_with_vars(PredicateKind::Clause(new), bound_vars),
+        )
+        .expect_clause()
     }
 }
 
@@ -1189,13 +1264,41 @@ impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for Clause<'tcx> {
+impl<'tcx> ToPredicate<'tcx> for ClauseKind<'tcx> {
     #[inline(always)]
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         tcx.mk_predicate(ty::Binder::dummy(ty::PredicateKind::Clause(self)))
     }
 }
 
+impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, ClauseKind<'tcx>> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        tcx.mk_predicate(self.map_bound(ty::PredicateKind::Clause))
+    }
+}
+
+impl<'tcx> ToPredicate<'tcx> for Clause<'tcx> {
+    #[inline(always)]
+    fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        self.as_predicate()
+    }
+}
+
+impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for ClauseKind<'tcx> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        tcx.mk_predicate(Binder::dummy(ty::PredicateKind::Clause(self))).expect_clause()
+    }
+}
+
+impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for Binder<'tcx, ClauseKind<'tcx>> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        tcx.mk_predicate(self.map_bound(|clause| ty::PredicateKind::Clause(clause))).expect_clause()
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx> for TraitRef<'tcx> {
     #[inline(always)]
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
@@ -1203,6 +1306,29 @@ impl<'tcx> ToPredicate<'tcx> for TraitRef<'tcx> {
     }
 }
 
+impl<'tcx> ToPredicate<'tcx, TraitPredicate<'tcx>> for TraitRef<'tcx> {
+    #[inline(always)]
+    fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> TraitPredicate<'tcx> {
+        self.without_const()
+    }
+}
+
+impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for TraitRef<'tcx> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.to_predicate(tcx);
+        p.expect_clause()
+    }
+}
+
+impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for TraitPredicate<'tcx> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.to_predicate(tcx);
+        p.expect_clause()
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, TraitRef<'tcx>> {
     #[inline(always)]
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
@@ -1211,6 +1337,14 @@ impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, TraitRef<'tcx>> {
     }
 }
 
+impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let pred: PolyTraitPredicate<'tcx> = self.to_predicate(tcx);
+        pred.to_predicate(tcx)
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx, PolyTraitPredicate<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
     #[inline(always)]
     fn to_predicate(self, _: TyCtxt<'tcx>) -> PolyTraitPredicate<'tcx> {
@@ -1236,31 +1370,45 @@ impl<'tcx> ToPredicate<'tcx, PolyTraitPredicate<'tcx>> for TraitPredicate<'tcx>
 
 impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        self.map_bound(|p| PredicateKind::Clause(Clause::Trait(p))).to_predicate(tcx)
+        self.map_bound(|p| PredicateKind::Clause(ClauseKind::Trait(p))).to_predicate(tcx)
+    }
+}
+
+impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for PolyTraitPredicate<'tcx> {
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.to_predicate(tcx);
+        p.expect_clause()
     }
 }
 
 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        self.map_bound(|p| PredicateKind::Clause(Clause::RegionOutlives(p))).to_predicate(tcx)
+        self.map_bound(|p| PredicateKind::Clause(ClauseKind::RegionOutlives(p))).to_predicate(tcx)
     }
 }
 
 impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        self.map_bound(|p| PredicateKind::Clause(Clause::TypeOutlives(p))).to_predicate(tcx)
+        self.map_bound(|p| PredicateKind::Clause(ClauseKind::TypeOutlives(p))).to_predicate(tcx)
     }
 }
 
 impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        self.map_bound(|p| PredicateKind::Clause(Clause::Projection(p))).to_predicate(tcx)
+        self.map_bound(|p| PredicateKind::Clause(ClauseKind::Projection(p))).to_predicate(tcx)
+    }
+}
+
+impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for PolyProjectionPredicate<'tcx> {
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.to_predicate(tcx);
+        p.expect_clause()
     }
 }
 
 impl<'tcx> ToPredicate<'tcx> for TraitPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        PredicateKind::Clause(Clause::Trait(self)).to_predicate(tcx)
+        PredicateKind::Clause(ClauseKind::Trait(self)).to_predicate(tcx)
     }
 }
 
@@ -1268,63 +1416,76 @@ impl<'tcx> Predicate<'tcx> {
     pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> {
         let predicate = self.kind();
         match predicate.skip_binder() {
-            PredicateKind::Clause(Clause::Trait(t)) => Some(predicate.rebind(t)),
-            PredicateKind::Clause(Clause::Projection(..))
-            | PredicateKind::Clause(Clause::ConstArgHasType(..))
+            PredicateKind::Clause(ClauseKind::Trait(t)) => Some(predicate.rebind(t)),
+            PredicateKind::Clause(ClauseKind::Projection(..))
+            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
             | PredicateKind::AliasRelate(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
-            | PredicateKind::Clause(Clause::RegionOutlives(..))
-            | PredicateKind::WellFormed(..)
+            | PredicateKind::Clause(ClauseKind::RegionOutlives(..))
+            | PredicateKind::Clause(ClauseKind::WellFormed(..))
             | PredicateKind::ObjectSafe(..)
             | PredicateKind::ClosureKind(..)
-            | PredicateKind::Clause(Clause::TypeOutlives(..))
-            | PredicateKind::ConstEvaluatable(..)
+            | PredicateKind::Clause(ClauseKind::TypeOutlives(..))
+            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(..))
             | PredicateKind::ConstEquate(..)
-            | PredicateKind::Ambiguous
-            | PredicateKind::TypeWellFormedFromEnv(..) => None,
+            | PredicateKind::Ambiguous => None,
         }
     }
 
     pub fn to_opt_poly_projection_pred(self) -> Option<PolyProjectionPredicate<'tcx>> {
         let predicate = self.kind();
         match predicate.skip_binder() {
-            PredicateKind::Clause(Clause::Projection(t)) => Some(predicate.rebind(t)),
-            PredicateKind::Clause(Clause::Trait(..))
-            | PredicateKind::Clause(Clause::ConstArgHasType(..))
+            PredicateKind::Clause(ClauseKind::Projection(t)) => Some(predicate.rebind(t)),
+            PredicateKind::Clause(ClauseKind::Trait(..))
+            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
             | PredicateKind::AliasRelate(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
-            | PredicateKind::Clause(Clause::RegionOutlives(..))
-            | PredicateKind::WellFormed(..)
+            | PredicateKind::Clause(ClauseKind::RegionOutlives(..))
+            | PredicateKind::Clause(ClauseKind::WellFormed(..))
             | PredicateKind::ObjectSafe(..)
             | PredicateKind::ClosureKind(..)
-            | PredicateKind::Clause(Clause::TypeOutlives(..))
-            | PredicateKind::ConstEvaluatable(..)
+            | PredicateKind::Clause(ClauseKind::TypeOutlives(..))
+            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(..))
             | PredicateKind::ConstEquate(..)
-            | PredicateKind::Ambiguous
-            | PredicateKind::TypeWellFormedFromEnv(..) => None,
+            | PredicateKind::Ambiguous => None,
         }
     }
 
     pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
         let predicate = self.kind();
         match predicate.skip_binder() {
-            PredicateKind::Clause(Clause::TypeOutlives(data)) => Some(predicate.rebind(data)),
-            PredicateKind::Clause(Clause::Trait(..))
-            | PredicateKind::Clause(Clause::ConstArgHasType(..))
-            | PredicateKind::Clause(Clause::Projection(..))
+            PredicateKind::Clause(ClauseKind::TypeOutlives(data)) => Some(predicate.rebind(data)),
+            PredicateKind::Clause(ClauseKind::Trait(..))
+            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
+            | PredicateKind::Clause(ClauseKind::Projection(..))
             | PredicateKind::AliasRelate(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
-            | PredicateKind::Clause(Clause::RegionOutlives(..))
-            | PredicateKind::WellFormed(..)
+            | PredicateKind::Clause(ClauseKind::RegionOutlives(..))
+            | PredicateKind::Clause(ClauseKind::WellFormed(..))
             | PredicateKind::ObjectSafe(..)
             | PredicateKind::ClosureKind(..)
-            | PredicateKind::ConstEvaluatable(..)
+            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(..))
             | PredicateKind::ConstEquate(..)
-            | PredicateKind::Ambiguous
-            | PredicateKind::TypeWellFormedFromEnv(..) => None,
+            | PredicateKind::Ambiguous => None,
+        }
+    }
+
+    /// Matches a `PredicateKind::Clause` and turns it into a `Clause`, otherwise returns `None`.
+    pub fn as_clause(self) -> Option<Clause<'tcx>> {
+        match self.kind().skip_binder() {
+            PredicateKind::Clause(..) => Some(self.expect_clause()),
+            _ => None,
+        }
+    }
+
+    /// Assert that the predicate is a clause.
+    pub fn expect_clause(self) -> Clause<'tcx> {
+        match self.kind().skip_binder() {
+            PredicateKind::Clause(..) => Clause(self.0),
+            _ => bug!("{self} is not a clause"),
         }
     }
 }
@@ -1350,7 +1511,7 @@ impl<'tcx> Predicate<'tcx> {
 /// [usize:Bar<isize>]]`.
 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct InstantiatedPredicates<'tcx> {
-    pub predicates: Vec<Predicate<'tcx>>,
+    pub predicates: Vec<Clause<'tcx>>,
     pub spans: Vec<Span>,
 }
 
@@ -1369,9 +1530,9 @@ impl<'tcx> InstantiatedPredicates<'tcx> {
 }
 
 impl<'tcx> IntoIterator for InstantiatedPredicates<'tcx> {
-    type Item = (Predicate<'tcx>, Span);
+    type Item = (Clause<'tcx>, Span);
 
-    type IntoIter = std::iter::Zip<std::vec::IntoIter<Predicate<'tcx>>, std::vec::IntoIter<Span>>;
+    type IntoIter = std::iter::Zip<std::vec::IntoIter<Clause<'tcx>>, std::vec::IntoIter<Span>>;
 
     fn into_iter(self) -> Self::IntoIter {
         debug_assert_eq!(self.predicates.len(), self.spans.len());
@@ -1380,10 +1541,10 @@ impl<'tcx> IntoIterator for InstantiatedPredicates<'tcx> {
 }
 
 impl<'a, 'tcx> IntoIterator for &'a InstantiatedPredicates<'tcx> {
-    type Item = (Predicate<'tcx>, Span);
+    type Item = (Clause<'tcx>, Span);
 
     type IntoIter = std::iter::Zip<
-        std::iter::Copied<std::slice::Iter<'a, Predicate<'tcx>>>,
+        std::iter::Copied<std::slice::Iter<'a, Clause<'tcx>>>,
         std::iter::Copied<std::slice::Iter<'a, Span>>,
     >;
 
@@ -1496,7 +1657,7 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
 /// regions/types/consts within the same universe simply have an unknown relationship to one
 /// another.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
 #[derive(HashStable, TyEncodable, TyDecodable)]
 pub struct Placeholder<T> {
     pub universe: UniverseIndex,
@@ -1533,7 +1694,7 @@ pub struct ParamEnv<'tcx> {
     /// want `Reveal::All`.
     ///
     /// Note: This is packed, use the reveal() method to access it.
-    packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>,
+    packed: CopyTaggedPtr<&'tcx List<Clause<'tcx>>, ParamTag, true>,
 }
 
 #[derive(Copy, Clone)]
@@ -1599,7 +1760,7 @@ impl<'tcx> ParamEnv<'tcx> {
     }
 
     #[inline]
-    pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> {
+    pub fn caller_bounds(self) -> &'tcx List<Clause<'tcx>> {
         self.packed.pointer()
     }
 
@@ -1633,7 +1794,7 @@ impl<'tcx> ParamEnv<'tcx> {
     /// Construct a trait environment with the given set of predicates.
     #[inline]
     pub fn new(
-        caller_bounds: &'tcx List<Predicate<'tcx>>,
+        caller_bounds: &'tcx List<Clause<'tcx>>,
         reveal: Reveal,
         constness: hir::Constness,
     ) -> Self {
@@ -1874,6 +2035,22 @@ impl VariantDef {
 
         &self.fields[FieldIdx::from_u32(0)]
     }
+
+    /// Returns the last field in this variant, if present.
+    #[inline]
+    pub fn tail_opt(&self) -> Option<&FieldDef> {
+        self.fields.raw.last()
+    }
+
+    /// Returns the last field in this variant.
+    ///
+    /// # Panics
+    ///
+    /// Panics, if the variant has no fields.
+    #[inline]
+    pub fn tail(&self) -> &FieldDef {
+        self.tail_opt().expect("expected unsized ADT to have a tail field")
+    }
 }
 
 impl PartialEq for VariantDef {
diff --git a/compiler/rustc_middle/src/ty/opaque_types.rs b/compiler/rustc_middle/src/ty/opaque_types.rs
index 1b336b7bf..b10921eff 100644
--- a/compiler/rustc_middle/src/ty/opaque_types.rs
+++ b/compiler/rustc_middle/src/ty/opaque_types.rs
@@ -141,7 +141,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseMapper<'tcx> {
                     )
                     .emit();
 
-                self.interner().mk_re_error(e)
+                ty::Region::new_error(self.interner(), e)
             }
         }
     }
@@ -150,17 +150,17 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseMapper<'tcx> {
         match *ty.kind() {
             ty::Closure(def_id, substs) => {
                 let substs = self.fold_closure_substs(def_id, substs);
-                self.tcx.mk_closure(def_id, substs)
+                Ty::new_closure(self.tcx, def_id, substs)
             }
 
             ty::Generator(def_id, substs, movability) => {
                 let substs = self.fold_closure_substs(def_id, substs);
-                self.tcx.mk_generator(def_id, substs, movability)
+                Ty::new_generator(self.tcx, def_id, substs, movability)
             }
 
             ty::GeneratorWitnessMIR(def_id, substs) => {
                 let substs = self.fold_closure_substs(def_id, substs);
-                self.tcx.mk_generator_witness_mir(def_id, substs)
+                Ty::new_generator_witness_mir(self.tcx, def_id, substs)
             }
 
             ty::Param(param) => {
@@ -186,7 +186,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseMapper<'tcx> {
                                 .emit();
                         }
 
-                        self.interner().ty_error_misc()
+                        Ty::new_misc_error(self.tcx)
                     }
                 }
             }
@@ -216,7 +216,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseMapper<'tcx> {
                             })
                             .emit_unless(self.ignore_errors);
 
-                        self.interner().const_error(ct.ty(), guar)
+                        ty::Const::new_error(self.tcx, guar, ct.ty())
                     }
                 }
             }
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index a2e77d9cd..cc2b26a5e 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -73,6 +73,7 @@ trivially_parameterized_over_tcx! {
     ty::fast_reject::SimplifiedType,
     rustc_ast::Attribute,
     rustc_ast::DelimArgs,
+    rustc_ast::expand::StrippedCfgItem<rustc_hir::def_id::DefIndex>,
     rustc_attr::ConstStability,
     rustc_attr::DefaultBodyStability,
     rustc_attr::Deprecation,
@@ -128,5 +129,6 @@ parameterized_over_tcx! {
     ty::Const,
     ty::Predicate,
     ty::Clause,
+    ty::ClauseKind,
     ty::GeneratorDiagnosticData,
 }
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index 64e7480e6..2de0a3f75 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -123,7 +123,7 @@ pub trait Printer<'tcx>: Sized {
                         impl_trait_ref.map(|i| i.subst(self.tcx(), substs)),
                     )
                 } else {
-                    (self_ty.0, impl_trait_ref.map(|i| i.0))
+                    (self_ty.subst_identity(), impl_trait_ref.map(|i| i.subst_identity()))
                 };
                 self.print_impl_path(def_id, substs, self_ty, impl_trait_ref)
             }
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index d6c88ea96..96cf36eb9 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -94,6 +94,10 @@ macro_rules! define_helper {
                     $tl.with(|c| c.set(self.0))
                 }
             }
+
+            pub fn $name() -> bool {
+                $tl.with(|c| c.get())
+            }
         )+
     }
 }
@@ -184,7 +188,7 @@ impl<'tcx> RegionHighlightMode<'tcx> {
 
     /// Convenience wrapper for `highlighting_region`.
     pub fn highlighting_region_vid(&mut self, vid: ty::RegionVid, number: usize) {
-        self.highlighting_region(self.tcx.mk_re_var(vid), number)
+        self.highlighting_region(ty::Region::new_var(self.tcx, vid), number)
     }
 
     /// Returns `Some(n)` with the number to use for the given region, if any.
@@ -676,7 +680,7 @@ pub trait PrettyPrinter<'tcx>:
                 p!(")")
             }
             ty::FnDef(def_id, substs) => {
-                if NO_QUERIES.with(|q| q.get()) {
+                if with_no_queries() {
                     p!(print_def_path(def_id, substs));
                 } else {
                     let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
@@ -685,29 +689,30 @@ pub trait PrettyPrinter<'tcx>:
             }
             ty::FnPtr(ref bare_fn) => p!(print(bare_fn)),
             ty::Infer(infer_ty) => {
-                let verbose = self.should_print_verbose();
+                if self.should_print_verbose() {
+                    p!(write("{:?}", ty.kind()));
+                    return Ok(self);
+                }
+
                 if let ty::TyVar(ty_vid) = infer_ty {
                     if let Some(name) = self.ty_infer_name(ty_vid) {
                         p!(write("{}", name))
                     } else {
-                        if verbose {
-                            p!(write("{:?}", infer_ty))
-                        } else {
-                            p!(write("{}", infer_ty))
-                        }
+                        p!(write("{}", infer_ty))
                     }
                 } else {
-                    if verbose { p!(write("{:?}", infer_ty)) } else { p!(write("{}", infer_ty)) }
+                    p!(write("{}", infer_ty))
                 }
             }
             ty::Error(_) => p!("{{type error}}"),
             ty::Param(ref param_ty) => p!(print(param_ty)),
             ty::Bound(debruijn, bound_ty) => match bound_ty.kind {
-                ty::BoundTyKind::Anon => debug_bound_var(&mut self, debruijn, bound_ty.var)?,
+                ty::BoundTyKind::Anon => {
+                    rustc_type_ir::debug_bound_var(&mut self, debruijn, bound_ty.var)?
+                }
                 ty::BoundTyKind::Param(_, s) => match self.should_print_verbose() {
-                    true if debruijn == ty::INNERMOST => p!(write("^{}", s)),
-                    true => p!(write("^{}_{}", debruijn.index(), s)),
-                    false => p!(write("{}", s)),
+                    true => p!(write("{:?}", ty.kind())),
+                    false => p!(write("{s}")),
                 },
             },
             ty::Adt(def, substs) => {
@@ -730,8 +735,8 @@ pub trait PrettyPrinter<'tcx>:
             ty::Foreign(def_id) => {
                 p!(print_def_path(def_id, &[]));
             }
-            ty::Alias(ty::Projection | ty::Inherent, ref data) => {
-                if !(self.should_print_verbose() || NO_QUERIES.with(|q| q.get()))
+            ty::Alias(ty::Projection | ty::Inherent | ty::Weak, ref data) => {
+                if !(self.should_print_verbose() || with_no_queries())
                     && self.tcx().is_impl_trait_in_trait(data.def_id)
                 {
                     return self.pretty_print_opaque_impl_type(data.def_id, data.substs);
@@ -740,10 +745,11 @@ pub trait PrettyPrinter<'tcx>:
                 }
             }
             ty::Placeholder(placeholder) => match placeholder.bound.kind {
-                ty::BoundTyKind::Anon => {
-                    debug_placeholder_var(&mut self, placeholder.universe, placeholder.bound.var)?;
-                }
-                ty::BoundTyKind::Param(_, name) => p!(write("{}", name)),
+                ty::BoundTyKind::Anon => p!(write("{placeholder:?}")),
+                ty::BoundTyKind::Param(_, name) => match self.should_print_verbose() {
+                    true => p!(write("{:?}", ty.kind())),
+                    false => p!(write("{name}")),
+                },
             },
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
                 // We use verbose printing in 'NO_QUERIES' mode, to
@@ -777,7 +783,7 @@ pub trait PrettyPrinter<'tcx>:
                         return Ok(self);
                     }
                     _ => {
-                        if NO_QUERIES.with(|q| q.get()) {
+                        if with_no_queries() {
                             p!(print_def_path(def_id, &[]));
                             return Ok(self);
                         } else {
@@ -926,7 +932,7 @@ pub trait PrettyPrinter<'tcx>:
             let bound_predicate = predicate.kind();
 
             match bound_predicate.skip_binder() {
-                ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => {
+                ty::ClauseKind::Trait(pred) => {
                     let trait_ref = bound_predicate.rebind(pred.trait_ref);
 
                     // Don't print + Sized, but rather + ?Sized if absent.
@@ -937,7 +943,7 @@ pub trait PrettyPrinter<'tcx>:
 
                     self.insert_trait_and_projection(trait_ref, None, &mut traits, &mut fn_traits);
                 }
-                ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => {
+                ty::ClauseKind::Projection(pred) => {
                     let proj_ref = bound_predicate.rebind(pred);
                     let trait_ref = proj_ref.required_poly_trait_ref(tcx);
 
@@ -951,7 +957,7 @@ pub trait PrettyPrinter<'tcx>:
                         &mut fn_traits,
                     );
                 }
-                ty::PredicateKind::Clause(ty::Clause::TypeOutlives(outlives)) => {
+                ty::ClauseKind::TypeOutlives(outlives) => {
                     lifetimes.push(outlives.1);
                 }
                 _ => {}
@@ -1222,7 +1228,7 @@ pub trait PrettyPrinter<'tcx>:
                 // in order to place the projections inside the `<...>`.
                 if !resugared {
                     // Use a type that can't appear in defaults of type parameters.
-                    let dummy_cx = cx.tcx().mk_fresh_ty(0);
+                    let dummy_cx = Ty::new_fresh(cx.tcx(), 0);
                     let principal = principal.with_self_ty(cx.tcx(), dummy_cx);
 
                     let args = cx
@@ -1372,11 +1378,9 @@ pub trait PrettyPrinter<'tcx>:
             }
 
             ty::ConstKind::Bound(debruijn, bound_var) => {
-                debug_bound_var(&mut self, debruijn, bound_var)?
+                rustc_type_ir::debug_bound_var(&mut self, debruijn, bound_var)?
             }
-            ty::ConstKind::Placeholder(placeholder) => {
-                debug_placeholder_var(&mut self, placeholder.universe, placeholder.bound)?;
-            },
+            ty::ConstKind::Placeholder(placeholder) => p!(write("{placeholder:?}")),
             // FIXME(generic_const_exprs):
             // write out some legible representation of an abstract const?
             ty::ConstKind::Expr(_) => p!("{{const expr}}"),
@@ -1389,11 +1393,12 @@ pub trait PrettyPrinter<'tcx>:
         self,
         scalar: Scalar,
         ty: Ty<'tcx>,
-        print_ty: bool,
     ) -> Result<Self::Const, Self::Error> {
         match scalar {
-            Scalar::Ptr(ptr, _size) => self.pretty_print_const_scalar_ptr(ptr, ty, print_ty),
-            Scalar::Int(int) => self.pretty_print_const_scalar_int(int, ty, print_ty),
+            Scalar::Ptr(ptr, _size) => self.pretty_print_const_scalar_ptr(ptr, ty),
+            Scalar::Int(int) => {
+                self.pretty_print_const_scalar_int(int, ty, /* print_ty */ true)
+            }
         }
     }
 
@@ -1401,7 +1406,6 @@ pub trait PrettyPrinter<'tcx>:
         mut self,
         ptr: Pointer,
         ty: Ty<'tcx>,
-        print_ty: bool,
     ) -> Result<Self::Const, Self::Error> {
         define_scoped_cx!(self);
 
@@ -1455,7 +1459,7 @@ pub trait PrettyPrinter<'tcx>:
             _ => {}
         }
         // Any pointer values not covered by a branch above
-        self = self.pretty_print_const_pointer(ptr, ty, print_ty)?;
+        self = self.pretty_print_const_pointer(ptr, ty)?;
         Ok(self)
     }
 
@@ -1523,24 +1527,18 @@ pub trait PrettyPrinter<'tcx>:
     /// This is overridden for MIR printing because we only want to hide alloc ids from users, not
     /// from MIR where it is actually useful.
     fn pretty_print_const_pointer<Prov: Provenance>(
-        mut self,
+        self,
         _: Pointer<Prov>,
         ty: Ty<'tcx>,
-        print_ty: bool,
     ) -> Result<Self::Const, Self::Error> {
-        if print_ty {
-            self.typed_value(
-                |mut this| {
-                    this.write_str("&_")?;
-                    Ok(this)
-                },
-                |this| this.print_type(ty),
-                ": ",
-            )
-        } else {
-            self.write_str("&_")?;
-            Ok(self)
-        }
+        self.typed_value(
+            |mut this| {
+                this.write_str("&_")?;
+                Ok(this)
+            },
+            |this| this.print_type(ty),
+            ": ",
+        )
     }
 
     fn pretty_print_byte_str(mut self, byte_str: &'tcx [u8]) -> Result<Self::Const, Self::Error> {
@@ -1597,7 +1595,8 @@ pub trait PrettyPrinter<'tcx>:
             }
             // Aggregates, printed as array/tuple/struct/variant construction syntax.
             (ty::ValTree::Branch(_), ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) => {
-                let contents = self.tcx().destructure_const(self.tcx().mk_const(valtree, ty));
+                let contents =
+                    self.tcx().destructure_const(ty::Const::new_value(self.tcx(), valtree, ty));
                 let fields = contents.fields.iter().copied();
                 match *ty.kind() {
                     ty::Array(..) => {
@@ -1746,7 +1745,8 @@ impl DerefMut for FmtPrinter<'_, '_> {
 
 impl<'a, 'tcx> FmtPrinter<'a, 'tcx> {
     pub fn new(tcx: TyCtxt<'tcx>, ns: Namespace) -> Self {
-        Self::new_with_limit(tcx, ns, tcx.type_length_limit())
+        let limit = if with_no_queries() { Limit::new(1048576) } else { tcx.type_length_limit() };
+        Self::new_with_limit(tcx, ns, limit)
     }
 
     pub fn new_with_limit(tcx: TyCtxt<'tcx>, ns: Namespace, type_length_limit: Limit) -> Self {
@@ -2150,7 +2150,6 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
         self,
         p: Pointer<Prov>,
         ty: Ty<'tcx>,
-        print_ty: bool,
     ) -> Result<Self::Const, Self::Error> {
         let print = |mut this: Self| {
             define_scoped_cx!(this);
@@ -2161,11 +2160,7 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
             }
             Ok(this)
         };
-        if print_ty {
-            self.typed_value(print, |this| this.print_type(ty), ": ")
-        } else {
-            print(self)
-        }
+        self.typed_value(print, |this| this.print_type(ty), ": ")
     }
 }
 
@@ -2303,7 +2298,7 @@ impl<'a, 'tcx> ty::TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> {
         };
         if let ty::ReLateBound(debruijn1, br) = *region {
             assert_eq!(debruijn1, ty::INNERMOST);
-            self.tcx.mk_re_late_bound(self.current_index, br)
+            ty::Region::new_late_bound(self.tcx, self.current_index, br)
         } else {
             region
         }
@@ -2415,7 +2410,8 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                         if let Some(lt_idx) = lifetime_idx {
                             if lt_idx > binder_level_idx {
                                 let kind = ty::BrNamed(CRATE_DEF_ID.to_def_id(), name);
-                                return tcx.mk_re_late_bound(
+                                return ty::Region::new_late_bound(
+                                    tcx,
                                     ty::INNERMOST,
                                     ty::BoundRegion { var: br.var, kind },
                                 );
@@ -2430,7 +2426,8 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                         if let Some(lt_idx) = lifetime_idx {
                             if lt_idx > binder_level_idx {
                                 let kind = ty::BrNamed(def_id, name);
-                                return tcx.mk_re_late_bound(
+                                return ty::Region::new_late_bound(
+                                    tcx,
                                     ty::INNERMOST,
                                     ty::BoundRegion { var: br.var, kind },
                                 );
@@ -2443,7 +2440,8 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                         if let Some(lt_idx) = lifetime_idx {
                             if lt_idx > binder_level_idx {
                                 let kind = br.kind;
-                                return tcx.mk_re_late_bound(
+                                return ty::Region::new_late_bound(
+                                    tcx,
                                     ty::INNERMOST,
                                     ty::BoundRegion { var: br.var, kind },
                                 );
@@ -2458,7 +2456,11 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                     start_or_continue(&mut self, "for<", ", ");
                     do_continue(&mut self, name);
                 }
-                tcx.mk_re_late_bound(ty::INNERMOST, ty::BoundRegion { var: br.var, kind })
+                ty::Region::new_late_bound(
+                    tcx,
+                    ty::INNERMOST,
+                    ty::BoundRegion { var: br.var, kind },
+                )
             };
             let mut folder = RegionFolder {
                 tcx,
@@ -2734,7 +2736,7 @@ define_print_and_forward_display! {
 
     ty::ExistentialTraitRef<'tcx> {
         // Use a type that can't appear in defaults of type parameters.
-        let dummy_self = cx.tcx().mk_fresh_ty(0);
+        let dummy_self = Ty::new_fresh(cx.tcx(),0);
         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
         p!(print(trait_ref.print_only_trait_path()))
     }
@@ -2857,20 +2859,35 @@ define_print_and_forward_display! {
         p!(print(binder))
     }
 
+    ty::Clause<'tcx> {
+        p!(print(self.kind()))
+    }
+
+    ty::ClauseKind<'tcx> {
+        match *self {
+            ty::ClauseKind::Trait(ref data) => {
+                p!(print(data))
+            }
+            ty::ClauseKind::RegionOutlives(predicate) => p!(print(predicate)),
+            ty::ClauseKind::TypeOutlives(predicate) => p!(print(predicate)),
+            ty::ClauseKind::Projection(predicate) => p!(print(predicate)),
+            ty::ClauseKind::ConstArgHasType(ct, ty) => {
+                p!("the constant `", print(ct), "` has type `", print(ty), "`")
+            },
+            ty::ClauseKind::WellFormed(arg) => p!(print(arg), " well-formed"),
+            ty::ClauseKind::ConstEvaluatable(ct) => {
+                p!("the constant `", print(ct), "` can be evaluated")
+            }
+        }
+    }
+
     ty::PredicateKind<'tcx> {
         match *self {
-            ty::PredicateKind::Clause(ty::Clause::Trait(ref data)) => {
+            ty::PredicateKind::Clause(data) => {
                 p!(print(data))
             }
             ty::PredicateKind::Subtype(predicate) => p!(print(predicate)),
             ty::PredicateKind::Coerce(predicate) => p!(print(predicate)),
-            ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => p!(print(predicate)),
-            ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => p!(print(predicate)),
-            ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => p!(print(predicate)),
-            ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(ct, ty)) => {
-                p!("the constant `", print(ct), "` has type `", print(ty), "`")
-            },
-            ty::PredicateKind::WellFormed(arg) => p!(print(arg), " well-formed"),
             ty::PredicateKind::ObjectSafe(trait_def_id) => {
                 p!("the trait `", print_def_path(trait_def_id, &[]), "` is object-safe")
             }
@@ -2879,15 +2896,9 @@ define_print_and_forward_display! {
                 print_value_path(closure_def_id, &[]),
                 write("` implements the trait `{}`", kind)
             ),
-            ty::PredicateKind::ConstEvaluatable(ct) => {
-                p!("the constant `", print(ct), "` can be evaluated")
-            }
             ty::PredicateKind::ConstEquate(c1, c2) => {
                 p!("the constant `", print(c1), "` equals `", print(c2), "`")
             }
-            ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
-                p!("the type `", print(ty), "` is found in the environment")
-            }
             ty::PredicateKind::Ambiguous => p!("ambiguous"),
             ty::PredicateKind::AliasRelate(t1, t2, dir) => p!(print(t1), write(" {} ", dir), print(t2)),
         }
@@ -2980,7 +2991,7 @@ fn for_each_def(tcx: TyCtxt<'_>, mut collect_fn: impl for<'b> FnMut(&'b Ident, N
 ///
 /// The implementation uses similar import discovery logic to that of 'use' suggestions.
 ///
-/// See also [`DelayDm`](rustc_error_messages::DelayDm) and [`with_no_trimmed_paths`].
+/// See also [`DelayDm`](rustc_error_messages::DelayDm) and [`with_no_trimmed_paths!`].
 fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> FxHashMap<DefId, Symbol> {
     let mut map: FxHashMap<DefId, Symbol> = FxHashMap::default();
 
@@ -3065,27 +3076,3 @@ pub struct OpaqueFnEntry<'tcx> {
     fn_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
     return_ty: Option<ty::Binder<'tcx, Term<'tcx>>>,
 }
-
-pub fn debug_bound_var<T: std::fmt::Write>(
-    fmt: &mut T,
-    debruijn: ty::DebruijnIndex,
-    var: ty::BoundVar,
-) -> Result<(), std::fmt::Error> {
-    if debruijn == ty::INNERMOST {
-        write!(fmt, "^{}", var.index())
-    } else {
-        write!(fmt, "^{}_{}", debruijn.index(), var.index())
-    }
-}
-
-pub fn debug_placeholder_var<T: std::fmt::Write>(
-    fmt: &mut T,
-    universe: ty::UniverseIndex,
-    bound: ty::BoundVar,
-) -> Result<(), std::fmt::Error> {
-    if universe == ty::UniverseIndex::ROOT {
-        write!(fmt, "!{}", bound.index())
-    } else {
-        write!(fmt, "!{}_{}", universe.index(), bound.index())
-    }
-}
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index 3bbe6a23b..5741832c9 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -391,13 +391,13 @@ impl<'tcx> Relate<'tcx> for Ty<'tcx> {
 /// Relates `a` and `b` structurally, calling the relation for all nested values.
 /// Any semantic equality, e.g. of projections, and inference variables have to be
 /// handled by the caller.
+#[instrument(level = "trace", skip(relation), ret)]
 pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
     relation: &mut R,
     a: Ty<'tcx>,
     b: Ty<'tcx>,
 ) -> RelateResult<'tcx, Ty<'tcx>> {
     let tcx = relation.tcx();
-    debug!("structurally_relate_tys: a={:?} b={:?}", a, b);
     match (a.kind(), b.kind()) {
         (&ty::Infer(_), _) | (_, &ty::Infer(_)) => {
             // The caller should handle these cases!
@@ -408,7 +408,7 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             bug!("bound types encountered in structurally_relate_tys")
         }
 
-        (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(tcx.ty_error(guar)),
+        (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(Ty::new_error(tcx, guar)),
 
         (&ty::Never, _)
         | (&ty::Char, _)
@@ -428,10 +428,10 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
 
         (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs)) if a_def == b_def => {
             let substs = relation.relate_item_substs(a_def.did(), a_substs, b_substs)?;
-            Ok(tcx.mk_adt(a_def, substs))
+            Ok(Ty::new_adt(tcx, a_def, substs))
         }
 
-        (&ty::Foreign(a_id), &ty::Foreign(b_id)) if a_id == b_id => Ok(tcx.mk_foreign(a_id)),
+        (&ty::Foreign(a_id), &ty::Foreign(b_id)) if a_id == b_id => Ok(Ty::new_foreign(tcx, a_id)),
 
         (&ty::Dynamic(a_obj, a_region, a_repr), &ty::Dynamic(b_obj, b_region, b_repr))
             if a_repr == b_repr =>
@@ -439,7 +439,7 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             let region_bound = relation.with_cause(Cause::ExistentialRegionBound, |relation| {
                 relation.relate(a_region, b_region)
             })?;
-            Ok(tcx.mk_dynamic(relation.relate(a_obj, b_obj)?, region_bound, a_repr))
+            Ok(Ty::new_dynamic(tcx, relation.relate(a_obj, b_obj)?, region_bound, a_repr))
         }
 
         (&ty::Generator(a_id, a_substs, movability), &ty::Generator(b_id, b_substs, _))
@@ -449,7 +449,7 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             // the (anonymous) type of the same generator expression. So
             // all of their regions should be equated.
             let substs = relation.relate(a_substs, b_substs)?;
-            Ok(tcx.mk_generator(a_id, substs, movability))
+            Ok(Ty::new_generator(tcx, a_id, substs, movability))
         }
 
         (&ty::GeneratorWitness(a_types), &ty::GeneratorWitness(b_types)) => {
@@ -459,7 +459,7 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             let b_types = b_types.map_bound(GeneratorWitness);
             // Then remove the GeneratorWitness for the result
             let types = relation.relate(a_types, b_types)?.map_bound(|witness| witness.0);
-            Ok(tcx.mk_generator_witness(types))
+            Ok(Ty::new_generator_witness(tcx, types))
         }
 
         (&ty::GeneratorWitnessMIR(a_id, a_substs), &ty::GeneratorWitnessMIR(b_id, b_substs))
@@ -469,7 +469,7 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             // the (anonymous) type of the same generator expression. So
             // all of their regions should be equated.
             let substs = relation.relate(a_substs, b_substs)?;
-            Ok(tcx.mk_generator_witness_mir(a_id, substs))
+            Ok(Ty::new_generator_witness_mir(tcx, a_id, substs))
         }
 
         (&ty::Closure(a_id, a_substs), &ty::Closure(b_id, b_substs)) if a_id == b_id => {
@@ -477,12 +477,12 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             // the (anonymous) type of the same closure expression. So
             // all of their regions should be equated.
             let substs = relation.relate(a_substs, b_substs)?;
-            Ok(tcx.mk_closure(a_id, &substs))
+            Ok(Ty::new_closure(tcx, a_id, &substs))
         }
 
         (&ty::RawPtr(a_mt), &ty::RawPtr(b_mt)) => {
             let mt = relate_type_and_mut(relation, a_mt, b_mt, a)?;
-            Ok(tcx.mk_ptr(mt))
+            Ok(Ty::new_ptr(tcx, mt))
         }
 
         (&ty::Ref(a_r, a_ty, a_mutbl), &ty::Ref(b_r, b_ty, b_mutbl)) => {
@@ -490,13 +490,13 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             let a_mt = ty::TypeAndMut { ty: a_ty, mutbl: a_mutbl };
             let b_mt = ty::TypeAndMut { ty: b_ty, mutbl: b_mutbl };
             let mt = relate_type_and_mut(relation, a_mt, b_mt, a)?;
-            Ok(tcx.mk_ref(r, mt))
+            Ok(Ty::new_ref(tcx, r, mt))
         }
 
         (&ty::Array(a_t, sz_a), &ty::Array(b_t, sz_b)) => {
             let t = relation.relate(a_t, b_t)?;
             match relation.relate(sz_a, sz_b) {
-                Ok(sz) => Ok(tcx.mk_array_with_const_len(t, sz)),
+                Ok(sz) => Ok(Ty::new_array_with_const_len(tcx, t, sz)),
                 Err(err) => {
                     // Check whether the lengths are both concrete/known values,
                     // but are unequal, for better diagnostics.
@@ -519,12 +519,15 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
 
         (&ty::Slice(a_t), &ty::Slice(b_t)) => {
             let t = relation.relate(a_t, b_t)?;
-            Ok(tcx.mk_slice(t))
+            Ok(Ty::new_slice(tcx, t))
         }
 
         (&ty::Tuple(as_), &ty::Tuple(bs)) => {
             if as_.len() == bs.len() {
-                Ok(tcx.mk_tup_from_iter(iter::zip(as_, bs).map(|(a, b)| relation.relate(a, b)))?)
+                Ok(Ty::new_tup_from_iter(
+                    tcx,
+                    iter::zip(as_, bs).map(|(a, b)| relation.relate(a, b)),
+                )?)
             } else if !(as_.is_empty() || bs.is_empty()) {
                 Err(TypeError::TupleSize(expected_found(relation, as_.len(), bs.len())))
             } else {
@@ -536,25 +539,16 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             if a_def_id == b_def_id =>
         {
             let substs = relation.relate_item_substs(a_def_id, a_substs, b_substs)?;
-            Ok(tcx.mk_fn_def(a_def_id, substs))
+            Ok(Ty::new_fn_def(tcx, a_def_id, substs))
         }
 
         (&ty::FnPtr(a_fty), &ty::FnPtr(b_fty)) => {
             let fty = relation.relate(a_fty, b_fty)?;
-            Ok(tcx.mk_fn_ptr(fty))
-        }
-
-        // these two are already handled downstream in case of lazy normalization
-        (&ty::Alias(ty::Projection, a_data), &ty::Alias(ty::Projection, b_data)) => {
-            let projection_ty = relation.relate(a_data, b_data)?;
-            Ok(tcx.mk_projection(projection_ty.def_id, projection_ty.substs))
-        }
-
-        (&ty::Alias(ty::Inherent, a_data), &ty::Alias(ty::Inherent, b_data)) => {
-            let alias_ty = relation.relate(a_data, b_data)?;
-            Ok(tcx.mk_alias(ty::Inherent, tcx.mk_alias_ty(alias_ty.def_id, alias_ty.substs)))
+            Ok(Ty::new_fn_ptr(tcx, fty))
         }
 
+        // The substs of opaque types may not all be invariant, so we have
+        // to treat them separately from other aliases.
         (
             &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, substs: a_substs, .. }),
             &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, substs: b_substs, .. }),
@@ -568,7 +562,20 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
                 b_substs,
                 false, // do not fetch `type_of(a_def_id)`, as it will cause a cycle
             )?;
-            Ok(tcx.mk_opaque(a_def_id, substs))
+            Ok(Ty::new_opaque(tcx, a_def_id, substs))
+        }
+
+        // Alias tend to mostly already be handled downstream due to normalization.
+        (&ty::Alias(a_kind, a_data), &ty::Alias(b_kind, b_data)) => {
+            // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): This if can be removed
+            // and the assert uncommented once the new desugaring is stable.
+            if a_kind == b_kind {
+                let alias_ty = relation.relate(a_data, b_data)?;
+                // assert_eq!(a_kind, b_kind);
+                Ok(Ty::new_alias(tcx, a_kind, alias_ty))
+            } else {
+                Err(TypeError::Sorts(expected_found(relation, a, b)))
+            }
         }
 
         _ => Err(TypeError::Sorts(expected_found(relation, a, b))),
@@ -589,17 +596,6 @@ pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>(
     debug!("{}.structurally_relate_consts(a = {:?}, b = {:?})", relation.tag(), a, b);
     let tcx = relation.tcx();
 
-    // HACK(const_generics): We still need to eagerly evaluate consts when
-    // relating them because during `normalize_param_env_or_error`,
-    // we may relate an evaluated constant in a obligation against
-    // an unnormalized (i.e. unevaluated) const in the param-env.
-    // FIXME(generic_const_exprs): Once we always lazily unify unevaluated constants
-    // these `eval` calls can be removed.
-    if !tcx.features().generic_const_exprs {
-        a = a.eval(tcx, relation.param_env());
-        b = b.eval(tcx, relation.param_env());
-    }
-
     if tcx.features().generic_const_exprs {
         a = tcx.expand_abstract_consts(a);
         b = tcx.expand_abstract_consts(b);
@@ -634,7 +630,11 @@ pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>(
                 au.substs,
                 bu.substs,
             )?;
-            return Ok(tcx.mk_const(ty::UnevaluatedConst { def: au.def, substs }, a.ty()));
+            return Ok(ty::Const::new_unevaluated(
+                tcx,
+                ty::UnevaluatedConst { def: au.def, substs },
+                a.ty(),
+            ));
         }
         // Before calling relate on exprs, it is necessary to ensure that the nested consts
         // have identical types.
@@ -675,8 +675,7 @@ pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>(
                 }
                 _ => return Err(TypeError::ConstMismatch(expected_found(r, a, b))),
             };
-            let kind = ty::ConstKind::Expr(expr);
-            return Ok(tcx.mk_const(kind, a.ty()));
+            return Ok(ty::Const::new_expr(tcx, expr, a.ty()));
         }
         _ => false,
     };
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 16cb6c910..7220d133f 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -11,6 +11,7 @@ use crate::ty::{self, AliasTy, InferConst, Lift, Term, TermKind, Ty, TyCtxt};
 use rustc_hir::def::Namespace;
 use rustc_index::{Idx, IndexVec};
 use rustc_target::abi::TyAndLayout;
+use rustc_type_ir::ConstKind;
 
 use std::fmt;
 use std::ops::ControlFlow;
@@ -88,7 +89,35 @@ impl fmt::Debug for ty::FreeRegion {
 
 impl<'tcx> fmt::Debug for ty::FnSig<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "({:?}; c_variadic: {})->{:?}", self.inputs(), self.c_variadic, self.output())
+        let ty::FnSig { inputs_and_output: _, c_variadic, unsafety, abi } = self;
+
+        write!(f, "{}", unsafety.prefix_str())?;
+        match abi {
+            rustc_target::spec::abi::Abi::Rust => (),
+            abi => write!(f, "extern \"{abi:?}\" ")?,
+        };
+
+        write!(f, "fn(")?;
+        let inputs = self.inputs();
+        match inputs.len() {
+            0 if *c_variadic => write!(f, "...)")?,
+            0 => write!(f, ")")?,
+            _ => {
+                for ty in &self.inputs()[0..(self.inputs().len() - 1)] {
+                    write!(f, "{ty:?}, ")?;
+                }
+                write!(f, "{:?}", self.inputs().last().unwrap())?;
+                if *c_variadic {
+                    write!(f, "...")?;
+                }
+                write!(f, ")")?;
+            }
+        }
+
+        match self.output().kind() {
+            ty::Tuple(list) if list.is_empty() => Ok(()),
+            _ => write!(f, " -> {:?}", self.output()),
+        }
     }
 }
 
@@ -145,12 +174,22 @@ impl<'tcx> fmt::Debug for ty::Predicate<'tcx> {
 
 impl<'tcx> fmt::Debug for ty::Clause<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}", self.kind())
+    }
+}
+
+impl<'tcx> fmt::Debug for ty::ClauseKind<'tcx> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
-            ty::Clause::ConstArgHasType(ct, ty) => write!(f, "ConstArgHasType({ct:?}, {ty:?})"),
-            ty::Clause::Trait(ref a) => a.fmt(f),
-            ty::Clause::RegionOutlives(ref pair) => pair.fmt(f),
-            ty::Clause::TypeOutlives(ref pair) => pair.fmt(f),
-            ty::Clause::Projection(ref pair) => pair.fmt(f),
+            ty::ClauseKind::ConstArgHasType(ct, ty) => write!(f, "ConstArgHasType({ct:?}, {ty:?})"),
+            ty::ClauseKind::Trait(ref a) => a.fmt(f),
+            ty::ClauseKind::RegionOutlives(ref pair) => pair.fmt(f),
+            ty::ClauseKind::TypeOutlives(ref pair) => pair.fmt(f),
+            ty::ClauseKind::Projection(ref pair) => pair.fmt(f),
+            ty::ClauseKind::WellFormed(ref data) => write!(f, "WellFormed({:?})", data),
+            ty::ClauseKind::ConstEvaluatable(ct) => {
+                write!(f, "ConstEvaluatable({ct:?})")
+            }
         }
     }
 }
@@ -161,20 +200,13 @@ impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
             ty::PredicateKind::Clause(ref a) => a.fmt(f),
             ty::PredicateKind::Subtype(ref pair) => pair.fmt(f),
             ty::PredicateKind::Coerce(ref pair) => pair.fmt(f),
-            ty::PredicateKind::WellFormed(data) => write!(f, "WellFormed({:?})", data),
             ty::PredicateKind::ObjectSafe(trait_def_id) => {
                 write!(f, "ObjectSafe({:?})", trait_def_id)
             }
             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
                 write!(f, "ClosureKind({:?}, {:?}, {:?})", closure_def_id, closure_substs, kind)
             }
-            ty::PredicateKind::ConstEvaluatable(ct) => {
-                write!(f, "ConstEvaluatable({ct:?})")
-            }
             ty::PredicateKind::ConstEquate(c1, c2) => write!(f, "ConstEquate({:?}, {:?})", c1, c2),
-            ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
-                write!(f, "TypeWellFormedFromEnv({:?})", ty)
-            }
             ty::PredicateKind::Ambiguous => write!(f, "Ambiguous"),
             ty::PredicateKind::AliasRelate(t1, t2, dir) => {
                 write!(f, "AliasRelate({t1:?}, {dir:?}, {t2:?})")
@@ -210,22 +242,21 @@ impl<'tcx> fmt::Debug for ty::Const<'tcx> {
     }
 }
 
-impl<'tcx> fmt::Debug for ty::ConstKind<'tcx> {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        use ty::ConstKind::*;
-        match self {
-            Param(param) => write!(f, "{param:?}"),
-            Infer(var) => write!(f, "{var:?}"),
-            Bound(debruijn, var) => ty::print::debug_bound_var(f, *debruijn, *var),
-            Placeholder(placeholder) => {
-                ty::print::debug_placeholder_var(f, placeholder.universe, placeholder.bound)
-            }
-            Unevaluated(uv) => {
-                f.debug_tuple("Unevaluated").field(&uv.substs).field(&uv.def).finish()
-            }
-            Value(valtree) => write!(f, "{valtree:?}"),
-            Error(_) => write!(f, "[const error]"),
-            Expr(expr) => write!(f, "{expr:?}"),
+impl fmt::Debug for ty::BoundTy {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.kind {
+            ty::BoundTyKind::Anon => write!(f, "{:?}", self.var),
+            ty::BoundTyKind::Param(_, sym) => write!(f, "{sym:?}"),
+        }
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for ty::Placeholder<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.universe == ty::UniverseIndex::ROOT {
+            write!(f, "!{:?}", self.bound)
+        } else {
+            write!(f, "!{}_{:?}", self.universe.index(), self.bound)
         }
     }
 }
@@ -294,13 +325,14 @@ TrivialTypeTraversalAndLiftImpls! {
     crate::ty::AliasRelationDirection,
     crate::ty::Placeholder<crate::ty::BoundRegion>,
     crate::ty::Placeholder<crate::ty::BoundTy>,
+    crate::ty::Placeholder<ty::BoundVar>,
     crate::ty::ClosureKind,
     crate::ty::FreeRegion,
     crate::ty::InferTy,
     crate::ty::IntVarValue,
     crate::ty::ParamConst,
     crate::ty::ParamTy,
-    crate::ty::adjustment::PointerCast,
+    crate::ty::adjustment::PointerCoercion,
     crate::ty::RegionVid,
     crate::ty::UniverseIndex,
     crate::ty::Variance,
@@ -310,7 +342,6 @@ TrivialTypeTraversalAndLiftImpls! {
     interpret::Scalar,
     rustc_target::abi::Size,
     ty::BoundVar,
-    ty::Placeholder<ty::BoundVar>,
 }
 
 TrivialTypeTraversalAndLiftImpls! {
@@ -609,12 +640,28 @@ impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
     }
 }
 
+// FIXME(clause): This is wonky
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Clause<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        Ok(folder.try_fold_predicate(self.as_predicate())?.expect_clause())
+    }
+}
+
 impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
     fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         visitor.visit_predicate(*self)
     }
 }
 
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ty::Clause<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+        visitor.visit_predicate(self.as_predicate())
+    }
+}
+
 impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
     fn try_super_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
@@ -634,12 +681,12 @@ impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<ty::Predicate<'tcx>> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<ty::Clause<'tcx>> {
     fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
-        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_predicates(v))
+        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_clauses(v))
     }
 }
 
@@ -664,9 +711,20 @@ impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Const<'tcx> {
         folder: &mut F,
     ) -> Result<Self, F::Error> {
         let ty = self.ty().try_fold_with(folder)?;
-        let kind = self.kind().try_fold_with(folder)?;
+        let kind = match self.kind() {
+            ConstKind::Param(p) => ConstKind::Param(p.try_fold_with(folder)?),
+            ConstKind::Infer(i) => ConstKind::Infer(i.try_fold_with(folder)?),
+            ConstKind::Bound(d, b) => {
+                ConstKind::Bound(d.try_fold_with(folder)?, b.try_fold_with(folder)?)
+            }
+            ConstKind::Placeholder(p) => ConstKind::Placeholder(p.try_fold_with(folder)?),
+            ConstKind::Unevaluated(uv) => ConstKind::Unevaluated(uv.try_fold_with(folder)?),
+            ConstKind::Value(v) => ConstKind::Value(v.try_fold_with(folder)?),
+            ConstKind::Error(e) => ConstKind::Error(e.try_fold_with(folder)?),
+            ConstKind::Expr(e) => ConstKind::Expr(e.try_fold_with(folder)?),
+        };
         if ty != self.ty() || kind != self.kind() {
-            Ok(folder.interner().mk_const(kind, ty))
+            Ok(folder.interner().mk_ct_from_kind(kind, ty))
         } else {
             Ok(self)
         }
@@ -679,7 +737,19 @@ impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::Const<'tcx> {
         visitor: &mut V,
     ) -> ControlFlow<V::BreakTy> {
         self.ty().visit_with(visitor)?;
-        self.kind().visit_with(visitor)
+        match self.kind() {
+            ConstKind::Param(p) => p.visit_with(visitor),
+            ConstKind::Infer(i) => i.visit_with(visitor),
+            ConstKind::Bound(d, b) => {
+                d.visit_with(visitor)?;
+                b.visit_with(visitor)
+            }
+            ConstKind::Placeholder(p) => p.visit_with(visitor),
+            ConstKind::Unevaluated(uv) => uv.visit_with(visitor),
+            ConstKind::Value(v) => v.visit_with(visitor),
+            ConstKind::Error(e) => e.visit_with(visitor),
+            ConstKind::Expr(e) => e.visit_with(visitor),
+        }
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index e6d51c4ec..94746fbdc 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -15,16 +15,18 @@ use hir::def::DefKind;
 use polonius_engine::Atom;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::intern::Interned;
-use rustc_errors::{DiagnosticArgValue, IntoDiagnosticArg};
+use rustc_error_messages::DiagnosticMessage;
+use rustc_errors::{DiagnosticArgValue, ErrorGuaranteed, IntoDiagnosticArg, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::LangItem;
 use rustc_index::Idx;
 use rustc_macros::HashStable;
 use rustc_span::symbol::{kw, sym, Symbol};
-use rustc_span::Span;
+use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
 use rustc_target::spec::abi::{self, Abi};
+use std::assert_matches::debug_assert_matches;
 use std::borrow::Cow;
 use std::cmp::Ordering;
 use std::fmt;
@@ -33,13 +35,17 @@ use std::ops::{ControlFlow, Deref, Range};
 use ty::util::IntTypeExt;
 
 use rustc_type_ir::sty::TyKind::*;
-use rustc_type_ir::RegionKind as IrRegionKind;
 use rustc_type_ir::TyKind as IrTyKind;
+use rustc_type_ir::{CollectAndApply, ConstKind as IrConstKind};
+use rustc_type_ir::{DynKind, RegionKind as IrRegionKind};
+
+use super::GenericParamDefKind;
 
 // Re-export the `TyKind` from `rustc_type_ir` here for convenience
 #[rustc_diagnostic_item = "TyKind"]
 pub type TyKind<'tcx> = IrTyKind<TyCtxt<'tcx>>;
 pub type RegionKind<'tcx> = IrRegionKind<TyCtxt<'tcx>>;
+pub type ConstKind<'tcx> = IrConstKind<TyCtxt<'tcx>>;
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
@@ -568,7 +574,7 @@ impl<'tcx> GeneratorSubsts<'tcx> {
         let layout = tcx.generator_layout(def_id).unwrap();
         layout.variant_fields.iter().map(move |variant| {
             variant.iter().map(move |field| {
-                ty::EarlyBinder(layout.field_tys[*field].ty).subst(tcx, self.substs)
+                ty::EarlyBinder::bind(layout.field_tys[*field].ty).subst(tcx, self.substs)
             })
         })
     }
@@ -715,7 +721,7 @@ impl<'tcx> PolyExistentialPredicate<'tcx> {
     /// Given an existential predicate like `?Self: PartialEq<u32>` (e.g., derived from `dyn PartialEq<u32>`),
     /// and a concrete type `self_ty`, returns a full predicate where the existentially quantified variable `?Self`
     /// has been replaced with `self_ty` (e.g., `self_ty: PartialEq<u32>`, in our example).
-    pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
+    pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Clause<'tcx> {
         use crate::ty::ToPredicate;
         match self.skip_binder() {
             ExistentialPredicate::Trait(tr) => {
@@ -1007,7 +1013,10 @@ impl BoundVariableKind {
 /// `Decodable` and `Encodable` are implemented for `Binder<T>` using the `impl_binder_encode_decode!` macro.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 #[derive(HashStable, Lift)]
-pub struct Binder<'tcx, T>(T, &'tcx List<BoundVariableKind>);
+pub struct Binder<'tcx, T> {
+    value: T,
+    bound_vars: &'tcx List<BoundVariableKind>,
+}
 
 impl<'tcx, T> Binder<'tcx, T>
 where
@@ -1023,15 +1032,15 @@ where
             !value.has_escaping_bound_vars(),
             "`{value:?}` has escaping bound vars, so it cannot be wrapped in a dummy binder."
         );
-        Binder(value, ty::List::empty())
+        Binder { value, bound_vars: ty::List::empty() }
     }
 
-    pub fn bind_with_vars(value: T, vars: &'tcx List<BoundVariableKind>) -> Binder<'tcx, T> {
+    pub fn bind_with_vars(value: T, bound_vars: &'tcx List<BoundVariableKind>) -> Binder<'tcx, T> {
         if cfg!(debug_assertions) {
-            let mut validator = ValidateBoundVars::new(vars);
+            let mut validator = ValidateBoundVars::new(bound_vars);
             value.visit_with(&mut validator);
         }
-        Binder(value, vars)
+        Binder { value, bound_vars }
     }
 }
 
@@ -1053,30 +1062,30 @@ impl<'tcx, T> Binder<'tcx, T> {
     /// - comparing the self type of a PolyTraitRef to see if it is equal to
     ///   a type parameter `X`, since the type `X` does not reference any regions
     pub fn skip_binder(self) -> T {
-        self.0
+        self.value
     }
 
     pub fn bound_vars(&self) -> &'tcx List<BoundVariableKind> {
-        self.1
+        self.bound_vars
     }
 
     pub fn as_ref(&self) -> Binder<'tcx, &T> {
-        Binder(&self.0, self.1)
+        Binder { value: &self.value, bound_vars: self.bound_vars }
     }
 
     pub fn as_deref(&self) -> Binder<'tcx, &T::Target>
     where
         T: Deref,
     {
-        Binder(&self.0, self.1)
+        Binder { value: &self.value, bound_vars: self.bound_vars }
     }
 
     pub fn map_bound_ref_unchecked<F, U>(&self, f: F) -> Binder<'tcx, U>
     where
         F: FnOnce(&T) -> U,
     {
-        let value = f(&self.0);
-        Binder(value, self.1)
+        let value = f(&self.value);
+        Binder { value, bound_vars: self.bound_vars }
     }
 
     pub fn map_bound_ref<F, U: TypeVisitable<TyCtxt<'tcx>>>(&self, f: F) -> Binder<'tcx, U>
@@ -1090,12 +1099,13 @@ impl<'tcx, T> Binder<'tcx, T> {
     where
         F: FnOnce(T) -> U,
     {
-        let value = f(self.0);
+        let Binder { value, bound_vars } = self;
+        let value = f(value);
         if cfg!(debug_assertions) {
-            let mut validator = ValidateBoundVars::new(self.1);
+            let mut validator = ValidateBoundVars::new(bound_vars);
             value.visit_with(&mut validator);
         }
-        Binder(value, self.1)
+        Binder { value, bound_vars }
     }
 
     pub fn try_map_bound<F, U: TypeVisitable<TyCtxt<'tcx>>, E>(
@@ -1105,12 +1115,13 @@ impl<'tcx, T> Binder<'tcx, T> {
     where
         F: FnOnce(T) -> Result<U, E>,
     {
-        let value = f(self.0)?;
+        let Binder { value, bound_vars } = self;
+        let value = f(value)?;
         if cfg!(debug_assertions) {
-            let mut validator = ValidateBoundVars::new(self.1);
+            let mut validator = ValidateBoundVars::new(bound_vars);
             value.visit_with(&mut validator);
         }
-        Ok(Binder(value, self.1))
+        Ok(Binder { value, bound_vars })
     }
 
     /// Wraps a `value` in a binder, using the same bound variables as the
@@ -1126,11 +1137,7 @@ impl<'tcx, T> Binder<'tcx, T> {
     where
         U: TypeVisitable<TyCtxt<'tcx>>,
     {
-        if cfg!(debug_assertions) {
-            let mut validator = ValidateBoundVars::new(self.bound_vars());
-            value.visit_with(&mut validator);
-        }
-        Binder(value, self.1)
+        Binder::bind_with_vars(value, self.bound_vars)
     }
 
     /// Unwraps and returns the value within, but only if it contains
@@ -1147,7 +1154,7 @@ impl<'tcx, T> Binder<'tcx, T> {
     where
         T: TypeVisitable<TyCtxt<'tcx>>,
     {
-        if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
+        if self.value.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
     }
 
     /// Splits the contents into two things that share the same binder
@@ -1160,22 +1167,23 @@ impl<'tcx, T> Binder<'tcx, T> {
     where
         F: FnOnce(T) -> (U, V),
     {
-        let (u, v) = f(self.0);
-        (Binder(u, self.1), Binder(v, self.1))
+        let Binder { value, bound_vars } = self;
+        let (u, v) = f(value);
+        (Binder { value: u, bound_vars }, Binder { value: v, bound_vars })
     }
 }
 
 impl<'tcx, T> Binder<'tcx, Option<T>> {
     pub fn transpose(self) -> Option<Binder<'tcx, T>> {
-        let bound_vars = self.1;
-        self.0.map(|v| Binder(v, bound_vars))
+        let Binder { value, bound_vars } = self;
+        value.map(|value| Binder { value, bound_vars })
     }
 }
 
 impl<'tcx, T: IntoIterator> Binder<'tcx, T> {
     pub fn iter(self) -> impl Iterator<Item = ty::Binder<'tcx, T::Item>> {
-        let bound_vars = self.1;
-        self.0.into_iter().map(|v| Binder(v, bound_vars))
+        let Binder { value, bound_vars } = self;
+        value.into_iter().map(|value| Binder { value, bound_vars })
     }
 }
 
@@ -1184,7 +1192,7 @@ where
     T: IntoDiagnosticArg,
 {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        self.0.into_diagnostic_arg()
+        self.value.into_diagnostic_arg()
     }
 }
 
@@ -1231,12 +1239,13 @@ impl<'tcx> AliasTy<'tcx> {
             DefKind::AssocTy if let DefKind::Impl { of_trait: false } = tcx.def_kind(tcx.parent(self.def_id)) => ty::Inherent,
             DefKind::AssocTy | DefKind::ImplTraitPlaceholder => ty::Projection,
             DefKind::OpaqueTy => ty::Opaque,
+            DefKind::TyAlias => ty::Weak,
             kind => bug!("unexpected DefKind in AliasTy: {kind:?}"),
         }
     }
 
     pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
-        tcx.mk_alias(self.kind(tcx), self)
+        Ty::new_alias(tcx, self.kind(tcx), self)
     }
 }
 
@@ -1427,7 +1436,7 @@ impl<'tcx> ParamTy {
 
     #[inline]
     pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
-        tcx.mk_ty_param(self.index, self.name)
+        Ty::new_param(tcx, self.index, self.name)
     }
 
     pub fn span_from_generics(&self, tcx: TyCtxt<'tcx>, item_with_generics: DefId) -> Span {
@@ -1459,6 +1468,103 @@ impl ParamConst {
 #[rustc_pass_by_value]
 pub struct Region<'tcx>(pub Interned<'tcx, RegionKind<'tcx>>);
 
+impl<'tcx> Region<'tcx> {
+    #[inline]
+    pub fn new_early_bound(
+        tcx: TyCtxt<'tcx>,
+        early_bound_region: ty::EarlyBoundRegion,
+    ) -> Region<'tcx> {
+        tcx.intern_region(ty::ReEarlyBound(early_bound_region))
+    }
+
+    #[inline]
+    pub fn new_late_bound(
+        tcx: TyCtxt<'tcx>,
+        debruijn: ty::DebruijnIndex,
+        bound_region: ty::BoundRegion,
+    ) -> Region<'tcx> {
+        // Use a pre-interned one when possible.
+        if let ty::BoundRegion { var, kind: ty::BrAnon(None) } = bound_region
+            && let Some(inner) = tcx.lifetimes.re_late_bounds.get(debruijn.as_usize())
+            && let Some(re) = inner.get(var.as_usize()).copied()
+        {
+            re
+        } else {
+            tcx.intern_region(ty::ReLateBound(debruijn, bound_region))
+        }
+    }
+
+    #[inline]
+    pub fn new_free(
+        tcx: TyCtxt<'tcx>,
+        scope: DefId,
+        bound_region: ty::BoundRegionKind,
+    ) -> Region<'tcx> {
+        tcx.intern_region(ty::ReFree(ty::FreeRegion { scope, bound_region }))
+    }
+
+    #[inline]
+    pub fn new_var(tcx: TyCtxt<'tcx>, v: ty::RegionVid) -> Region<'tcx> {
+        // Use a pre-interned one when possible.
+        tcx.lifetimes
+            .re_vars
+            .get(v.as_usize())
+            .copied()
+            .unwrap_or_else(|| tcx.intern_region(ty::ReVar(v)))
+    }
+
+    #[inline]
+    pub fn new_placeholder(tcx: TyCtxt<'tcx>, placeholder: ty::PlaceholderRegion) -> Region<'tcx> {
+        tcx.intern_region(ty::RePlaceholder(placeholder))
+    }
+
+    /// Constructs a `RegionKind::ReError` region.
+    #[track_caller]
+    pub fn new_error(tcx: TyCtxt<'tcx>, reported: ErrorGuaranteed) -> Region<'tcx> {
+        tcx.intern_region(ty::ReError(reported))
+    }
+
+    /// Constructs a `RegionKind::ReError` region and registers a `delay_span_bug` to ensure it
+    /// gets used.
+    #[track_caller]
+    pub fn new_error_misc(tcx: TyCtxt<'tcx>) -> Region<'tcx> {
+        Region::new_error_with_message(
+            tcx,
+            DUMMY_SP,
+            "RegionKind::ReError constructed but no error reported",
+        )
+    }
+
+    /// Constructs a `RegionKind::ReError` region and registers a `delay_span_bug` with the given
+    /// `msg` to ensure it gets used.
+    #[track_caller]
+    pub fn new_error_with_message<S: Into<MultiSpan>>(
+        tcx: TyCtxt<'tcx>,
+        span: S,
+        msg: &'static str,
+    ) -> Region<'tcx> {
+        let reported = tcx.sess.delay_span_bug(span, msg);
+        Region::new_error(tcx, reported)
+    }
+
+    /// Avoid this in favour of more specific `new_*` methods, where possible,
+    /// to avoid the cost of the `match`.
+    pub fn new_from_kind(tcx: TyCtxt<'tcx>, kind: RegionKind<'tcx>) -> Region<'tcx> {
+        match kind {
+            ty::ReEarlyBound(region) => Region::new_early_bound(tcx, region),
+            ty::ReLateBound(debruijn, region) => Region::new_late_bound(tcx, debruijn, region),
+            ty::ReFree(ty::FreeRegion { scope, bound_region }) => {
+                Region::new_free(tcx, scope, bound_region)
+            }
+            ty::ReStatic => tcx.lifetimes.re_static,
+            ty::ReVar(vid) => Region::new_var(tcx, vid),
+            ty::RePlaceholder(region) => Region::new_placeholder(tcx, region),
+            ty::ReErased => tcx.lifetimes.re_erased,
+            ty::ReError(reported) => Region::new_error(tcx, reported),
+        }
+    }
+}
+
 impl<'tcx> Deref for Region<'tcx> {
     type Target = RegionKind<'tcx>;
 
@@ -1484,7 +1590,7 @@ pub struct EarlyBoundRegion {
 
 impl fmt::Debug for EarlyBoundRegion {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}, {}", self.index, self.name)
+        write!(f, "{:?}, {}, {}", self.def_id, self.index, self.name)
     }
 }
 
@@ -1511,10 +1617,11 @@ impl Atom for RegionVid {
 
 rustc_index::newtype_index! {
     #[derive(HashStable)]
+    #[debug_format = "{}"]
     pub struct BoundVar {}
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub struct BoundTy {
     pub var: BoundVar,
@@ -1770,6 +1877,390 @@ impl<'tcx> Region<'tcx> {
     }
 }
 
+/// Constructors for `Ty`
+impl<'tcx> Ty<'tcx> {
+    // Avoid this in favour of more specific `new_*` methods, where possible.
+    #[allow(rustc::usage_of_ty_tykind)]
+    #[inline]
+    pub fn new(tcx: TyCtxt<'tcx>, st: TyKind<'tcx>) -> Ty<'tcx> {
+        tcx.mk_ty_from_kind(st)
+    }
+
+    #[inline]
+    pub fn new_infer(tcx: TyCtxt<'tcx>, infer: ty::InferTy) -> Ty<'tcx> {
+        Ty::new(tcx, TyKind::Infer(infer))
+    }
+
+    #[inline]
+    pub fn new_var(tcx: TyCtxt<'tcx>, v: ty::TyVid) -> Ty<'tcx> {
+        // Use a pre-interned one when possible.
+        tcx.types
+            .ty_vars
+            .get(v.as_usize())
+            .copied()
+            .unwrap_or_else(|| Ty::new(tcx, Infer(TyVar(v))))
+    }
+
+    #[inline]
+    pub fn new_int_var(tcx: TyCtxt<'tcx>, v: ty::IntVid) -> Ty<'tcx> {
+        Ty::new_infer(tcx, IntVar(v))
+    }
+
+    #[inline]
+    pub fn new_float_var(tcx: TyCtxt<'tcx>, v: ty::FloatVid) -> Ty<'tcx> {
+        Ty::new_infer(tcx, FloatVar(v))
+    }
+
+    #[inline]
+    pub fn new_fresh(tcx: TyCtxt<'tcx>, n: u32) -> Ty<'tcx> {
+        // Use a pre-interned one when possible.
+        tcx.types
+            .fresh_tys
+            .get(n as usize)
+            .copied()
+            .unwrap_or_else(|| Ty::new_infer(tcx, ty::FreshTy(n)))
+    }
+
+    #[inline]
+    pub fn new_fresh_int(tcx: TyCtxt<'tcx>, n: u32) -> Ty<'tcx> {
+        // Use a pre-interned one when possible.
+        tcx.types
+            .fresh_int_tys
+            .get(n as usize)
+            .copied()
+            .unwrap_or_else(|| Ty::new_infer(tcx, ty::FreshIntTy(n)))
+    }
+
+    #[inline]
+    pub fn new_fresh_float(tcx: TyCtxt<'tcx>, n: u32) -> Ty<'tcx> {
+        // Use a pre-interned one when possible.
+        tcx.types
+            .fresh_float_tys
+            .get(n as usize)
+            .copied()
+            .unwrap_or_else(|| Ty::new_infer(tcx, ty::FreshFloatTy(n)))
+    }
+
+    #[inline]
+    pub fn new_param(tcx: TyCtxt<'tcx>, index: u32, name: Symbol) -> Ty<'tcx> {
+        tcx.mk_ty_from_kind(Param(ParamTy { index, name }))
+    }
+
+    #[inline]
+    pub fn new_bound(
+        tcx: TyCtxt<'tcx>,
+        index: ty::DebruijnIndex,
+        bound_ty: ty::BoundTy,
+    ) -> Ty<'tcx> {
+        Ty::new(tcx, Bound(index, bound_ty))
+    }
+
+    #[inline]
+    pub fn new_placeholder(tcx: TyCtxt<'tcx>, placeholder: ty::PlaceholderType) -> Ty<'tcx> {
+        Ty::new(tcx, Placeholder(placeholder))
+    }
+
+    #[inline]
+    pub fn new_alias(
+        tcx: TyCtxt<'tcx>,
+        kind: ty::AliasKind,
+        alias_ty: ty::AliasTy<'tcx>,
+    ) -> Ty<'tcx> {
+        debug_assert_matches!(
+            (kind, tcx.def_kind(alias_ty.def_id)),
+            (ty::Opaque, DefKind::OpaqueTy)
+                | (ty::Projection | ty::Inherent, DefKind::AssocTy)
+                | (ty::Opaque | ty::Projection, DefKind::ImplTraitPlaceholder)
+                | (ty::Weak, DefKind::TyAlias)
+        );
+        Ty::new(tcx, Alias(kind, alias_ty))
+    }
+
+    #[inline]
+    pub fn new_opaque(tcx: TyCtxt<'tcx>, def_id: DefId, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
+        Ty::new_alias(tcx, ty::Opaque, tcx.mk_alias_ty(def_id, substs))
+    }
+
+    /// Constructs a `TyKind::Error` type with current `ErrorGuaranteed`
+    pub fn new_error(tcx: TyCtxt<'tcx>, reported: ErrorGuaranteed) -> Ty<'tcx> {
+        Ty::new(tcx, Error(reported))
+    }
+
+    /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` to ensure it gets used.
+    #[track_caller]
+    pub fn new_misc_error(tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
+        Ty::new_error_with_message(tcx, DUMMY_SP, "TyKind::Error constructed but no error reported")
+    }
+
+    /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` with the given `msg` to
+    /// ensure it gets used.
+    #[track_caller]
+    pub fn new_error_with_message<S: Into<MultiSpan>>(
+        tcx: TyCtxt<'tcx>,
+        span: S,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> Ty<'tcx> {
+        let reported = tcx.sess.delay_span_bug(span, msg);
+        Ty::new(tcx, Error(reported))
+    }
+
+    #[inline]
+    pub fn new_int(tcx: TyCtxt<'tcx>, i: ty::IntTy) -> Ty<'tcx> {
+        use ty::IntTy::*;
+        match i {
+            Isize => tcx.types.isize,
+            I8 => tcx.types.i8,
+            I16 => tcx.types.i16,
+            I32 => tcx.types.i32,
+            I64 => tcx.types.i64,
+            I128 => tcx.types.i128,
+        }
+    }
+
+    #[inline]
+    pub fn new_uint(tcx: TyCtxt<'tcx>, ui: ty::UintTy) -> Ty<'tcx> {
+        use ty::UintTy::*;
+        match ui {
+            Usize => tcx.types.usize,
+            U8 => tcx.types.u8,
+            U16 => tcx.types.u16,
+            U32 => tcx.types.u32,
+            U64 => tcx.types.u64,
+            U128 => tcx.types.u128,
+        }
+    }
+
+    #[inline]
+    pub fn new_float(tcx: TyCtxt<'tcx>, f: ty::FloatTy) -> Ty<'tcx> {
+        use ty::FloatTy::*;
+        match f {
+            F32 => tcx.types.f32,
+            F64 => tcx.types.f64,
+        }
+    }
+
+    #[inline]
+    pub fn new_ref(tcx: TyCtxt<'tcx>, r: Region<'tcx>, tm: TypeAndMut<'tcx>) -> Ty<'tcx> {
+        Ty::new(tcx, Ref(r, tm.ty, tm.mutbl))
+    }
+
+    #[inline]
+    pub fn new_mut_ref(tcx: TyCtxt<'tcx>, r: Region<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+        Ty::new_ref(tcx, r, TypeAndMut { ty, mutbl: hir::Mutability::Mut })
+    }
+
+    #[inline]
+    pub fn new_imm_ref(tcx: TyCtxt<'tcx>, r: Region<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+        Ty::new_ref(tcx, r, TypeAndMut { ty, mutbl: hir::Mutability::Not })
+    }
+
+    #[inline]
+    pub fn new_ptr(tcx: TyCtxt<'tcx>, tm: TypeAndMut<'tcx>) -> Ty<'tcx> {
+        Ty::new(tcx, RawPtr(tm))
+    }
+
+    #[inline]
+    pub fn new_mut_ptr(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+        Ty::new_ptr(tcx, TypeAndMut { ty, mutbl: hir::Mutability::Mut })
+    }
+
+    #[inline]
+    pub fn new_imm_ptr(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+        Ty::new_ptr(tcx, TypeAndMut { ty, mutbl: hir::Mutability::Not })
+    }
+
+    #[inline]
+    pub fn new_adt(tcx: TyCtxt<'tcx>, def: AdtDef<'tcx>, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
+        Ty::new(tcx, Adt(def, substs))
+    }
+
+    #[inline]
+    pub fn new_foreign(tcx: TyCtxt<'tcx>, def_id: DefId) -> Ty<'tcx> {
+        Ty::new(tcx, Foreign(def_id))
+    }
+
+    #[inline]
+    pub fn new_array(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, n: u64) -> Ty<'tcx> {
+        Ty::new(tcx, Array(ty, ty::Const::from_target_usize(tcx, n)))
+    }
+
+    #[inline]
+    pub fn new_array_with_const_len(
+        tcx: TyCtxt<'tcx>,
+        ty: Ty<'tcx>,
+        ct: ty::Const<'tcx>,
+    ) -> Ty<'tcx> {
+        Ty::new(tcx, Array(ty, ct))
+    }
+
+    #[inline]
+    pub fn new_slice(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+        Ty::new(tcx, Slice(ty))
+    }
+
+    #[inline]
+    pub fn new_tup(tcx: TyCtxt<'tcx>, ts: &[Ty<'tcx>]) -> Ty<'tcx> {
+        if ts.is_empty() { tcx.types.unit } else { Ty::new(tcx, Tuple(tcx.mk_type_list(&ts))) }
+    }
+
+    pub fn new_tup_from_iter<I, T>(tcx: TyCtxt<'tcx>, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<Ty<'tcx>, Ty<'tcx>>,
+    {
+        T::collect_and_apply(iter, |ts| Ty::new_tup(tcx, ts))
+    }
+
+    #[inline]
+    pub fn new_fn_def(
+        tcx: TyCtxt<'tcx>,
+        def_id: DefId,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
+    ) -> Ty<'tcx> {
+        let substs = tcx.check_and_mk_substs(def_id, substs);
+        Ty::new(tcx, FnDef(def_id, substs))
+    }
+
+    #[inline]
+    pub fn new_fn_ptr(tcx: TyCtxt<'tcx>, fty: PolyFnSig<'tcx>) -> Ty<'tcx> {
+        Ty::new(tcx, FnPtr(fty))
+    }
+
+    #[inline]
+    pub fn new_dynamic(
+        tcx: TyCtxt<'tcx>,
+        obj: &'tcx List<PolyExistentialPredicate<'tcx>>,
+        reg: ty::Region<'tcx>,
+        repr: DynKind,
+    ) -> Ty<'tcx> {
+        Ty::new(tcx, Dynamic(obj, reg, repr))
+    }
+
+    #[inline]
+    pub fn new_projection(
+        tcx: TyCtxt<'tcx>,
+        item_def_id: DefId,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
+    ) -> Ty<'tcx> {
+        Ty::new_alias(tcx, ty::Projection, tcx.mk_alias_ty(item_def_id, substs))
+    }
+
+    #[inline]
+    pub fn new_closure(
+        tcx: TyCtxt<'tcx>,
+        def_id: DefId,
+        closure_substs: SubstsRef<'tcx>,
+    ) -> Ty<'tcx> {
+        debug_assert_eq!(
+            closure_substs.len(),
+            tcx.generics_of(tcx.typeck_root_def_id(def_id)).count() + 3,
+            "closure constructed with incorrect substitutions"
+        );
+        Ty::new(tcx, Closure(def_id, closure_substs))
+    }
+
+    #[inline]
+    pub fn new_generator(
+        tcx: TyCtxt<'tcx>,
+        def_id: DefId,
+        generator_substs: SubstsRef<'tcx>,
+        movability: hir::Movability,
+    ) -> Ty<'tcx> {
+        debug_assert_eq!(
+            generator_substs.len(),
+            tcx.generics_of(tcx.typeck_root_def_id(def_id)).count() + 5,
+            "generator constructed with incorrect number of substitutions"
+        );
+        Ty::new(tcx, Generator(def_id, generator_substs, movability))
+    }
+
+    #[inline]
+    pub fn new_generator_witness(
+        tcx: TyCtxt<'tcx>,
+        types: ty::Binder<'tcx, &'tcx List<Ty<'tcx>>>,
+    ) -> Ty<'tcx> {
+        Ty::new(tcx, GeneratorWitness(types))
+    }
+
+    #[inline]
+    pub fn new_generator_witness_mir(
+        tcx: TyCtxt<'tcx>,
+        id: DefId,
+        substs: SubstsRef<'tcx>,
+    ) -> Ty<'tcx> {
+        Ty::new(tcx, GeneratorWitnessMIR(id, substs))
+    }
+
+    // misc
+
+    #[inline]
+    pub fn new_unit(tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
+        tcx.types.unit
+    }
+
+    #[inline]
+    pub fn new_static_str(tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
+        Ty::new_imm_ref(tcx, tcx.lifetimes.re_static, tcx.types.str_)
+    }
+
+    #[inline]
+    pub fn new_diverging_default(tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
+        if tcx.features().never_type_fallback { tcx.types.never } else { tcx.types.unit }
+    }
+
+    // lang and diagnostic tys
+
+    fn new_generic_adt(tcx: TyCtxt<'tcx>, wrapper_def_id: DefId, ty_param: Ty<'tcx>) -> Ty<'tcx> {
+        let adt_def = tcx.adt_def(wrapper_def_id);
+        let substs =
+            InternalSubsts::for_item(tcx, wrapper_def_id, |param, substs| match param.kind {
+                GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => bug!(),
+                GenericParamDefKind::Type { has_default, .. } => {
+                    if param.index == 0 {
+                        ty_param.into()
+                    } else {
+                        assert!(has_default);
+                        tcx.type_of(param.def_id).subst(tcx, substs).into()
+                    }
+                }
+            });
+        Ty::new(tcx, Adt(adt_def, substs))
+    }
+
+    #[inline]
+    pub fn new_lang_item(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, item: LangItem) -> Option<Ty<'tcx>> {
+        let def_id = tcx.lang_items().get(item)?;
+        Some(Ty::new_generic_adt(tcx, def_id, ty))
+    }
+
+    #[inline]
+    pub fn new_diagnostic_item(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, name: Symbol) -> Option<Ty<'tcx>> {
+        let def_id = tcx.get_diagnostic_item(name)?;
+        Some(Ty::new_generic_adt(tcx, def_id, ty))
+    }
+
+    #[inline]
+    pub fn new_box(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+        let def_id = tcx.require_lang_item(LangItem::OwnedBox, None);
+        Ty::new_generic_adt(tcx, def_id, ty)
+    }
+
+    #[inline]
+    pub fn new_maybe_uninit(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+        let def_id = tcx.require_lang_item(LangItem::MaybeUninit, None);
+        Ty::new_generic_adt(tcx, def_id, ty)
+    }
+
+    /// Creates a `&mut Context<'_>` [`Ty`] with erased lifetimes.
+    pub fn new_task_context(tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
+        let context_did = tcx.require_lang_item(LangItem::Context, None);
+        let context_adt_ref = tcx.adt_def(context_did);
+        let context_substs = tcx.mk_substs(&[tcx.lifetimes.re_erased.into()]);
+        let context_ty = Ty::new_adt(tcx, context_adt_ref, context_substs);
+        Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, context_ty)
+    }
+}
+
 /// Type utilities
 impl<'tcx> Ty<'tcx> {
     #[inline(always)]
@@ -2213,7 +2704,7 @@ impl<'tcx> Ty<'tcx> {
                 let assoc_items = tcx.associated_item_def_ids(
                     tcx.require_lang_item(hir::LangItem::DiscriminantKind, None),
                 );
-                tcx.mk_projection(assoc_items[0], tcx.mk_substs(&[self.into()]))
+                Ty::new_projection(tcx, assoc_items[0], tcx.mk_substs(&[self.into()]))
             }
 
             ty::Bool
@@ -2366,7 +2857,7 @@ impl<'tcx> Ty<'tcx> {
 
             ty::Tuple(tys) => tys.iter().all(|ty| ty.is_trivially_sized(tcx)),
 
-            ty::Adt(def, _substs) => def.sized_constraint(tcx).0.is_empty(),
+            ty::Adt(def, _substs) => def.sized_constraint(tcx).skip_binder().is_empty(),
 
             ty::Alias(..) | ty::Param(_) | ty::Placeholder(..) => false,
 
diff --git a/compiler/rustc_middle/src/ty/subst.rs b/compiler/rustc_middle/src/ty/subst.rs
index 43f95635a..4d5f5b865 100644
--- a/compiler/rustc_middle/src/ty/subst.rs
+++ b/compiler/rustc_middle/src/ty/subst.rs
@@ -11,6 +11,7 @@ use rustc_errors::{DiagnosticArgValue, IntoDiagnosticArg};
 use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
 use rustc_serialize::{self, Decodable, Encodable};
+use rustc_span::sym;
 use rustc_type_ir::WithCachedTypeInfo;
 use smallvec::SmallVec;
 
@@ -451,6 +452,10 @@ impl<'tcx> InternalSubsts<'tcx> {
     pub fn truncate_to(&self, tcx: TyCtxt<'tcx>, generics: &ty::Generics) -> SubstsRef<'tcx> {
         tcx.mk_substs_from_iter(self.iter().take(generics.count()))
     }
+
+    pub fn host_effect_param(&'tcx self) -> Option<ty::Const<'tcx>> {
+        self.consts().rfind(|x| matches!(x.kind(), ty::ConstKind::Param(p) if p.name == sym::host))
+    }
 }
 
 impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for SubstsRef<'tcx> {
@@ -538,15 +543,21 @@ impl<'tcx, T: TypeVisitable<TyCtxt<'tcx>>> TypeVisitable<TyCtxt<'tcx>> for &'tcx
 /// [`subst_identity`](EarlyBinder::subst_identity) or [`skip_binder`](EarlyBinder::skip_binder).
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 #[derive(Encodable, Decodable, HashStable)]
-pub struct EarlyBinder<T>(pub T);
+pub struct EarlyBinder<T> {
+    value: T,
+}
 
 /// For early binders, you should first call `subst` before using any visitors.
 impl<'tcx, T> !TypeFoldable<TyCtxt<'tcx>> for ty::EarlyBinder<T> {}
 impl<'tcx, T> !TypeVisitable<TyCtxt<'tcx>> for ty::EarlyBinder<T> {}
 
 impl<T> EarlyBinder<T> {
+    pub fn bind(value: T) -> EarlyBinder<T> {
+        EarlyBinder { value }
+    }
+
     pub fn as_ref(&self) -> EarlyBinder<&T> {
-        EarlyBinder(&self.0)
+        EarlyBinder { value: &self.value }
     }
 
     pub fn map_bound_ref<F, U>(&self, f: F) -> EarlyBinder<U>
@@ -560,20 +571,20 @@ impl<T> EarlyBinder<T> {
     where
         F: FnOnce(T) -> U,
     {
-        let value = f(self.0);
-        EarlyBinder(value)
+        let value = f(self.value);
+        EarlyBinder { value }
     }
 
     pub fn try_map_bound<F, U, E>(self, f: F) -> Result<EarlyBinder<U>, E>
     where
         F: FnOnce(T) -> Result<U, E>,
     {
-        let value = f(self.0)?;
-        Ok(EarlyBinder(value))
+        let value = f(self.value)?;
+        Ok(EarlyBinder { value })
     }
 
     pub fn rebind<U>(&self, value: U) -> EarlyBinder<U> {
-        EarlyBinder(value)
+        EarlyBinder { value }
     }
 
     /// Skips the binder and returns the "bound" value.
@@ -582,22 +593,26 @@ impl<T> EarlyBinder<T> {
     /// arguments of an `FnSig`). Otherwise, consider using
     /// [`subst_identity`](EarlyBinder::subst_identity).
     ///
+    /// To skip the binder on `x: &EarlyBinder<T>` to obtain `&T`, leverage
+    /// [`EarlyBinder::as_ref`](EarlyBinder::as_ref): `x.as_ref().skip_binder()`.
+    ///
     /// See also [`Binder::skip_binder`](super::Binder::skip_binder), which is
     /// the analogous operation on [`super::Binder`].
     pub fn skip_binder(self) -> T {
-        self.0
+        self.value
     }
 }
 
 impl<T> EarlyBinder<Option<T>> {
     pub fn transpose(self) -> Option<EarlyBinder<T>> {
-        self.0.map(|v| EarlyBinder(v))
+        self.value.map(|value| EarlyBinder { value })
     }
 }
 
 impl<T, U> EarlyBinder<(T, U)> {
     pub fn transpose_tuple2(self) -> (EarlyBinder<T>, EarlyBinder<U>) {
-        (EarlyBinder(self.0.0), EarlyBinder(self.0.1))
+        let EarlyBinder { value: (lhs, rhs) } = self;
+        (EarlyBinder { value: lhs }, EarlyBinder { value: rhs })
     }
 }
 
@@ -610,13 +625,13 @@ where
         tcx: TyCtxt<'tcx>,
         substs: &'s [GenericArg<'tcx>],
     ) -> SubstIter<'s, 'tcx, I> {
-        SubstIter { it: self.0.into_iter(), tcx, substs }
+        SubstIter { it: self.value.into_iter(), tcx, substs }
     }
 
     /// Similar to [`subst_identity`](EarlyBinder::subst_identity),
     /// but on an iterator of `TypeFoldable` values.
     pub fn subst_identity_iter(self) -> I::IntoIter {
-        self.0.into_iter()
+        self.value.into_iter()
     }
 }
 
@@ -633,7 +648,7 @@ where
     type Item = I::Item;
 
     fn next(&mut self) -> Option<Self::Item> {
-        Some(EarlyBinder(self.it.next()?).subst(self.tcx, self.substs))
+        Some(EarlyBinder { value: self.it.next()? }.subst(self.tcx, self.substs))
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
@@ -647,7 +662,7 @@ where
     I::Item: TypeFoldable<TyCtxt<'tcx>>,
 {
     fn next_back(&mut self) -> Option<Self::Item> {
-        Some(EarlyBinder(self.it.next_back()?).subst(self.tcx, self.substs))
+        Some(EarlyBinder { value: self.it.next_back()? }.subst(self.tcx, self.substs))
     }
 }
 
@@ -668,13 +683,13 @@ where
         tcx: TyCtxt<'tcx>,
         substs: &'s [GenericArg<'tcx>],
     ) -> SubstIterCopied<'s, 'tcx, I> {
-        SubstIterCopied { it: self.0.into_iter(), tcx, substs }
+        SubstIterCopied { it: self.value.into_iter(), tcx, substs }
     }
 
     /// Similar to [`subst_identity`](EarlyBinder::subst_identity),
     /// but on an iterator of values that deref to a `TypeFoldable`.
     pub fn subst_identity_iter_copied(self) -> impl Iterator<Item = <I::Item as Deref>::Target> {
-        self.0.into_iter().map(|v| *v)
+        self.value.into_iter().map(|v| *v)
     }
 }
 
@@ -692,7 +707,7 @@ where
     type Item = <I::Item as Deref>::Target;
 
     fn next(&mut self) -> Option<Self::Item> {
-        Some(EarlyBinder(*self.it.next()?).subst(self.tcx, self.substs))
+        self.it.next().map(|value| EarlyBinder { value: *value }.subst(self.tcx, self.substs))
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
@@ -707,7 +722,7 @@ where
     <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>,
 {
     fn next_back(&mut self) -> Option<Self::Item> {
-        Some(EarlyBinder(*self.it.next_back()?).subst(self.tcx, self.substs))
+        self.it.next_back().map(|value| EarlyBinder { value: *value }.subst(self.tcx, self.substs))
     }
 }
 
@@ -725,7 +740,7 @@ pub struct EarlyBinderIter<T> {
 
 impl<T: IntoIterator> EarlyBinder<T> {
     pub fn transpose_iter(self) -> EarlyBinderIter<T::IntoIter> {
-        EarlyBinderIter { t: self.0.into_iter() }
+        EarlyBinderIter { t: self.value.into_iter() }
     }
 }
 
@@ -733,7 +748,7 @@ impl<T: Iterator> Iterator for EarlyBinderIter<T> {
     type Item = EarlyBinder<T::Item>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.t.next().map(|i| EarlyBinder(i))
+        self.t.next().map(|value| EarlyBinder { value })
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
@@ -744,7 +759,7 @@ impl<T: Iterator> Iterator for EarlyBinderIter<T> {
 impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>>> ty::EarlyBinder<T> {
     pub fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> T {
         let mut folder = SubstFolder { tcx, substs, binders_passed: 0 };
-        self.0.fold_with(&mut folder)
+        self.value.fold_with(&mut folder)
     }
 
     /// Makes the identity substitution `T0 => T0, ..., TN => TN`.
@@ -756,12 +771,12 @@ impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>>> ty::EarlyBinder<T> {
     /// - Inside of the body of `foo`, we treat `T` as a placeholder by calling
     /// `subst_identity` to discharge the `EarlyBinder`.
     pub fn subst_identity(self) -> T {
-        self.0
+        self.value
     }
 
     /// Returns the inner value, but only if it contains no bound vars.
     pub fn no_bound_vars(self) -> Option<T> {
-        if !self.0.has_param() { Some(self.0) } else { None }
+        if !self.value.has_param() { Some(self.value) } else { None }
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs
index e61037e5e..98c70e330 100644
--- a/compiler/rustc_middle/src/ty/trait_def.rs
+++ b/compiler/rustc_middle/src/ty/trait_def.rs
@@ -52,6 +52,16 @@ pub struct TraitDef {
     /// List of functions from `#[rustc_must_implement_one_of]` attribute one of which
     /// must be implemented.
     pub must_implement_one_of: Option<Box<[Ident]>>,
+
+    /// Whether to add a builtin `dyn Trait: Trait` implementation.
+    /// This is enabled for all traits except ones marked with
+    /// `#[rustc_deny_explicit_impl(implement_via_object = false)]`.
+    pub implement_via_object: bool,
+
+    /// Whether a trait is fully built-in, and any implementation is disallowed.
+    /// This only applies to built-in traits, and is marked via
+    /// `#[rustc_deny_explicit_impl(implement_via_object = ...)]`.
+    pub deny_explicit_impl: bool,
 }
 
 /// Whether this trait is treated specially by the standard library
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index e04dbbff9..8cbffa148 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -155,11 +155,7 @@ pub struct TypeckResults<'tcx> {
     /// We also store the type here, so that the compiler can use it as a hint
     /// for figuring out hidden types, even if they are only set in dead code
     /// (which doesn't show up in MIR).
-    ///
-    /// These types are mapped back to the opaque's identity substitutions
-    /// (with erased regions), which is why we don't associated substs with any
-    /// of these usages.
-    pub concrete_opaque_types: FxIndexMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
+    pub concrete_opaque_types: FxIndexMap<ty::OpaqueTypeKey<'tcx>, ty::OpaqueHiddenType<'tcx>>,
 
     /// Tracks the minimum captures required for a closure;
     /// see `MinCaptureInformationMap` for more details.
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index ba0513563..e2e4a2dbd 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -1,7 +1,6 @@
 //! Miscellaneous type-system utilities that are too small to deserve their own modules.
 
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
-use crate::mir;
 use crate::query::Providers;
 use crate::ty::layout::IntegerExt;
 use crate::ty::{
@@ -11,13 +10,12 @@ use crate::ty::{
 use crate::ty::{GenericArgKind, SubstsRef};
 use rustc_apfloat::Float as _;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_data_structures::stable_hasher::{Hash64, HashStable, StableHasher};
+use rustc_data_structures::stable_hasher::{Hash128, HashStable, StableHasher};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Res};
-use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_index::bit_set::GrowableBitSet;
-use rustc_index::{Idx, IndexVec};
 use rustc_macros::HashStable;
 use rustc_session::Limit;
 use rustc_span::sym;
@@ -129,7 +127,7 @@ impl IntTypeExt for IntegerType {
 impl<'tcx> TyCtxt<'tcx> {
     /// Creates a hash of the type `Ty` which will be the same no matter what crate
     /// context it's calculated within. This is used by the `type_id` intrinsic.
-    pub fn type_id_hash(self, ty: Ty<'tcx>) -> Hash64 {
+    pub fn type_id_hash(self, ty: Ty<'tcx>) -> Hash128 {
         // We want the type_id be independent of the types free regions, so we
         // erase them. The erase_regions() call will also anonymize bound
         // regions, which is desirable too.
@@ -173,18 +171,6 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
-        if let ty::Adt(def, substs) = *ty.kind() {
-            for field in def.all_fields() {
-                let field_ty = field.ty(self, substs);
-                if let ty::Error(_) = field_ty.kind() {
-                    return true;
-                }
-            }
-        }
-        false
-    }
-
     /// Attempts to returns the deeply last field of nested structures, but
     /// does not apply any normalization in its search. Returns the same type
     /// if input `ty` is not a structure at all.
@@ -237,14 +223,14 @@ impl<'tcx> TyCtxt<'tcx> {
                 };
                 let reported =
                     self.sess.emit_err(crate::error::RecursionLimitReached { ty, suggested_limit });
-                return self.ty_error(reported);
+                return Ty::new_error(self, reported);
             }
             match *ty.kind() {
                 ty::Adt(def, substs) => {
                     if !def.is_struct() {
                         break;
                     }
-                    match def.non_enum_variant().fields.raw.last() {
+                    match def.non_enum_variant().tail_opt() {
                         Some(field) => {
                             f();
                             ty = field.ty(self, substs);
@@ -318,7 +304,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
                     if a_def == b_def && a_def.is_struct() =>
                 {
-                    if let Some(f) = a_def.non_enum_variant().fields.raw.last() {
+                    if let Some(f) = a_def.non_enum_variant().tail_opt() {
                         a = f.ty(self, a_substs);
                         b = f.ty(self, b_substs);
                     } else {
@@ -624,12 +610,12 @@ impl<'tcx> TyCtxt<'tcx> {
         closure_substs: SubstsRef<'tcx>,
         env_region: ty::Region<'tcx>,
     ) -> Option<Ty<'tcx>> {
-        let closure_ty = self.mk_closure(closure_def_id, closure_substs);
+        let closure_ty = Ty::new_closure(self, closure_def_id, closure_substs);
         let closure_kind_ty = closure_substs.as_closure().kind_ty();
         let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
         let env_ty = match closure_kind {
-            ty::ClosureKind::Fn => self.mk_imm_ref(env_region, closure_ty),
-            ty::ClosureKind::FnMut => self.mk_mut_ref(env_region, closure_ty),
+            ty::ClosureKind::Fn => Ty::new_imm_ref(self, env_region, closure_ty),
+            ty::ClosureKind::FnMut => Ty::new_mut_ref(self, env_region, closure_ty),
             ty::ClosureKind::FnOnce => closure_ty,
         };
         Some(env_ty)
@@ -670,12 +656,12 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn thread_local_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
         let static_ty = self.type_of(def_id).subst_identity();
         if self.is_mutable_static(def_id) {
-            self.mk_mut_ptr(static_ty)
+            Ty::new_mut_ptr(self, static_ty)
         } else if self.is_foreign_item(def_id) {
-            self.mk_imm_ptr(static_ty)
+            Ty::new_imm_ptr(self, static_ty)
         } else {
             // FIXME: These things don't *really* have 'static lifetime.
-            self.mk_imm_ref(self.lifetimes.re_static, static_ty)
+            Ty::new_imm_ref(self, self.lifetimes.re_static, static_ty)
         }
     }
 
@@ -690,11 +676,11 @@ impl<'tcx> TyCtxt<'tcx> {
         // Make sure that accesses to unsafe statics end up using raw pointers.
         // For thread-locals, this needs to be kept in sync with `Rvalue::ty`.
         if self.is_mutable_static(def_id) {
-            self.mk_mut_ptr(static_ty)
+            Ty::new_mut_ptr(self, static_ty)
         } else if self.is_foreign_item(def_id) {
-            self.mk_imm_ptr(static_ty)
+            Ty::new_imm_ptr(self, static_ty)
         } else {
-            self.mk_imm_ref(self.lifetimes.re_erased, static_ty)
+            Ty::new_imm_ref(self, self.lifetimes.re_erased, static_ty)
         }
     }
 
@@ -709,7 +695,7 @@ impl<'tcx> TyCtxt<'tcx> {
             .as_ref()
             .map_or_else(|| [].iter(), |l| l.field_tys.iter())
             .filter(|decl| !decl.ignore_for_traits)
-            .map(|decl| ty::EarlyBinder(decl.ty))
+            .map(|decl| ty::EarlyBinder::bind(decl.ty))
     }
 
     /// Normalizes all opaque types in the given value, replacing them
@@ -750,80 +736,6 @@ impl<'tcx> TyCtxt<'tcx> {
         if visitor.found_recursion { Err(expanded_type) } else { Ok(expanded_type) }
     }
 
-    /// Returns names of captured upvars for closures and generators.
-    ///
-    /// Here are some examples:
-    ///  - `name__field1__field2` when the upvar is captured by value.
-    ///  - `_ref__name__field` when the upvar is captured by reference.
-    ///
-    /// For generators this only contains upvars that are shared by all states.
-    pub fn closure_saved_names_of_captured_variables(
-        self,
-        def_id: DefId,
-    ) -> SmallVec<[String; 16]> {
-        let body = self.optimized_mir(def_id);
-
-        body.var_debug_info
-            .iter()
-            .filter_map(|var| {
-                let is_ref = match var.value {
-                    mir::VarDebugInfoContents::Place(place)
-                        if place.local == mir::Local::new(1) =>
-                    {
-                        // The projection is either `[.., Field, Deref]` or `[.., Field]`. It
-                        // implies whether the variable is captured by value or by reference.
-                        matches!(place.projection.last().unwrap(), mir::ProjectionElem::Deref)
-                    }
-                    _ => return None,
-                };
-                let prefix = if is_ref { "_ref__" } else { "" };
-                Some(prefix.to_owned() + var.name.as_str())
-            })
-            .collect()
-    }
-
-    // FIXME(eddyb) maybe precompute this? Right now it's computed once
-    // per generator monomorphization, but it doesn't depend on substs.
-    pub fn generator_layout_and_saved_local_names(
-        self,
-        def_id: DefId,
-    ) -> (
-        &'tcx ty::GeneratorLayout<'tcx>,
-        IndexVec<mir::GeneratorSavedLocal, Option<rustc_span::Symbol>>,
-    ) {
-        let tcx = self;
-        let body = tcx.optimized_mir(def_id);
-        let generator_layout = body.generator_layout().unwrap();
-        let mut generator_saved_local_names =
-            IndexVec::from_elem(None, &generator_layout.field_tys);
-
-        let state_arg = mir::Local::new(1);
-        for var in &body.var_debug_info {
-            let mir::VarDebugInfoContents::Place(place) = &var.value else { continue };
-            if place.local != state_arg {
-                continue;
-            }
-            match place.projection[..] {
-                [
-                    // Deref of the `Pin<&mut Self>` state argument.
-                    mir::ProjectionElem::Field(..),
-                    mir::ProjectionElem::Deref,
-                    // Field of a variant of the state.
-                    mir::ProjectionElem::Downcast(_, variant),
-                    mir::ProjectionElem::Field(field, _),
-                ] => {
-                    let name = &mut generator_saved_local_names
-                        [generator_layout.variant_fields[variant][field]];
-                    if name.is_none() {
-                        name.replace(var.name);
-                    }
-                }
-                _ => {}
-            }
-        }
-        (generator_layout, generator_saved_local_names)
-    }
-
     /// Query and get an English description for the item's kind.
     pub fn def_descr(self, def_id: DefId) -> &'static str {
         self.def_kind_descr(self.def_kind(def_id), def_id)
@@ -857,6 +769,26 @@ impl<'tcx> TyCtxt<'tcx> {
             _ => def_kind.article(),
         }
     }
+
+    /// Return `true` if the supplied `CrateNum` is "user-visible," meaning either a [public]
+    /// dependency, or a [direct] private dependency. This is used to decide whether the crate can
+    /// be shown in `impl` suggestions.
+    ///
+    /// [public]: TyCtxt::is_private_dep
+    /// [direct]: rustc_session::cstore::ExternCrate::is_direct
+    pub fn is_user_visible_dep(self, key: CrateNum) -> bool {
+        // | Private | Direct | Visible |                    |
+        // |---------|--------|---------|--------------------|
+        // | Yes     | Yes    | Yes     | !true || true   |
+        // | No      | Yes    | Yes     | !false || true  |
+        // | Yes     | No     | No      | !true || false  |
+        // | No      | No     | Yes     | !false || false |
+        !self.is_private_dep(key)
+            // If `extern_crate` is `None`, then the crate was injected (e.g., by the allocator).
+            // Treat that kind of crate as "indirect", since it's an implementation detail of
+            // the language.
+            || self.extern_crate(key.as_def_id()).map_or(false, |e| e.is_direct())
+    }
 }
 
 struct OpaqueTypeExpander<'tcx> {
@@ -922,7 +854,7 @@ impl<'tcx> OpaqueTypeExpander<'tcx> {
                         let hidden_ty = bty.subst(self.tcx, substs);
                         self.fold_ty(hidden_ty);
                     }
-                    let expanded_ty = self.tcx.mk_generator_witness_mir(def_id, substs);
+                    let expanded_ty = Ty::new_generator_witness_mir(self.tcx, def_id, substs);
                     self.expanded_cache.insert((def_id, substs), expanded_ty);
                     expanded_ty
                 }
@@ -964,7 +896,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
 
     fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
         if let ty::PredicateKind::Clause(clause) = p.kind().skip_binder()
-            && let ty::Clause::Projection(projection_pred) = clause
+            && let ty::ClauseKind::Projection(projection_pred) = clause
         {
             p.kind()
                 .rebind(ty::ProjectionPredicate {
@@ -1374,7 +1306,7 @@ pub fn needs_drop_components<'tcx>(
         ty::Array(elem_ty, size) => {
             match needs_drop_components(*elem_ty, target_layout) {
                 Ok(v) if v.is_empty() => Ok(v),
-                res => match size.kind().try_to_bits(target_layout.pointer_size) {
+                res => match size.try_to_bits(target_layout.pointer_size) {
                     // Arrays of size zero don't need drop, even if their element
                     // type does.
                     Some(0) => Ok(SmallVec::new()),
@@ -1487,8 +1419,8 @@ pub struct AlwaysRequiresDrop;
 /// with their underlying types.
 pub fn reveal_opaque_types_in_bounds<'tcx>(
     tcx: TyCtxt<'tcx>,
-    val: &'tcx ty::List<ty::Predicate<'tcx>>,
-) -> &'tcx ty::List<ty::Predicate<'tcx>> {
+    val: &'tcx ty::List<ty::Clause<'tcx>>,
+) -> &'tcx ty::List<ty::Clause<'tcx>> {
     let mut visitor = OpaqueTypeExpander {
         seen_opaque_tys: FxHashSet::default(),
         expanded_cache: FxHashMap::default(),
diff --git a/compiler/rustc_middle/src/ty/vtable.rs b/compiler/rustc_middle/src/ty/vtable.rs
index b9b1cd73a..443791d0a 100644
--- a/compiler/rustc_middle/src/ty/vtable.rs
+++ b/compiler/rustc_middle/src/ty/vtable.rs
@@ -73,7 +73,7 @@ pub(super) fn vtable_allocation_provider<'tcx>(
     let ptr_align = tcx.data_layout.pointer_align.abi;
 
     let vtable_size = ptr_size * u64::try_from(vtable_entries.len()).unwrap();
-    let mut vtable = Allocation::uninit(vtable_size, ptr_align, /* panic_on_fail */ true).unwrap();
+    let mut vtable = Allocation::uninit(vtable_size, ptr_align);
 
     // No need to do any alignment checks on the memory accesses below, because we know the
     // allocation is correctly aligned as we created it above. Also we're only offsetting by
diff --git a/compiler/rustc_middle/src/values.rs b/compiler/rustc_middle/src/values.rs
index c62c33d4d..b0961d917 100644
--- a/compiler/rustc_middle/src/values.rs
+++ b/compiler/rustc_middle/src/values.rs
@@ -16,7 +16,7 @@ impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for Ty<'_> {
     fn from_cycle_error(tcx: TyCtxt<'tcx>, _: &[QueryInfo<DepKind>]) -> Self {
         // SAFETY: This is never called when `Self` is not `Ty<'tcx>`.
         // FIXME: Represent the above fact in the trait system somehow.
-        unsafe { std::mem::transmute::<Ty<'tcx>, Ty<'_>>(tcx.ty_error_misc()) }
+        unsafe { std::mem::transmute::<Ty<'tcx>, Ty<'_>>(Ty::new_misc_error(tcx)) }
     }
 }
 
@@ -34,7 +34,7 @@ impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::SymbolName<'_> {
 
 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::Binder<'_, ty::FnSig<'_>> {
     fn from_cycle_error(tcx: TyCtxt<'tcx>, stack: &[QueryInfo<DepKind>]) -> Self {
-        let err = tcx.ty_error_misc();
+        let err = Ty::new_misc_error(tcx);
 
         let arity = if let Some(frame) = stack.get(0)
             && frame.query.dep_kind == DepKind::fn_sig
@@ -96,19 +96,22 @@ impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for Representability {
 
 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::EarlyBinder<Ty<'_>> {
     fn from_cycle_error(tcx: TyCtxt<'tcx>, cycle: &[QueryInfo<DepKind>]) -> Self {
-        ty::EarlyBinder(Ty::from_cycle_error(tcx, cycle))
+        ty::EarlyBinder::bind(Ty::from_cycle_error(tcx, cycle))
     }
 }
 
 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::EarlyBinder<ty::Binder<'_, ty::FnSig<'_>>> {
     fn from_cycle_error(tcx: TyCtxt<'tcx>, cycle: &[QueryInfo<DepKind>]) -> Self {
-        ty::EarlyBinder(ty::Binder::from_cycle_error(tcx, cycle))
+        ty::EarlyBinder::bind(ty::Binder::from_cycle_error(tcx, cycle))
     }
 }
 
-impl<'tcx, T> Value<TyCtxt<'tcx>, DepKind> for Result<T, ty::layout::LayoutError<'_>> {
+impl<'tcx, T> Value<TyCtxt<'tcx>, DepKind> for Result<T, &'_ ty::layout::LayoutError<'_>> {
     fn from_cycle_error(_tcx: TyCtxt<'tcx>, _cycle: &[QueryInfo<DepKind>]) -> Self {
-        Err(ty::layout::LayoutError::Cycle)
+        // tcx.arena.alloc cannot be used because we are not allowed to use &'tcx LayoutError under
+        // min_specialization. Since this is an error path anyways, leaking doesn't matter (and really,
+        // tcx.arena.alloc is pretty much equal to leaking).
+        Err(Box::leak(Box::new(ty::layout::LayoutError::Cycle)))
     }
 }