Rollup merge of #125968 - BoxyUwU:shrink_ty_expr, r=oli-obk

Store the types of `ty::Expr` arguments in the `ty::Expr`

Part of #125958

In attempting to remove the `ty` field on `Const` it will become necessary to store the `Ty<'tcx>` inside of `Expr<'tcx>`. In order to do this without blowing up the size of `ConstKind`, we start storing the type/const args as `GenericArgs`

r? `@oli-obk`

13 files changed, 259 insertions, 165 deletions

diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index 6416bbbe889..384a4e7009d 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -24,7 +24,7 @@ pub type ConstKind<'tcx> = ir::ConstKind<TyCtxt<'tcx>>;
 pub type UnevaluatedConst<'tcx> = ir::UnevaluatedConst<TyCtxt<'tcx>>;
 
 #[cfg(target_pointer_width = "64")]
-rustc_data_structures::static_assert_size!(ConstKind<'_>, 32);
+rustc_data_structures::static_assert_size!(ConstKind<'_>, 24);
 
 /// Use this rather than `ConstData`, whenever possible.
 #[derive(Copy, Clone, PartialEq, Eq, Hash, HashStable)]
@@ -58,7 +58,7 @@ pub struct ConstData<'tcx> {
 }
 
 #[cfg(target_pointer_width = "64")]
-rustc_data_structures::static_assert_size!(ConstData<'_>, 40);
+rustc_data_structures::static_assert_size!(ConstData<'_>, 32);
 
 impl<'tcx> Const<'tcx> {
     #[inline]
diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs
index d7ae050ed4d..5f29acf5ed2 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -1,7 +1,7 @@
 use super::Const;
 use crate::mir;
 use crate::ty::abstract_const::CastKind;
-use crate::ty::{self, visit::TypeVisitableExt as _, List, Ty, TyCtxt};
+use crate::ty::{self, visit::TypeVisitableExt as _, Ty, TyCtxt};
 use rustc_macros::{extension, HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 
 #[extension(pub(crate) trait UnevaluatedConstEvalExt<'tcx>)]
@@ -40,14 +40,125 @@ impl<'tcx> ty::UnevaluatedConst<'tcx> {
     }
 }
 
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
+#[derive(HashStable, TyEncodable, TyDecodable, TypeVisitable, TypeFoldable)]
+pub enum ExprKind {
+    Binop(mir::BinOp),
+    UnOp(mir::UnOp),
+    FunctionCall,
+    Cast(CastKind),
+}
 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
 #[derive(HashStable, TyEncodable, TyDecodable, TypeVisitable, TypeFoldable)]
-pub enum Expr<'tcx> {
-    Binop(mir::BinOp, Const<'tcx>, Const<'tcx>),
-    UnOp(mir::UnOp, Const<'tcx>),
-    FunctionCall(Const<'tcx>, &'tcx List<Const<'tcx>>),
-    Cast(CastKind, Const<'tcx>, Ty<'tcx>),
+pub struct Expr<'tcx> {
+    pub kind: ExprKind,
+    args: ty::GenericArgsRef<'tcx>,
+}
+impl<'tcx> Expr<'tcx> {
+    pub fn new_binop(
+        tcx: TyCtxt<'tcx>,
+        binop: mir::BinOp,
+        lhs_ty: Ty<'tcx>,
+        rhs_ty: Ty<'tcx>,
+        lhs_ct: Const<'tcx>,
+        rhs_ct: Const<'tcx>,
+    ) -> Self {
+        let args = tcx.mk_args_from_iter::<_, ty::GenericArg<'tcx>>(
+            [lhs_ty.into(), rhs_ty.into(), lhs_ct.into(), rhs_ct.into()].into_iter(),
+        );
+
+        Self { kind: ExprKind::Binop(binop), args }
+    }
+
+    pub fn binop_args(self) -> (Ty<'tcx>, Ty<'tcx>, Const<'tcx>, Const<'tcx>) {
+        assert!(matches!(self.kind, ExprKind::Binop(_)));
+
+        match self.args().as_slice() {
+            [lhs_ty, rhs_ty, lhs_ct, rhs_ct] => (
+                lhs_ty.expect_ty(),
+                rhs_ty.expect_ty(),
+                lhs_ct.expect_const(),
+                rhs_ct.expect_const(),
+            ),
+            _ => bug!("Invalid args for `Binop` expr {self:?}"),
+        }
+    }
+
+    pub fn new_unop(tcx: TyCtxt<'tcx>, unop: mir::UnOp, ty: Ty<'tcx>, ct: Const<'tcx>) -> Self {
+        let args =
+            tcx.mk_args_from_iter::<_, ty::GenericArg<'tcx>>([ty.into(), ct.into()].into_iter());
+
+        Self { kind: ExprKind::UnOp(unop), args }
+    }
+
+    pub fn unop_args(self) -> (Ty<'tcx>, Const<'tcx>) {
+        assert!(matches!(self.kind, ExprKind::UnOp(_)));
+
+        match self.args().as_slice() {
+            [ty, ct] => (ty.expect_ty(), ct.expect_const()),
+            _ => bug!("Invalid args for `UnOp` expr {self:?}"),
+        }
+    }
+
+    pub fn new_call(
+        tcx: TyCtxt<'tcx>,
+        func_ty: Ty<'tcx>,
+        func_expr: Const<'tcx>,
+        arguments: impl Iterator<Item = Const<'tcx>>,
+    ) -> Self {
+        let args = tcx.mk_args_from_iter::<_, ty::GenericArg<'tcx>>(
+            [func_ty.into(), func_expr.into()].into_iter().chain(arguments.map(|ct| ct.into())),
+        );
+
+        Self { kind: ExprKind::FunctionCall, args }
+    }
+
+    pub fn call_args(self) -> (Ty<'tcx>, Const<'tcx>, impl Iterator<Item = Const<'tcx>>) {
+        assert!(matches!(self.kind, ExprKind::FunctionCall));
+
+        match self.args().as_slice() {
+            [func_ty, func, rest @ ..] => (
+                func_ty.expect_ty(),
+                func.expect_const(),
+                rest.iter().map(|arg| arg.expect_const()),
+            ),
+            _ => bug!("Invalid args for `Call` expr {self:?}"),
+        }
+    }
+
+    pub fn new_cast(
+        tcx: TyCtxt<'tcx>,
+        cast: CastKind,
+        value_ty: Ty<'tcx>,
+        value: Const<'tcx>,
+        to_ty: Ty<'tcx>,
+    ) -> Self {
+        let args = tcx.mk_args_from_iter::<_, ty::GenericArg<'tcx>>(
+            [value_ty.into(), value.into(), to_ty.into()].into_iter(),
+        );
+
+        Self { kind: ExprKind::Cast(cast), args }
+    }
+
+    pub fn cast_args(self) -> (Ty<'tcx>, Const<'tcx>, Ty<'tcx>) {
+        assert!(matches!(self.kind, ExprKind::Cast(_)));
+
+        match self.args().as_slice() {
+            [value_ty, value, to_ty] => {
+                (value_ty.expect_ty(), value.expect_const(), to_ty.expect_ty())
+            }
+            _ => bug!("Invalid args for `Cast` expr {self:?}"),
+        }
+    }
+
+    pub fn new(kind: ExprKind, args: ty::GenericArgsRef<'tcx>) -> Self {
+        Self { kind, args }
+    }
+
+    pub fn args(&self) -> ty::GenericArgsRef<'tcx> {
+        self.args
+    }
 }
 
 #[cfg(target_pointer_width = "64")]
-rustc_data_structures::static_assert_size!(Expr<'_>, 24);
+rustc_data_structures::static_assert_size!(Expr<'_>, 16);
diff --git a/compiler/rustc_middle/src/ty/flags.rs b/compiler/rustc_middle/src/ty/flags.rs
index 4de7d532c96..93a51d3a334 100644
--- a/compiler/rustc_middle/src/ty/flags.rs
+++ b/compiler/rustc_middle/src/ty/flags.rs
@@ -374,26 +374,7 @@ impl FlagComputation {
                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
             }
             ty::ConstKind::Value(_) => {}
-            ty::ConstKind::Expr(e) => {
-                use ty::Expr;
-                match e {
-                    Expr::Binop(_, l, r) => {
-                        self.add_const(l);
-                        self.add_const(r);
-                    }
-                    Expr::UnOp(_, v) => self.add_const(v),
-                    Expr::FunctionCall(f, args) => {
-                        self.add_const(f);
-                        for arg in args {
-                            self.add_const(arg);
-                        }
-                    }
-                    Expr::Cast(_, c, t) => {
-                        self.add_ty(t);
-                        self.add_const(c);
-                    }
-                }
-            }
+            ty::ConstKind::Expr(e) => self.add_args(e.args()),
             ty::ConstKind::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
         }
     }
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 3fdcb966960..c6028ef74a9 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -87,7 +87,7 @@ pub use self::closure::{
     CAPTURE_STRUCT_LOCAL,
 };
 pub use self::consts::{
-    Const, ConstData, ConstInt, ConstKind, Expr, ScalarInt, UnevaluatedConst, ValTree,
+    Const, ConstData, ConstInt, ConstKind, Expr, ExprKind, ScalarInt, UnevaluatedConst, ValTree,
 };
 pub use self::context::{
     tls, CtxtInterners, CurrentGcx, DeducedParamAttrs, Feed, FreeRegionInfo, GlobalCtxt, Lift,
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index af7784d6b8e..1b37078e703 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1533,8 +1533,10 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         print_ty: bool,
     ) -> Result<(), PrintError> {
         define_scoped_cx!(self);
-        match expr {
-            Expr::Binop(op, c1, c2) => {
+        match expr.kind {
+            ty::ExprKind::Binop(op) => {
+                let (_, _, c1, c2) = expr.binop_args();
+
                 let precedence = |binop: rustc_middle::mir::BinOp| {
                     use rustc_ast::util::parser::AssocOp;
                     AssocOp::from_ast_binop(binop.to_hir_binop().into()).precedence()
@@ -1543,22 +1545,26 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 let formatted_op = op.to_hir_binop().as_str();
                 let (lhs_parenthesized, rhs_parenthesized) = match (c1.kind(), c2.kind()) {
                     (
-                        ty::ConstKind::Expr(Expr::Binop(lhs_op, _, _)),
-                        ty::ConstKind::Expr(Expr::Binop(rhs_op, _, _)),
+                        ty::ConstKind::Expr(ty::Expr { kind: ty::ExprKind::Binop(lhs_op), .. }),
+                        ty::ConstKind::Expr(ty::Expr { kind: ty::ExprKind::Binop(rhs_op), .. }),
                     ) => (precedence(lhs_op) < op_precedence, precedence(rhs_op) < op_precedence),
-                    (ty::ConstKind::Expr(Expr::Binop(lhs_op, ..)), ty::ConstKind::Expr(_)) => {
-                        (precedence(lhs_op) < op_precedence, true)
-                    }
-                    (ty::ConstKind::Expr(_), ty::ConstKind::Expr(Expr::Binop(rhs_op, ..))) => {
-                        (true, precedence(rhs_op) < op_precedence)
-                    }
+                    (
+                        ty::ConstKind::Expr(ty::Expr { kind: ty::ExprKind::Binop(lhs_op), .. }),
+                        ty::ConstKind::Expr(_),
+                    ) => (precedence(lhs_op) < op_precedence, true),
+                    (
+                        ty::ConstKind::Expr(_),
+                        ty::ConstKind::Expr(ty::Expr { kind: ty::ExprKind::Binop(rhs_op), .. }),
+                    ) => (true, precedence(rhs_op) < op_precedence),
                     (ty::ConstKind::Expr(_), ty::ConstKind::Expr(_)) => (true, true),
-                    (ty::ConstKind::Expr(Expr::Binop(lhs_op, ..)), _) => {
-                        (precedence(lhs_op) < op_precedence, false)
-                    }
-                    (_, ty::ConstKind::Expr(Expr::Binop(rhs_op, ..))) => {
-                        (false, precedence(rhs_op) < op_precedence)
-                    }
+                    (
+                        ty::ConstKind::Expr(ty::Expr { kind: ty::ExprKind::Binop(lhs_op), .. }),
+                        _,
+                    ) => (precedence(lhs_op) < op_precedence, false),
+                    (
+                        _,
+                        ty::ConstKind::Expr(ty::Expr { kind: ty::ExprKind::Binop(rhs_op), .. }),
+                    ) => (false, precedence(rhs_op) < op_precedence),
                     (ty::ConstKind::Expr(_), _) => (true, false),
                     (_, ty::ConstKind::Expr(_)) => (false, true),
                     _ => (false, false),
@@ -1574,7 +1580,9 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     rhs_parenthesized,
                 )?;
             }
-            Expr::UnOp(op, ct) => {
+            ty::ExprKind::UnOp(op) => {
+                let (_, ct) = expr.unop_args();
+
                 use rustc_middle::mir::UnOp;
                 let formatted_op = match op {
                     UnOp::Not => "!",
@@ -1583,7 +1591,9 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 };
                 let parenthesized = match ct.kind() {
                     _ if op == UnOp::PtrMetadata => true,
-                    ty::ConstKind::Expr(Expr::UnOp(c_op, ..)) => c_op != op,
+                    ty::ConstKind::Expr(ty::Expr { kind: ty::ExprKind::UnOp(c_op), .. }) => {
+                        c_op != op
+                    }
                     ty::ConstKind::Expr(_) => true,
                     _ => false,
                 };
@@ -1593,61 +1603,37 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     parenthesized,
                 )?
             }
-            Expr::FunctionCall(fn_def, fn_args) => {
-                use ty::TyKind;
-                match fn_def.ty().kind() {
-                    TyKind::FnDef(def_id, gen_args) => {
-                        p!(print_value_path(*def_id, gen_args), "(");
-                        if print_ty {
-                            let tcx = self.tcx();
-                            let sig = tcx.fn_sig(def_id).instantiate(tcx, gen_args).skip_binder();
-
-                            let mut args_with_ty = fn_args.iter().map(|ct| (ct, ct.ty()));
-                            let output_ty = sig.output();
-
-                            if let Some((ct, ty)) = args_with_ty.next() {
-                                self.typed_value(
-                                    |this| this.pretty_print_const(ct, print_ty),
-                                    |this| this.pretty_print_type(ty),
-                                    ": ",
-                                )?;
-                                for (ct, ty) in args_with_ty {
-                                    p!(", ");
-                                    self.typed_value(
-                                        |this| this.pretty_print_const(ct, print_ty),
-                                        |this| this.pretty_print_type(ty),
-                                        ": ",
-                                    )?;
-                                }
-                            }
-                            p!(write(") -> {output_ty}"));
-                        } else {
-                            p!(comma_sep(fn_args.iter()), ")");
-                        }
-                    }
-                    _ => bug!("unexpected type of fn def"),
-                }
+            ty::ExprKind::FunctionCall => {
+                let (_, fn_def, fn_args) = expr.call_args();
+
+                write!(self, "(")?;
+                self.pretty_print_const(fn_def, print_ty)?;
+                p!(")(", comma_sep(fn_args), ")");
             }
-            Expr::Cast(kind, ct, ty) => {
+            ty::ExprKind::Cast(kind) => {
+                let (_, value, to_ty) = expr.cast_args();
+
                 use ty::abstract_const::CastKind;
                 if kind == CastKind::As || (kind == CastKind::Use && self.should_print_verbose()) {
-                    let parenthesized = match ct.kind() {
-                        ty::ConstKind::Expr(Expr::Cast(_, _, _)) => false,
+                    let parenthesized = match value.kind() {
+                        ty::ConstKind::Expr(ty::Expr {
+                            kind: ty::ExprKind::Cast { .. }, ..
+                        }) => false,
                         ty::ConstKind::Expr(_) => true,
                         _ => false,
                     };
                     self.maybe_parenthesized(
                         |this| {
                             this.typed_value(
-                                |this| this.pretty_print_const(ct, print_ty),
-                                |this| this.pretty_print_type(ty),
+                                |this| this.pretty_print_const(value, print_ty),
+                                |this| this.pretty_print_type(to_ty),
                                 " as ",
                             )
                         },
                         parenthesized,
                     )?;
                 } else {
-                    self.pretty_print_const(ct, print_ty)?
+                    self.pretty_print_const(value, print_ty)?
                 }
             }
         }
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index b4179858890..a621d255a03 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -6,8 +6,8 @@
 
 use crate::ty::error::{ExpectedFound, TypeError};
 use crate::ty::{
-    self, ExistentialPredicate, ExistentialPredicateStableCmpExt as _, Expr, GenericArg,
-    GenericArgKind, GenericArgsRef, ImplSubject, Term, TermKind, Ty, TyCtxt, TypeFoldable,
+    self, ExistentialPredicate, ExistentialPredicateStableCmpExt as _, GenericArg, GenericArgKind,
+    GenericArgsRef, ImplSubject, Term, TermKind, Ty, TyCtxt, TypeFoldable,
 };
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
@@ -665,46 +665,18 @@ pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>(
                 a.ty(),
             ));
         }
-        // Before calling relate on exprs, it is necessary to ensure that the nested consts
-        // have identical types.
         (ty::ConstKind::Expr(ae), ty::ConstKind::Expr(be)) => {
-            let r = relation;
-
-            // FIXME(generic_const_exprs): is it possible to relate two consts which are not identical
-            // exprs? Should we care about that?
-            // FIXME(generic_const_exprs): relating the `ty()`s is a little weird since it is supposed to
-            // ICE If they mismatch. Unfortunately `ConstKind::Expr` is a little special and can be thought
-            // of as being generic over the argument types, however this is implicit so these types don't get
-            // related when we relate the args of the item this const arg is for.
-            let expr = match (ae, be) {
-                (Expr::Binop(a_op, al, ar), Expr::Binop(b_op, bl, br)) if a_op == b_op => {
-                    r.relate(al.ty(), bl.ty())?;
-                    r.relate(ar.ty(), br.ty())?;
-                    Expr::Binop(a_op, r.consts(al, bl)?, r.consts(ar, br)?)
-                }
-                (Expr::UnOp(a_op, av), Expr::UnOp(b_op, bv)) if a_op == b_op => {
-                    r.relate(av.ty(), bv.ty())?;
-                    Expr::UnOp(a_op, r.consts(av, bv)?)
-                }
-                (Expr::Cast(ak, av, at), Expr::Cast(bk, bv, bt)) if ak == bk => {
-                    r.relate(av.ty(), bv.ty())?;
-                    Expr::Cast(ak, r.consts(av, bv)?, r.tys(at, bt)?)
-                }
-                (Expr::FunctionCall(af, aa), Expr::FunctionCall(bf, ba))
-                    if aa.len() == ba.len() =>
-                {
-                    r.relate(af.ty(), bf.ty())?;
-                    let func = r.consts(af, bf)?;
-                    let mut related_args = Vec::with_capacity(aa.len());
-                    for (a_arg, b_arg) in aa.iter().zip(ba.iter()) {
-                        related_args.push(r.consts(a_arg, b_arg)?);
-                    }
-                    let related_args = tcx.mk_const_list(&related_args);
-                    Expr::FunctionCall(func, related_args)
-                }
+            match (ae.kind, be.kind) {
+                (ty::ExprKind::Binop(a_binop), ty::ExprKind::Binop(b_binop))
+                    if a_binop == b_binop => {}
+                (ty::ExprKind::UnOp(a_unop), ty::ExprKind::UnOp(b_unop)) if a_unop == b_unop => {}
+                (ty::ExprKind::FunctionCall, ty::ExprKind::FunctionCall) => {}
+                (ty::ExprKind::Cast(a_kind), ty::ExprKind::Cast(b_kind)) if a_kind == b_kind => {}
                 _ => return Err(TypeError::ConstMismatch(expected_found(a, b))),
-            };
-            return Ok(ty::Const::new_expr(tcx, expr, a.ty()));
+            }
+
+            let args = relation.relate(ae.args(), be.args())?;
+            return Ok(ty::Const::new_expr(tcx, ty::Expr::new(ae.kind, args), a.ty()));
         }
         _ => false,
     };
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 90791bdd20d..7a291b4dbff 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -147,14 +147,27 @@ impl<'tcx> DebugWithInfcx<TyCtxt<'tcx>> for ty::consts::Expr<'tcx> {
         this: WithInfcx<'_, Infcx, &Self>,
         f: &mut core::fmt::Formatter<'_>,
     ) -> core::fmt::Result {
-        match this.data {
-            ty::Expr::Binop(op, lhs, rhs) => {
-                write!(f, "({op:?}: {:?}, {:?})", &this.wrap(lhs), &this.wrap(rhs))
+        match this.data.kind {
+            ty::ExprKind::Binop(op) => {
+                let (lhs_ty, rhs_ty, lhs, rhs) = this.data.binop_args();
+                write!(
+                    f,
+                    "({op:?}: ({:?}: {:?}), ({:?}: {:?}))",
+                    &this.wrap(lhs),
+                    &this.wrap(lhs_ty),
+                    &this.wrap(rhs),
+                    &this.wrap(rhs_ty),
+                )
             }
-            ty::Expr::UnOp(op, rhs) => write!(f, "({op:?}: {:?})", &this.wrap(rhs)),
-            ty::Expr::FunctionCall(func, args) => {
-                write!(f, "{:?}(", &this.wrap(func))?;
-                for arg in args.as_slice().iter().rev().skip(1).rev() {
+            ty::ExprKind::UnOp(op) => {
+                let (rhs_ty, rhs) = this.data.unop_args();
+                write!(f, "({op:?}: ({:?}: {:?}))", &this.wrap(rhs), &this.wrap(rhs_ty))
+            }
+            ty::ExprKind::FunctionCall => {
+                let (func_ty, func, args) = this.data.call_args();
+                let args = args.collect::<Vec<_>>();
+                write!(f, "({:?}: {:?})(", &this.wrap(func), &this.wrap(func_ty))?;
+                for arg in args.iter().rev().skip(1).rev() {
                     write!(f, "{:?}, ", &this.wrap(arg))?;
                 }
                 if let Some(arg) = args.last() {
@@ -163,8 +176,15 @@ impl<'tcx> DebugWithInfcx<TyCtxt<'tcx>> for ty::consts::Expr<'tcx> {
 
                 write!(f, ")")
             }
-            ty::Expr::Cast(cast_kind, lhs, rhs) => {
-                write!(f, "({cast_kind:?}: {:?}, {:?})", &this.wrap(lhs), &this.wrap(rhs))
+            ty::ExprKind::Cast(kind) => {
+                let (value_ty, value, to_ty) = this.data.cast_args();
+                write!(
+                    f,
+                    "({kind:?}: ({:?}: {:?}), {:?})",
+                    &this.wrap(value),
+                    &this.wrap(value_ty),
+                    &this.wrap(to_ty)
+                )
             }
         }
     }
diff --git a/compiler/rustc_middle/src/ty/walk.rs b/compiler/rustc_middle/src/ty/walk.rs
index a9421aacff8..58f69d772ec 100644
--- a/compiler/rustc_middle/src/ty/walk.rs
+++ b/compiler/rustc_middle/src/ty/walk.rs
@@ -222,24 +222,7 @@ fn push_inner<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent: GenericArg<'tcx>)
                 | ty::ConstKind::Value(_)
                 | ty::ConstKind::Error(_) => {}
 
-                ty::ConstKind::Expr(expr) => match expr {
-                    ty::Expr::UnOp(_, v) => push_inner(stack, v.into()),
-                    ty::Expr::Binop(_, l, r) => {
-                        push_inner(stack, r.into());
-                        push_inner(stack, l.into())
-                    }
-                    ty::Expr::FunctionCall(func, args) => {
-                        for a in args.iter().rev() {
-                            push_inner(stack, a.into());
-                        }
-                        push_inner(stack, func.into());
-                    }
-                    ty::Expr::Cast(_, c, t) => {
-                        push_inner(stack, t.into());
-                        push_inner(stack, c.into());
-                    }
-                },
-
+                ty::ConstKind::Expr(expr) => stack.extend(expr.args().iter().rev()),
                 ty::ConstKind::Unevaluated(ct) => {
                     stack.extend(ct.args.iter().rev());
                 }
diff --git a/compiler/rustc_ty_utils/src/consts.rs b/compiler/rustc_ty_utils/src/consts.rs
index e9112d232cb..8a42298f216 100644
--- a/compiler/rustc_ty_utils/src/consts.rs
+++ b/compiler/rustc_ty_utils/src/consts.rs
@@ -148,17 +148,24 @@ fn recurse_build<'tcx>(
             for &id in args.iter() {
                 new_args.push(recurse_build(tcx, body, id, root_span)?);
             }
-            let new_args = tcx.mk_const_list(&new_args);
-            ty::Const::new_expr(tcx, Expr::FunctionCall(fun, new_args), node.ty)
+            ty::Const::new_expr(
+                tcx,
+                Expr::new_call(tcx, fun.ty(), fun, new_args.into_iter()),
+                node.ty,
+            )
         }
         &ExprKind::Binary { op, lhs, rhs } if check_binop(op) => {
             let lhs = recurse_build(tcx, body, lhs, root_span)?;
             let rhs = recurse_build(tcx, body, rhs, root_span)?;
-            ty::Const::new_expr(tcx, Expr::Binop(op, lhs, rhs), node.ty)
+            ty::Const::new_expr(
+                tcx,
+                Expr::new_binop(tcx, op, lhs.ty(), rhs.ty(), lhs, rhs),
+                node.ty,
+            )
         }
         &ExprKind::Unary { op, arg } if check_unop(op) => {
             let arg = recurse_build(tcx, body, arg, root_span)?;
-            ty::Const::new_expr(tcx, Expr::UnOp(op, arg), node.ty)
+            ty::Const::new_expr(tcx, Expr::new_unop(tcx, op, arg.ty(), arg), node.ty)
         }
         // This is necessary so that the following compiles:
         //
@@ -178,12 +185,22 @@ fn recurse_build<'tcx>(
         // "coercion cast" i.e. using a coercion or is a no-op.
         // This is important so that `N as usize as usize` doesn't unify with `N as usize`. (untested)
         &ExprKind::Use { source } => {
-            let arg = recurse_build(tcx, body, source, root_span)?;
-            ty::Const::new_expr(tcx, Expr::Cast(CastKind::Use, arg, node.ty), node.ty)
+            let value_ty = body.exprs[source].ty;
+            let value = recurse_build(tcx, body, source, root_span)?;
+            ty::Const::new_expr(
+                tcx,
+                Expr::new_cast(tcx, CastKind::Use, value_ty, value, node.ty),
+                node.ty,
+            )
         }
         &ExprKind::Cast { source } => {
-            let arg = recurse_build(tcx, body, source, root_span)?;
-            ty::Const::new_expr(tcx, Expr::Cast(CastKind::As, arg, node.ty), node.ty)
+            let value_ty = body.exprs[source].ty;
+            let value = recurse_build(tcx, body, source, root_span)?;
+            ty::Const::new_expr(
+                tcx,
+                Expr::new_cast(tcx, CastKind::As, value_ty, value, node.ty),
+                node.ty,
+            )
         }
         ExprKind::Borrow { arg, .. } => {
             let arg_node = &body.exprs[*arg];
diff --git a/tests/ui/const-generics/generic_const_exprs/eval-privacy.rs b/tests/ui/const-generics/generic_const_exprs/eval-privacy.rs
index 8023b998a40..af17a37bf23 100644
--- a/tests/ui/const-generics/generic_const_exprs/eval-privacy.rs
+++ b/tests/ui/const-generics/generic_const_exprs/eval-privacy.rs
@@ -15,6 +15,7 @@ where
 {
     type AssocTy = Const<{ my_const_fn(U) }>;
     //~^ ERROR private type
+    //~| ERROR private type
     fn assoc_fn() -> Self::AssocTy {
         Const
     }
diff --git a/tests/ui/const-generics/generic_const_exprs/eval-privacy.stderr b/tests/ui/const-generics/generic_const_exprs/eval-privacy.stderr
index 043fa34d605..df0d43bef87 100644
--- a/tests/ui/const-generics/generic_const_exprs/eval-privacy.stderr
+++ b/tests/ui/const-generics/generic_const_exprs/eval-privacy.stderr
@@ -7,6 +7,17 @@ LL |     type AssocTy = Const<{ my_const_fn(U) }>;
 LL | const fn my_const_fn(val: u8) -> u8 {
    | ----------------------------------- `fn(u8) -> u8 {my_const_fn}` declared as private
 
-error: aborting due to 1 previous error
+error[E0446]: private type `fn(u8) -> u8 {my_const_fn}` in public interface
+  --> $DIR/eval-privacy.rs:16:5
+   |
+LL |     type AssocTy = Const<{ my_const_fn(U) }>;
+   |     ^^^^^^^^^^^^ can't leak private type
+...
+LL | const fn my_const_fn(val: u8) -> u8 {
+   | ----------------------------------- `fn(u8) -> u8 {my_const_fn}` declared as private
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0446`.
diff --git a/tests/ui/privacy/where-priv-type.rs b/tests/ui/privacy/where-priv-type.rs
index cd9cce7ec3e..a62feace2da 100644
--- a/tests/ui/privacy/where-priv-type.rs
+++ b/tests/ui/privacy/where-priv-type.rs
@@ -74,6 +74,7 @@ where
 {
     type AssocTy = Const<{ my_const_fn(U) }>;
     //~^ ERROR private type
+    //~| ERROR private type
     fn assoc_fn() -> Self::AssocTy {
         Const
     }
diff --git a/tests/ui/privacy/where-priv-type.stderr b/tests/ui/privacy/where-priv-type.stderr
index 126330b14a6..8ea2e17c436 100644
--- a/tests/ui/privacy/where-priv-type.stderr
+++ b/tests/ui/privacy/where-priv-type.stderr
@@ -77,6 +77,17 @@ LL |     type AssocTy = Const<{ my_const_fn(U) }>;
 LL | const fn my_const_fn(val: u8) -> u8 {
    | ----------------------------------- `fn(u8) -> u8 {my_const_fn}` declared as private
 
-error: aborting due to 1 previous error; 5 warnings emitted
+error[E0446]: private type `fn(u8) -> u8 {my_const_fn}` in public interface
+  --> $DIR/where-priv-type.rs:75:5
+   |
+LL |     type AssocTy = Const<{ my_const_fn(U) }>;
+   |     ^^^^^^^^^^^^ can't leak private type
+...
+LL | const fn my_const_fn(val: u8) -> u8 {
+   | ----------------------------------- `fn(u8) -> u8 {my_const_fn}` declared as private
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 2 previous errors; 5 warnings emitted
 
 For more information about this error, try `rustc --explain E0446`.