diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 01cefc75194fd..ef88b253864bd 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -1817,11 +1817,11 @@ mod size_asserts {
     use super::*;
     use rustc_data_structures::static_assert_size;
     // tidy-alphabetical-start
-    static_assert_size!(BasicBlockData<'_>, 144);
+    static_assert_size!(BasicBlockData<'_>, 128);
     static_assert_size!(LocalDecl<'_>, 40);
     static_assert_size!(SourceScopeData<'_>, 64);
     static_assert_size!(Statement<'_>, 32);
-    static_assert_size!(Terminator<'_>, 112);
+    static_assert_size!(Terminator<'_>, 96);
     static_assert_size!(VarDebugInfo<'_>, 88);
     // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 0fc84ea5c6212..2c2884f189743 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -730,7 +730,7 @@ pub enum TerminatorKind<'tcx> {
         /// reused across function calls without duplicating the contents.
         /// The span for each arg is also included
         /// (e.g. `a` and `b` in `x.foo(a, b)`).
-        args: Vec<Spanned<Operand<'tcx>>>,
+        args: Box<[Spanned<Operand<'tcx>>]>,
         /// Where the returned value will be written
         destination: Place<'tcx>,
         /// Where to go after this call returns. If none, the call necessarily diverges.
@@ -837,7 +837,7 @@ pub enum TerminatorKind<'tcx> {
         template: &'tcx [InlineAsmTemplatePiece],
 
         /// The operands for the inline assembly, as `Operand`s or `Place`s.
-        operands: Vec<InlineAsmOperand<'tcx>>,
+        operands: Box<[InlineAsmOperand<'tcx>]>,
 
         /// Miscellaneous options for the inline assembly.
         options: InlineAsmOptions,
@@ -849,7 +849,7 @@ pub enum TerminatorKind<'tcx> {
         /// Valid targets for the inline assembly.
         /// The first element is the fallthrough destination, unless
         /// InlineAsmOptions::NORETURN is set.
-        targets: Vec<BasicBlock>,
+        targets: Box<[BasicBlock]>,
 
         /// Action to be taken if the inline assembly unwinds. This is present
         /// if and only if InlineAsmOptions::MAY_UNWIND is set.
@@ -1561,6 +1561,6 @@ mod size_asserts {
     static_assert_size!(PlaceElem<'_>, 24);
     static_assert_size!(Rvalue<'_>, 40);
     static_assert_size!(StatementKind<'_>, 16);
-    static_assert_size!(TerminatorKind<'_>, 96);
+    static_assert_size!(TerminatorKind<'_>, 80);
     // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs b/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
index 7549481c1b301..94ab2fb45818d 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
+++ b/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
@@ -170,7 +170,7 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
                     .map(|arg|
                         Ok(Spanned { node: self.parse_operand(*arg)?, span: self.thir.exprs[*arg].span  } )
                     )
-                    .collect::<PResult<Vec<_>>>()?;
+                    .collect::<PResult<Box<[_]>>>()?;
                 Ok(TerminatorKind::Call {
                     func: fun,
                     args,
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
index 9f9b566bb8fa3..c5ee6db5999a5 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
@@ -152,10 +152,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     source_info,
                     TerminatorKind::Call {
                         func: exchange_malloc,
-                        args: vec![
+                        args: [
                             Spanned { node: Operand::Move(size), span: DUMMY_SP },
                             Spanned { node: Operand::Move(align), span: DUMMY_SP },
-                        ],
+                        ]
+                        .into(),
                         destination: storage,
                         target: Some(success),
                         unwind: UnwindAction::Continue,
diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/build/expr/into.rs
index 6b4dd8b64a425..76bdc26a501a6 100644
--- a/compiler/rustc_mir_build/src/build/expr/into.rs
+++ b/compiler/rustc_mir_build/src/build/expr/into.rs
@@ -238,7 +238,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
             ExprKind::Call { ty: _, fun, ref args, from_hir_call, fn_span } => {
                 let fun = unpack!(block = this.as_local_operand(block, fun));
-                let args: Vec<_> = args
+                let args: Box<[_]> = args
                     .into_iter()
                     .copied()
                     .map(|arg| Spanned {
@@ -485,7 +485,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         operands,
                         options,
                         line_spans,
-                        targets,
+                        targets: targets.into_boxed_slice(),
                         unwind: if options.contains(InlineAsmOptions::MAY_UNWIND) {
                             UnwindAction::Continue
                         } else {
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs
index 11d3e2a8180f5..d29874a5ad4ba 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/build/matches/test.rs
@@ -324,7 +324,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     user_ty: None,
                     const_: method,
                 })),
-                args: vec![Spanned { node: Operand::Move(ref_src), span }],
+                args: [Spanned { node: Operand::Move(ref_src), span }].into(),
                 destination: temp,
                 target: Some(target_block),
                 unwind: UnwindAction::Continue,
@@ -486,10 +486,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
                     const_: method,
                 })),
-                args: vec![
+                args: [
                     Spanned { node: Operand::Copy(val), span: DUMMY_SP },
                     Spanned { node: expect, span: DUMMY_SP },
-                ],
+                ]
+                .into(),
                 destination: eq_result,
                 target: Some(eq_block),
                 unwind: UnwindAction::Continue,
diff --git a/compiler/rustc_mir_dataflow/src/elaborate_drops.rs b/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
index 654020164db8b..e0da9600ae37f 100644
--- a/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
+++ b/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
@@ -650,10 +650,8 @@ where
                         [ty.into()],
                         self.source_info.span,
                     ),
-                    args: vec![Spanned {
-                        node: Operand::Move(Place::from(ref_place)),
-                        span: DUMMY_SP,
-                    }],
+                    args: [Spanned { node: Operand::Move(Place::from(ref_place)), span: DUMMY_SP }]
+                        .into(),
                     destination: unit_temp,
                     target: Some(succ),
                     unwind: unwind.into_action(),
diff --git a/compiler/rustc_mir_dataflow/src/framework/tests.rs b/compiler/rustc_mir_dataflow/src/framework/tests.rs
index 6b338efd56974..52db931b68e1e 100644
--- a/compiler/rustc_mir_dataflow/src/framework/tests.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/tests.rs
@@ -34,7 +34,7 @@ fn mock_body<'tcx>() -> mir::Body<'tcx> {
         2,
         mir::TerminatorKind::Call {
             func: mir::Operand::Copy(dummy_place.clone()),
-            args: vec![],
+            args: [].into(),
             destination: dummy_place.clone(),
             target: Some(mir::START_BLOCK),
             unwind: mir::UnwindAction::Continue,
@@ -48,7 +48,7 @@ fn mock_body<'tcx>() -> mir::Body<'tcx> {
         4,
         mir::TerminatorKind::Call {
             func: mir::Operand::Copy(dummy_place.clone()),
-            args: vec![],
+            args: [].into(),
             destination: dummy_place.clone(),
             target: Some(mir::START_BLOCK),
             unwind: mir::UnwindAction::Continue,
diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs
index bf79b4e133a91..05674792426f1 100644
--- a/compiler/rustc_mir_transform/src/coroutine.rs
+++ b/compiler/rustc_mir_transform/src/coroutine.rs
@@ -677,8 +677,8 @@ fn transform_async_context<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 
 fn eliminate_get_context_call<'tcx>(bb_data: &mut BasicBlockData<'tcx>) -> Local {
     let terminator = bb_data.terminator.take().unwrap();
-    if let TerminatorKind::Call { mut args, destination, target, .. } = terminator.kind {
-        let arg = args.pop().unwrap();
+    if let TerminatorKind::Call { args, destination, target, .. } = terminator.kind {
+        let [arg] = *Box::try_from(args).unwrap();
         let local = arg.node.place().unwrap().local;
 
         let arg = Rvalue::Use(arg.node);
diff --git a/compiler/rustc_mir_transform/src/coverage/tests.rs b/compiler/rustc_mir_transform/src/coverage/tests.rs
index 048547dc9f543..63a9f303b8521 100644
--- a/compiler/rustc_mir_transform/src/coverage/tests.rs
+++ b/compiler/rustc_mir_transform/src/coverage/tests.rs
@@ -134,7 +134,7 @@ impl<'tcx> MockBlocks<'tcx> {
             some_from_block,
             TerminatorKind::Call {
                 func: Operand::Copy(self.dummy_place.clone()),
-                args: vec![],
+                args: [].into(),
                 destination: self.dummy_place.clone(),
                 target: Some(TEMP_BLOCK),
                 unwind: UnwindAction::Continue,
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 32b5d8120252f..0a5fc697d0321 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -624,8 +624,7 @@ impl<'tcx> Inliner<'tcx> {
         };
 
         // Copy the arguments if needed.
-        let args: Vec<_> =
-            self.make_call_args(args, &callsite, caller_body, &callee_body, return_block);
+        let args = self.make_call_args(args, &callsite, caller_body, &callee_body, return_block);
 
         let mut integrator = Integrator {
             args: &args,
@@ -736,12 +735,12 @@ impl<'tcx> Inliner<'tcx> {
 
     fn make_call_args(
         &self,
-        args: Vec<Spanned<Operand<'tcx>>>,
+        args: Box<[Spanned<Operand<'tcx>>]>,
         callsite: &CallSite<'tcx>,
         caller_body: &mut Body<'tcx>,
         callee_body: &Body<'tcx>,
         return_block: Option<BasicBlock>,
-    ) -> Vec<Local> {
+    ) -> Box<[Local]> {
         let tcx = self.tcx;
 
         // There is a bit of a mismatch between the *caller* of a closure and the *callee*.
@@ -768,7 +767,8 @@ impl<'tcx> Inliner<'tcx> {
         //
         // and the vector is `[closure_ref, tmp0, tmp1, tmp2]`.
         if callsite.fn_sig.abi() == Abi::RustCall && callee_body.spread_arg.is_none() {
-            let mut args = args.into_iter();
+            // FIXME(edition_2024): switch back to a normal method call.
+            let mut args = <_>::into_iter(args);
             let self_ = self.create_temp_if_necessary(
                 args.next().unwrap().node,
                 callsite,
@@ -802,7 +802,8 @@ impl<'tcx> Inliner<'tcx> {
 
             closure_ref_arg.chain(tuple_tmp_args).collect()
         } else {
-            args.into_iter()
+            // FIXME(edition_2024): switch back to a normal method call.
+            <_>::into_iter(args)
                 .map(|a| self.create_temp_if_necessary(a.node, callsite, caller_body, return_block))
                 .collect()
         }
diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs
index 6806c517c17de..8209e5e27111c 100644
--- a/compiler/rustc_mir_transform/src/instsimplify.rs
+++ b/compiler/rustc_mir_transform/src/instsimplify.rs
@@ -1,6 +1,7 @@
 //! Performs various peephole optimizations.
 
 use crate::simplify::simplify_duplicate_switch_targets;
+use crate::take_array;
 use rustc_ast::attr;
 use rustc_middle::bug;
 use rustc_middle::mir::*;
@@ -285,7 +286,8 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
             return;
         }
 
-        let Some(arg_place) = args.pop().unwrap().node.place() else { return };
+        let Ok([arg]) = take_array(args) else { return };
+        let Some(arg_place) = arg.node.place() else { return };
 
         statements.push(Statement {
             source_info: terminator.source_info,
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index fe195f0112f8d..f7056702cb4ed 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -160,8 +160,9 @@ fn remap_mir_for_const_eval_select<'tcx>(
             } if let ty::FnDef(def_id, _) = *const_.ty().kind()
                 && tcx.is_intrinsic(def_id, sym::const_eval_select) =>
             {
-                let [tupled_args, called_in_const, called_at_rt]: [_; 3] =
-                    std::mem::take(args).try_into().unwrap();
+                let Ok([tupled_args, called_in_const, called_at_rt]) = take_array(args) else {
+                    unreachable!()
+                };
                 let ty = tupled_args.node.ty(&body.local_decls, tcx);
                 let fields = ty.tuple_fields();
                 let num_args = fields.len();
@@ -211,6 +212,11 @@ fn remap_mir_for_const_eval_select<'tcx>(
     body
 }
 
+fn take_array<T, const N: usize>(b: &mut Box<[T]>) -> Result<[T; N], Box<[T]>> {
+    let b: Box<[T; N]> = std::mem::take(b).try_into()?;
+    Ok(*b)
+}
+
 fn is_mir_available(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
     tcx.mir_keys(()).contains(&def_id)
 }
diff --git a/compiler/rustc_mir_transform/src/lower_intrinsics.rs b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
index 3ffc447217d7d..6aa9039435547 100644
--- a/compiler/rustc_mir_transform/src/lower_intrinsics.rs
+++ b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
@@ -1,5 +1,6 @@
 //! Lowers intrinsic calls
 
+use crate::take_array;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::{bug, span_bug};
@@ -50,42 +51,34 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                     }
                     sym::copy_nonoverlapping => {
                         let target = target.unwrap();
-                        let mut args = args.drain(..);
+                        let Ok([src, dst, count]) = take_array(args) else {
+                            bug!("Wrong arguments for copy_non_overlapping intrinsic");
+                        };
                         block.statements.push(Statement {
                             source_info: terminator.source_info,
                             kind: StatementKind::Intrinsic(Box::new(
                                 NonDivergingIntrinsic::CopyNonOverlapping(
                                     rustc_middle::mir::CopyNonOverlapping {
-                                        src: args.next().unwrap().node,
-                                        dst: args.next().unwrap().node,
-                                        count: args.next().unwrap().node,
+                                        src: src.node,
+                                        dst: dst.node,
+                                        count: count.node,
                                     },
                                 ),
                             )),
                         });
-                        assert_eq!(
-                            args.next(),
-                            None,
-                            "Extra argument for copy_non_overlapping intrinsic"
-                        );
-                        drop(args);
                         terminator.kind = TerminatorKind::Goto { target };
                     }
                     sym::assume => {
                         let target = target.unwrap();
-                        let mut args = args.drain(..);
+                        let Ok([arg]) = take_array(args) else {
+                            bug!("Wrong arguments for assume intrinsic");
+                        };
                         block.statements.push(Statement {
                             source_info: terminator.source_info,
                             kind: StatementKind::Intrinsic(Box::new(
-                                NonDivergingIntrinsic::Assume(args.next().unwrap().node),
+                                NonDivergingIntrinsic::Assume(arg.node),
                             )),
                         });
-                        assert_eq!(
-                            args.next(),
-                            None,
-                            "Extra argument for copy_non_overlapping intrinsic"
-                        );
-                        drop(args);
                         terminator.kind = TerminatorKind::Goto { target };
                     }
                     sym::wrapping_add
@@ -100,13 +93,9 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                     | sym::unchecked_shl
                     | sym::unchecked_shr => {
                         let target = target.unwrap();
-                        let lhs;
-                        let rhs;
-                        {
-                            let mut args = args.drain(..);
-                            lhs = args.next().unwrap();
-                            rhs = args.next().unwrap();
-                        }
+                        let Ok([lhs, rhs]) = take_array(args) else {
+                            bug!("Wrong arguments for {} intrinsic", intrinsic.name);
+                        };
                         let bin_op = match intrinsic.name {
                             sym::wrapping_add => BinOp::Add,
                             sym::wrapping_sub => BinOp::Sub,
@@ -132,13 +121,9 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                     }
                     sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
                         if let Some(target) = *target {
-                            let lhs;
-                            let rhs;
-                            {
-                                let mut args = args.drain(..);
-                                lhs = args.next().unwrap();
-                                rhs = args.next().unwrap();
-                            }
+                            let Ok([lhs, rhs]) = take_array(args) else {
+                                bug!("Wrong arguments for {} intrinsic", intrinsic.name);
+                            };
                             let bin_op = match intrinsic.name {
                                 sym::add_with_overflow => BinOp::AddWithOverflow,
                                 sym::sub_with_overflow => BinOp::SubWithOverflow,
@@ -174,7 +159,7 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                         }
                     }
                     sym::read_via_copy => {
-                        let [arg] = args.as_slice() else {
+                        let Ok([arg]) = take_array(args) else {
                             span_bug!(terminator.source_info.span, "Wrong number of arguments");
                         };
                         let derefed_place = if let Some(place) = arg.node.place()
@@ -207,7 +192,7 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                     }
                     sym::write_via_move => {
                         let target = target.unwrap();
-                        let Ok([ptr, val]) = <[_; 2]>::try_from(std::mem::take(args)) else {
+                        let Ok([ptr, val]) = take_array(args) else {
                             span_bug!(
                                 terminator.source_info.span,
                                 "Wrong number of arguments for write_via_move intrinsic",
@@ -247,7 +232,7 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                     }
                     sym::offset => {
                         let target = target.unwrap();
-                        let Ok([ptr, delta]) = <[_; 2]>::try_from(std::mem::take(args)) else {
+                        let Ok([ptr, delta]) = take_array(args) else {
                             span_bug!(
                                 terminator.source_info.span,
                                 "Wrong number of arguments for offset intrinsic",
@@ -264,7 +249,7 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                     }
                     sym::transmute | sym::transmute_unchecked => {
                         let dst_ty = destination.ty(local_decls, tcx).ty;
-                        let Ok([arg]) = <[_; 1]>::try_from(std::mem::take(args)) else {
+                        let Ok([arg]) = take_array(args) else {
                             span_bug!(
                                 terminator.source_info.span,
                                 "Wrong number of arguments for transmute intrinsic",
@@ -289,7 +274,7 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                         }
                     }
                     sym::aggregate_raw_ptr => {
-                        let Ok([data, meta]) = <[_; 2]>::try_from(std::mem::take(args)) else {
+                        let Ok([data, meta]) = take_array(args) else {
                             span_bug!(
                                 terminator.source_info.span,
                                 "Wrong number of arguments for aggregate_raw_ptr intrinsic",
@@ -317,7 +302,7 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                         terminator.kind = TerminatorKind::Goto { target };
                     }
                     sym::ptr_metadata => {
-                        let Ok([ptr]) = <[_; 1]>::try_from(std::mem::take(args)) else {
+                        let Ok([ptr]) = take_array(args) else {
                             span_bug!(
                                 terminator.source_info.span,
                                 "Wrong number of arguments for ptr_metadata intrinsic",
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index 825f8957187e1..25577e88e2831 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -562,7 +562,7 @@ impl<'tcx> CloneShimBuilder<'tcx> {
             vec![statement],
             TerminatorKind::Call {
                 func,
-                args: vec![Spanned { node: Operand::Move(ref_loc), span: DUMMY_SP }],
+                args: [Spanned { node: Operand::Move(ref_loc), span: DUMMY_SP }].into(),
                 destination: dest,
                 target: Some(next),
                 unwind: UnwindAction::Cleanup(cleanup),
@@ -843,7 +843,7 @@ fn build_call_shim<'tcx>(
     };
 
     // BB #0
-    let args = args.into_iter().map(|a| Spanned { node: a, span: DUMMY_SP }).collect::<Vec<_>>();
+    let args = args.into_iter().map(|a| Spanned { node: a, span: DUMMY_SP }).collect();
     block(
         &mut blocks,
         statements,
diff --git a/compiler/rustc_type_ir/src/fold.rs b/compiler/rustc_type_ir/src/fold.rs
index 26e365f64faa3..64da068395c98 100644
--- a/compiler/rustc_type_ir/src/fold.rs
+++ b/compiler/rustc_type_ir/src/fold.rs
@@ -323,6 +323,12 @@ impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Vec<T> {
     }
 }
 
+impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Box<[T]> {
+    fn try_fold_with<F: FallibleTypeFolder<I>>(self, folder: &mut F) -> Result<Self, F::Error> {
+        Vec::from(self).try_fold_with(folder).map(Vec::into_boxed_slice)
+    }
+}
+
 impl<I: Interner, T: TypeFoldable<I>, Ix: Idx> TypeFoldable<I> for IndexVec<Ix, T> {
     fn try_fold_with<F: FallibleTypeFolder<I>>(self, folder: &mut F) -> Result<Self, F::Error> {
         self.raw.try_fold_with(folder).map(IndexVec::from_raw)