diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 0221bc6c36383..02333f4575344 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -310,6 +310,14 @@ impl<'tcx> CoroutineInfo<'tcx> {
     }
 }
 
+/// Some item that needs to monomorphize successfully for a MIR body to be considered well-formed.
+#[derive(Copy, Clone, PartialEq, Debug, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeFoldable, TypeVisitable)]
+pub enum RequiredItem<'tcx> {
+    Fn(DefId, GenericArgsRef<'tcx>),
+    Drop(Ty<'tcx>),
+}
+
 /// The lowered representation of a single function.
 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Body<'tcx> {
@@ -375,6 +383,9 @@ pub struct Body<'tcx> {
     /// We hold in this field all the constants we are not able to evaluate yet.
     pub required_consts: Vec<ConstOperand<'tcx>>,
 
+    /// Further items that need to monomorphize successfully for this MIR to be well-formed.
+    pub required_items: Vec<RequiredItem<'tcx>>,
+
     /// Does this body use generic parameters. This is used for the `ConstEvaluatable` check.
     ///
     /// Note that this does not actually mean that this body is not computable right now.
@@ -445,6 +456,7 @@ impl<'tcx> Body<'tcx> {
             var_debug_info,
             span,
             required_consts: Vec::new(),
+            required_items: Vec::new(),
             is_polymorphic: false,
             injection_phase: None,
             tainted_by_errors,
@@ -473,6 +485,7 @@ impl<'tcx> Body<'tcx> {
             spread_arg: None,
             span: DUMMY_SP,
             required_consts: Vec::new(),
+            required_items: Vec::new(),
             var_debug_info: Vec::new(),
             is_polymorphic: false,
             injection_phase: None,
diff --git a/compiler/rustc_mir_build/src/build/custom/mod.rs b/compiler/rustc_mir_build/src/build/custom/mod.rs
index c2bff9084c67e..0ad6b22ee5405 100644
--- a/compiler/rustc_mir_build/src/build/custom/mod.rs
+++ b/compiler/rustc_mir_build/src/build/custom/mod.rs
@@ -56,6 +56,7 @@ pub(super) fn build_custom_mir<'tcx>(
         var_debug_info: Vec::new(),
         span,
         required_consts: Vec::new(),
+        required_items: Vec::new(),
         is_polymorphic: false,
         tainted_by_errors: None,
         injection_phase: None,
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index f6a0945c22297..22911d1ac82c1 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -565,7 +565,8 @@ impl<'tcx> Inliner<'tcx> {
         mut callee_body: Body<'tcx>,
     ) {
         let terminator = caller_body[callsite.block].terminator.take().unwrap();
-        let TerminatorKind::Call { args, destination, unwind, target, .. } = terminator.kind else {
+        let TerminatorKind::Call { func, args, destination, unwind, target, .. } = terminator.kind
+        else {
             bug!("unexpected terminator kind {:?}", terminator.kind);
         };
 
@@ -717,6 +718,18 @@ impl<'tcx> Inliner<'tcx> {
                 Const::Val(..) | Const::Unevaluated(..) => true,
             },
         ));
+        //  Now that we incorporated the callee's `required_consts`, we can remove the callee from
+        //  `required_items` -- but we have to take their `required_consts` in return.
+        let callee_item = {
+            // We need to reconstruct the `required_item` for the callee.
+            let func_ty = func.ty(caller_body, self.tcx);
+            match func_ty.kind() {
+                ty::FnDef(def_id, args) => RequiredItem::Fn(*def_id, args),
+                _ => bug!(),
+            }
+        };
+        caller_body.required_items.retain(|item| *item != callee_item);
+        caller_body.required_items.extend(callee_body.required_items);
     }
 
     fn make_call_args(
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index cd9b98e4f32cd..b76ee39b1ba97 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -344,11 +344,14 @@ fn mir_promoted(
     }
 
     let mut required_consts = Vec::new();
-    let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
+    let mut required_items = Vec::new();
+    let mut required_consts_visitor =
+        RequiredConstsVisitor::new(tcx, &body, &mut required_consts, &mut required_items);
     for (bb, bb_data) in traversal::reverse_postorder(&body) {
         required_consts_visitor.visit_basic_block_data(bb, bb_data);
     }
     body.required_consts = required_consts;
+    body.required_items = required_items;
 
     // What we need to run borrowck etc.
     let promote_pass = promote_consts::PromoteTemps::default();
diff --git a/compiler/rustc_mir_transform/src/required_consts.rs b/compiler/rustc_mir_transform/src/required_consts.rs
index abde6a47e83aa..a888956b39a90 100644
--- a/compiler/rustc_mir_transform/src/required_consts.rs
+++ b/compiler/rustc_mir_transform/src/required_consts.rs
@@ -1,14 +1,23 @@
 use rustc_middle::mir::visit::Visitor;
-use rustc_middle::mir::{Const, ConstOperand, Location};
-use rustc_middle::ty::ConstKind;
+use rustc_middle::mir::{self, Const, ConstOperand, Location, RequiredItem};
+use rustc_middle::ty::{self, ConstKind, TyCtxt};
 
+#[allow(unused)]
 pub struct RequiredConstsVisitor<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    body: &'a mir::Body<'tcx>,
     required_consts: &'a mut Vec<ConstOperand<'tcx>>,
+    required_items: &'a mut Vec<RequiredItem<'tcx>>,
 }
 
 impl<'a, 'tcx> RequiredConstsVisitor<'a, 'tcx> {
-    pub fn new(required_consts: &'a mut Vec<ConstOperand<'tcx>>) -> Self {
-        RequiredConstsVisitor { required_consts }
+    pub fn new(
+        tcx: TyCtxt<'tcx>,
+        body: &'a mir::Body<'tcx>,
+        required_consts: &'a mut Vec<ConstOperand<'tcx>>,
+        required_items: &'a mut Vec<RequiredItem<'tcx>>,
+    ) -> Self {
+        RequiredConstsVisitor { tcx, body, required_consts, required_items }
     }
 }
 
@@ -21,7 +30,27 @@ impl<'tcx> Visitor<'tcx> for RequiredConstsVisitor<'_, 'tcx> {
                 _ => bug!("only ConstKind::Param/Value should be encountered here, got {:#?}", c),
             },
             Const::Unevaluated(..) => self.required_consts.push(*constant),
-            Const::Val(..) => {}
+            Const::Val(_val, ty) => {
+                // This is how function items get referenced: via zero-sized constants of `FnDef` type
+                if let ty::FnDef(def_id, args) = ty.kind() {
+                    debug!("adding to required_items: {def_id:?}");
+                    self.required_items.push(RequiredItem::Fn(*def_id, args));
+                }
+            }
         }
     }
+
+    /*fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) {
+        self.super_terminator(terminator, location);
+
+        match terminator.kind {
+            // We don't need to handle `Call` as we already handled all function type operands in
+            // `visit_constant`. But we do need to handle `Drop`.
+            mir::TerminatorKind::Drop { place, .. } => {
+                let ty = place.ty(self.body, self.tcx).ty;
+                self.required_items.push(RequiredItem::Drop(ty));
+            }
+            _ => {}
+        }
+    }*/
 }
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 32f823a5ac68f..e62861d42edbf 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -345,7 +345,7 @@ fn collect_items_rec<'tcx>(
         return;
     }
 
-    let mut used_items = Vec::new();
+    let mut used_items = MonoItems::new();
     let recursion_depth_reset;
 
     // Post-monomorphization errors MVP
@@ -734,6 +734,19 @@ impl<'a, 'tcx> MirUsedCollector<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
+    fn visit_body(&mut self, body: &mir::Body<'tcx>) {
+        self.super_body(body);
+
+        // Go over `required_items` *after* body, so if an item appears in both we reach it the
+        // "normal" way, via the body.
+        for item in &body.required_items {
+            // All these also need monomorphization to ensure that if that leads to error, we find
+            // those errors.
+            let item = self.monomorphize(*item);
+            visit_required_item(self.tcx, item, self.output);
+        }
+    }
+
     fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
         debug!("visiting rvalue {:?}", *rvalue);
 
@@ -915,6 +928,25 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
     }
 }
 
+fn visit_required_item<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    item: mir::RequiredItem<'tcx>,
+    output: &mut MonoItems<'tcx>,
+) {
+    let instance = match item {
+        mir::RequiredItem::Fn(def_id, args) => {
+            Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args)
+        }
+        mir::RequiredItem::Drop(ty) => Instance::resolve_drop_in_place(tcx, ty),
+    };
+    // We pretend this is a direct call, just to make sure this is visited at all.
+    // "indirect" would mean we also generate some shims, but we don't care about the
+    // generated code, just about the side-effect of code generation causing errors, so we
+    // can skip the shims.
+    // FIXME: track the span so that we can show it here.
+    visit_instance_use(tcx, instance, /*is_direct_call*/ true, DUMMY_SP, output);
+}
+
 fn visit_drop_use<'tcx>(
     tcx: TyCtxt<'tcx>,
     ty: Ty<'tcx>,
@@ -953,7 +985,7 @@ fn visit_instance_use<'tcx>(
     source: Span,
     output: &mut MonoItems<'tcx>,
 ) {
-    debug!("visit_item_use({:?}, is_direct_call={:?})", instance, is_direct_call);
+    debug!("visit_instance_use({:?}, is_direct_call={:?})", instance, is_direct_call);
     if !should_codegen_locally(tcx, &instance) {
         return;
     }
diff --git a/tests/coverage/async.cov-map b/tests/coverage/async.cov-map
index e06d1676358fb..67d149076837a 100644
--- a/tests/coverage/async.cov-map
+++ b/tests/coverage/async.cov-map
@@ -37,21 +37,21 @@ Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 17, 20) to (start + 0, 25)
 
-Function name: async::e (unused)
-Raw bytes (9): 0x[01, 01, 00, 01, 00, 13, 01, 00, 14]
+Function name: async::e
+Raw bytes (9): 0x[01, 01, 00, 01, 01, 13, 01, 00, 14]
 Number of files: 1
 - file 0 => global file 1
 Number of expressions: 0
 Number of file 0 mappings: 1
-- Code(Zero) at (prev + 19, 1) to (start + 0, 20)
+- Code(Counter(0)) at (prev + 19, 1) to (start + 0, 20)
 
-Function name: async::e::{closure#0} (unused)
-Raw bytes (9): 0x[01, 01, 00, 01, 00, 13, 14, 00, 19]
+Function name: async::e::{closure#0}
+Raw bytes (9): 0x[01, 01, 00, 01, 01, 13, 14, 00, 19]
 Number of files: 1
 - file 0 => global file 1
 Number of expressions: 0
 Number of file 0 mappings: 1
-- Code(Zero) at (prev + 19, 20) to (start + 0, 25)
+- Code(Counter(0)) at (prev + 19, 20) to (start + 0, 25)
 
 Function name: async::f
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 15, 01, 00, 14]
@@ -69,21 +69,21 @@ Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 21, 20) to (start + 0, 25)
 
-Function name: async::foo (unused)
-Raw bytes (9): 0x[01, 01, 00, 01, 00, 17, 01, 00, 1e]
+Function name: async::foo
+Raw bytes (9): 0x[01, 01, 00, 01, 01, 17, 01, 00, 1e]
 Number of files: 1
 - file 0 => global file 1
 Number of expressions: 0
 Number of file 0 mappings: 1
-- Code(Zero) at (prev + 23, 1) to (start + 0, 30)
+- Code(Counter(0)) at (prev + 23, 1) to (start + 0, 30)
 
-Function name: async::foo::{closure#0} (unused)
-Raw bytes (9): 0x[01, 01, 00, 01, 00, 17, 1e, 00, 2d]
+Function name: async::foo::{closure#0}
+Raw bytes (9): 0x[01, 01, 00, 01, 01, 17, 1e, 00, 2d]
 Number of files: 1
 - file 0 => global file 1
 Number of expressions: 0
 Number of file 0 mappings: 1
-- Code(Zero) at (prev + 23, 30) to (start + 0, 45)
+- Code(Counter(0)) at (prev + 23, 30) to (start + 0, 45)
 
 Function name: async::g
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 19, 01, 00, 17]
diff --git a/tests/coverage/closure.cov-map b/tests/coverage/closure.cov-map
index 9f0d33745bcb5..2f2b75b8f3dd6 100644
--- a/tests/coverage/closure.cov-map
+++ b/tests/coverage/closure.cov-map
@@ -33,16 +33,20 @@ Number of file 0 mappings: 24
 - Code(Expression(1, Add)) at (prev + 1, 5) to (start + 3, 2)
     = (c1 + (c0 - c1))
 
-Function name: closure::main::{closure#0} (unused)
-Raw bytes (24): 0x[01, 01, 00, 04, 00, 28, 05, 02, 14, 00, 02, 15, 02, 0a, 00, 02, 0a, 00, 0b, 00, 01, 09, 01, 06]
+Function name: closure::main::{closure#0}
+Raw bytes (28): 0x[01, 01, 02, 01, 05, 05, 02, 04, 01, 28, 05, 02, 14, 05, 02, 15, 02, 0a, 02, 02, 0a, 00, 0b, 07, 01, 09, 01, 06]
 Number of files: 1
 - file 0 => global file 1
-Number of expressions: 0
+Number of expressions: 2
+- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
+- expression 1 operands: lhs = Counter(1), rhs = Expression(0, Sub)
 Number of file 0 mappings: 4
-- Code(Zero) at (prev + 40, 5) to (start + 2, 20)
-- Code(Zero) at (prev + 2, 21) to (start + 2, 10)
-- Code(Zero) at (prev + 2, 10) to (start + 0, 11)
-- Code(Zero) at (prev + 1, 9) to (start + 1, 6)
+- Code(Counter(0)) at (prev + 40, 5) to (start + 2, 20)
+- Code(Counter(1)) at (prev + 2, 21) to (start + 2, 10)
+- Code(Expression(0, Sub)) at (prev + 2, 10) to (start + 0, 11)
+    = (c0 - c1)
+- Code(Expression(1, Add)) at (prev + 1, 9) to (start + 1, 6)
+    = (c1 + (c0 - c1))
 
 Function name: closure::main::{closure#10} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 9b, 01, 07, 00, 21]
diff --git a/tests/ui/consts/const-eval/erroneous-const.stderr b/tests/ui/consts/const-eval/erroneous-const.stderr
deleted file mode 100644
index bd25e96c2cf13..0000000000000
--- a/tests/ui/consts/const-eval/erroneous-const.stderr
+++ /dev/null
@@ -1,15 +0,0 @@
-error[E0080]: evaluation of `PrintName::<i32>::VOID` failed
-  --> $DIR/erroneous-const.rs:6:22
-   |
-LL |     const VOID: () = [()][2];
-   |                      ^^^^^^^ index out of bounds: the length is 1 but the index is 2
-
-note: erroneous constant encountered
-  --> $DIR/erroneous-const.rs:13:13
-   |
-LL |             PrintName::<T>::VOID;
-   |             ^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/const-eval/erroneous-const2.stderr b/tests/ui/consts/const-eval/erroneous-const2.stderr
deleted file mode 100644
index 6a5839e3dfb41..0000000000000
--- a/tests/ui/consts/const-eval/erroneous-const2.stderr
+++ /dev/null
@@ -1,15 +0,0 @@
-error[E0080]: evaluation of `PrintName::<i32>::VOID` failed
-  --> $DIR/erroneous-const2.rs:6:22
-   |
-LL |     const VOID: () = [()][2];
-   |                      ^^^^^^^ index out of bounds: the length is 1 but the index is 2
-
-note: erroneous constant encountered
-  --> $DIR/erroneous-const2.rs:13:9
-   |
-LL |         PrintName::<i32>::VOID;
-   |         ^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/const-eval/unused-broken-const-late.stderr b/tests/ui/consts/const-eval/unused-broken-const-late.stderr
deleted file mode 100644
index c2cf2f3813c5e..0000000000000
--- a/tests/ui/consts/const-eval/unused-broken-const-late.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error[E0080]: evaluation of `PrintName::<i32>::VOID` failed
-  --> $DIR/unused-broken-const-late.rs:8:22
-   |
-LL |     const VOID: () = panic!();
-   |                      ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/unused-broken-const-late.rs:8:22
-   |
-   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/required-consts/dead-code-in-called-fn.no-opt.stderr b/tests/ui/consts/required-consts/dead-code-in-called-fn.no-opt.stderr
new file mode 100644
index 0000000000000..9a072ac1df697
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-called-fn.no-opt.stderr
@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-called-fn.rs:9:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-called-fn.rs:9:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn called::<i32>`
+  --> $DIR/dead-code-in-called-fn.rs:23:5
+   |
+LL |     called::<i32>();
+   |     ^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/required-consts/dead-code-in-called-fn.opt.stderr b/tests/ui/consts/required-consts/dead-code-in-called-fn.opt.stderr
new file mode 100644
index 0000000000000..9a072ac1df697
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-called-fn.opt.stderr
@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-called-fn.rs:9:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-called-fn.rs:9:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn called::<i32>`
+  --> $DIR/dead-code-in-called-fn.rs:23:5
+   |
+LL |     called::<i32>();
+   |     ^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/const-eval/unused-broken-const-late.rs b/tests/ui/consts/required-consts/dead-code-in-called-fn.rs
similarity index 54%
rename from tests/ui/consts/const-eval/unused-broken-const-late.rs
rename to tests/ui/consts/required-consts/dead-code-in-called-fn.rs
index c4916061f9e5a..2dd58b9e71d75 100644
--- a/tests/ui/consts/const-eval/unused-broken-const-late.rs
+++ b/tests/ui/consts/required-consts/dead-code-in-called-fn.rs
@@ -1,20 +1,24 @@
+//@revisions: opt no-opt
 //@ build-fail
-//@ compile-flags: -O
+//@[opt] compile-flags: -O
 //! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
 //! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
 
-struct PrintName<T>(T);
-impl<T> PrintName<T> {
-    const VOID: () = panic!(); //~ERROR evaluation of `PrintName::<i32>::VOID` failed
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //~ERROR evaluation of `Fail::<i32>::C` failed
 }
 
-fn no_codegen<T>() {
+#[inline(never)]
+fn called<T>() {
     // Any function that is called is guaranteed to have all consts that syntactically
     // appear in its body evaluated, even if they only appear in dead code.
+    // This relies on mono-item collection checking `required_consts` in collected functions.
     if false {
-        let _ = PrintName::<T>::VOID;
+        let _ = Fail::<T>::C;
     }
 }
+
 pub fn main() {
-    no_codegen::<i32>();
+    called::<i32>();
 }
diff --git a/tests/ui/consts/required-consts/dead-code-in-const-called-fn.no-opt.stderr b/tests/ui/consts/required-consts/dead-code-in-const-called-fn.no-opt.stderr
new file mode 100644
index 0000000000000..feacf51cfca0e
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-const-called-fn.no-opt.stderr
@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-const-called-fn.rs:8:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-const-called-fn.rs:8:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: erroneous constant encountered
+  --> $DIR/dead-code-in-const-called-fn.rs:17:9
+   |
+LL |         Fail::<T>::C;
+   |         ^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/required-consts/dead-code-in-const-called-fn.opt.stderr b/tests/ui/consts/required-consts/dead-code-in-const-called-fn.opt.stderr
new file mode 100644
index 0000000000000..feacf51cfca0e
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-const-called-fn.opt.stderr
@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-const-called-fn.rs:8:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-const-called-fn.rs:8:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: erroneous constant encountered
+  --> $DIR/dead-code-in-const-called-fn.rs:17:9
+   |
+LL |         Fail::<T>::C;
+   |         ^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/const-eval/erroneous-const.rs b/tests/ui/consts/required-consts/dead-code-in-const-called-fn.rs
similarity index 54%
rename from tests/ui/consts/const-eval/erroneous-const.rs
rename to tests/ui/consts/required-consts/dead-code-in-const-called-fn.rs
index 74d44c5259a3e..03af0da78a3e3 100644
--- a/tests/ui/consts/const-eval/erroneous-const.rs
+++ b/tests/ui/consts/required-consts/dead-code-in-const-called-fn.rs
@@ -1,16 +1,20 @@
+//@revisions: opt no-opt
+//@[opt] compile-flags: -O
 //! Make sure we error on erroneous consts even if they are unused.
 #![allow(unconditional_panic)]
 
-struct PrintName<T>(T);
-impl<T> PrintName<T> {
-    const VOID: () = [()][2]; //~ERROR evaluation of `PrintName::<i32>::VOID` failed
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //~ERROR evaluation of `Fail::<i32>::C` failed
 }
 
+#[inline(never)]
 const fn no_codegen<T>() {
     if false {
         // This bad constant is only used in dead code in a no-codegen function... and yet we still
         // must make sure that the build fails.
-            PrintName::<T>::VOID; //~ constant
+        // This relies on const-eval evaluating all `required_consts` of `const fn`.
+        Fail::<T>::C; //~ constant
     }
 }
 
diff --git a/tests/ui/consts/required-consts/dead-code-in-dead-drop.noopt.stderr b/tests/ui/consts/required-consts/dead-code-in-dead-drop.noopt.stderr
new file mode 100644
index 0000000000000..14fe323272f0d
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-dead-drop.noopt.stderr
@@ -0,0 +1,14 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-dead-drop.rs:12:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-dead-drop.rs:12:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn <Fail<i32> as std::ops::Drop>::drop`
+  --> $SRC_DIR/core/src/ptr/mod.rs:LL:COL
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/required-consts/dead-code-in-dead-drop.rs b/tests/ui/consts/required-consts/dead-code-in-dead-drop.rs
new file mode 100644
index 0000000000000..d6ec873e99df1
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-dead-drop.rs
@@ -0,0 +1,33 @@
+//@revisions: noopt opt
+//@[noopt] build-fail
+//@[opt] compile-flags: -O
+//FIXME: `opt` revision currently does not stop with an error due to
+//<https://github.com/rust-lang/rust/issues/107503>.
+//@[opt] build-pass
+//! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
+//! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
+
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //[noopt]~ERROR evaluation of `Fail::<i32>::C` failed
+}
+
+// This function is not actually called, but is mentioned implicitly as destructor in dead code in a
+// function that is called. Make sure we still find this error.
+impl<T> Drop for Fail<T> {
+    fn drop(&mut self) {
+        let _ = Fail::<T>::C;
+    }
+}
+
+#[inline(never)]
+fn called<T>(x: T) {
+    if false {
+        let v = Fail(x);
+        drop(v);
+    }
+}
+
+pub fn main() {
+    called::<i32>(0);
+}
diff --git a/tests/ui/consts/required-consts/dead-code-in-dead-fn.no-opt.stderr b/tests/ui/consts/required-consts/dead-code-in-dead-fn.no-opt.stderr
new file mode 100644
index 0000000000000..5c410fc7c4570
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-dead-fn.no-opt.stderr
@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-dead-fn.rs:9:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-dead-fn.rs:9:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn not_called::<i32>`
+  --> $DIR/dead-code-in-dead-fn.rs:26:9
+   |
+LL |         not_called::<T>();
+   |         ^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/required-consts/dead-code-in-dead-fn.opt.stderr b/tests/ui/consts/required-consts/dead-code-in-dead-fn.opt.stderr
new file mode 100644
index 0000000000000..4c4c5f85f697e
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-dead-fn.opt.stderr
@@ -0,0 +1,13 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-dead-fn.rs:9:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-dead-fn.rs:9:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn not_called::<i32>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/required-consts/dead-code-in-dead-fn.rs b/tests/ui/consts/required-consts/dead-code-in-dead-fn.rs
new file mode 100644
index 0000000000000..826149ca2a81f
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-dead-fn.rs
@@ -0,0 +1,32 @@
+//@revisions: opt no-opt
+//@ build-fail
+//@[opt] compile-flags: -O
+//! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
+//! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
+
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //~ERROR evaluation of `Fail::<i32>::C` failed
+}
+
+// This function is not actually called, but it is mentioned in dead code in a function that is
+// called. Make sure we still find this error.
+// This relies on mono-item collection checking `required_consts` in functions that syntactically
+// are called in collected functions (even inside dead code).
+#[inline(never)]
+fn not_called<T>() {
+    if false {
+        let _ = Fail::<T>::C;
+    }
+}
+
+#[inline(never)]
+fn called<T>() {
+    if false {
+        not_called::<T>();
+    }
+}
+
+pub fn main() {
+    called::<i32>();
+}
diff --git a/tests/ui/consts/required-consts/dead-code-in-dead-vtable.noopt.stderr b/tests/ui/consts/required-consts/dead-code-in-dead-vtable.noopt.stderr
new file mode 100644
index 0000000000000..ab60450049546
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-dead-vtable.noopt.stderr
@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-dead-vtable.rs:12:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-dead-vtable.rs:12:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: the above error was encountered while instantiating `fn <std::vec::Vec<i32> as MyTrait>::not_called`
+  --> $DIR/dead-code-in-dead-vtable.rs:35:40
+   |
+LL |         let gen_vtable: &dyn MyTrait = &v; // vtable "appears" here
+   |                                        ^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/required-consts/dead-code-in-dead-vtable.rs b/tests/ui/consts/required-consts/dead-code-in-dead-vtable.rs
new file mode 100644
index 0000000000000..f21a1cc1fc2fd
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-dead-vtable.rs
@@ -0,0 +1,41 @@
+//@revisions: noopt opt
+//@[noopt] build-fail
+//@[opt] compile-flags: -O
+//FIXME: `opt` revision currently does not stop with an error due to
+//<https://github.com/rust-lang/rust/issues/107503>.
+//@[opt] build-pass
+//! Make sure we detect erroneous constants post-monomorphization even when they are unused. This is
+//! crucial, people rely on it for soundness. (https://github.com/rust-lang/rust/issues/112090)
+
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //[noopt]~ERROR evaluation of `Fail::<i32>::C` failed
+}
+
+trait MyTrait {
+    fn not_called(&self);
+}
+
+// This function is not actually called, but it is mentioned in a vtable in a function that is
+// called. Make sure we still find this error.
+// This relies on mono-item collection checking `required_consts` in functions that are referenced
+// in vtables that syntactically appear in collected functions (even inside dead code).
+impl<T> MyTrait for Vec<T> {
+    fn not_called(&self) {
+        if false {
+            let _ = Fail::<T>::C;
+        }
+    }
+}
+
+#[inline(never)]
+fn called<T>() {
+    if false {
+        let v: Vec<T> = Vec::new();
+        let gen_vtable: &dyn MyTrait = &v; // vtable "appears" here
+    }
+}
+
+pub fn main() {
+    called::<i32>();
+}
diff --git a/tests/ui/consts/required-consts/dead-code-in-static.no-opt.stderr b/tests/ui/consts/required-consts/dead-code-in-static.no-opt.stderr
new file mode 100644
index 0000000000000..b64e2fc45f430
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-static.no-opt.stderr
@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-static.rs:8:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-static.rs:8:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: erroneous constant encountered
+  --> $DIR/dead-code-in-static.rs:16:9
+   |
+LL |         Fail::<i32>::C;
+   |         ^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/required-consts/dead-code-in-static.opt.stderr b/tests/ui/consts/required-consts/dead-code-in-static.opt.stderr
new file mode 100644
index 0000000000000..b64e2fc45f430
--- /dev/null
+++ b/tests/ui/consts/required-consts/dead-code-in-static.opt.stderr
@@ -0,0 +1,17 @@
+error[E0080]: evaluation of `Fail::<i32>::C` failed
+  --> $DIR/dead-code-in-static.rs:8:19
+   |
+LL |     const C: () = panic!();
+   |                   ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/dead-code-in-static.rs:8:19
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: erroneous constant encountered
+  --> $DIR/dead-code-in-static.rs:16:9
+   |
+LL |         Fail::<i32>::C;
+   |         ^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/const-eval/erroneous-const2.rs b/tests/ui/consts/required-consts/dead-code-in-static.rs
similarity index 51%
rename from tests/ui/consts/const-eval/erroneous-const2.rs
rename to tests/ui/consts/required-consts/dead-code-in-static.rs
index 61f2955f2d822..b1da8153e944b 100644
--- a/tests/ui/consts/const-eval/erroneous-const2.rs
+++ b/tests/ui/consts/required-consts/dead-code-in-static.rs
@@ -1,16 +1,19 @@
+//@revisions: opt no-opt
+//@[opt] compile-flags: -O
 //! Make sure we error on erroneous consts even if they are unused.
 #![allow(unconditional_panic)]
 
-struct PrintName<T>(T);
-impl<T> PrintName<T> {
-    const VOID: () = [()][2]; //~ERROR evaluation of `PrintName::<i32>::VOID` failed
+struct Fail<T>(T);
+impl<T> Fail<T> {
+    const C: () = panic!(); //~ERROR evaluation of `Fail::<i32>::C` failed
 }
 
 pub static FOO: () = {
     if false {
         // This bad constant is only used in dead code in a static initializer... and yet we still
         // must make sure that the build fails.
-        PrintName::<i32>::VOID; //~ constant
+        // This relies on const-eval evaluating all `required_consts` of the `static` MIR body.
+        Fail::<i32>::C; //~ constant
     }
 };