3 files changed, 24 insertions, 7 deletions
diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index 1ba1951afde..2639bbee86f 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -37,6 +37,7 @@ macro_rules! throw_machine_stop_str {
     ($($tt:tt)*) => {{
         // We make a new local type for it. The type itself does not carry any information,
         // but its vtable (for the `MachineStopType` trait) does.
+        #[derive(Debug)]
         struct Zst;
         // Printing this type shows the desired string.
         impl std::fmt::Display for Zst {
@@ -44,7 +45,17 @@ macro_rules! throw_machine_stop_str {
                 write!(f, $($tt)*)
             }
         }
-        impl rustc_middle::mir::interpret::MachineStopType for Zst {}
+
+        impl rustc_middle::mir::interpret::MachineStopType for Zst {
+            fn diagnostic_message(&self) -> rustc_errors::DiagnosticMessage {
+                self.to_string().into()
+            }
+
+            fn add_args(
+                self: Box<Self>,
+                _: &mut dyn FnMut(std::borrow::Cow<'static, str>, rustc_errors::DiagnosticArgValue<'static>),
+            ) {}
+        }
         throw_machine_stop!(Zst)
     }};
 }
@@ -367,7 +378,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 op
             }
             Err(e) => {
-                trace!("get_const failed: {}", e);
+                trace!("get_const failed: {e:?}");
                 return None;
             }
         };
diff --git a/compiler/rustc_mir_transform/src/const_prop_lint.rs b/compiler/rustc_mir_transform/src/const_prop_lint.rs
index 0fe49b8a1bb..61cc76e6646 100644
--- a/compiler/rustc_mir_transform/src/const_prop_lint.rs
+++ b/compiler/rustc_mir_transform/src/const_prop_lint.rs
@@ -232,7 +232,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 op
             }
             Err(e) => {
-                trace!("get_const failed: {}", e);
+                trace!("get_const failed: {e:?}");
                 return None;
             }
         };
@@ -272,8 +272,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 // dedicated error variants should be introduced instead.
                 assert!(
                     !error.kind().formatted_string(),
-                    "const-prop encountered formatting error: {}",
-                    error
+                    "const-prop encountered formatting error: {error:?}",
                 );
                 None
             }
diff --git a/compiler/rustc_mir_transform/src/errors.rs b/compiler/rustc_mir_transform/src/errors.rs
index 602e40d5131..22f71bb0851 100644
--- a/compiler/rustc_mir_transform/src/errors.rs
+++ b/compiler/rustc_mir_transform/src/errors.rs
@@ -163,7 +163,14 @@ impl<'a, P: std::fmt::Debug> DecorateLint<'a, ()> for AssertLint<P> {
         self,
         diag: &'b mut DiagnosticBuilder<'a, ()>,
     ) -> &'b mut DiagnosticBuilder<'a, ()> {
-        diag.span_label(self.span(), format!("{:?}", self.panic()));
+        let span = self.span();
+        let assert_kind = self.panic();
+        let message = assert_kind.diagnostic_message();
+        assert_kind.add_args(&mut |name, value| {
+            diag.set_arg(name, value);
+        });
+        diag.span_label(span, message);
+
         diag
     }
 
@@ -191,7 +198,7 @@ impl<P> AssertLint<P> {
             AssertLint::ArithmeticOverflow(sp, _) | AssertLint::UnconditionalPanic(sp, _) => *sp,
         }
     }
-    pub fn panic(&self) -> &AssertKind<P> {
+    pub fn panic(self) -> AssertKind<P> {
         match self {
             AssertLint::ArithmeticOverflow(_, p) | AssertLint::UnconditionalPanic(_, p) => p,
         }