diff --git a/tests/fail/function_calls/arg_inplace_mutate.rs b/tests/fail/function_calls/arg_inplace_mutate.rs
index 625a8bda8a..d47af50d40 100644
--- a/tests/fail/function_calls/arg_inplace_mutate.rs
+++ b/tests/fail/function_calls/arg_inplace_mutate.rs
@@ -8,13 +8,13 @@ pub struct S(i32);
 #[custom_mir(dialect = "runtime", phase = "optimized")]
 fn main() {
     mir! {
-        let unit: ();
+        let _unit: ();
         {
             let non_copy = S(42);
             let ptr = std::ptr::addr_of_mut!(non_copy);
             // Inside `callee`, the first argument and `*ptr` are basically
             // aliasing places!
-            Call(unit, after_call, callee(Move(*ptr), ptr))
+            Call(_unit = callee(Move(*ptr), ptr), after_call)
         }
         after_call = {
             Return()
diff --git a/tests/fail/function_calls/arg_inplace_mutate.stack.stderr b/tests/fail/function_calls/arg_inplace_mutate.stack.stderr
index 471dc1dd6d..381442e69b 100644
--- a/tests/fail/function_calls/arg_inplace_mutate.stack.stderr
+++ b/tests/fail/function_calls/arg_inplace_mutate.stack.stderr
@@ -10,7 +10,7 @@ help: <TAG> was created by a SharedReadWrite retag at offsets [0x0..0x4]
   --> $DIR/arg_inplace_mutate.rs:LL:CC
    |
 LL | /     mir! {
-LL | |         let unit: ();
+LL | |         let _unit: ();
 LL | |         {
 LL | |             let non_copy = S(42);
 ...  |
@@ -27,8 +27,8 @@ LL |     unsafe { ptr.write(S(0)) };
 note: inside `main`
   --> $DIR/arg_inplace_mutate.rs:LL:CC
    |
-LL |             Call(unit, after_call, callee(Move(*ptr), ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(_unit = callee(Move(*ptr), ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the macro `::core::intrinsics::mir::__internal_remove_let` which comes from the expansion of the macro `mir` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/tests/fail/function_calls/arg_inplace_mutate.tree.stderr b/tests/fail/function_calls/arg_inplace_mutate.tree.stderr
index 8393b80f25..544cd575ad 100644
--- a/tests/fail/function_calls/arg_inplace_mutate.tree.stderr
+++ b/tests/fail/function_calls/arg_inplace_mutate.tree.stderr
@@ -12,7 +12,7 @@ help: the accessed tag <TAG> was created here
   --> $DIR/arg_inplace_mutate.rs:LL:CC
    |
 LL | /     mir! {
-LL | |         let unit: ();
+LL | |         let _unit: ();
 LL | |         {
 LL | |             let non_copy = S(42);
 ...  |
@@ -29,8 +29,8 @@ LL |     unsafe { ptr.write(S(0)) };
 note: inside `main`
   --> $DIR/arg_inplace_mutate.rs:LL:CC
    |
-LL |             Call(unit, after_call, callee(Move(*ptr), ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(_unit = callee(Move(*ptr), ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the macro `::core::intrinsics::mir::__internal_remove_let` which comes from the expansion of the macro `mir` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/tests/fail/function_calls/arg_inplace_observe_after.rs b/tests/fail/function_calls/arg_inplace_observe_after.rs
index 093b55759f..ea773048dd 100644
--- a/tests/fail/function_calls/arg_inplace_observe_after.rs
+++ b/tests/fail/function_calls/arg_inplace_observe_after.rs
@@ -6,12 +6,12 @@ pub struct S(i32);
 #[custom_mir(dialect = "runtime", phase = "optimized")]
 fn main() {
     mir! {
-        let unit: ();
+        let _unit: ();
         let _observe: i32;
         {
             let non_copy = S(42);
             // This could change `non_copy` in-place
-            Call(unit, after_call, change_arg(Move(non_copy)))
+            Call(_unit = change_arg(Move(non_copy)), after_call)
         }
         after_call = {
             // So now we must not be allowed to observe non-copy again.
diff --git a/tests/fail/function_calls/arg_inplace_observe_during.none.stderr b/tests/fail/function_calls/arg_inplace_observe_during.none.stderr
index baa9148479..cba23c21d1 100644
--- a/tests/fail/function_calls/arg_inplace_observe_during.none.stderr
+++ b/tests/fail/function_calls/arg_inplace_observe_during.none.stderr
@@ -11,8 +11,8 @@ LL |     unsafe { ptr.read() };
 note: inside `main`
   --> $DIR/arg_inplace_observe_during.rs:LL:CC
    |
-LL |             Call(unit, after_call, change_arg(Move(*ptr), ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(_unit = change_arg(Move(*ptr), ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
diff --git a/tests/fail/function_calls/arg_inplace_observe_during.rs b/tests/fail/function_calls/arg_inplace_observe_during.rs
index 2e57872db9..8c6a7df7a6 100644
--- a/tests/fail/function_calls/arg_inplace_observe_during.rs
+++ b/tests/fail/function_calls/arg_inplace_observe_during.rs
@@ -9,12 +9,12 @@ pub struct S(i32);
 #[custom_mir(dialect = "runtime", phase = "optimized")]
 fn main() {
     mir! {
-        let unit: ();
+        let _unit: ();
         {
             let non_copy = S(42);
             let ptr = std::ptr::addr_of_mut!(non_copy);
             // This could change `non_copy` in-place
-            Call(unit, after_call, change_arg(Move(*ptr), ptr))
+            Call(_unit = change_arg(Move(*ptr), ptr), after_call)
         }
         after_call = {
             Return()
diff --git a/tests/fail/function_calls/arg_inplace_observe_during.stack.stderr b/tests/fail/function_calls/arg_inplace_observe_during.stack.stderr
index a842d3a804..f8532186be 100644
--- a/tests/fail/function_calls/arg_inplace_observe_during.stack.stderr
+++ b/tests/fail/function_calls/arg_inplace_observe_during.stack.stderr
@@ -10,7 +10,7 @@ help: <TAG> was created by a SharedReadWrite retag at offsets [0x0..0x4]
   --> $DIR/arg_inplace_observe_during.rs:LL:CC
    |
 LL | /     mir! {
-LL | |         let unit: ();
+LL | |         let _unit: ();
 LL | |         {
 LL | |             let non_copy = S(42);
 ...  |
@@ -27,8 +27,8 @@ LL |     x.0 = 0;
 note: inside `main`
   --> $DIR/arg_inplace_observe_during.rs:LL:CC
    |
-LL |             Call(unit, after_call, change_arg(Move(*ptr), ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(_unit = change_arg(Move(*ptr), ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the macro `::core::intrinsics::mir::__internal_remove_let` which comes from the expansion of the macro `mir` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/tests/fail/function_calls/arg_inplace_observe_during.tree.stderr b/tests/fail/function_calls/arg_inplace_observe_during.tree.stderr
index 5af4856bbe..c33645bdd2 100644
--- a/tests/fail/function_calls/arg_inplace_observe_during.tree.stderr
+++ b/tests/fail/function_calls/arg_inplace_observe_during.tree.stderr
@@ -12,7 +12,7 @@ help: the accessed tag <TAG> was created here
   --> $DIR/arg_inplace_observe_during.rs:LL:CC
    |
 LL | /     mir! {
-LL | |         let unit: ();
+LL | |         let _unit: ();
 LL | |         {
 LL | |             let non_copy = S(42);
 ...  |
@@ -29,8 +29,8 @@ LL |     x.0 = 0;
 note: inside `main`
   --> $DIR/arg_inplace_observe_during.rs:LL:CC
    |
-LL |             Call(unit, after_call, change_arg(Move(*ptr), ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(_unit = change_arg(Move(*ptr), ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the macro `::core::intrinsics::mir::__internal_remove_let` which comes from the expansion of the macro `mir` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/tests/fail/function_calls/return_pointer_aliasing.none.stderr b/tests/fail/function_calls/return_pointer_aliasing.none.stderr
index 9d9dfc89f8..0a31adabf7 100644
--- a/tests/fail/function_calls/return_pointer_aliasing.none.stderr
+++ b/tests/fail/function_calls/return_pointer_aliasing.none.stderr
@@ -11,8 +11,8 @@ LL |     unsafe { ptr.read() };
 note: inside `main`
   --> $DIR/return_pointer_aliasing.rs:LL:CC
    |
-LL |             Call(*ptr, after_call, myfun(ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(*ptr = myfun(ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
diff --git a/tests/fail/function_calls/return_pointer_aliasing.rs b/tests/fail/function_calls/return_pointer_aliasing.rs
index 829809102f..3d560af3d5 100644
--- a/tests/fail/function_calls/return_pointer_aliasing.rs
+++ b/tests/fail/function_calls/return_pointer_aliasing.rs
@@ -15,7 +15,7 @@ pub fn main() {
             let ptr = &raw mut x;
             // We arrange for `myfun` to have a pointer that aliases
             // its return place. Even just reading from that pointer is UB.
-            Call(*ptr, after_call, myfun(ptr))
+            Call(*ptr = myfun(ptr), after_call)
         }
 
         after_call = {
diff --git a/tests/fail/function_calls/return_pointer_aliasing.stack.stderr b/tests/fail/function_calls/return_pointer_aliasing.stack.stderr
index d486dcb95d..875cc5edad 100644
--- a/tests/fail/function_calls/return_pointer_aliasing.stack.stderr
+++ b/tests/fail/function_calls/return_pointer_aliasing.stack.stderr
@@ -27,8 +27,8 @@ LL |     unsafe { ptr.read() };
 note: inside `main`
   --> $DIR/return_pointer_aliasing.rs:LL:CC
    |
-LL |             Call(*ptr, after_call, myfun(ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(*ptr = myfun(ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the macro `::core::intrinsics::mir::__internal_remove_let` which comes from the expansion of the macro `mir` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/tests/fail/function_calls/return_pointer_aliasing.tree.stderr b/tests/fail/function_calls/return_pointer_aliasing.tree.stderr
index c491a904a1..66c2fb8db1 100644
--- a/tests/fail/function_calls/return_pointer_aliasing.tree.stderr
+++ b/tests/fail/function_calls/return_pointer_aliasing.tree.stderr
@@ -29,8 +29,8 @@ LL |     unsafe { ptr.read() };
 note: inside `main`
   --> $DIR/return_pointer_aliasing.rs:LL:CC
    |
-LL |             Call(*ptr, after_call, myfun(ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(*ptr = myfun(ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the macro `::core::intrinsics::mir::__internal_remove_let` which comes from the expansion of the macro `mir` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/tests/fail/function_calls/return_pointer_aliasing2.rs b/tests/fail/function_calls/return_pointer_aliasing2.rs
index 7e9a632002..9d53faccd1 100644
--- a/tests/fail/function_calls/return_pointer_aliasing2.rs
+++ b/tests/fail/function_calls/return_pointer_aliasing2.rs
@@ -9,11 +9,11 @@ use std::intrinsics::mir::*;
 pub fn main() {
     mir! {
         {
-            let x = 0;
-            let ptr = &raw mut x;
+            let _x = 0;
+            let ptr = &raw mut _x;
             // We arrange for `myfun` to have a pointer that aliases
             // its return place. Even just reading from that pointer is UB.
-            Call(x, after_call, myfun(ptr))
+            Call(_x = myfun(ptr), after_call)
         }
 
         after_call = {
diff --git a/tests/fail/function_calls/return_pointer_aliasing2.stderr b/tests/fail/function_calls/return_pointer_aliasing2.stderr
index 33a8a4b46b..443ee8643f 100644
--- a/tests/fail/function_calls/return_pointer_aliasing2.stderr
+++ b/tests/fail/function_calls/return_pointer_aliasing2.stderr
@@ -13,8 +13,8 @@ help: the accessed tag <TAG> was created here
    |
 LL | /     mir! {
 LL | |         {
-LL | |             let x = 0;
-LL | |             let ptr = &raw mut x;
+LL | |             let _x = 0;
+LL | |             let ptr = &raw mut _x;
 ...  |
 LL | |         }
 LL | |     }
@@ -29,8 +29,8 @@ LL |     unsafe { ptr.write(0) };
 note: inside `main`
   --> $DIR/return_pointer_aliasing2.rs:LL:CC
    |
-LL |             Call(x, after_call, myfun(ptr))
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             Call(_x = myfun(ptr), after_call)
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the macro `::core::intrinsics::mir::__internal_remove_let` which comes from the expansion of the macro `mir` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/tests/pass/function_calls/return_place_on_heap.rs b/tests/pass/function_calls/return_place_on_heap.rs
index dcfebd0f82..d410a875b1 100644
--- a/tests/pass/function_calls/return_place_on_heap.rs
+++ b/tests/pass/function_calls/return_place_on_heap.rs
@@ -11,7 +11,7 @@ pub fn main() {
         {
             let x = 0;
             let ptr = &raw mut x;
-            Call(*ptr, after_call, myfun())
+            Call(*ptr = myfun(), after_call)
         }
 
         after_call = {