Showcase fix

third_party/move/move-compiler-v2/src/bytecode_generator.rs

@@ -1271,8 +1271,13 @@ impl<'env> Generator<'env> {
     ) {
         match pat {
             Pattern::Wildcard(_) => {
-                // Nothing to do
-                // TODO(#12475) Should we copy to a temp here?
+                let ty = self.temp_type(arg).to_owned();
+                let temp = self.new_temp(ty);
+                // Assign to a temporary to allow stackless bytecode checkers to report any errors
+                // due to the assignment.
+                self.emit_with(id, |attr| {
+                    Bytecode::Assign(attr, temp, arg, AssignKind::Inferred)
+                })
             },
             Pattern::Var(var_id, sym) => {
                 let local = self.find_local_for_pattern(*var_id, *sym, next_scope);

third_party/move/move-compiler-v2/tests/bytecode-generator/moved_var_not_simplified3.exp

@@ -21,11 +21,20 @@ public fun m::test(): u8 {
      var $t0: u8
      var $t1: u8
      var $t2: u8
+     var $t3: u8
   0: $t1 := 40
   1: $t2 := move($t1)
-  2: $t0 := infer($t2)
-  3: return $t0
+  2: $t3 := infer($t1)
+  3: $t0 := infer($t2)
+  4: return $t0
 }
 
 
-============ bytecode verification succeeded ========
+Diagnostics:
+error: cannot move local `x` since it is still in use
+  ┌─ tests/bytecode-generator/moved_var_not_simplified3.move:4:17
+  │
+4 │         let y = move x;
+  │                 ^^^^^^ attempted to move here
+5 │         let _ = x;
+  │             - used here

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard2.exp

@@ -15,9 +15,16 @@ module 0xc0ffee::m {
 
 [variant baseline]
 public fun m::baz() {
-     var $t0: u64 [unused]
-  0: return ()
+     var $t0: u64
+     var $t1: u64
+  0: $t1 := infer($t0)
+  1: return ()
 }
 
 
-============ bytecode verification succeeded ========
+Diagnostics:
+error: use of unassigned local `x`
+  ┌─ tests/bytecode-generator/wildcard2.move:4:13
+  │
+4 │         let _ = x;
+  │             ^

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard3.exp

@@ -26,27 +26,31 @@ module 0xc0ffee::m {
 public fun m::bar() {
      var $t0: m::S
      var $t1: bool
+     var $t2: m::S
   0: $t1 := false
   1: $t0 := pack m::S($t1)
-  2: return ()
+  2: $t2 := infer($t0)
+  3: return ()
 }
 
 
 [variant baseline]
 public fun m::foo($t0: m::S) {
-  0: return ()
+     var $t1: m::S
+  0: $t1 := infer($t0)
+  1: return ()
 }
 
 
 Diagnostics:
-error: local `s` of type `m::S` does not have the `drop` ability
-  ┌─ tests/bytecode-generator/wildcard3.move:5:18
+error: value of type `m::S` does not have the `drop` ability
+  ┌─ tests/bytecode-generator/wildcard3.move:5:13
   │
 5 │         let _ = s;
-  │                  ^ implicitly dropped here since it is no longer used
+  │             ^ implicitly dropped here since it is no longer used
 
-error: local `s` of type `m::S` does not have the `drop` ability
-  ┌─ tests/bytecode-generator/wildcard3.move:9:17
-  │
-9 │         let s = S{};
-  │                 ^^^ implicitly dropped here since it is no longer used
+error: value of type `m::S` does not have the `drop` ability
+   ┌─ tests/bytecode-generator/wildcard3.move:10:13
+   │
+10 │         let _ = s;
+   │             ^ implicitly dropped here since it is no longer used

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard4.exp

@@ -26,14 +26,16 @@ fun m::test() {
      var $t1: &mut u64
      var $t2: &mut u64
      var $t3: &u64
-     var $t4: u64
+     var $t4: &u64
+     var $t5: u64
   0: $t0 := 3
   1: $t1 := borrow_local($t0)
   2: $t2 := borrow_local($t0)
   3: $t3 := freeze_ref($t2)
-  4: $t4 := 4
-  5: write_ref($t1, $t4)
-  6: return ()
+  4: $t4 := infer($t3)
+  5: $t5 := 4
+  6: write_ref($t1, $t5)
+  7: return ()
 }