Addressing code review comments.

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard1.exp

@@ -1,6 +1,6 @@
 
 Diagnostics:
-error: the left-hand side has 2 items but the right-hand side provided 1
+error: the left-hand side has 1 item but the right-hand side provided 2
   ┌─ tests/bytecode-generator/wildcard1.move:7:13
   │
 7 │         let _ = tup();

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard5.exp

@@ -0,0 +1,35 @@
+// -- Model dump before bytecode pipeline
+module 0xc0ffee::m {
+    struct S {
+        x: u64,
+        y: u64,
+    }
+    public fun test() {
+        {
+          let s: m::S = pack m::S(3, 4);
+          {
+            let m::S{ x: _, y: _ }: m::S = s;
+            Tuple()
+          }
+        }
+    }
+} // end 0xc0ffee::m
+
+============ initial bytecode ================
+
+[variant baseline]
+public fun m::test() {
+     var $t0: m::S
+     var $t1: u64
+     var $t2: u64
+     var $t3: u64
+     var $t4: u64
+  0: $t1 := 3
+  1: $t2 := 4
+  2: $t0 := pack m::S($t1, $t2)
+  3: ($t3, $t4) := unpack m::S($t0)
+  4: return ()
+}
+
+
+============ bytecode verification succeeded ========

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard5.move

@@ -0,0 +1,11 @@
+module 0xc0ffee::m {
+    struct S {
+        x: u64,
+        y: u64
+    }
+
+    public fun test() {
+        let s = S {x: 3, y: 4};
+        let S {x: _, y: _} = s;
+    }
+}

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard6.exp

@@ -0,0 +1,39 @@
+// -- Model dump before bytecode pipeline
+module 0xc0ffee::m {
+    public fun test2(): u64 {
+        {
+          let x: u64 = 40;
+          {
+            let (y: u64, _): (u64, u64) = Tuple(Move(x), x);
+            y
+          }
+        }
+    }
+} // end 0xc0ffee::m
+
+============ initial bytecode ================
+
+[variant baseline]
+public fun m::test2(): u64 {
+     var $t0: u64
+     var $t1: u64
+     var $t2: u64
+     var $t3: u64
+     var $t4: u64
+  0: $t1 := 40
+  1: $t3 := move($t1)
+  2: $t2 := infer($t3)
+  3: $t4 := infer($t1)
+  4: $t0 := infer($t2)
+  5: return $t0
+}
+
+
+Diagnostics:
+error: cannot move local `x` since it is still in use
+  ┌─ tests/bytecode-generator/wildcard6.move:4:23
+  │
+4 │         let (y, _) = (move x, x);
+  │             ------    ^^^^^^ attempted to move here
+  │             │
+  │             used here

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard6.move

@@ -0,0 +1,7 @@
+module 0xc0ffee::m {
+    public fun test2(): u64 {
+        let x = 40;
+        let (y, _) = (move x, x);
+        y
+    }
+}

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard7.exp

@@ -0,0 +1,52 @@
+
+Diagnostics:
+warning: Unused local variable `q`. Consider removing or prefixing with an underscore: `_q`
+  ┌─ tests/bytecode-generator/wildcard7.move:6:17
+  │
+6 │         let (_, q) = (x, z);
+  │                 ^
+
+// -- Model dump before bytecode pipeline
+module 0xc0ffee::m {
+    public fun test(): u8 {
+        {
+          let x: u8 = 40;
+          {
+            let y: u8 = Move(x);
+            {
+              let (_, q: u64): (u8, u64) = Tuple(x, 30);
+              y
+            }
+          }
+        }
+    }
+} // end 0xc0ffee::m
+
+============ initial bytecode ================
+
+[variant baseline]
+public fun m::test(): u8 {
+     var $t0: u8
+     var $t1: u8
+     var $t2: u8
+     var $t3: u64
+     var $t4: u8
+     var $t5: u64
+  0: $t1 := 40
+  1: $t2 := move($t1)
+  2: $t4 := infer($t1)
+  3: $t5 := 30
+  4: $t3 := infer($t5)
+  5: $t0 := infer($t2)
+  6: return $t0
+}
+
+
+Diagnostics:
+error: cannot move local `x` since it is still in use
+  ┌─ tests/bytecode-generator/wildcard7.move:5:17
+  │
+5 │         let y = move x;
+  │                 ^^^^^^ attempted to move here
+6 │         let (_, q) = (x, z);
+  │             ------ used here

third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard7.move

@@ -0,0 +1,9 @@
+module 0xc0ffee::m {
+    public fun test(): u8 {
+        let x = 40;
+        let z = 30;
+        let y = move x;
+        let (_, q) = (x, z);
+        y
+    }
+}

third_party/move/move-compiler-v2/tests/checking/typing/v1-commands/pop_weird.exp

@@ -6,7 +6,7 @@ error: the left-hand side has 2 items but the right-hand side provided 0
 13 │         (_, _) = ();
    │         ^^^^^^
 
-error: the left-hand side has 0 items but the right-hand side provided 1
+error: the left-hand side has 1 item but the right-hand side provided 0
    ┌─ tests/checking/typing/v1-commands/pop_weird.move:14:9
    │
 14 │         (_) = ();

third_party/move/move-model/src/builder/exp_builder.rs

@@ -2214,7 +2214,7 @@ impl<'env, 'translator, 'module_translator> ExpTranslator<'env, 'translator, 'mo
                     let specialized_expected_type = self.subs.specialize(expected_type);
                     if let Type::Tuple(tys) = specialized_expected_type {
                         if tys.len() != 1 {
-                            self.error(loc, &context.arity_mismatch(false, 1, tys.len()));
+                            self.error(loc, &context.arity_mismatch(false, tys.len(), 1));
                             return self.new_error_pat(loc);
                         }
                     }