fix corner case in hoist_props & unused (#5455)

fixes #5454

lib/compress.js

@@ -7240,6 +7240,7 @@ Compressor.prototype.compress = function(node) {
                             });
                             var index = indexOf_assign(sym, def);
                             if (index >= 0) assign_in_use[sym.id][index] = assign;
+                            sym.assignments++;
                             sym.eliminated++;
                             return assign;
                         }));

test/compress/destructured.js

@@ -3567,3 +3567,32 @@ issue_5423: {
     expect_stdout: "function"
     node_version: ">=6"
 }
+
+issue_5454: {
+    options = {
+        hoist_props: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f(a) {
+            var a = 42, a = {
+                p: [ a ] = [],
+            };
+            return "PASS";
+        }
+        console.log(f());
+    }
+    expect: {
+        console.log(function(a) {
+            a = 42, a = {
+                p: [ a ] = [],
+            };
+            return "PASS";
+        }());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}