suppress false positives due to nested objects (#4597)

test/compress/sandbox.js

@@ -98,6 +98,31 @@ log_global: {
     expect_stdout: "[object global]"
 }
 
+log_nested: {
+    options = {
+        unused: true,
+    }
+    input: {
+        var o = { p: 42 };
+        for (var i = 0; i < 10; i++)
+            o = {
+                p: o,
+                q: function foo() {},
+            };
+        console.log(o);
+    }
+    expect: {
+        var o = { p: 42 };
+        for (var i = 0; i < 10; i++)
+            o = {
+                p: o,
+                q: function() {},
+            };
+        console.log(o);
+    }
+    expect_stdout: true
+}
+
 timers: {
     options = {
         reduce_vars: true,

test/sandbox.js

@@ -126,7 +126,7 @@ function setup(global, builtins, setup_log, setup_tty) {
             if (arguments.length == 1 && typeof msg == "string") return log("%s", msg);
             return log.apply(null, [].map.call(arguments, function(arg) {
                 return safe_log(arg, {
-                    level: 3,
+                    level: 5,
                     original: [],
                     replaced: [],
                 });
@@ -189,7 +189,7 @@ function setup(global, builtins, setup_log, setup_tty) {
             arg.constructor.toString();
             var index = cache.original.indexOf(arg);
             if (index >= 0) return cache.replaced[index];
-            if (--cache.level < 0) break;
+            if (--cache.level < 0) return "[object Object]";
             var value = {};
             cache.original.push(arg);
             cache.replaced.push(value);