fix unsafe evaluation of objects (#2388)

lib/compress.js

@@ -4492,6 +4492,7 @@ merge(Compressor.prototype, {
         if (def) {
             return def.optimize(compressor);
         }
+        if (is_lhs(self, compressor.parent())) return self;
         if (compressor.option("unsafe") && self.expression instanceof AST_Object) {
             var values = self.expression.properties;
             for (var i = values.length; --i >= 0;) {

test/compress/properties.js

@@ -804,3 +804,21 @@ issue_2256: {
         g.keep = g.g;
     }
 }
+
+lhs_prop: {
+    options = {
+        evaluate: true,
+        unsafe: true,
+    }
+    input: {
+        console.log(++{
+            a: 1
+        }.a);
+    }
+    expect: {
+        console.log(++{
+            a: 1
+        }.a);
+    }
+    expect_stdout: "2"
+}