What about --mangle-props being on and --mangle being off?

lib/output.js

@@ -1187,6 +1187,11 @@ function OutputStream(options) {
             output.print(':');
             output.space();
             output.print(def.mangled_name);
+        } else if (!(def && def.mangled_name) && self.mangled_key) {
+            output.print(name);
+            output.print(':');
+            output.space();
+            output.print(def.name);
         } else {
             output.print(name);
         }

test/parser.js

@@ -118,13 +118,6 @@ module.exports = function () {
     ok.equal(expanding_def.name.names[0].TYPE, 'SymbolVar');
     ok.equal(expanding_def.name.names[1].TYPE, 'Expansion');
     ok.equal(expanding_def.name.names[1].symbol.TYPE, 'SymbolVar');
-
-    ok.throws(function () {
-        // Note: this *is* a valid destructuring, but before we implement
-        // destructuring (right now it's only destructuring *arguments*),
-        // this won't do.
-        UglifyJS.parse('[{a}]');
-    });
 }
 
 // Run standalone