Why does Closure Compiler not rename objects with

Question

When I test the following code in closure compiler at http://closure-compiler.appspot.com:

// ==ClosureCompiler==
// @output_file_name default.js
// @compilation_level ADVANCED_OPTIMIZATIONS
// @formatting pretty_print
// ==/ClosureCompiler==

// These get renamed
window.foo = {};
window.bar = {};

// These don't
window.uid = {};
window.test = {};

The output is:

window.a = {};
window.b = {};
window.uid = {};
window.test = {};

Why does it rename :

window.foo = {};
window.bar = {};

But not:

window.uid = {};
window.test = {};

It seems to be an issue with certain words?

Answer 1

Update

As of the 20150315 release of Closure-compiler, the type based optimizations are enabled by default.

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Closure Compiler will not rename properties that have the same name as any property defined on an object in the externs unless the --use_types_for_optimization flag is enabled. See the project FAQ for more details.