为什么UglifyJS没有破坏某些属性？

Question

为什么UglifyJS不会破坏某些属性，即使我明确要求它这样做？特别是，它不会破坏test，action，type，types，text。

> type tmp.js
var a;
a = { foo: 1 };
a = { test: 1 };
a = { tests: 1 };
a = { action: 1};
a = { actions: 1 };
a = { type: 1 };
a = { types: 1 };
a = { text: 1 };
a = { texts: 1 };

> uglifyjs --version
uglify-js 3.3.6

> uglifyjs tmp.js -m --mangle-props
var a;a={t:1};a={test:1};a={s:1};a={action:1};a={o:1};a={type:1};a={types:1};a={text:1};a={i:1};

> uglifyjs tmp.js -m --mangle-props regex="/^foo$/"
var a;a={t:1};a={test:1};a={tests:1};a={action:1};a={actions:1};a={type:1};a={types:1};a={text:1};a={texts:1};

> uglifyjs tmp.js -m --mangle-props regex="/^(foo|test|tests|action|actions|type|types|text|texts)$/"
var a;a={t:1};a={test:1};a={s:1};a={action:1};a={o:1};a={type:1};a={types:1};a={text:1};a={i:1};