Bug 440929

Description Mark Macdonald 2014-07-31 16:11:51 EDT

The "browser" environment, which we typically code against, exports a ton of global symbols, including many commonly used variable names:
> close, closed, find, focus, length, location, name, open, parent, stop, top, ...

1) I've often made the mistake of defining some local variable that shadows one of these names:

> /*eslint-env browser*/
> var name = file.Name;
> console.log("Writing to file:" + name);

2) Later when I refactor the code and delete/rename the variable, I forget to update some references. Those references now resolve to the global symbol, so there is no "{x} is undefined" warning from the linter:

> /*eslint-env browser*/
> var filename = file.Name;
> console.log("Writing to file:" + name); // now refers to window.name

3) The code fails at runtime.

We should consider making a rule that warns when a local variable shadows a global symbol:

> var name = file.Name;      // 'name' shadows a symbol from the 'browser' environment.

This could check parameter names as well as variable names.