This PR unbreaks the jQuery code I mentioned #1052 and adds only 6 bytes gzipped, looks good to me from that perspective. 👍

@gibson042 you had some doubts about this approach, could you elaborate?

Actually, as @kzc pointed out in jquery/jquery#3075 (comment), it'd be good to have test cases with a single function declaration as well as then the braces are stripped which may result in a different output.

Could you add such test cases?

@mgol Actually my point was that uglify's parser is not nearly as strict as a full-fledged JS linter, and generally would not be able to catch errors in parsing its own output. An independent parser would be better to validate the output.

$ echo '"use strict";!function(){if(window)function i(){}}();' | uglifyjs | uglifyjs 
"use strict";!function(){if(window)function i(){}}();

Just to be clear are you asking for an uglify parser change to fail the parse if functions are declared within blocks of statements? If so, a new issue should be opened for that.

@kzc I meand that I'd like another test case where the original source has only one function declarations to make sure that it's not converted to if(!sth)function f(){}. With two functions braces couldn't have been lost so it might be behaving differently.

PR looks good to me.

LGTM!