"find" with RegExp is unfaithful with "^" char

[gjtorikian]

Consider this small test file:

console.log('test: <test>')
var b = "hi";
console.log(b);

A search for ^\w+ finds TWO results: var and b.

I've isolated the problem to this line of code: https://github.com/ajaxorg/ace/blob/master/lib/ace/search.js#L140

It seems that the startIndex--in this case, anyway--is 4, which chops the var string off, which makes the match think that b is the beginning of a line.

[nightwing]

merging into #2059