qquote can fail when spans are slightly off

[nikomatsakis]

The following code #ast{*$(x)} fails with an assertion failure. It seems to be that the size of the span for $(x) is off by one. #ast{*$(x) } works fine.

[nikomatsakis]

@kevina I can't figure out how to assign this to you for some reason but at least I'll add you into it with a comment.

[kevina]

okay I'll look into it

[kevina]

@nikomatsakis I think I found the problem, please try the above commit and let me know if you get any more assertion failures in the qquote code.

[kevina]

@nikomatsakis sorry for the rebase noise. Just use the latest commit.

[kevina]

@nikomatsakis, now that pull request number #1808 is accepted, I think you can close this bug.