[boost] [xpressive] Compiler error; seems like normal usage?

Subject: [boost] [xpressive] Compiler error; seems like normal usage?
From: Robert Dailey (rcdailey_at_[hidden])
Date: 2012-03-13 12:37:02

My regex is as follows:

        sregex re =
            "Content-Disposition:" >> +_s >> (s1=!"inline;") >> -*_ >>
"size=" >> (s2=+_d) >> ';'
            ;

This seems to be the part causing the compiler errors: (s1=!"inline;")

When I change it to this: !(s1="inline;")

It compiles just fine. I'm on VS2008 SP1.

Anyone know why the former usage does not work? I still want the group to
capture an empty string if the string "inline;" does not match, which is
why I put the ! inside the capture group. Does this matter?

---------
Robert Dailey