Selector contains "!important" when there is no whitespace following a mixin

[orottier]

• Node Version: 6.11.1
• NPM Version: 5.3.0
• postcss-less Version: 1.1.0

LESS

a {
    .mixin(val)!important;
}

JavaScript

console.dir(require("postcss-less").parse('a{.mixin(val)!important;}'), {colors: true, depth: null})

Expected Behavior

{
            selector: '.mixin(val)',
            params: '(val) !important',
            mixin: true,
            important: true
}

Actual Behavior

{
            selector: '.mixin(val)!important',
            params: '(val)!important',
            mixin: true,
            important: true
}

Going upstream from prettier/prettier#2880

[shellscape]

Would be happy to review a PR for a fix for this