Multiple comment slashes lead to error

[vmx]

When you have more than three slashes, you will get an expected item after attributes
error. This should be a special case and not expect a doc attribute. Here's code that reproduces the issue.

fn main() {
    //// x
}

The same it true for more than two stars is a multiline comment (/*** x */).

[alexcrichton]

I'm very ok with this (this has bitten me more than once), but this is a language change that should be discussed a little further than just my own opinion.

[emberian]

Yes, definitely.