rustdoc fails on block comments for methods

[zetok]

Fails with both 1.7 and nightly 2016-04-07

$ rustdoc --version --verbose
rustdoc 1.7.0 (a5d1e7a59 2016-02-29)
binary: rustdoc
commit-hash: a5d1e7a59a2a3413c377b003075349f854304b5e
commit-date: 2016-02-29
host: x86_64-unknown-linux-gnu
release: 1.7.0

Reproducible: Always

reproducible with

#!/bin/bash

cargo new broken
cd broken
echo '

pub struct Somestruct;

impl Somestruct {
    /** Documentation

        `and` the failing part of it.
    */
    pub fn somefn() {
        println!("works");
    }
}
' >> src/lib.rs

cargo doc

results in:

<stdin>:1:4: 1:5 error: unknown start of token: `
<stdin>:1    `and` the failing part of it.
             ^
thread '<unnamed>' panicked at 'Box<Any>', ../src/libsyntax/parse/lexer/mod.rs:1437
stack backtrace:
   1:     0x7f9028126d50 - <unknown>
Could not document `broken`.

To learn more, run the command again with --verbose.

[mitaa]

This is a dup of #12834

[alexcrichton]

Indeed!