A tentative and very crude answer for http://www.reddit.com/r/rust/comments/2bvd33/is_there_a_tool_to_output_the_type_for_a_rust_name/

rustdef

#!/bin/bash

if [[ $# != 1 ]] ; then
   echo "Usage: $0 <type/struct/trait/fn>"
   exit 1
fi

if [[ $1 =~ '::' ]] ; then
   query=$1
else
   query=$(curl -L -s http://doc.rust-lang.org/std/prelude | sed -ne 's/^.*title=.\([^'\'']*\).>'$1'<.*$/\1/p')
fi
query=${query//::/\/}

path=$(dirname $query)
leaf=$(basename $query)

function do_query {
   for q in $@ ; do
      curl -s -f http://doc.rust-lang.org/${q}.html | sed -n '1h;1!H;${g;s/^.*\n<pre class[^>]*>\(.*\)<\/pre><.*$/\1\n/;s/<[^>]*>//g;s/&lt;/</g;s/&gt;/>/g;p}'
      if [[ ${PIPESTATUS[0]} -eq 0 ]] ; then
         break
      fi
   done
}

case $(basename $query) in
   [A-Z]*) query=($path/{type,struct,trait}.$leaf) ;;
   [a-z]*) query=$path/fn.$leaf ;;
   *) echo "sorry couldn't parse $1" ; exit 1;;
esac

do_query ${query[*]}

or even

> rustdef Result
pub enum Result<T, E> {
    Ok(T),
    Err(E),
}