
\documentclass{article}
\usepackage[body={8cm,8cm}]{geometry}
\usepackage{lmodern}
\usepackage{mathtools}
\newcommand\dhrightarrow{%
  \mathrel{\ooalign{$\rightarrow$%
    \cr$\mkern3.5mu\rightarrow$}}
}
\newcommand\dhxrightarrow[2][]{%
  \mathrel{\ooalign{$\xrightarrow[%
    #1\mkern4mu]{#2\mkern4mu}$\cr%
    \hidewidth$\rightarrow%
    \mkern4mu$}}
}
\pagestyle{empty}
\begin{document}
\begin{alignat*}{3}
  A \rightarrow   B  &&\qquad  
  A \xrightarrow[C]{D} B    &&\qquad 
  A \xrightarrow{\text{Long texte%
  \dots}} B 
  & \\
  A \dhrightarrow B  &&\qquad 
  A \dhxrightarrow[C]{D} B  &&\qquad 
  A \dhxrightarrow{\text{Long texte%
  \dots}} B  
  & \\
\end{alignat*}
\end{document}
