    \documentclass[draft]{article}

    \usepackage{agda}

    \begin{document}

    Lemma~\ref{code:B} below shows that $\AgdaPrimitiveType{Set1}$ is inhabited.
    %
    A preliminary definition:
    %
    \begin{code}[number]
      A : Set1
      A = Set
    \end{code}
    %
    Lemma~\ref{code:B2}:
    %
    \begin{code}[number=code:B,number=code:B2]
      B : Set1
      B = A
    \end{code}

    \begin{code}[hide,number=code:Invisible]
      Invisible : Set1
      Invisible = Set
    \end{code}

    Numbers are not generated for inline code, like
    %
    \begin{code}[inline*,number=code:Inline1]
      Inline1 = Set
    \end{code}
    %
    and
    %
    \begin{code}[inline,number=code:Inline2]
      Inline2 = Set
    \end{code}.

    A wide piece of code:
    %
    \begin{code}[number]
      Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa = Set
    \end{code}

    \end{document}