How to draw over minipage in tikz?

Question

I've got a code snippet, that I'd like to annotate with arrows, boxes, and bubbles pointing to the various parts of the code.

Right now, I've got the code in a minted environment, inside a minipage, inside a tikzpicture.

I'm wondering, is it possible to draw on top of the minipage, so that I can point to various parts of the code inside the minipage with arrows?

What I have:

\documentclass{article}
\usepackage{tikz}
\usepackage{minted}

\begin{document}

\tikzstyle{mybox} = [draw=blue, fill=green!20, very thick,
    rectangle, rounded corners, inner sep=10pt, inner ysep=20pt]
%
\begin{tikzpicture}[transform shape,  baseline=-3.5cm]
\node [mybox] (box) {%
\begin{minipage}[t!]{0.5\linewidth}
Foo
\end{minipage}

    \begin{minipage}[t!]{0.5\linewidth}
        \begin{minted}{haskell}   
let 
  map = \f -> \l -> case l of
    [] -> []
    (a :: b) -> (f a) :: (map f b)
in case map (\x->x) [1,2] of
        (h :: t) -> (h,t)
\end{minted}
\end{minipage}

};
\end{tikzpicture}
%

\end{document}

What I want:

Answer 1

If you can change to listings, with tikzmark, tikzmarklistings library and tcolorbox's comment and listing option you can do something similar to what you want. This is just a starting example. You will need to customize tcolorbox and listing, but also fight with how to define comment to fit your needs.

Following code shows how to do it. tcolorbox offers a listing and comment option which allows to include any text beside a listing. A mybox has been declared with a parameter which can be used to define the comment you want.

Because \usetikzmarlibrary{listings} is loaded several tikzmarks are defined for every listing line. You need to name every code fragment with name=..., then pic cs:line-name-... can be used for pointing arrows. While writing this I think that code name should be another parameter but ... I told you, it's just a starting example ;-)

\documentclass[a4paper]{article}
\usepackage{tikz}
\usepackage[most]{tcolorbox}
\usetikzlibrary{tikzmark}
\usetikzmarklibrary{listings}
\usepackage{lipsum}

\newtcblisting{mybox}[1]{
notitle,
colback=green!30,
colframe=blue,
listing only,
listing options={language=haskell, basicstyle=\ttfamily, name=code},
comment side listing,
lefthand width=.24\linewidth,
#1
}

\begin{document}

\lipsum[1]

\begin{mybox}{comment={\begin{tabular}{l}
Explanation\tikzmark{a}\tikz[remember picture,overlay]{\draw (pic cs: a)--(pic cs:line-code-1-start);}\\
\rule{0pt}{1cm}
More Explanation\tikzmark{b}
\end{tabular}
\tikz[remember picture,overlay]{
\draw[->,red] (pic cs:b)--(pic cs:line-code-6-first);}
}}
let 
  map = \f -> \l -> case l of
    [] -> []
    (a :: b) -> (f a) :: (map f b)
in case map (\x->x) [1,2] of
        (h :: t) -> (h,t)
\end{mybox}

\end{document}

Answer 2

This is as far as I got. I can only run minted in draft mode and could not get escapeinside to work for any characters.

\documentclass[draft]{article}
\usepackage{tikz}
\usetikzlibrary{tikzmark,calc,shapes.geometric}
\usepackage{minted}

\begin{document}

\noindent\begin{tikzpicture}[remember picture,baseline=(n1.north)]
\node[minimum width=0.5\textwidth,minimum height=3cm] (box) {};
\node[right,green] at (box.west) {Foo:};
\node[draw,ellipse] (n1) at ($(box.south)!.667!(box.north)$) {Explanation};
\node[draw] (n2) at ($(box.south)!.333!(box.north)$) {More explanation};
\end{tikzpicture}%
\begin{minipage}[t]{0.5\linewidth}
\begin{minted}[escapeinside=||] {haskell}
let 
  |\tikzmark{p1}|map = \f -> \l -> case l of
    [] -> []
    (a :: b) -> (f a) :: (map f b)
in case map (\x->x) [1,2] of
        |\tikzmark{p2}|(h :: t) -> (h,t)
\end{minted}
\end{minipage}

\begin{tikzpicture}[remember picture,overlay]
\draw[->] (n1.east) -- (pic cs:p1);
\draw[->] (n2.east) -- (pic cs:p2);
\end{tikzpicture}

\end{document}