Shadowing clauses detection

el.erl

-module(el).

-export([warn/2, warn_case/1]).
-export([clean/2, clean_case/1]).

warn(X, Y) ->
    {just, X and Y};
warn(6, 6) ->
    {six, 6}.

warn_case(X) ->
    {_, X} =
        if X == 6 ->
               {six, 6};
           is_integer(X) andalso X == 6 ->
               {also_six, 6};
           true ->
               {other, X};
           true ->
               {yet_another, X}
        end,
    case X of
        _ ->
            {just, X};
        6 ->
            {six, 6};
        X ->
            {other, X}
    end.

clean_case(X) ->
    case X of
        X ->
            {just, X};
        X when X == 6 ->
            {six, 6};
        6 ->
            {still_six, 6};
        X when X == 6 ->
            {six_again, 6};
        X ->
            {other, X}
    end.

clean(V, V) ->
    {same, V};
clean(X, Y) when X == Y ->
    {also_same, X};
clean(6, 6) ->
    {six, 6};
clean(X, Y) ->
    case {X, Y} of
        {V, V} ->
            {same, V};
        {X, Y} when X == Y ->
            {also_same, X};
        {6, 6} ->
            {six, 6};
        {X, Y} ->
            {other, X, Y}
    end.