MATLAB: Can anyone explain how can this happen

Question

function myfunctest
  subfcn_set('notafunc');
  whos
  which notafunc
  notafunc
  subfcn_set('sin');
  whos
  which sin
  sin
end
function subfcn_set(n)
  assignin('caller', n, ['I am ',n]);
end

running myfunctest in matlab gives

>> myfunctest
  Name          Size            Bytes  Class    Attributes
    notafunc      1x13               26  char               
notafunc is a variable.
notafunc =
I am notafunc
    Name          Size            Bytes  Class    Attributes
    notafunc      1x13               26  char               
    sin           1x8                16  char               
sin is a variable.
Error using sin
Not enough input arguments.
Error in myfunctest (line 13)
sin

The builtin sin function is called even when a local variable "sin" exists.

Answer 1

I found the doc.

http://www.mathworks.com/help/matlab/matlab_prog/variable-names.html#btcg64o-1

Another potential source of name conflicts occurs when you define a function that calls load or eval (or similar functions) to add variables to the workspace. In some cases, load or eval add variables that have the same names as functions. Unless these variables are in the function workspace before the call to load or eval, the MATLAB parser interprets the variable names as function names.