I think that CPython treats TypeError specially in the generator expression. So do PyPy.

info.md

Related issue: http://bugs.python.org/issue4806

pypy2.0.0-beta.py

>>>> def f(a): raise TypeError                                                         
>>>> def do(*args): return args
>>>> do(*(f(i) for i in '123'))                                                        
Traceback (most recent call last):
  File "<console>", line 1, in <module>
TypeError: argument after * must be a sequence, not generator
>>>> def f(a): raise LookupError                                                       
>>>> do(*(f(i) for i in '123'))
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "<console>", line 1, in <genexpr>
  File "<console>", line 1, in f
LookupError
>>>> 

python2.7.2.py

>>> def f(a):
...     raise Exception 
... 
>>> def seq(*args):
...     return args 
... 
>>> seq(*(f(i) for i in 'asdf'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in <genexpr>
  File "<stdin>", line 1, in f
Exception
>>> def f(a):
...     raise TypeError
... 
>>> seq(*(f(i) for i in 'asdf'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: seq() argument after * must be a sequence, not generator
>>> 

python3.3.0.py

>>> def broken(a): raise TypeError
... 
>>> def do(*args): return args
... 
>>> do(*(broken(i) for i in 'asdf'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: do() argument after * must be a sequence, not generator
>>> do(*map(broken, 'asdf'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: do() argument after * must be a sequence, not map
>>> def f(a): raise Exception
... 
>>> do(*map(f, 'asdf'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in f
Exception
>>>