[PRL] disallowing shadowing

[Dave Herman]

In lambda calculus you can always rebind an already-bound name, but in 
practice, there are lots of limitations imposed on rebinding in real 
languages: top-level module bindings can't be redefined in mzscheme, 
operations of type classes can't be redefined at the top level in 
Haskell, etc. What happens if you take this to the extreme and disallow 
shadowing entirely in a lexically scoped language? [1]

At first I thought this would cause problems for macros, but in a 
hygienic system that renames everything to something fresh anyway, it 
probably wouldn't matter.

Other than being an annoyance when you want to reuse a name for some 
other purpose (which is arguably bad style anyway), what problems would 
disallowing local rebinding cause?

Dave

[1] http://www.mail-archive.com/haskell@haskell.org/msg01268.html