Inferred Type for Explicit Cast

[Jonathan Marler via Digitalmars-d]

What are peoples thoughts on having an inferred type for "cast"? 
Good/Bad idea? If good, how helpful would this be? Would this 
break existing code somehow? I think this feature would be a nice 
added convenience.  Not super helpful but nice to have.

Here's the details
-------------------
Typed Cast: cast(T)v
  try to cast v to T
Type Inferred Cast: cast(auto)v
  try to cast v to whatever type is required in the current 
context

void foo(string s)
{
  // ...
}
void main()
{
    const(char)[] s = "hello";
    foo(cast(string)s); // Current
    foo(cast(auto) s);  // The type of the cast is inferred to be 
a string
    foo(cast() s);      // Another possible syntax
}

This would help refactoribility.  If a function argument changes 
it's type, and the caller is using a cast, then the caller's cast 
type will be updated automatically.  Note that if it changes to 
an invalid type, the cast will still fail like normal.