coercion. Overload resolution uses this argument deduction when
dealing with generic functions, to determine when we can invoke a
generic function. When a generic function is selected, we create a
SpecializeExpr wrapping the DeclRefExpr to the generic function.
This is sufficient to type-check calls to simple things like a call to
func identity<T>(x : T) -> T { return x }
with a value of known type. However, it's missing far too many pieces
to enumerate.
Swift SVN r2230
