About ref used for performance reasons with struct

[deadalnix]

On Monday, 11 February 2013 at 14:54:48 UTC, kinke wrote:
> I'd propose a small change so that suited structs are passed 
> transparently byref only if the parameter is not mutable, e.g., 
> for a function foo(const BigStruct s). The compiler would 
> therefore not need to analyze the code flow in the callee to 
> determine if the parameter is modified and hence a copy is 
> needed.
>

That is overly restrictive. See sample code given in this thread, 
foo couldn't get the struct by ref in such a case if A contains 
any indirection.