Library Typedefs are fundamentally broken

[Meta via Digitalmars-d]

On Monday, 22 September 2014 at 09:39:29 UTC, Don wrote:
> My feeling is that almost every time when you want to create a 
> new type from an existing one, you actually want to restrict 
> the operations which can be performed on it. (Eg if you have  
> typedef money = double; then money*money doesn't make much 
> sense). For most typedefs I think you're better off with 'alias 
> this'.

`alias this` doesn't restrict what operations can be performed on 
the supertype.

struct Money
{
	this(double d)
	{
		amount = d;
	}
	
	double amount;
	alias amount this;
}

void main()
{
         //This doesn't compile without a constructor defined
         //that takes a double... I thought alias this took
         //care of that, but apparently not
	Money m = 2.0;
	Money n = m * m;
	assert(n == 4.0);
}