how come is this legal? 'void fun(int){ }' ?

[Maxim Fomin via Digitalmars-d-learn]

On Sunday, 14 June 2015 at 01:20:39 UTC, Timothee Cour wrote:
> I understand this is legal for declaration wo definition (void 
> fun(int);)
> but why allow this:
> void test(int){} ?

Actually it is void test(int _param_0) { }
You can test by compiling void test(int) { _param_0 = 0; }

Nameless parameters are simulated by providing internal symbol as 
above.