calling a function inside visual D debugger: partially possible, want better support

[timotheecour]

short version:
how to call a (non extern-C) function from visualD's debugger? ( 
I can do it with extern C)
how to call a function with arguments that are stack variables (I 
can do it with actual numeric values, eg actual pointer addresses)

long version:

when debugging a session inside visual D, it can be very useful 
to call functions directly, eg:

* to print variables that visual D doesn't display properly (such 
as dynamic arrays, where visualD just prints the length and 
pointer)

* for interactive purposes (eg trying a function with different 
parameters)

Currently, visualD's support for this is limited, but I was able 
to do certain useful things (I'm not sure if many people realized 
one can do this in visuald, but this can be useful):

suppose we compile a D program into Main.exe:
we can call extern(C) functions as follows, by adding a watch 
variable in visual studio debugger and entering in the name field:
Main.exe!main_test at test1(2)
=> will show value=25, type=int, and will print in the command 
prompt "res=25"

now get address of z1 by looking into "Locals":
it shows:
-		z1	{length=4 ptr=0x01f20f40 {1} }	int[]
then display the dynamic array z1:
Main.exe!main_test at writelnPtr(3,0x01f20f40)

This is nice but not very convenient. Is there a way (if not, can 
that be addressed in the near future) to support the following?

* Main.exe!main_test at writeln2(z1)
=>currently returns: identifier "z1" is undefined	

* Main.exe!main_test at writeln2([1,2,3])
=>currently returns: expected a type specifier

* Main.exe!main_test at writeln3()
=>currently returns: identifier "main_test at writeln3" is undefined	

I also tried with the mangled name of writeln3 but that didn't 
work with visuald D. However, it DOES work on OSX, after 
compiling with debug symbols and then running under lldb:

b _Dmain
r
(lldb) expr (int) _D5tests16test_scratch_tim8testfun5FiZi (4)
=> doesn't work
(lldb) expr (int) D5tests16test_scratch_tim8testfun5FiZi (4)
=> successfully runs the underlying function once we remove the 
leading underscore

----
module main_test;
void main(){
     int[]z1=[1,2,3];
//breakpoint here
     writeln(z1);
}
extern(C)auto test1(int x){
	auto y=x*x;
	writeln("res=",y);
	return y;
}
extern(C)void writelnPtr(size_t n,void*ptr){
	writeln((cast(int*)ptr)[0..n]);
}
extern(C)void writeln2(int[]z){
	writeln(z);
}
void writeln3(){
	writeln("test");
}
----