Need DMD AST expertise

[Guillaume Chatelet via Digitalmars-d]

On Monday, 20 June 2016 at 18:59:09 UTC, Jacob Carlborg wrote:
> On 2016-06-20 14:33, Guillaume Chatelet wrote:
>
>> Problem 2:
>> ----------
>> Template arguments that are of basic types are mangled in a 
>> special way
>> which requires to understand which 'int' is which.
>>
>>> extern(C++) A foo(A, B)(B, A, B);
>>> static assert(foo!(int,int).mangleof == 
>>> "_Z3fooIiiET_T0_S0_S1_");
>>
>> In the example above the first 'int' is not the same as the 
>> second one,
>> it's a distinct substitution.
>>
>> Question:
>> ---------
>> - How can I know which is which since from the AST 
>> perspective, the
>> FunDeclaration's Parameters are just TypeBasic 'int'?
>>
>> ------------------------------------------------------------
>
> Not sure I understand the question.

Sorry about not being too clear.

> Are you saying that the two integers are mangled differently 
> because there are two template parameters?

Yes exactly.

> I'm guessing you need to look at the template declaration to 
> get more information about the template parameters.

The TemplateInstance [1] gives me `tiargs` and `tdtypes`.

     // Array of Types/Expressions of template
     // instance arguments [int*, char, 10*10]
     Objects* tiargs;

     // Array of Types/Expressions corresponding
     // to TemplateDeclaration.parameters
     // [int, char, 100]
     Objects tdtypes;

I'm using `tiargs` right now (I'm not really sure what `tdtypes` 
is).

AFAIU I can access TemplateDeclaration from TemplateInstance 
through `tempdecl` even though it's stored as a Dsymbol.

I'll have a look at `parameters` from TemplateDeclaration [2] but 
I still need to match it to the function arguments somehow. The 
following example illustrates the process of pairing the int to 
the template parameter.

     extern(C++) B foo(A, B)(*B, ref const A);

     foo!(int, int) => int foo(*int, ref const int);
           ^    ^       ^        ^              ^
           1    2       2        1              2

1. https://github.com/dlang/dmd/blob/master/src/dtemplate.d#L5895
2. https://github.com/dlang/dmd/blob/master/src/dtemplate.d#L406