[Issue 23059] New: importC: calls to D template functions don't convert some argument types

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23059

          Issue ID: 23059
           Summary: importC: calls to D template functions don't convert
                    some argument types
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: ImportC
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: duser at neet.fi
                CC: duser at neet.fi

// dmodule.di
void my_builtin_bswap16()(short x){}
void my_atomic_store_n(T)(T* ptr, T val, int memorder){}

// main.c
__import dmodule;
int main()
{
        int x;
        // Error: none of the overloads are callable using argument types
`!()(int)`
        // same with other bswap builtins when passed a bigger type than they
expect
        my_builtin_bswap16(x);
        //my_builtin_bswap16((short)x); // works

        int *p;
        // Error: none of the overloads are callable using argument types
`!()(int**, int, int)`
        my_atomic_store_n(&p, 0, 0);
        //my_atomic_store_n(&p, (int *)0, 0); // works
}

1. affects __builtin_bswapN() in druntime (when passed a larger type than they
expect): the variable isn't converted to the smaller type in the call, so the
template fails to match

2. affects my implementation of some gcc atomic builtins: when T is inferred as
a pointer type by the first argument, passing "0" (or a number variable) as the
second argument doesn't convert it to a pointer type

both are different from what you'd get when calling a non-templated C or D
function, or the equivalent builtins in gcc

it would be nice if these worked more like in C so the templates didn't need to
implement the conversions themselves

--