This problem appears only if one of the parameters is an interface. Without it or using any other type as a second parameter instead of the interface, it compiles. Also it compiles if the passed interface is null. The example below uses short/ushort, but I found the same behaviour for any combination of integral types of the same bitsize (byte/ubyte/char, ushort/short/wchar, int/uint/dchar, long/ulong)

D 2.066.1

interface I {}
class C: I {}

void func(ushort s, I i)
{
    writeln("ushort overload");
}

void func(short s, I i)
{
    writeln("short overload");
}

void call(short s)
{
    C c = new C();
    I d = new C();
    func(s, c); // ---- ERROR ---- see below

    //but these are ok

    func(s, cast(I)c) //ok
    func(s, d) //ok
    func(s, null) //ok

}

main.func called with argument types (short, C) matches both:	
main.func(short s, I i)	
main.func(ushort s, I i)	

On Sunday, 15 February 2015 at 23:48:50 UTC, rumbu wrote:
>
> This problem appears only if one of the parameters is an interface. Without it or using any other type as a second parameter instead of the interface, it compiles. Also it compiles if the passed interface is null. The example below uses short/ushort, but I found the same behaviour for any combination of integral types of the same bitsize (byte/ubyte/char, ushort/short/wchar, int/uint/dchar, long/ulong)
>
> D 2.066.1
>
> interface I {}
> class C: I {}
>
> void func(ushort s, I i)
> {
>     writeln("ushort overload");
> }
>
> void func(short s, I i)
> {
>     writeln("short overload");
> }
>
> void call(short s)
> {
>     C c = new C();
>     I d = new C();
>     func(s, c); // ---- ERROR ---- see below
>
>     //but these are ok
>
>     func(s, cast(I)c) //ok
>     func(s, d) //ok
>     func(s, null) //ok
>
> }
>
> main.func called with argument types (short, C) matches both:	
> main.func(short s, I i)	
> main.func(ushort s, I i)

it's intereting to note that if func() are rewritten:

---
void func(ref ushort s, I i){}
void func(ref short s, I i){}
---

or even

---
void func(const ref ushort s, I i){}
void func(const ref short s, I i){}
---

the problem doesn't happend.

On Sunday, 15 February 2015 at 23:48:50 UTC, rumbu wrote:
>
> This problem appears only if one of the parameters is an interface. Without it or using any other type as a second parameter instead of the interface, it compiles. Also it compiles if the passed interface is null. The example below uses short/ushort, but I found the same behaviour for any combination of integral types of the same bitsize (byte/ubyte/char, ushort/short/wchar, int/uint/dchar, long/ulong)
>
> D 2.066.1
>
> interface I {}
> class C: I {}
>
> void func(ushort s, I i)
> {
>     writeln("ushort overload");
> }
>
> void func(short s, I i)
> {
>     writeln("short overload");
> }
>
> void call(short s)
> {
>     C c = new C();
>     I d = new C();
>     func(s, c); // ---- ERROR ---- see below
>
>     //but these are ok
>
>     func(s, cast(I)c) //ok
>     func(s, d) //ok
>     func(s, null) //ok
>
> }
>
> main.func called with argument types (short, C) matches both:	
> main.func(short s, I i)	
> main.func(ushort s, I i)	

I have submitted a bug report here:

https://issues.dlang.org/show_bug.cgi?id=14187