I don't understand a const

[Simen kjaeraas]

bearophile <bearophileHUGS at lycos.com> wrote:

> This program doesn't compile, dmd prints the errors:
> test.d(4): Error: template test.foo(T) does not match any function  
> template declaration
> test.d(4): Error: template test.foo(T) cannot deduce template function  
> from argument types !()(const(int),int)
> test.d(9): Error: template instance test.bar!(int) error instantiating
>
> Are you able to tell me what is the error in this code?
>
>
> void foo(T)(const T a, out T b) {}
>
> void bar(T)(const T x, out T y) {
>     foo(x, y); // line 4
> }
>
> void main() {
>     int s1, s2;
>     bar(s1, s2); // line 9
> }
>
>
> Bye, and thank you,
> bearophile

Simpler test case:

void bar(T)(const T x, out T y) {}

void main() {
     const int s1;
     int s2;
     bar(s1, s2);
}

It seems DMD is confused by const(int) being such a nice fit for the
first parameter. This might have to do with s2 = s1 being ok.

It is probably worth noting that this works:


import std.traits;

void bar(T)(const T x, out T y) {}

void main() {
     const int s1;
     int s2;
     bar!(CommonType!(s1,s2))(s1, s2);
}


-- 
Simen