Re: Function overload with template alias error

[Timon Gehr]

On 12/24/2011 11:23 AM, André Stein wrote:
Hi,
I'm trying to write a template function which takes a templated alias to
another type:

struct test(T)
{
}

template aliasT(T)
{
alias test!(T) aliasT;
}

void foo(T)(test!T t) { // works
}

void foo2(T)(aliasT!T t) { // doesn't work
}

int main(string[] args)
{
test!(int) t;
aliasT!(int) t2;
foo(t);
foo2(t2); // error
return 0;
}


When foo2(t2) is called which takes an alias to test!T as argument I get
the following error from dmd:

*(21): Error: template variant.foo2(T) does not match any function
template declaration
*(21): Error: template variant.foo2(T) cannot deduce template function
from argument types !()(test!(int))

I thought that aliasT!T and test!T have the same internal types and the
compiler would be able deduce the template parameters. Am I missing
something or is this a bug in DMD? This is a reduced test case from a
piece of code where I tried to write an templated overload to
std.variant.Algebraic.

Thanks,
André

IFTI can only deduce template parameters for symbols that are defined 
inside the template instantiation because then the symbol remembers the 
template parameters. IFTI cannot reverse-instantiate templates.