Re: How is std.traits.isInstanceOf supposed to work?

[Ali Çehreli]

On 11/10/2013 05:03 PM, Tommi wrote:

On Sunday, 10 November 2013 at 23:43:21 UTC, TheFlyingFiddle wrote:

The template isInstanceOf checks to see if the second parameter is a
template instantiation of the first parameter.

But in this example of mine:
isInstanceOf!(SuperSt, SubSt)
...the second parameter is not a template instantiation of the first
parameter, yet isInstanceOf evaluates to true.


I think what this all boils down to is that this is a compiler-bug:

struct A(T)
{}

struct B
{
     A!int _a;
     alias _a this;
}

void main()
{
     static assert(!is(B == A!int)); // OK
     static assert(is(B == A!T, T)); // BUG (shouldn't compile)
}

The compiler magically deduces T as int:

struct A(T)
{}

struct B
{
    A!int _a;
    alias _a this;
}

void main()
{
    static if (is(B == A!T, T)) {
        pragma(msg, T);    // prints int
    }
}

Ali