celtschk@web.de ("Christopher Eltschka") writes:

> Are classes/"constructor calls" are looked up via Koenig lookup?

No. 3.4.2 specifies that only postfix expressions in function calls,
as explained in 5.2.2, are subject to argument-dependent lookup,
i.e. the result of the lookup must be an expression, or a function
name. If your code was well-formed, you'd have an explicit type
conversion as explained in 5.2.3, where you'd need a
simple-type-specifier before the parentheses. Type specifiers are
never found by Koenig lookup.

> Therefore it _does_ find X::B, but doesn't consider the constructor a
> match. Changing B(A) to B(A&) doesn't change this. Is this correct
> behaviour?

I think so (not surprisingly :-) Interestingly enough, Sun CC 5.2 reports

"a.cc", line 16: Error: Unexpected type name "X::B" encountered.

so it also finds X::B ...

Regards,
Martin

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Are classes/"constructor calls" are looked up via Koenig lookup?

That is, should the following code compile?

namespace X
{
  class A {};

  class B
  {
    B(A) {}
  };
}

int main()
{
  X::A a;
  B(a); // creates temporary object of type X::B, or error?
}

Since there's no ::B, and from the syntax it might be a function call
(in some sense it _is_, namely a constructor call), the compiler will
inevitably look into namespace X during Koenig lookup. Now inside X,
it should find class B. Or does it only specifically look for "real"
functions?

BTW, g++ 2.95.2 gives a very interesting error message:

test.cc: In function `int main()':
test.cc:14: no match for call to `(X::B) (X::A &)'

Therefore it _does_ find X::B, but doesn't consider the constructor a
match. Changing B(A) to B(A&) doesn't change this. Is this correct
behaviour?

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