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Add a clang-specific impl->projection conversion operator #1274

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Merged
kennykerr merged 5 commits into from
Feb 23, 2023
+25 −0
Merged

Add a clang-specific impl->projection conversion operator #1274

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22b8c72
Remove unnecessary const qualifier on conversion returns
DHowett Feb 14, 2023
b48a2f3
Switch to a clang-only operator I
DHowett Feb 23, 2023
a21756f
Merge remote-tracking branch 'origin/master'
DHowett Feb 23, 2023
7e69a1a
Add a uniform initialization test
DHowett Feb 23, 2023
42c8bb7
Did you not have enough coffee?
DHowett Feb 23, 2023
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15 changes: 15 additions & 0 deletions strings/base_implements.h
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Original file line number Diff line number Diff line change
Expand Up @@ -110,10 +110,25 @@ namespace winrt::impl
template <typename D, typename I, typename Enable>
struct producer_convert : producer<D, typename default_interface<I>::type>
{
#ifdef __clang__
// This is sub-optimal in that it requires an AddRef and Release of the
// implementation type for every conversion, but it works around an
// issue where Clang ignores the conversion of producer_ref<I> const
// to I&& (an rvalue ref that cannot bind a const rvalue).
// See CWG rev. 110 active issue 2077, "Overload resolution and invalid
// rvalue-reference initialization"
operator I() const noexcept
{
I result{ nullptr };
copy_from_abi(result, (produce<D, typename default_interface<I>::type>*)this);
return result;
}
#else
operator producer_ref<I> const() const noexcept
{
return { (produce<D, typename default_interface<I>::type>*)this };
}
#endif

operator producer_vtable<I> const() const noexcept
{
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10 changes: 10 additions & 0 deletions test/old_tests/UnitTests/as_implements.cpp
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Expand Up @@ -74,6 +74,16 @@ TEST_CASE("as_implements")
REQUIRE(foo.get() == foo2.get());
}

TEST_CASE("as_implements_uniform_initialization")
{
// uniform initialization relies on IStringable(IStringable&&),
// which requires non-const rvalue semantics.
com_ptr<Foo> foo = make_self<Foo>();
IStringable stringable{ foo.as<IStringable>() };
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@kennykerr kennykerr Feb 23, 2023

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Suggested change
IStringable stringable{ foo.as<IStringable>() };
IStringable stringable{ *foo };

Isn't something like this required to actually invoke the implicit conversion operator? Otherwise you're just calling the explicit as method provided by com_ptr which in turn calls QI.

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@DHowett DHowett Feb 23, 2023

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facepalm

com_ptr<Foo> foo2 = stringable.as<Foo>();
REQUIRE(foo.get() == foo2.get());
}

TEST_CASE("as_implements_inheritance")
{
com_ptr<Bar> bar = make_self<Bar>();
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