Various problems with CTAD and disignated initialisers

[h-2]

Bugzilla Link	51401
Version	12.0
OS	All
CC	@alagner,@zygoloid

Extended Description

All the code below builds with GCC>=10 and -std=c++20.
All except the two marked examples also build with MSVC.

Everything after "Outer2 o22" fails with Clang.

struct Inner
{
    int i = 0;
};

struct Outer1
{
    Inner s{};
};

template <typename T = int>
struct Outer2
{
    Inner s{};
};

template <typename T>
struct Outer3
{
    T s{};
};

int main()
{
    Outer1 o1{};
    Outer1 o2{{}};
    Outer1 o3{Inner{}};
    Outer1 o4{Inner{1}};
    Outer1 o5{.s = Inner{}};
    Outer1 o6{.s = Inner{ .i = 1}};

    Outer2 o21{};
    Outer2 o22{{}};
    Outer2 o23{Inner{}};                // fails in MSVC
    Outer2 o24{Inner{1}};               // fails in MSVC
    Outer2 o25{.s = Inner{}};
    Outer2 o26{.s = Inner{ .i = 1}};

    Outer3 o33{Inner{}};
    Outer3 o34{Inner{1}};
    Outer3 o35{.s = Inner{}};
    Outer3 o36{.s = Inner{ .i = 1}};
}

[alagner]

I'd like to add one more, possibly related (or I can create a separate bug if you think it's a different issue):
https://gcc.godbolt.org/z/ohaW4W45o

Exact excerpts from standard that explain it are here:
https://stackoverflow.com/a/68688850/4885321

struct A { int i; };
struct B { A a; };

int main() {
[[maybe_unused]] B z{.a = 1}; //this should not compile
}

[h-2]

I'd like to add one more, possibly related (or I can create a separate bug
if you think it's a different issue):
https://gcc.godbolt.org/z/ohaW4W45o

Exact excerpts from standard that explain it are here:
https://stackoverflow.com/a/68688850/4885321

struct A { int i; };
struct B { A a; };

int main() {
[[maybe_unused]] B z{.a = 1}; //this should not compile
}

I think it would be good to have yours separate, because it is of the kind "accepts-invalid", while mine are of the kind "rejects-valid".

[h-2]

Any news on this issue? Can you confirm?

Thanks!

[ilya-biryukov]

These are examples for an unimplemented parts of C++20: #54049 and #54050

[yuanfang-chen]

duplicate #54049 and #54050

[llvmbot]

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