aaron.ballman added a comment.
In D158540#4643563 <https://reviews.llvm.org/D158540#4643563>, @NoumanAmir657
wrote:
> **Code:**
>
> struct Base {
> constexpr Base() = default;
> };
> struct Derived : virtual Base {
> constexpr Derived() = default;
> };
>
> struct NoCopyMove {
> constexpr NoCopyMove() {}
> NoCopyMove(const NoCopyMove&);
> NoCopyMove(NoCopyMove&&);
> };
> struct S2 {
> constexpr S2() = default;
> constexpr S2(const S2&) = default;
> constexpr S2(S2&&) = default;
> NoCopyMove ncm;
> };
>
> **Error Generated**
>
> ../../llvm-test/x.cpp:5:3: error: default constructor cannot be 'constexpr'
> in a class with virtual base class
> 5 | constexpr Derived() = default;
> | ^
> ../../llvm-test/x.cpp:4:18: note: virtual base class declared here
> 4 | struct Derived : virtual Base {
> | ^
> ../../llvm-test/x.cpp:15:3: error: defaulted definition of copy constructor
> is not constexpr
> 15 | constexpr S2(const S2&) = default;
> | ^
> ../../llvm-test/x.cpp:16:3: error: defaulted definition of move constructor
> is not constexpr
> 16 | constexpr S2(S2&&) = default;
> | ^
> 3 errors generated.
>
> @aaron.ballman do you mean like this? This now generates different
> diagnostics depending on whether a virtual base class is present or not
Yes, this is along the lines of what I was thinking.
In D158540#4648361 <https://reviews.llvm.org/D158540#4648361>, @NoumanAmir657
wrote:
> @aaron.ballman
> why the member is not an constexpr can be seen from getNumVBases(). The
> 'defaultedSpecialMemberIsConstexpr' returns false whenever getVNumBases is
> true for this so we can use that to identify when to give which error
> diagnostic.
> Can you verify whether this would work or is there any problem with this. I
> haven't uploaded the diff yet
That sounds like a reasonable direction to me!
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D158540/new/
https://reviews.llvm.org/D158540
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