clang tries to match exception specification for an explictly defaulted but implicitly deleted function

[llvmbot]

Bugzilla Link	18662
Version	trunk
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@zygoloid

Extended Description

The following example seems to fail to compile because clang tries to match the exception specification for the explicitly defaulted but implicitly deleted move assignment operator of Wrapper with a bogus exception specification it calculated for the implicitly deleted function.

class Value {
public:
  Value();
  Value& operator=(const Value& other);
  Value& operator=(Value&& other) noexcept;
};

template <typename T>
struct Wrapper {
   T value;

   Wrapper& operator=(const Wrapper&) = default;
   Wrapper& operator=(Wrapper&&) noexcept = default;
};

Wrapper<const Value> value;

lang++ -std=c++11 test.cpp
test.cpp:13:13: error: exception specification of explicitly defaulted move assignment operator does not match the calculated one
   Wrapper& operator=(Wrapper&&) noexcept = default;
            ^
test.cpp:16:22: note: in instantiation of template class 'Wrapper<const Value>' requested here
Wrapper<const Value> value;
                     ^
1 error generated.

[ec04fc15-fa35-46f2-80e1-5d271f2ef708]

This should be fixed when we implement DR1778.