Make MemberList nothrow move constructible.

libsolidity/ast/Types.h

@@ -95,9 +95,7 @@ public:
 
 	using MemberMap = std::vector<Member>;
 
-	MemberList() {}
 	explicit MemberList(MemberMap const& _members): m_memberTypes(_members) {}
-	MemberList& operator=(MemberList&& _other);
 	void combine(MemberList const& _other);
 	TypePointer memberType(std::string const& _name) const
 	{
@@ -132,6 +130,8 @@ private:
 	mutable std::unique_ptr<StorageOffsets> m_storageOffsets;
 };
 
+static_assert(std::is_nothrow_move_constructible<MemberList>::value, "MemberList should be noexcept move constructible");
+
 /**
  * Abstract base class that forms the root of the type hierarchy.
  */