Consider following code snippet with C++20 using-enum-declaration: namespace A { enum A {}; }; using namespace A; using enum A; gcc-trunk rejects it with: <source>:4:12: error: reference to ‘A’ is ambiguous 4 | using enum A; | ^ <source>:1:20: note: candidates are: ‘enum A::A’ 1 | namespace A { enum A {}; }; | ^ ..
Category : using-declaration
We know that a ‘using declaration’ for a namespace’s member name in a scope where another entity is defined there with the same name, causes a compile time error: "symbol x is already defined". The error is detected at the point the ‘using declaration’ appears not at use point like a ‘using directive’. A using ..
According to the C++ 17 Standard (10.3.3 The using declaration) 1 Each using-declarator in a using-declaration98 introduces a set of declarations into the declarative region in which the using-declaration appears. and 10 A using-declaration is a declaration and can therefore be used repeatedly where (and only where) multiple declarations are allowed. and (The C++ 17 ..
According to cppreference, both gcc and msvc have completed the implementation of C++20 feature using enum, which means we can using-declaration with an enum: struct A { enum e { /* … */ }; }; struct S { using enum A::e; }; But when I apply it to the templates: template <class T> struct S ..
With ‘using declarations’ I can introduce a base class member into definition of my class: class Base { public: void baseMemberFn(); /* … */ }; class Derived : private Base { public: using Base::baseMemberFn; }; However, in my case, I want to only ‘use’ one specific overload of the member from the base class. Is ..
After reading the accepted answer from this question, I thought I understood why the program failed, since the using declaration does not actually declare the entity i in the region. However names introduced by a using declaration can be used just like any other name and acts like a declaration. With GCC, this fails #include ..
I stumbled upon a question of the using-declared inheriting constructor yesterday. And after carefully reading the answer as well as the linked standard draft N3337, I found there might be some inconsistency (or at least my misunderstanding) when the direct base class also uses using to inherit constructors from the virtual base. Here is an ..
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