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Redeclaring members from a base class to avoid name hiding

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If a using-declaration occurs at class scope, it is only allowed to redeclare a member of a base class. For example, using std::cout is not allowed at class scope.

Often, the name redeclared is one that would otherwise be hidden. For example, in the below code, d1.foo only refers to Derived1::foo(const char*) and a compilation error will occur. The function Base::foo(int) is hidden not considered at all. However, d2.foo(42) is fine because the using-declaration brings Base::foo(int) into the set of entities named foo in Derived2. Name lookup then finds both foos and overload resolution selects Base::foo. 

struct Base {
    void foo(int);
};
struct Derived1 : Base {
    void foo(const char*);
};
struct Derived2 : Base {
    using Base::foo;
    void foo(const char*);
};
int main() {
    Derived1 d1;
    d1.foo(42);  // error
    Derived2 d2;
    d2.foo(42);  // OK
}
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Using declaration:
* Using declaration
* Importing names individually from a namespace
* Redeclaring members from a base class to avoid name hiding
* Inheriting constructors
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0 Getting started
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2 Basic type keywords
3 Operator precedence
4 Floating point arithmetic
5 Bit operators
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35 std::iomanip
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42 Returning multiple values from a function
43 References
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61 Rule of three, five and zero
62 RAII
63 Exceptions
64 Implementation-defined behavior
65 Special member functions
66 Random numbers
67 Sorting
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69 Perfect forwarding
70 Virtual member functions
71 Undefined behavior
72 Overload resolution
73 Move semantics
74 Pimpl idiom
75 Copy elision
76 Fold expressions
77 Unnamed types
78 Singleton
79 ISO C++ Standard
80 User-defined literals
81 Type erasure
82 Memory management
83 Explicit type conversions
84 RTTI
85 Standard library algorithms
86 Expression templates
87 Scopes
88 Atomic types
89 static assert
90 constexpr
91 Date and time with std::chrono
92 Trailing return type
93 Function template overloading
94 Common compile linker errors
95 Design patterns
96 Optimizations
97 Compiling and building
98 Type traits
99 One definition rule
100 Unspecified behavio
101 Argument dependent name lookup
102 Attributes
103 Internationalization
104 Profiling
105 Return type covariance
106 Non-static member functions
107 Recursion
108 Callable objects
109 Constant class member functions
110 C++ vs. C++ 11 vs C++ 17
111 Inline functions
112 Client server examples
113 Header files
114 Const correctness
115 Refactoring techniques
116 Parameter packs
117 Iteration
118 type deduction
119 C++ 11 memory model
120 Build systems
121 Concurrency with OpenMP
122 Type inference
123 Resource management
124 Storage class specifiers
125 Alignment
126 Inline variables
127 Linkage specifications
128 Curiusly recurring template pattern
129 Using declaration
130 Typedef and type aliases
131 Layout of object types
132 C incompatibilities
133 Optimization
134 Semaphore
135 Thread synchronization
136 Debugging
137 Futures and promises
138 More undefined behaviors
139 Mutexes
140 Recursive mutex
141 Unit testing
142 decltype
143 Digit separators
144 C++ Containers
145 Arithmetic meta-programming
146 Contributors