[LLVMbugs] [Bug 14826] New: Trying to give a default argument to a lambda operator() by a friend declaration talks about "lambda expression"

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=14826

             Bug #: 14826
           Summary: Trying to give a default argument to a lambda
                    operator() by a friend declaration talks about "lambda
                    expression"
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++11
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: schaub.johannes at googlemail.com
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified


I tried to induce a default argument to operator()

#include <iostream>

auto x = [](int a) { std::cout << a << std::endl; };

struct X {
  friend void decltype(x)::operator()(int a = 0) const;
};

int main() {
  x(); 
}


Clang gets confused and says

main.cpp:6:43: warning: C++11 forbids default arguments for lambda expressions
[-Wlambda-extensions]
  friend void decltype(x)::operator()(int a = 0) const;

However I am not putting the default argument in the lambda expression, but
trying to do so in a friend declaration. It should complain about *that*.
Perhaps the reason for this is that it does not do so in other cases either:

#include <iostream>

struct A { void operator()(int a) const; } x;

struct X {
  friend void decltype(x)::operator()(int a = 0) const;
};

int main() {
  x(); 
}

Should fail to compile, but allows the specification of the default argument.

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