"Changes of default constructor" build failure(s) — clang 6.0

This code is a defect of the C++ standard:
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1344
class foo {
    int a;
    foo(int);
};

foo::foo(int c = 5) : a(c) {

}

PackageVersionSupposed error messageFull log Bug report
gem 1:0.93.3-16gemlist_matrix.cpp:37:46: error: addition of default argument on redeclaration makes this constructor a default constructor Log
gtkguitune 0.8-6lcdview.cc:26:31: error: addition of default argument on redeclaration makes this constructor a default constructor Log
ucimf-openvanilla 2.10.11-3openvanilla.cpp:32:33: error: addition of default argument on redeclaration makes this constructor a default constructor Log 753337

3 errors