[Bug c++/90769] Template instantiation recursion when trying to do a conversion template

[ensadc at mailnesia dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90769

ensadc at mailnesia dot com changed:

           What    |Removed                     |Added
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                 CC|                            |ensadc at mailnesia dot com

--- Comment #3 from ensadc at mailnesia dot com ---
It seems that `f == B` triggers overload resolution which treats `operator==`
declared latter as a candidate, which then causes the instantiation of the
constructor template, which requires overload resolution for `f == B`....

Reduced:

enum E {B};

struct X
{
  template <E f = B, int = (f == B, 0)>
  constexpr X(int v);
};

bool operator==(X const& lhs, int) { 
    return X(1);
}