"error: expected unqualified-id before ‘(’ token" on std::assert [duplicate]

  assert, c++, gcc, libstdc++, macros

I have an unusual case of the error in the title, where std::assert gives the error but assert() from assert.h gives no error. This is g++ and the GNU libstdc++.

void HealthMembership::calculateCharges(void)
    float fee;
    fee = this->in_months * this->fee_rates[this->fee_type];
    std::cout << std::fixed << std::showpoint << std::setprecision(2);
    std::cout << "The total charges are $" << fee << 'n';
Q8.cxx:37:7: error: expected unqualified-id before ‘(’ token
   37 |  std::assert(fee_type);
      |       ^~~~~~

It’s difficult to understand the origin of the error, since it’s defined like this.

#  define assert(expr)                          
     (static_cast <bool> (expr)                     
      ? void (0)                            
      : __assert_fail (#expr, __FILE__, __LINE__, __ASSERT_FUNCTION))

Source: Windows Questions C++