A0-1-1: initialization of constexpr used as NTTP is detected as useless assignment

[fjatWbyT]

Affected rules

• A0-1-1 (useless assignment)

Description

Constant expression used as non-type template parameter (NTTP) produces useless-assignment false positive. It can be reproduced with integer NTTP.

Example

#include <ratio>

int main() {
  constexpr int one      = 1;     // True positive, this one is indeed unused (therefore, assignment is useless).
  constexpr int thirteen = 13;    // False positive, used in the second argument:
                                  // it can be verified that main returns 13.
  std::ratio<1, thirteen> ratio;
  return ratio.den;
}

Both definitions of one and thirteen are alerted as unused on query cpp/autosar/src/rules/A0-1-1/UselessAssignment.ql.