A7-1-2: Consider constexpr function behaviour

[lcartey]

Affected rules

• A7-1-2

Description

A constexpr function only returns a compile-time constant when provided with compile-time constants as arguments. The query currently incorrectly considers constexpr functions to always return constants.

Example

This function should only be considerd

constexpr int add(int x, int y) {
  return x + y;
}

void test(int p) {
  int x = add(1,2); // NON_COMPLIANT - could be marked constexpr
  int y = add(1,p); // COMPLIANT - cannot be marked constexpr