M5-0-12: Incorrect alerts on assignments of valid numerical values

[rvermeulen]

Affected rules

• cpp/autosar/signed-char-and-unsigned-char-type-shall-only-be-used-for-the-storage-and-use-of-numeric-values

Description

The implementation incorrectly implements the identification of numeric values.
Characters will have type char while numeric values will be promoted to int or unsigned int.
However, in the case of templates, the type of the numeric value will be the fully converted expressions type. That is, unsigned char in the example below.

Example

The following is compliant per example in the standard, however is still seen as a contravention.

template <typename T, T value>
class C1 {
  public:
    C1() : m_value(value) {}
  private:
    T m_value;
};

void fp_test() {
  C1<std::uint8_t, 10> l1;  // NON_COMPLIANT - signed numeric value assigned to explicitly unsigned char
  C1<std::uint8_t, 10U> l2; // COMPLIANT
}