clang-tidy: use of signed integer operand with binary bitwise

[MaJerle]

void
my_func(uint16_t hex, char* ascii) {
    for (uint8_t idx = 4U; idx != 0; --idx) {
        uint8_t aux = (hex >> (4U * (idx - 1U))) & 0x0FU;

        aux = (aux <= 9U) ? (aux + 0x30U) : (aux + 0x57U);
        ascii[4U - idx] = (char)aux;
    }
    ascii[4] = '\0';
}

returns use of a signed integer operand with a biary bitwise operator and points to line uint8_t aux = (hex >> (4U * (idx - 1U))) & 0x0FU;

Adding (uint8_t) cast infront, solves the issue.

This is part of hicpp-signed-bitwise

Version 17.0.5

Why? Doesn't tidy understand it is all unsigned already?

[PiotrZSL]

    |           |   `-BinaryOperator <col:24, col:47> 'int' '>>'
    |           |     |-ImplicitCastExpr <col:24> 'int' <IntegralCast>
    |           |     | `-ImplicitCastExpr <col:24> 'uint16_t':'unsigned short' <LValueToRValue>
    |           |     |   `-DeclRefExpr <col:24> 'uint16_t':'unsigned short' lvalue ParmVar 0x564691aef6f0 'hex' 'uint16_t':'unsigned short'
    |           |     `-ParenExpr <col:31, col:47> 'unsigned int'
    |           |       `-BinaryOperator <col:32, col:46> 'unsigned int' '*'
    |           |         |-IntegerLiteral <col:32> 'unsigned int' 4
    |           |         `-ParenExpr <col:37, col:46> 'unsigned int'
    |           |           `-BinaryOperator <col:38, col:44> 'unsigned int' '-'
    |           |             |-ImplicitCastExpr <col:38> 'unsigned int' <IntegralCast>
    |           |             | `-ImplicitCastExpr <col:38> 'uint8_t':'unsigned char' <LValueToRValue>
    |           |             |   `-DeclRefExpr <col:38> 'uint8_t':'unsigned char' lvalue Var 0x564691aef970 'idx' 'uint8_t':'unsigned char'
    |           |             `-IntegerLiteral <col:44> 'unsigned int' 1

There is implicit cast to int because its uint32 vs uint16 and uint16 is casted to int.

[MaJerle]

is the warning expected and therefore not considered bug?