SA0052: Unusual shift operation

Function	Determines shift operation (bit shift) on signed variables. However, the IEC 61131-3 standard only permits shift operations to bit fields. See also strict rule SA0147: Unusual shift operation - strict.
Reason	TwinCAT allows shift operations on signed data types. However, such operations are unusual and can be confusing. The IEC-61131-3 standard does not provide for such operations, so you should avoid them.
Exception	Shift operation on bit field data types (byte, DWORD, LWORD, WORD) do not result in a SA0052 error.
Importance	Medium

Samples:

PROGRAM MAIN
VAR
    nINT   : INT;
    nDINT  : DINT;
    nULINT : ULINT;
    nSINT  : SINT;
    nUSINT : USINT;
    nLINT  : LINT;
 
    nDWORD : DWORD;
    nBYTE  : BYTE;
END_VAR

nINT   := SHL(nINT, BYTE#2);     // => SA0052 
nDINT  := SHR(nDINT, BYTE#4);    // => SA0052 
nULINT := ROL(nULINT, BYTE#1);   // no error because this is an unsigned data type
nSINT  := ROL(nSINT, BYTE#2);    // => SA0052 
nUSINT := ROR(nUSINT, BYTE#3);   // no error because this is an unsigned data type
nLINT  := ROR(nLINT, BYTE#2);    // => SA0052 
 
nDWORD := SHL(nDWORD, BYTE#3);   // no error because DWORD is a bit field data type
nBYTE  := SHR(nBYTE, BYTE#1);    // no error because BYTE is a bit field data type