How To Fix WL490 - Operation '&' between data type '&' and '&' not allowed

SAP Error Message - Details

• Message type: E = Error

• Message class: WL - Workflow: run-time messages

• Message number: 490

• Message text: Operation '&' between data type '&' and '&' not allowed

What causes this issue?

You have tried to compare two container elements or expressions or link
them in an arithmetic operation (addition etc.). However, the selected
operation is not allowed or not worthwhile on the underlying data
types.
Example:
numbers cannot be compared with objects
character strings cannot be added to numbers
the result of an operation must be compatible with the operands used
assignment to a constant is not possible
The following abbreviations are used in the message:
l,,Integers (ABAP Dictionary data type <AB>Int1</>, <AB>Int2</>,
<AB>Int4</>)
P,,Packed numbers with decimal places and signs (<AB>Dec</>, <AB>Packed
</>)
N,,Character string with numeric values (<AB>Numc</>)
C,,Character string (<AB>Character</>)
D,,Date (<AB>Date</>)
T,,Time (<AB>Time</>)
O o,,Objects from the Business Object Repository

How to fix this error?

Only use elements or expressions which can be linked with the selected
operation, that is only define the operation between compatible ABAP
data types or between object types.
You can only calculate using numbers (type I, P).
Exception: the following operations are permitted with date/time:
'Date - Date' returns an integer
'Date - number' returns a date
'Time - number' returns a time
'Time - Time' returns an integer
You can only compare numbers with numbers (type I, P, N), date with
date, time with time, character-based types (C, N). Objects can be
compared to see whether they are the same (o).
The type of the result of an arithmetic operation or an assignment must
be compatible with the type of the operand(s).
Hexadecimal numbers (X, RAW) and floating point numbers (F, FLTP) are
not supported in container operations at present. If necessary, define
object methods to implement operations with these types in a program.
Further information can be found in the online help in the ABAP editor
on the ABAP key words <AB>Data</> and <AB>Move</>.

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message WL490 - Operation '&' between data type '&' and '&' not allowed ?

  The SAP error message WL490 indicates that there is an operation being attempted between incompatible data types in your ABAP code or configuration. This typically occurs when you are trying to perform an operation (like addition, subtraction, or concatenation) between two variables that are not compatible with each other.
  Cause:
  
  Incompatible Data Types: The most common cause is that the operation involves two different data types that cannot be directly operated on. For example, trying to add a string to a number or trying to concatenate two different types of structures.
  Incorrect Variable Declaration: Sometimes, the variables may not be declared correctly, leading to type mismatches.
  Implicit Type Conversion Failure: SAP ABAP does not always perform implicit type conversions, and if the types are not compatible, it will throw this error.
  
  Solution:
  
  Check Data Types: Review the data types of the variables involved in the operation. Ensure that they are compatible. You can use the ABAP Data Dictionary (SE11) to check the definitions of the data types.
  Explicit Type Conversion: If the data types are incompatible, consider using explicit type conversion functions. For example, you can use CONCATENATE for strings or CAST for converting between types.
  Modify the Operation: If the operation is not valid, you may need to change the logic of your code to ensure that the operation is performed between compatible types.
  Debugging: Use the ABAP debugger to step through the code and identify the exact line where the error occurs. This can help you understand the context and the data types involved.
  
  Related Information:
  
  ABAP Data Types: Familiarize yourself with the different data types in ABAP, such as CHAR, NUMC, INT, STRING, etc.
  Type Conversion Functions: Look into ABAP functions for type conversion, such as CONVERT, CAST, and others.
  SAP Notes: Check SAP Notes for any known issues or additional guidance related to this error message.
  Documentation: Refer to the official SAP documentation for more details on data types and operations in ABAP.
  
  By following these steps, you should be able to resolve the WL490 error and ensure that your operations are performed on compatible data types.