# Analysis of integer values in C#

JetBrains Fleet can track the flow of integer values through your code and report redundant or possibly erroneous statements. It supports all C# integral numeric types — `int`

, `uint`

, `byte`

, `sbyte`

, `short`

, `ushort`

, `long`

, and `ulong`

— and warns you about the following issues:

relational/equality operators that always evaluate to

`true`

or`false`

,unreachable

`switch`

cases checking`int`

values,meaningless arithmetic operations, such as multiplication by

`1`

or addition of`0`

(except literals or constants: JetBrains Fleet assumes that expressions like`x + 0`

are intentional),possible

`int`

overflows,possible division by

`0`

,possible errors in invocations of

`System.Math`

methods,the above issues in enumeration types with the corresponding underlying types.

## How it works

JetBrains Fleet narrows down the possible range of values for each integer according to possible outcomes of all statements and expressions that can produce or affect that integer. Let's consider some examples.

JetBrains Fleet can deduce that `temp < 0`

in the example below will always evaluate to `false`

because Math.Abs always returns a non-negative value.

In the following example, JetBrains Fleet infers that by the last `return`

, the value of `input`

is in the range of `-100 ... 100`

, and when divided by a larger `divider`

, it will be truncated towards zero.

## Refine analysis with annotations

There are two JetBrains.Annotations attributes (`[NonNegativeValue]`

and `[ValueRange(from, to)]`

) for analysis of integer values.

You can use these attributes with type members returning `int`

and with `int`

parameters to specify known constraints and thus improve analysis precision.

Here is an example of annotating the method parameter with [NonNegativeValueAttribute] to refine the analysis within the method body. Knowing that the parameter is non-negative, JetBrains Fleet can report all redundant operations on that parameter:

The following example demonstrates how annotating a method can help find redundant checks around its usages: