IDE0072: False positive when using switch expression on integer

[omarjuul]

Version Used:
.NET SDK 7.0.102

Steps to Reproduce:
dotnet build the following:

Program.cs

static string TestSwitch(int foo)
    => foo switch
    {
        0 => "zero",
        < 0 => "negative",
        > 0 => "positive",
    };

ConsoleApp0.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0</TargetFramework>
    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
  </PropertyGroup>

</Project>

.editorconfig

[*.cs]
dotnet_diagnostic.IDE0072.severity = warning

Diagnostic Id: IDE0072

Expected Behavior:

IDE0072 is not raised: all cases are handled

Actual Behavior:
IDE0072 is raised. The suggested fix is to add a default arm. When I do that, I get a message that (correctly) informs me that The pattern has already been handled by a previous arm of the 'switch' expression

[Youssef1313]

Similar issue: #60784

[AdamSpeight2008]

The compiler doesn't have enough knowledge to determinate that on only a type level.
A types behavioral traits or effects are type specific and are not expressed in a way, that can effect compilation or validity of a program at compile-time.

Eg
For types that can consider to be "unsigned values"
Two fundemental conditions have to be satifised to met "all cases handled".

• The value Zero has be covered.
• All other values greater than Zero has to be covered.
  For "signed values" and addition condition has to be met
• All other values lesser than Zero has to covered.

This hard to tell just looking at the type and the operators it provides. As the operators < = > are not enough to assert that those conditions are met. A type is allowed to override the meaning, of them.
The compiler would be required to have specific knowledge of each type, and its intended meaning of each operator. Or that the type providers an interface or attribute, testifying to meaning.

[omarjuul]

Somehow the origin of the message that pops up when I apply the suggested fix does have this (type-specific) information.

This message seems to be originating from a different analyzer altogether. Is it just a regular build Error? dotnet build indicates

error CS8510: The pattern is unreachable. It has already been handled by a previous arm of the switch expression or it is impossible to match.

[CyrusNajmabadi]

The compiler doesn't have enough knowledge to determinate that

The Compiler definitely had enough knowledge here @AdamSpeight2008. This is an issue with the analyzer. Primarily that this analyzer was never intended to be used as something where the severity would be set.

[Youssef1313]

@CyrusNajmabadi If an analyzer is intended to be ever only with suggestion severity, why it's an analyzer in the first place and not a code refactoring? Is that a step we can take?

[CyrusNajmabadi]

Because we didn't have fix all for refactorings at the time. Now that we do, this can be converted to that.