IDE1006 fires on discard parameters

[Forge36]

Version Used:
Microsoft Visual Studio Professional 2019
Version 16.6.3

Steps to Reproduce:

1. Create a function with an unused parameter (I used _ and _1 to handle multiple discarded parameters)
   public object DiscardParameter(string _1)
2. Define .editorconfig rule
   dotnet_naming_rule.parameter_should_be_camelcase.severity = suggestion
   dotnet_naming_rule.parameter_should_be_camelcase.symbols = parameter
   dotnet_naming_rule.parameter_should_be_camelcase.style = camelcase

Expected Behavior:
No warning

Actual Behavior:

Severity	Code	Description	Project	File	Line	Suppression State	Priority
Message	IDE1006	Naming rule violation: Prefix '_' is not expected	***	***	903	Active	Normal

Reference:
https://docs.microsoft.com/en-us/visualstudio/code-quality/ca1801?view=vs-2019

This rule does not flag parameters that are named with the discard symbol, for example, _, _1, and _2

Incompatible rules are confusing

[Youssef1313]

The doc link you're referring to is for CA1801 which is unrelated to IDE1006.

The behavior I'm seeing for IDE1006 seems correct (camel case shouldn't start with _).

[Forge36]

The doc link you're referring to is for CA1801 which is unrelated to IDE1006.

The behavior I'm seeing for IDE1006 seems correct (camel case shouldn't start with _).

CA1801 defines discard parameters as _ or _1 ... .
IDE1006 defines _ as an exception to the naming rules.

This conflict causes fixes to CA1801 to raise IDE1006.

It appears to be a bug that the two rules don't share the same exceptions. Currently the only way to resolve this (when the parameters can't be removed, and are not used) is to add a suppression for one of the errors.

[kendrahavens]

Design Meeting Notes

• We should recognize this syntax and update the naming style analyzers to ignore "_<#>"
• We have concerns that "_1" can be used as a parameter and is not actually recognized as a "true" discard. It can be used like a regular parameter name and not get a warning. This makes us want the language itself to recognize these as discards. (Will bring forward at LDM)
  • For this case, we should add an analyzer to recommend using a true discard if a "fake" discard is used. Especially as when multiple discards are allowed in C#9.