Usage of _ in methods arguments raises SA1313

[Onzi12]

Usage of _ in method arguments raises SA1313.

Example:

public override void Foo( int arg, int _ )
{
...
}

Can you please make an exception to SA1313, to support '_' in method arguments?

[brinko99]

I agree. As is, an exception is made for lambda expressions...

In fact, I would request that any number of ignored parameters be supported in this way. This supports the cases where multiple parameters are to be ignored.

e.g. MyProperty.PropertyChanged += (_, __) => ...

[sharwell]

I'm not sure I agree with this one. Plus, it's going to conflict with #1949.

@brinko99 Your case is a duplicate of #1606.

[Onzi12]

Why are you not sure you agree?
The purpose of the _ is to acknowledge the arg is not in use.
Without this enhancement, users can use this feature ONLY in lambda handlers.

About the conflict with #1949 I agree. Implementing this should include an exception to #1949.

[sharwell]

Closing this one as won't fix. The recommended solution for method signatures when a parameter is intentionally not used is:

1. Give the parameter a meaningful name. This should match the original definition when applicable (see Implement SA1315: ParametersShouldMatchInheritedNames #1949).
2. Assign the parameter to a discard at the start of the method to clearly indicate to the reader that the parameter is intentionally unused.

For example:

public void Method(T value)
{
  _ = value;
}

[tutike2000]

Why close this as won't fix if so many people want it fixed?

[sharwell]

@tutike2000 There is no requirement that a project enable SA1313 or use it without modification. Options for resolving this externally include:

• SA1313 can be disabled, and a new rule implemented separately that is used instead. The new rule can be based on SA1313 and even start with its code under the MIT license.
• SA1313 can be left enabled, and a DiagnosticSuppressor implemented separately that prevents SA1313 from reporting in the location described by this issue. I faced a similar issue with VSTHRD200 and resolved it by writing RelaxTestNamingSuppressor.

[palenshus]

Currently IDE0060 suggests that we do in fact rename unused parameters to _:

IDE0060 Remove unused parameter 'sender' if it is not part of a shipped public
Avoid unused parameters in your code. If the parameter cannot be removed, then change its name so it starts with an underscore and is optionally followed by an integer, such as '_', '_1', '_2', etc. These are treated as special discard symbol names.

However, if we follow that advice, given by the IDE, then we run into this issue. That doesn't seem like a good thing to Won't Fix

[Lowlet]

This should be fixed