Analyzer proposal: mark anonymous functions as static

[xtqqczze]

Cause

An anonymous function that does not capture state from the enclosing scope is not marked as static.

Rule description

Lambdas and anonymous methods can be marked with the static modifier, to disallow capture of locals or instance state. Adding the static modifier to an anonymous function does not change the meaning of the program.

By applying this code fix, it can be ensured that future modifications to a program do not result in unexpected retention of captured objects or unexpected additional allocations.

Additional context

• https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-9.0/static-anonymous-functions
• Proposal: Use static keyword for lambdas to disallow capturing locals and parameters (VS 16.8, .NET 5) csharplang#275

[CyrusNajmabadi]

We explicitly decided not to do this as it would clutter up code that is intended to be terse unilaterally. static is intentionally intended to be a user controlled system whereby they annotate the lambdas tehy do not want capturing to ensure that no captures exist and no regressions happen in the future. It is not considered a 'better way' to do lambdas, or a pattern we would push people to use for all lambdas (even when applicable).

[NTaylorMullen]

Design Meeting Notes:

[Youssef1313]

@NTaylorMullen based on the design meeting notes, wouldn't it be better to offer it as a refactoring then?

[CyrusNajmabadi]

I'm not really a fan of refactorings taht do nothing but add a keyword to something. It can just be done manually with very little effort. st<tab> is likely enough.