Use ReadOnlySpan properties over array fields

[NewellClark]

While working on this analyzer I found and fixed several violations in dotnet/roslyn.

[CyrusNajmabadi]

There are likely similar hits in the non-compiler layers. If so, can you make a PR for that as well (independent of this one)? I'd be happy to review it and get it in asap for the higher layers.

[NewellClark]

There are likely similar hits in the non-compiler layers. If so, can you make a PR for that as well (independent of this one)? I'd be happy to review it and get it in asap for the higher layers.

I ran the analyzer on the entire dotnet/roslyn repository, not just the projects in the Compiler folder. I think the bot mislabeled this PR.

[CyrusNajmabadi]

I think the bot mislabeled this PR.

THe bot is correct here (since you only touched the compiler layer). I am surprised though as i'm sure we have read-only arrays at the IDE layer that could benefit from this. For example:

roslyn/src/Workspaces/Core/Portable/PatternMatching/PatternMatcher.cs

Line 27 in b88948f

private static readonly char[] s_dotCharacterArray = { '.' };

[NewellClark]

I think the bot mislabeled this PR.

THe bot is correct here (since you only touched the compiler layer). I am surprised though as i'm sure we have read-only arrays at the IDE layer that could benefit from this. For example:

roslyn/src/Workspaces/Core/Portable/PatternMatching/PatternMatcher.cs

Line 27 in b88948f

private static readonly char[] s_dotCharacterArray = { '.' };

At the moment, the analyzer only reports arrays for byte, sbyte, and bool because at present only arrays of those types containing all constant members are optimized by the compiler.

[CyrusNajmabadi]

At the moment, the analyzer only reports arrays for byte, sbyte, and bool because at present the inlining optimization only happens for 1-byte primitive types.

Ah. I'd like this not for any sort of optimization, but just for general safety. Those arrays should be immutable or ROS's so that no one can accidentally change their contents.

[NewellClark]

@CyrusNajmabadi It may be a good idea to create a separate rule that finds all static readonly array fields or auto-properties that are never mutated and suggests converting them to ImmutableArray. I'd be happy to implement it if it gets approved.

[CyrusNajmabadi]

Tagging @mavasani I think it would be great to have that. If he agrees then I think roslyn-analyzers would be the right place.

[jaredpar]

@RikkiGibson, @chsienki PTAL

[RikkiGibson]

LGTM, you can resolve the nit or not at your discretion and let us know when the PR is ready for merge.

[RikkiGibson]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 4 pipeline(s).

[RikkiGibson]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 4 pipeline(s).

[RikkiGibson]

Thanks for the contribution @NewellClark!