Roslyn: Proposal: Syntax Hightlighting for Discard

[jcouv]

@Ccursed commented on Sat Jun 30 2018

I propose to highlight the usage of underscore ( _ ), when used as discard character, to be treated like a keyword (this / default / await / etc.) by the syntax highlighting in Visual Studio.

Example:

SomeObject.SomeEvent += (value1, _) => { //Do Something with only value1 };

Where the underscore would be marked in blue (Dark Visual Studio Theme, colors accordingly for theme).

I think it would improve code readability and would make it more clear that the specified parameter is not neccesary for the required operation.

Edit: My example is bad.
Hopefully better:

var (value1, _, _) = CreateTupleWith3Values();

Where currently the discard underscores are not syntax hightlighted.

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@jnm2 commented on Sat Jun 30 2018

Is this covered by https://github.com/dotnet/csharplang/issues/111?

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@Ccursed commented on Sat Jun 30 2018

@jnm2 As far as I can tell, no.

It is not about existing or new ways of usage, but simply about syntax highlighting.

My current Visual Studio 17 (latest Updates) and running latest minor C# version does not highlight underscores used as discards.

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@yaakov-h commented on Sat Jun 30 2018

That example doesn't use a discard, IIRC...

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@Ccursed commented on Sat Jun 30 2018

@yaakov-h True. Updated first post.

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@HaloFour commented on Sat Jun 30 2018

This request belongs on the Roslyn repo as it doesn't change the semantics of the C# language, only the tooling. I want to say that I've seen an issue there for this but I couldn't find it with a quick search.

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@jnm2 commented on Sat Jun 30 2018

Scratch that, I could have sworn discards were highlighted as keywords, but apparently they aren't. Was there a change?

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@jnm2 commented on Sat Jun 30 2018

@Ccursed See https://github.com/dotnet/roslyn/issues/16667 and https://github.com/dotnet/roslyn/pull/20561. This looks intentional.

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@Ccursed commented on Sat Jun 30 2018

@jnm2 Yes I see. Thanks.

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@Joe4evr commented on Wed Jul 04 2018

It's a shame, though. I loved seeing that discard highlighted differently.

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@jnm2 commented on Wed Jul 04 2018

Me too! I thought it was cool. @jcouv, what are the possibilities if we were to move this issue to dotnet/roslyn?

[jcouv]

Moved the issue from csharplang.

[dpoeschl]

Design Meeting Notes:

We do think this should be classified as a keyword.

[Tragetaschen]

Referencing the CreateTupleWith3Values sample from above, does the classification do anything to improve the tool tip experience?

Currently, nothing happens when I move the mouse over the discard and I regularly think that I didn't hover right. Usually, there is some information about the variable like (local variable) int value1, so I'd like to propose something along the lines of (discard) int nameOfItem2.

[jcouv]

@Tragetaschen QuickInfo does pop-up for discards. It shows the type and an underscore as show in screencap:

The classification fix was merged, so I'll go ahead and close this issue.
Please file a separate issue about QuickInfo if you'd like further refinement. Thanks