dotnet/roslyn

The .NET Compiler Platform ("Roslyn") provides open-source C# and Visual Basic compilers with rich code analysis APIs.

Bernd Baumanns

@bernd5

I found:

https://github.com/dotnet/roslyn/blob/315c2e149ba7889b0937d872274c33fcbfe9af5f/src/Compilers/CSharp/Test/Symbol/Symbols/CompilationCreationTests.cs#L2802

global usings are only visible in script code

But how can we load a new net6.0 project with implicit usings?

Should we generate a CompilationUnit with those global usings?

Egil Hansen

@egilhansen:matrix.org

[m]

Hey people, just a sanity check before I waste more time... can I have a source generator create a class with a partial unimplemented method, and then have the user implement that method in a class they write manually?

Generation works, and the compiler complains afterword's that CS8795 Partial method 'MyClass.MyMethod(CancellationToken)' must have an implementation part because it has accessibility modifiers.

But when I in the user project create a class in the right namespace with the right name, the CS8795 error goes away but is replaced with a CS0759 No defining declaration found for implementing declaration of partial method 'MyClass.MeMethod(CancellationToken)'.

So that leads me to think that this approach is not possible?

Yair Halberstadt

@YairHalberstadt

It should work fine. Is that a VS error, or a compilation error?

I.e. does it work fine when you compile it.

Egil Hansen

@egilhansen:matrix.org

[m]

@YairHalberstadt it seems like a build time error

I am using c#10 and a rc1 nightly though

Egil Hansen

@egilhansen:matrix.org

[m]

Arrrg nevermind. Guess it was a chicken and eg thing. I had three partial method generated, and once I implemented all three all the errors went away.

well sort of, Visual Studio is still not happy and continue to report CS0759

Yair Halberstadt

@YairHalberstadt

Yeah visual studio tooling still isn't perfect with SGs.

You can report that as a roslyn bug and hopefully it'll get fixed some time.

egilhansen

@egilhansen:matrix.org

[m]

Yep, its the same with the blazor soruce generator. in gneral SGs are cool, but e.g. having the ability to delete generated files that are no longer relevant, e.g. because the user renamed or moved a file, is pretty high on the list of things to have.

Yair Halberstadt

@YairHalberstadt

I don't understand what that means? SGs generate a fresh set of files every compilation. You should never need to delete any.

egilhansen

@egilhansen:matrix.org

[m]

So e.g. i changed my analyzer to produce file1 instead of file_1, and the later was not removed, and was still picked up by the compiler.

If you rename a Blazor (.razor) file you sometimes have to restart vs to get things working again.

Yair Halberstadt

@YairHalberstadt

That sounds like a VS problem, not a roslyn problem. Should work fine from the compiler

Egil Hansen

@egilhansen:matrix.org

[m]

You might be right

Adam Speight

@AdamSpeight2008

Could Source Generators be used to generate the various Syntax Nodes and BoundNodes used by the compilers themself?
Eg Boot Strap build then nodes and then compile the rest of the selection.

CyrusNajmabadi

@CyrusNajmabadi

Source generators do that :)

That is how we generate the syntax nodes.

See CSharpSyntaxGenerator.

Adam Speight

@AdamSpeight2008

I meant using the language feature "Source Generators" to generate them, rather the "manually pre-source generators" way of generating source code.

CyrusNajmabadi

@CyrusNajmabadi

yes. that's what i'm saying

CSharpSyntaxGenerator uses the language feature 'Source Generators'

see: https://github.com/dotnet/roslyn/blob/main/src/Tools/Source/CompilerGeneratorTools/Source/CSharpSyntaxGenerator/CachingSourceGenerator.cs#L19

1 reply

and

https://github.com/dotnet/roslyn/blob/main/src/Tools/Source/CompilerGeneratorTools/Source/CSharpSyntaxGenerator/SourceGenerator.cs#L25

Bernd Baumanns

@bernd5

Project.GetSourceGeneratedDocumentsAsync seems to query / build the Compilation

(Project based on MSBuildWorkspace)

This is okay - but it takes quite a long time even if the project has no source generator

Is there some way to determine if a project has source generators?

Oh, new projects seem to have an implicit SourceGenerator

Bernd Baumanns

@bernd5

"System.Text.Json.SourceGeneration.JsonSourceGenerator"

that is the reason why https://github.com/dotnet/roslyn/blob/60a431bf454e78ae3cefc1930d356a72eaaba20c/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.cs#L1078 fails

Bernd Baumanns

@bernd5

Can we disable it?

I mean I don't want a JsonSourceGenerator for projects which do nothing with Json...

Where is it defined?

Bernd Baumanns

@bernd5

Is it intended or a bug?

CyrusNajmabadi

@CyrusNajmabadi

it's intentional if the project links in (Somehow) that generator.

it's possible it's built into the sdk.

you might need to create a discussion on the sdk side of things asking if there's a way to disable this.

Bernd Baumanns

@bernd5

@CyrusNajmabadi thanks

Do you know where I can create such a discussion? Which repo?

CyrusNajmabadi

@CyrusNajmabadi

probably: https://github.com/dotnet/sdk

Andrew Hill

@AartBluestoke

https://sharplab.io/#v2:EYLgxg9gTgpgtADwGwBYA0AXEBDAzgWwB8ABAJgEYBYAKGIGYACMhgYQYG8aHunGBLAHYYGAFSgBPABQBKDlx4LBw3AFd8AXgAMAbnkLuGCZ2r7TDAGbQGkpQz5btdgDzlNOuwGoP0vWdOr8D3U+XRMzAF8GMGwMMAALdnDfBWSeYgB2BgDQhSTqGl96OyEGADkIMSlZYz9bAIdU00soa1t7dz4XN0c+Lx8wv381IJDGpkzs3zyacKA=

    public int Try() {
        int sum=0;
        try{
            for (int i=0; i<100; i++)
                sum+=i;
        } catch{}

        return sum;
    }


    public int NoTry() {
        int sum=0;
            for (int i=0; i<100; i++)
                sum+=i;
        return sum;
    }

adding a try{...}catch{} around a trivial for loop can strongly affect its optimisation ; is this expected?

Antony Male

@canton7

The actual loop hasn't changed that much -- it's got a couple more movs

Andrew Hill

@AartBluestoke

those movs make it about 3x as slow when you benchmark.net it (but i don't know of an online code fragment benchmark)

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