dotnet/roslyn

"Unused using" incorrectly reported in IDE

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#67,473 opened on Mar 23, 2023

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Area-CompilersBugIDE-CodeStylehelp wanted

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Description

Using VS 17.6p3 and working on the compiler project at this commit: https://github.com/jcouv/roslyn/tree/unused-using-bug-67473

I open ExtensionTypeTests.cs and notice a greyed out using directive: image

But I remove this using, I get an error on line 5449 which uses VariableDeclaratorSyntax: image

I tried investigating whether the compiler is producing an incorrect HDN_UnusedUsingDirective hidden diagnostic, using a command-line build under debugger, but the hidden diagnostic was not produced. So I suspect there is some IDE issue, possibly with how the compilation is set up.

image

Contributor guide

Research direction
Reproduce the issue by opening ExtensionTypeTests.cs in the Roslyn IDE project. Check the unused using diagnostic computation for the using directive that is greyed out but actually needed by the VariableDeclaratorSyntax usage. Trace the diagnostic pipeline to see why the IDE reports it as unused.
Tech stack
csharp
Domain
compilersdeveloper experience
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75