dotnet/roslyn

need a better error message for invalid lambda capturing of ref-like types

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#22,058 opened on Sep 11, 2017

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Area-CompilersBugConcept-Diagnostic ClarityFeature - Readonly ReferencesLanguage-C#help wanted

Description

See the use of ERR_AnonDelegateCantUseLocal

We are reusing the same errors for ref variables and for ref-like values. In the second case it could be confusing, although coming up with a better error is not easy. It should not at least say "ref" - that is not a problem here, probably "ref-like types"

Contributor guide

Tech stack
csharp
Domain
tooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
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.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C# compiler internalserror message codesref like types
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Examine the code where ERR AnonDelegateCantUseLocal is defined and used. The error message likely resides in a resource file or diagnostic descriptor. Determine how the error is generated for ref like types vs ref variables, and propose a new distinct error message for ref like types. Ensure the change does not break existing tests.
need a better error message for invalid lambda capturing of ref-like types · dotnet/roslyn#22058 | Good First Issue