dotnet/roslyn

Quite confusing error message CS0282

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#32,305 opened on Jan 9, 2019

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Area-CompilersBugConcept-Diagnostic Clarityhelp wanted

Description

Version Used: Microsoft (R) Visual C# Compiler version 2.8.2.62916 (2ad4aabc)

Steps to Reproduce:

  1. Compile following code
using System;
using System.Runtime.InteropServices;

partial class Exception2
{
	protected event Action a;
}

[StructLayout (LayoutKind.Sequential)]
partial class Exception2
{
	protected event Action b;
}

Expected Behavior:

A warning which makes sense

Actual Behavior:

warning CS0282: There is no defined ordering between fields in multiple declarations of partial struct 'Exception2'. To specify an ordering, all instance fields must be in the same declaration.

  • there is no struct 'Exception2' (it's a class)
  • referring to events underlying implementation fields is also confusing

Contributor guide

Tech stack
csharp
Domain
developer experience
Issue type
bug
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#basic understanding of compiler error messages
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55
Research direction
Locate the CS0282 error message in the Roslyn source code. The error currently mentions struct but applies to a class, and refers to fields but events are involved. Update the message to correctly refer to 'class' and clarify that events have underlying fields. Check the ErrorCode enum and the resource string for CS0282.