dotnet/roslyn

Confusing error message when the target member cannot be located for an explicit interface implementation

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#38,467 opened on Sep 3, 2019

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Area-CompilersBugConcept-Diagnostic ClarityLanguage-C#help wanted

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Description

interface I100 { }

class C100 : I100
{
    object I100.M4() => null;
}

Observed:

 error CS0539: 'C100.M4()' in explicit interface declaration is not found among members of the interface that can be implemented

But C100 doesn't have member named M4.

Contributor guide

Research direction
Locate where error CS0539 is emitted and update the message to clarify that the method name may not exist in the interface.
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.
Half day
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.
Mostly clear
Prerequisites
C#
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70