dotnet/roslyn

It looks like OverloadResolution.GetParameterType doesn't perform complete check before digging through param array

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#20,249 opened on Jun 15, 2017

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Area-CompilersBugLanguage-C#help wanted

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Description

The check that the parameter is the last parameter is not performed, but I believe it should be see OverloadResolution.IsValidParams.

private static TypeSymbol GetParameterType(int argIndex, MemberAnalysisResult result, ImmutableArray<ParameterSymbol> parameters, out RefKind refKind)
        {
            int paramIndex = result.ParameterFromArgument(argIndex);
            ParameterSymbol parameter = parameters[paramIndex];
            refKind = parameter.RefKind;

            if (result.Kind == MemberResolutionKind.ApplicableInExpandedForm &&
                parameter.IsParams && parameter.Type.IsSZArray())
            {
                return ((ArrayTypeSymbol)parameter.Type).ElementType;
            }
            else
            {
                return parameter.Type;
            }
        }

Contributor guide

Research direction
Inspect the GetParameterType method in OverloadResolution.cs. Ensure it checks that the parameter is the last parameter before accessing the element type of a params array. Compare the logic with IsValidParams to ensure consistency.
Tech stack
csharp
Domain
compilers
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#compiler internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35