dotnet/roslyn

Main Method warnings are ignored if "main type" is specified

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#18,964 opened on Apr 24, 2017

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Area-CompilersBugConcept-Diagnostic Clarityhelp wanted

Description

In the CSharp entrypoint finder warnings that would otherwise be reported are simply ignored if a Main Type is provided to the compiler.

Example

static class Program {
    static void Main<T>() { }
    static void Main(string[] args) { }
}

compiling with csc /main:Program repro.cs produces no errors or diagnostics

compiling with csc repro.cs gives you:

repro.cs(2,17): warning CS0402: 'Program.Main<T>()': an entry point cannot be generic or in a generic type

Contributor guide

Tech stack
csharp
Domain
tooling
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# basicsfamiliarity with Roslyn compiler code
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the CSharp entry point finder at Microsoft.CodeAnalysis.CSharp/Compilation/CSharpCompilation.cs around line 1481. The issue is that warnings (e.g., CS0402 for generic entry points) are suppressed when /main is specified. Trace the logic where warnings are conditionally reported and modify it to ensure warnings are emitted regardless of the /main option. Check existing tests for entry point detection and add a test case for this scenario.