csharp-inconsistent-warning-ca1062's Introduction

csharp-inconsistent-warning-ca1062

This repository is related to issue 1416138.

Assigning an argument specified as a reference type (e.g. string) to an instance field (both in the constructor and in a plain method) does not trigger a CA1062 warning about a potential nullability issue.

The compiler only generates these two warnings:

warning CA1062: In externally visible method 'Foo.Foo(string x)', validate parameter 'x' is non-null before using it. If appropriate, throw an ArgumentNullException when the argument is null or add a Code Contract precondition asserting non-null argument.

warning CA1062: In externally visible method 'void Foo.SetX(string x)', validate parameter 'x' is non-null before using it. If appropriate, throw an ArgumentNullException when the argument is null or add a Code Contract precondition asserting non-null argument.

    public class Foo
    {
        public Foo(string x)
        {
            this.x = x; // does not warn
            this.len = x.Length; // warns (OK)
        }

        public void SetX(string x)
        {
            this.x = x; // does not warn
            this.len = x.Length; // warns (OK)
        }

        public string X => this.x;
        public int Len => this.len;

        private string x;
        private int len;
    }

I am expecting that if I assign x to this.x without checking that x is indeed not null, then I have the risk of using this.x in cases where it may not be null.

Context

The warnings are generated when following settings are used:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
    <LangVersion>latest</LangVersion>
    <Nullable>enable</Nullable>
    <EnableNETAnalyzers>true</EnableNETAnalyzers> <!-- enable analyzers -->
    <AnalysisMode>AllEnabledByDefault</AnalysisMode> <!-- enable ALL analyzers -->
  </PropertyGroup>
</Project>

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