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Handle nullable postcondition for non-static local function inside field initializer #76716

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Handle nullable postcondition for non-static local function inside field initializer #76716

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20d67da
WIP
RikkiGibson Jan 10, 2025
9a003b5
Add suggested test
RikkiGibson Jan 17, 2025
b5842f9
Address feedback
RikkiGibson Jan 27, 2025
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7 changes: 7 additions & 0 deletions src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -7188,6 +7188,13 @@ private int GetReceiverSlotForMemberPostConditions(MethodSymbol? method)
}
}

if (current.ContainingSymbol is FieldSymbol)
{
// Functions inside a field initializer are effectively static.
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// Functions inside a field initializer are effectively static.

Is this accurate? For example, it looks like in the following scenario both the lambda and the local function are implemented by an instance method.

#nullable enable

using System;
using System.Diagnostics.CodeAnalysis;

public class C(string p)
{
    public static string? field;

    public Action field2 = () =>
    {
        init();
        Console.WriteLine(field.Length);

        [MemberNotNull(nameof(field))]
        void init() => field ??= p;
    };
    
    string M() => p;
}

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You're right, when marked static the functions cannot use p. I'll adjust the comment and add the test.

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It looks like the comment got removed, but it feels like we still need some rational to explain why returning 0 is probably not 100% accurate, but OK thing to do.

Debug.Assert(method.MethodKind is MethodKind.LambdaMethod or MethodKind.LocalFunction);
return 0;
}

if (current.TryGetThisParameter(out var thisParameter) && thisParameter is not null)
{
return GetOrCreateSlot(thisParameter);
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58 changes: 58 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/LocalFunctionTests.cs
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Expand Up @@ -10588,5 +10588,63 @@ void M()
// [A(p)] void F() { }
Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "F").WithArguments("F").WithLocation(13, 21));
}

[Theory, WorkItem("https://github.com/dotnet/roslyn/issues/76528")]
[InlineData("")]
[InlineData("static ")]
public void Repro76528(string modifiers)
{
var source = $$"""
#nullable enable

using System;
using System.Diagnostics.CodeAnalysis;

public class C
{
public static string? field;

public Action Prop1 { get; } = () =>
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Consider testing also when the lambdas are marked static.

{
init();
Console.WriteLine(field.Length);

[MemberNotNull(nameof(field))]
{{modifiers}}void init() => field ??= "";
};
}
""";
var comp = CreateCompilation([source, MemberNotNullAttributeDefinition]);
comp.VerifyEmitDiagnostics();
}

[Theory, WorkItem("https://github.com/dotnet/roslyn/issues/76528")]
[InlineData("")]
[InlineData("static ")]
public void Repro76528_FieldInitializer(string modifiers)
{
var source = $$"""
#nullable enable

using System;
using System.Diagnostics.CodeAnalysis;

public class C
{
public static string? field;

public Action field2 = () =>
{
init();
Console.WriteLine(field.Length);

[MemberNotNull(nameof(field))]
{{modifiers}}void init() => field ??= "";
};
}
""";
var comp = CreateCompilation([source, MemberNotNullAttributeDefinition]);
comp.VerifyEmitDiagnostics();
}
}
}