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Reference conversion on this in init-only phase #50424

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Jan 28, 2021
Merged

Reference conversion on this in init-only phase #50424

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Reference conversion on this in init-only phase
jcouv Jan 12, 2021
8d828c8
Revert code changes
jcouv Jan 28, 2021
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56 changes: 56 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/InitOnlyMemberTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1660,6 +1660,62 @@ public string RegularProperty2
);
}

[Fact, WorkItem(50053, "https://github.com/dotnet/roslyn/issues/50053")]
public void PrivatelyImplementingInitOnlyProperty_ReferenceConversion()
{
string source = @"
var x = new DerivedType() { SomethingElse = 42 };
System.Console.Write(x.SomethingElse);

public interface ISomething { int Property { get; init; } }
public record BaseType : ISomething { int ISomething.Property { get; init; } }

public record DerivedType : BaseType
{
public int SomethingElse
{
get => ((ISomething)this).Property;
init => ((ISomething)this).Property = value;
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@AlekseyTs AlekseyTs Jan 15, 2021 •
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this [](start = 29, length = 4)

Consider adding a test with base. #Closed

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Also a test where this hides an init-only property from base.

In reply to: 558461131 [](ancestors = 558461131)

}
}
";

var comp = CreateCompilation(new[] { source, IsExternalInitTypeDefinition }, options: TestOptions.DebugExe);
comp.VerifyEmitDiagnostics(
// (13,17): error CS8852: Init-only property or indexer 'ISomething.Property' can only be assigned in an object initializer, or on 'this' or 'base' in an instance constructor or an 'init' accessor.
// init => ((ISomething)this).Property = value;
Diagnostic(ErrorCode.ERR_AssignmentInitOnly, "((ISomething)this).Property").WithArguments("ISomething.Property").WithLocation(13, 17)
);
}

[Fact, WorkItem(50053, "https://github.com/dotnet/roslyn/issues/50053")]
public void PrivatelyImplementingInitOnlyProperty_BoxingConversion()
{
string source = @"
var x = new Type() { SomethingElse = 42 };

public interface ISomething { int Property { get; init; } }

public struct Type : ISomething
{
int ISomething.Property { get; init; }

public int SomethingElse
{
get => throw null;
init => ((ISomething)this).Property = value;
}
}
";

var comp = CreateCompilation(new[] { source, IsExternalInitTypeDefinition }, options: TestOptions.DebugExe);
comp.VerifyDiagnostics(
// (13,17): error CS8852: Init-only property or indexer 'ISomething.Property' can only be assigned in an object initializer, or on 'this' or 'base' in an instance constructor or an 'init' accessor.
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Would it be reasonable to add a more specific error for this, or do you think that would be more effort than it's worth? The error as it exists is misleading.

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Looking at the code I don't think it would be a ton of work to add, and I really don't like the error as it exists because it's just wrong.

In reply to: 558627354 [](ancestors = 558627354)

// init => ((ISomething)this).Property = value;
Diagnostic(ErrorCode.ERR_AssignmentInitOnly, "((ISomething)this).Property").WithArguments("ISomething.Property").WithLocation(13, 17)
);
}

[Fact]
public void OverridingInitOnlyProperty()
{
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