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Generate init accessor for required properties inside readonly structs #80004

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Merged
merged 1 commit into from
Aug 21, 2025
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Generate init accessor for required properties inside readonly structs #80004

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6 changes: 4 additions & 2 deletions src/Features/CSharp/Portable/Snippets/CSharpProprSnippetProvider.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -53,11 +53,13 @@ protected override bool IsValidSnippetLocationCore(SnippetContext context, Cance
protected override AccessorDeclarationSyntax? GenerateSetAccessorDeclaration(CSharpSyntaxContext syntaxContext, SyntaxGenerator generator, CancellationToken cancellationToken)
{
// Having a property with `set` accessor in a readonly struct leads to a compiler error.
// So if user executes snippet inside a readonly struct the right thing to do is to not generate `set` accessor at all
// At the same time having a required property with no setter at all is also illegal.
// Thus out best guess here is to generate an `init` accessor. We can assume they are available
// as a language feature since `required` keyword has a higher minimal language version to use
if (syntaxContext.ContainingTypeDeclaration is StructDeclarationSyntax structDeclaration &&
syntaxContext.SemanticModel.GetDeclaredSymbol(structDeclaration, cancellationToken) is { IsReadOnly: true })
{
return null;
return SyntaxFactory.AccessorDeclaration(SyntaxKind.InitAccessorDeclaration).WithSemicolonToken(SemicolonToken);
}

return base.GenerateSetAccessorDeclaration(syntaxContext, generator, cancellationToken);
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10 changes: 7 additions & 3 deletions src/Features/CSharpTest/Snippets/CSharpProprSnippetProviderTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

using System.Diagnostics.CodeAnalysis;
using System.Threading.Tasks;
using Roslyn.Test.Utilities;
using Xunit;

namespace Microsoft.CodeAnalysis.CSharp.UnitTests.Snippets;
Expand All @@ -14,14 +15,16 @@ public sealed class CSharpProprSnippetProviderTests : AbstractCSharpAutoProperty

protected override string DefaultPropertyBlockText => "{ get; set; }";

[WorkItem("https://github.com/dotnet/roslyn/issues/79954")]
public override Task InsertSnippetInReadonlyStructTest()
=> VerifyPropertyAsync("""
readonly struct MyStruct
{
$$
}
""", "public required {|0:int|} {|1:MyProperty|} { get; }");
""", "public required {|0:int|} {|1:MyProperty|} { get; init; }");

[WorkItem("https://github.com/dotnet/roslyn/issues/79954")]
public override Task InsertSnippetInReadonlyStructTest_ReadonlyModifierInOtherPartialDeclaration()
=> VerifyPropertyAsync("""
partial struct MyStruct
Expand All @@ -32,8 +35,9 @@ partial struct MyStruct
readonly partial struct MyStruct
{
}
""", "public required {|0:int|} {|1:MyProperty|} { get; }");
""", "public required {|0:int|} {|1:MyProperty|} { get; init; }");

[WorkItem("https://github.com/dotnet/roslyn/issues/79954")]
public override Task InsertSnippetInReadonlyStructTest_ReadonlyModifierInOtherPartialDeclaration_MissingPartialModifier()
=> VerifyPropertyAsync("""
struct MyStruct
Expand All @@ -44,7 +48,7 @@ struct MyStruct
readonly partial struct MyStruct
{
}
""", "public required {|0:int|} {|1:MyProperty|} { get; }");
""", "public required {|0:int|} {|1:MyProperty|} { get; init; }");

public override Task VerifySnippetInInterfaceTest()
=> VerifySnippetIsAbsentAsync("""
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