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C#: Extract the implicit property backing field when referenced via the field keyword.

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This commit is contained in:
Michael Nebel
2026-02-11 14:10:14 +01:00
parent 7d17454a3b
commit edb2ed8df2
4 changed files with 82 additions and 1 deletions
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3
csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Factory.cs
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@@ -160,6 +160,9 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
case SyntaxKind.ThisExpression:
return This.CreateExplicit(info);
case SyntaxKind.FieldExpression:
return PropertyFieldAccess.Create(info);
case SyntaxKind.AddressOfExpression:
return Unary.Create(info.SetKind(ExprKind.ADDRESS_OF));

28
csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/PropertyFieldAccess.cs Normal file
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@@ -0,0 +1,28 @@
using System.IO;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Semmle.Extraction.Kinds;
namespace Semmle.Extraction.CSharp.Entities.Expressions
{
internal class PropertyFieldAccess : Expression<FieldExpressionSyntax>
{
private PropertyFieldAccess(ExpressionNodeInfo info) : base(info.SetKind(ExprKind.FIELD_ACCESS)) { }
public static Expression Create(ExpressionNodeInfo info) => new PropertyFieldAccess(info).TryPopulate();
protected override void PopulateExpression(TextWriter trapFile)
{
var symbolInfo = Context.GetSymbolInfo(Syntax);
if (symbolInfo.Symbol is IFieldSymbol field)
{
var target = PropertyField.Create(Context, field);
trapFile.expr_access(this, target);
if (!field.IsStatic)
{
This.CreateImplicit(Context, field.ContainingType, Location, this, -1);
}
}
}
}
}

2
csharp/extractor/Semmle.Extraction.CSharp/Entities/Field.cs
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@@ -10,7 +10,7 @@ namespace Semmle.Extraction.CSharp.Entities
{
internal class Field : CachedSymbol<IFieldSymbol>, IExpressionParentEntity
{
private Field(Context cx, IFieldSymbol init)
protected Field(Context cx, IFieldSymbol init)
: base(cx, init)
{
type = new Lazy<Type>(() => Entities.Type.Create(cx, Symbol.Type));

50
csharp/extractor/Semmle.Extraction.CSharp/Entities/PropertyField.cs Normal file
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@@ -0,0 +1,50 @@
using System.IO;
using Microsoft.CodeAnalysis;
using Semmle.Extraction.CSharp.Util;
using Semmle.Extraction.Kinds;
namespace Semmle.Extraction.CSharp.Entities
{
/// <summary>
/// Represents the autogenerated backing field `field` for a property.
/// It is only created for properties that use the `field` keyword in their getter or setter, and
/// is not created for auto-properties.
/// </summary>
internal class PropertyField : Field
{
protected PropertyField(Context cx, IFieldSymbol init)
: base(cx, init)
{
}
public static new PropertyField Create(Context cx, IFieldSymbol field) => PropertyFieldFactory.Instance.CreateEntity(cx, (field, field.AssociatedSymbol), field);
public override bool NeedsPopulation => true;
public override void Populate(TextWriter trapFile)
{
PopulateNullability(trapFile, Symbol.GetAnnotatedType());
var unboundFieldKey = PropertyField.Create(Context, Symbol.OriginalDefinition);
var name = Symbol.AssociatedSymbol is not null ? $"{Symbol.AssociatedSymbol.GetName()}.field" : Symbol.Name;
trapFile.fields(this, VariableKind.None, name, ContainingType!, Type.TypeRef, unboundFieldKey);
if (Context.OnlyScaffold)
{
return;
}
if (Context.ExtractLocation(Symbol))
{
WriteLocationsToTrap(trapFile.field_location, this, Locations);
}
}
private class PropertyFieldFactory : CachedEntityFactory<IFieldSymbol, PropertyField>
{
public static PropertyFieldFactory Instance { get; } = new PropertyFieldFactory();
public override PropertyField Create(Context cx, IFieldSymbol init) => new PropertyField(cx, init);
}
}
}