Handle various cases for field-backed properties

src/Compilers/CSharp/Portable/Binder/Binder_Statements.cs

@@ -1765,7 +1765,7 @@ private static bool AccessingAutoPropertyFromConstructor(BoundExpression receive
  var propertyIsStatic = propertySymbol.IsStatic;
 
  return (object)sourceProperty != null &&
- sourceProperty.IsAutoPropertyWithGetAccessor &&
+ sourceProperty.IsAutoProperty &&
  TypeSymbol.Equals(sourceProperty.ContainingType, fromMember.ContainingType, TypeCompareKind.AllIgnoreOptions) &&
  IsConstructorOrField(fromMember, isStatic: propertyIsStatic) &&
  (propertyIsStatic || receiver.Kind == BoundKind.ThisReference);

src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs

@@ -1879,8 +1879,7 @@ syntaxNode is ConstructorDeclarationSyntax constructorSyntax &&
  }
  else
  {
- var property = sourceMethod.AssociatedSymbol as SourcePropertySymbolBase;
- if (property is not null && property.IsAutoPropertyWithGetAccessor)
+ if (sourceMethod is SourcePropertyAccessorSymbol { IsAutoPropertyAccessor: true })
  {
  return MethodBodySynthesizer.ConstructAutoPropertyAccessorBody(sourceMethod);
  }

src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs

@@ -1075,7 +1075,7 @@ static IEnumerable<Symbol> getAllMembersToBeDefaulted(Symbol requiredMember)
  }
 
  static Symbol getFieldSymbolToBeInitialized(Symbol requiredMember)
- => requiredMember is SourcePropertySymbol { IsAutoPropertyWithGetAccessor: true } prop ? prop.BackingField : requiredMember;
+ => requiredMember is SourcePropertySymbol { IsAutoProperty: true } prop ? prop.BackingField : requiredMember;
  }
  }
  }

src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_AssignmentOperator.cs

@@ -281,7 +281,7 @@ private BoundExpression MakePropertyAssignment(
  if (setMethod is null)
  {
  var autoProp = (SourcePropertySymbolBase)property.OriginalDefinition;
- Debug.Assert(autoProp.IsAutoPropertyWithGetAccessor,
+ Debug.Assert(autoProp.IsAutoProperty,
  "only autoproperties can be assignable without having setters");
  Debug.Assert(property.Equals(autoProp, TypeCompareKind.IgnoreNullableModifiersForReferenceTypes));
 

src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs

@@ -485,6 +485,8 @@ internal sealed override bool IsDeclaredReadOnly
  }
  }
 
+ internal bool IsAutoPropertyAccessor => _isAutoPropertyAccessor;
+
  internal sealed override bool IsInitOnly => !IsStatic && _usesInit;
 
  private static DeclarationModifiers MakeModifiers(NamedTypeSymbol containingType, SyntaxTokenList modifiers, bool isExplicitInterfaceImplementation,

src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbol.cs

@@ -40,13 +40,16 @@ private static SourcePropertySymbol Create(
  GetAccessorDeclarations(
  syntax,
  diagnostics,
- out bool hasAccessorList,
- out bool accessorsHaveImplementation,
+ out bool isExpressionBodied,
+ out bool hasGetAccessorImplementation,
+ out bool hasSetAccessorImplementation,
  out bool usesFieldKeyword,
  out bool isInitOnly,
  out var getSyntax,
  out var setSyntax);
 
+ bool accessorsHaveImplementation = hasGetAccessorImplementation || hasSetAccessorImplementation; // PROTOTYPE: Remove if not needed.
+
  var explicitInterfaceSpecifier = GetExplicitInterfaceSpecifier(syntax);
  SyntaxTokenList modifiersTokenList = GetModifierTokensSyntax(syntax);
  bool isExplicitInterfaceImplementation = explicitInterfaceSpecifier is object;
@@ -60,8 +63,8 @@ private static SourcePropertySymbol Create(
  diagnostics,
  out _);
 
- bool isAutoProperty = (modifiers & DeclarationModifiers.Partial) == 0 && !accessorsHaveImplementation;
- bool isExpressionBodied = !hasAccessorList && GetArrowExpression(syntax) != null;
+ bool hasAutoPropertyGet = (modifiers & DeclarationModifiers.Partial) == 0 && getSyntax != null && !hasGetAccessorImplementation;
+ bool hasAutoPropertySet = (modifiers & DeclarationModifiers.Partial) == 0 && setSyntax != null && !hasSetAccessorImplementation;
 
  binder = binder.SetOrClearUnsafeRegionIfNecessary(modifiersTokenList);
  TypeSymbol? explicitInterfaceType;
@@ -78,7 +81,8 @@ private static SourcePropertySymbol Create(
  aliasQualifierOpt,
  modifiers,
  hasExplicitAccessMod: hasExplicitAccessMod,
- isAutoProperty: isAutoProperty,
+ hasAutoPropertyGet: hasAutoPropertyGet,
+ hasAutoPropertySet: hasAutoPropertySet,
  isExpressionBodied: isExpressionBodied,
  isInitOnly: isInitOnly,
  accessorsHaveImplementation: accessorsHaveImplementation,
@@ -98,7 +102,8 @@ private SourcePropertySymbol(
  string? aliasQualifierOpt,
  DeclarationModifiers modifiers,
  bool hasExplicitAccessMod,
- bool isAutoProperty,
+ bool hasAutoPropertyGet,
+ bool hasAutoPropertySet,
  bool isExpressionBodied,
  bool isInitOnly,
  bool accessorsHaveImplementation,
@@ -109,15 +114,16 @@ private SourcePropertySymbol(
  : base(
  containingType,
  syntax,
- hasGetAccessor,
- hasSetAccessor,
+ hasGetAccessor: hasGetAccessor,
+ hasSetAccessor: hasSetAccessor,
  isExplicitInterfaceImplementation,
  explicitInterfaceType,
  aliasQualifierOpt,
  modifiers,
  hasInitializer: HasInitializer(syntax),
  hasExplicitAccessMod: hasExplicitAccessMod,
- isAutoProperty: isAutoProperty,
+ hasAutoPropertyGet: hasAutoPropertyGet,
+ hasAutoPropertySet: hasAutoPropertySet,
  isExpressionBodied: isExpressionBodied,
  isInitOnly: isInitOnly,
  accessorsHaveImplementation: accessorsHaveImplementation,
@@ -202,23 +208,25 @@ public override OneOrMany<SyntaxList<AttributeListSyntax>> GetAttributeDeclarati
  private static void GetAccessorDeclarations(
  CSharpSyntaxNode syntaxNode,
  BindingDiagnosticBag diagnostics,
- out bool hasAccessorList,
- out bool accessorsHaveImplementation,
+ out bool isExpressionBodied,
+ out bool hasGetAccessorImplementation,
+ out bool hasSetAccessorImplementation,
  out bool usesFieldKeyword,
  out bool isInitOnly,
  out CSharpSyntaxNode? getSyntax,
  out CSharpSyntaxNode? setSyntax)
  {
  var syntax = (BasePropertyDeclarationSyntax)syntaxNode;
- hasAccessorList = syntax.AccessorList != null;
+ isExpressionBodied = syntax.AccessorList is null;
  getSyntax = null;
  setSyntax = null;
  isInitOnly = false;
 
- if (hasAccessorList)
+ if (!isExpressionBodied)
  {
  usesFieldKeyword = false;
- accessorsHaveImplementation = false;
+ hasGetAccessorImplementation = false;
+ hasSetAccessorImplementation = false;
  foreach (var accessor in syntax.AccessorList!.Accessors)
  {
  switch (accessor.Kind())
@@ -227,6 +235,7 @@ private static void GetAccessorDeclarations(
  if (getSyntax == null)
  {
  getSyntax = accessor;
+ hasGetAccessorImplementation = hasImplementation(accessor);
  }
  else
  {
@@ -238,6 +247,7 @@ private static void GetAccessorDeclarations(
  if (setSyntax == null)
  {
  setSyntax = accessor;
+ hasSetAccessorImplementation = hasImplementation(accessor);
  if (accessor.Keyword.IsKind(SyntaxKind.InitKeyword))
  {
  isInitOnly = true;
@@ -260,21 +270,22 @@ private static void GetAccessorDeclarations(
  throw ExceptionUtilities.UnexpectedValue(accessor.Kind());
  }
 
- var body = (SyntaxNode?)accessor.Body ?? accessor.ExpressionBody;
- if (body != null)
- {
- accessorsHaveImplementation = true;
- }
-
  usesFieldKeyword = usesFieldKeyword || containsFieldKeyword(accessor);
  }
  }
  else
  {
  var body = GetArrowExpression(syntax);
- accessorsHaveImplementation = body is object;
+ hasGetAccessorImplementation = body is object;
+ hasSetAccessorImplementation = false;
  usesFieldKeyword = body is { } && containsFieldKeyword(body);
- Debug.Assert(accessorsHaveImplementation); // it's not clear how this even parsed as a property if it has no accessor list and no arrow expression.
+ Debug.Assert(hasGetAccessorImplementation); // it's not clear how this even parsed as a property if it has no accessor list and no arrow expression.
+ }
+
+ static bool hasImplementation(AccessorDeclarationSyntax accessor)
+ {
+ var body = (SyntaxNode?)accessor.Body ?? accessor.ExpressionBody;
+ return body != null;
  }
 
  static bool containsFieldKeyword(SyntaxNode syntax)
@@ -324,7 +335,7 @@ private static (DeclarationModifiers modifiers, bool hasExplicitAccessMod) MakeM
  SyntaxTokenList modifiers,
  bool isExplicitInterfaceImplementation,
  bool isIndexer,
- bool accessorsHaveImplementation,
+ bool accessorsHaveImplementation, // PROTOTYPE: How is this used?
  Location location,
  BindingDiagnosticBag diagnostics,
  out bool modifierErrors)

src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbolBase.cs

@@ -29,11 +29,13 @@ internal abstract class SourcePropertySymbolBase : PropertySymbol, IAttributeTar
  private enum Flags : byte
  {
  IsExpressionBodied = 1 << 0,
- IsAutoProperty = 1 << 1,
- IsExplicitInterfaceImplementation = 1 << 2,
- HasInitializer = 1 << 3,
- AccessorsHaveImplementation = 1 << 4,
- HasExplicitAccessModifier = 1 << 5,
+ HasAutoPropertyGet = 1 << 1,
+ HasAutoPropertySet = 1 << 2,
+ UsesFieldKeyword = 1 << 3,
+ IsExplicitInterfaceImplementation = 1 << 4,
+ HasInitializer = 1 << 5,
+ AccessorsHaveImplementation = 1 << 6,
+ HasExplicitAccessModifier = 1 << 7,
  }
 
  // TODO (tomat): consider splitting into multiple subclasses/rare data.
@@ -80,7 +82,8 @@ protected SourcePropertySymbolBase(
  DeclarationModifiers modifiers,
  bool hasInitializer,
  bool hasExplicitAccessMod,
- bool isAutoProperty,
+ bool hasAutoPropertyGet,
+ bool hasAutoPropertySet,
  bool isExpressionBodied,
  bool isInitOnly,
  bool accessorsHaveImplementation,
@@ -91,7 +94,7 @@ protected SourcePropertySymbolBase(
  Location location,
  BindingDiagnosticBag diagnostics)
  {
- Debug.Assert(!isExpressionBodied || !isAutoProperty);
+ Debug.Assert(!isExpressionBodied || !(hasAutoPropertyGet || hasAutoPropertySet));
  Debug.Assert(!isExpressionBodied || !hasInitializer);
  Debug.Assert(!isExpressionBodied || accessorsHaveImplementation);
  Debug.Assert((modifiers & DeclarationModifiers.Required) == 0 || this is SourcePropertySymbol);
@@ -113,16 +116,33 @@ protected SourcePropertySymbolBase(
  }
 
  bool isIndexer = IsIndexer;
- isAutoProperty = isAutoProperty && !(containingType.IsInterface && !IsStatic) && !IsAbstract && !IsExtern && !isIndexer;
+ if (hasAutoPropertyGet || hasAutoPropertySet)
+ {
+ if ((containingType.IsInterface && !IsStatic) || IsAbstract || IsExtern || isIndexer)
+ {
+ hasAutoPropertyGet = false;
+ hasAutoPropertySet = false;
+ }
+ }
 
  if (hasExplicitAccessMod)
  {
  _propertyFlags |= Flags.HasExplicitAccessModifier;
  }
 
- if (isAutoProperty)
+ if (hasAutoPropertyGet)
+ {
+ _propertyFlags |= Flags.HasAutoPropertyGet;
+ }
+
+ if (hasAutoPropertySet)
+ {
+ _propertyFlags |= Flags.HasAutoPropertySet;
+ }
+
+ if (usesFieldKeyword)
  {
- _propertyFlags |= Flags.IsAutoProperty;
+ _propertyFlags |= Flags.UsesFieldKeyword;
  }
 
  if (hasInitializer)
@@ -158,7 +178,7 @@ protected SourcePropertySymbolBase(
  _name = _lazySourceName = memberName;
  }
 
- if (usesFieldKeyword || (isAutoProperty && hasGetAccessor) || hasInitializer)
+ if (usesFieldKeyword || hasAutoPropertyGet || hasAutoPropertySet || hasInitializer)
  {
  Debug.Assert(!IsIndexer);
  string fieldName = GeneratedNames.MakeBackingFieldName(_name);
@@ -175,12 +195,12 @@ protected SourcePropertySymbolBase(
 
  if (hasGetAccessor)
  {
- _getMethod = CreateGetAccessorSymbol(isAutoPropertyAccessor: isAutoProperty, diagnostics);
+ _getMethod = CreateGetAccessorSymbol(hasAutoPropertyGet, diagnostics);
  }
 
  if (hasSetAccessor)
  {
- _setMethod = CreateSetAccessorSymbol(isAutoPropertyAccessor: isAutoProperty, diagnostics);
+ _setMethod = CreateSetAccessorSymbol(hasAutoPropertySet, diagnostics);
  }
  }
 
@@ -640,14 +660,17 @@ public bool HasSkipLocalsInitAttribute
  }
  }
 
- internal bool IsAutoPropertyWithGetAccessor
- => IsAutoProperty && _getMethod is object;
+ internal bool IsAutoPropertyOrUsesFieldKeyword
+ => IsAutoProperty || UsesFieldKeyword;
+
+ protected bool UsesFieldKeyword
+ => (_propertyFlags & Flags.UsesFieldKeyword) != 0;
 
  protected bool HasExplicitAccessModifier
  => (_propertyFlags & Flags.HasExplicitAccessModifier) != 0;
 
- protected bool IsAutoProperty
- => (_propertyFlags & Flags.IsAutoProperty) != 0;
+ internal bool IsAutoProperty
+ => (_propertyFlags & (Flags.HasAutoPropertyGet | Flags.HasAutoPropertySet)) != 0;
 
  protected bool AccessorsHaveImplementation
  => (_propertyFlags & Flags.AccessorsHaveImplementation) != 0;
@@ -702,10 +725,8 @@ internal override void AfterAddingTypeMembersChecks(ConversionsBase conversions,
  diagnostics.Add(ErrorCode.ERR_RefReturningPropertiesCannotBeRequired, Location);
  }
 
- if (IsAutoPropertyWithGetAccessor)
+ if (IsAutoProperty)
  {
- Debug.Assert(GetMethod is object);
-
  if (!IsStatic && SetMethod is { IsInitOnly: false })
  {
  if (ContainingType.IsReadOnly)
@@ -1084,7 +1105,7 @@ private SynthesizedSealedPropertyAccessor MakeSynthesizedSealedAccessor()
  AttributeLocation IAttributeTargetSymbol.DefaultAttributeLocation => AttributeLocation.Property;
 
  AttributeLocation IAttributeTargetSymbol.AllowedAttributeLocations
- => IsAutoPropertyWithGetAccessor
+ => IsAutoPropertyOrUsesFieldKeyword
  ? AttributeLocation.Property | AttributeLocation.Field
  : AttributeLocation.Property;
 
@@ -1649,7 +1670,7 @@ protected virtual void ValidatePropertyType(BindingDiagnosticBag diagnostics)
  {
  diagnostics.Add(ErrorCode.ERR_FieldCantBeRefAny, TypeLocation, type);
  }
- else if (this.IsAutoPropertyWithGetAccessor && type.IsRefLikeOrAllowsRefLikeType() && (this.IsStatic || !this.ContainingType.IsRefLikeType))
+ else if (this.IsAutoPropertyOrUsesFieldKeyword && type.IsRefLikeOrAllowsRefLikeType() && (this.IsStatic || !this.ContainingType.IsRefLikeType))
  {
  diagnostics.Add(ErrorCode.ERR_FieldAutoPropCantBeByRefLike, TypeLocation, type);
  }

src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordEqualityContractProperty.cs

@@ -32,7 +32,8 @@ public SynthesizedRecordEqualityContractProperty(SourceMemberContainerTypeSymbol
  },
  hasInitializer: false,
  hasExplicitAccessMod: false,
- isAutoProperty: false,
+ hasAutoPropertyGet: false,
+ hasAutoPropertySet: false,
  isExpressionBodied: false,
  isInitOnly: false,
  accessorsHaveImplementation: true,

src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordPropertySymbol.cs

@@ -30,7 +30,8 @@ public SynthesizedRecordPropertySymbol(
  modifiers: DeclarationModifiers.Public | (isOverride ? DeclarationModifiers.Override : DeclarationModifiers.None),
  hasInitializer: true, // Synthesized record properties always have a synthesized initializer
  hasExplicitAccessMod: false,
- isAutoProperty: true,
+ hasAutoPropertyGet: true,
+ hasAutoPropertySet: true,
  isExpressionBodied: false,
  isInitOnly: ShouldUseInit(containingType),
  accessorsHaveImplementation: true,

src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedBackingFieldSymbol.cs

@@ -149,7 +149,7 @@ internal override void PostDecodeWellKnownAttributes(ImmutableArray<CSharpAttrib
  {
  base.PostDecodeWellKnownAttributes(boundAttributes, allAttributeSyntaxNodes, diagnostics, symbolPart, decodedData);
 
- if (!allAttributeSyntaxNodes.IsEmpty && _property.IsAutoPropertyWithGetAccessor)
+ if (!allAttributeSyntaxNodes.IsEmpty && _property.IsAutoPropertyOrUsesFieldKeyword)
  {
  CheckForFieldTargetedAttribute(diagnostics);
  }

src/Compilers/CSharp/Test/Emit/Emit/EmitMetadataTests.cs

@@ -1294,7 +1294,7 @@ private static void VerifyAutoProperty(PropertySymbol property, bool isFromSourc
  {
  if (property is SourcePropertySymbol sourceProperty)
  {
- Assert.True(sourceProperty.IsAutoPropertyWithGetAccessor);
+ Assert.True(sourceProperty.IsAutoProperty);
  }
  }
  else