Field-backed properties: interface properties (#75219)

dotnet · Sep 25, 2024 · f1b2823 · f1b2823
1 parent 2bb756e
commit f1b2823
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Showing 4 changed files with 831 additions and 117 deletions.
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbol.cs
@@ -63,7 +63,7 @@ private static SourcePropertySymbol Create(
                 out _);
 
             bool allowAutoPropertyAccessors = (modifiers & (DeclarationModifiers.Abstract | DeclarationModifiers.Extern | DeclarationModifiers.Indexer)) == 0 &&
-                (!containingType.IsInterface || (modifiers & DeclarationModifiers.Static) != 0) &&
+                (!containingType.IsInterface || hasGetAccessorImplementation || hasSetAccessorImplementation || (modifiers & DeclarationModifiers.Static) != 0) &&
                 ((modifiers & DeclarationModifiers.Partial) == 0 || hasGetAccessorImplementation || hasSetAccessorImplementation);
             bool hasAutoPropertyGet = allowAutoPropertyAccessors && getSyntax != null && !hasGetAccessorImplementation;
             bool hasAutoPropertySet = allowAutoPropertyAccessors && setSyntax != null && !hasSetAccessorImplementation;

diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbolBase.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbolBase.cs
@@ -853,6 +853,16 @@ internal override void AfterAddingTypeMembersChecks(ConversionsBase conversions,
                 }
             }
 
+            if (!IsStatic &&
+                ContainingType.IsInterface &&
+                IsSetOnEitherPart(Flags.RequiresBackingField) &&
+                // Should probably ignore initializer (and report ERR_InterfacesCantContainFields) if the
+                // property uses 'field' or has an auto-implemented accessor.
+                !IsSetOnEitherPart(Flags.HasInitializer))
+            {
+                diagnostics.Add(ErrorCode.ERR_InterfacesCantContainFields, Location);
+            }
+
             if (!IsExpressionBodied)
             {
                 bool hasGetAccessor = GetMethod is object;