Small fixes to source generator (#3466)

CHANGELOG.md

@@ -12,7 +12,7 @@
 * Made WebSocket error logging more verbose when using `AppConfiguration.UseManagedWebSockets = true`. [#3459](https://github.com/realm/realm-dotnet/pull/3459)
 
 ### Fixed
-* None
+* Added an error that is raised when interface based Realm classes are used with a language version lower than 8.0. At the same time, removed the use of `not` in the generated code, so that it's compatible with a minumum C# version of 8.0. (Issue [#3265](https://github.com/realm/realm-dotnet/issues/3265))
 
 ### Compatibility
 * Realm Studio: 13.0.0 or later.

Realm/Realm.SourceGenerator/ClassCodeBuilder.cs

@@ -476,7 +476,7 @@ public override bool Equals(object? obj)
         return !IsValid;
     }
 
-    if (obj is not Realms.IRealmObjectBase iro)
+    if (!(obj is Realms.IRealmObjectBase iro))
     {
         return false;
     }

Realm/Realm.SourceGenerator/Diagnostics.cs

@@ -53,6 +53,7 @@ private enum Id
             IndexedPrimaryKey = 28,
             InvalidCollectionInitializer = 29,
             InvalidCollectionInitializerInCtor = 30,
+            OldCSharpVersion = 100,
             InvalidGeneratorConfiguration = 1000,
         }
 
@@ -67,6 +68,15 @@ public static Diagnostic InvalidConfiguration(string field, string description)
                 Location.None);
         }
 
+        public static Diagnostic OldCSharpVersion()
+        {
+            return CreateDiagnosticError(
+                Id.OldCSharpVersion,
+                "Unsupported version of C#",
+                $"It is not possible to use the Realm source generator with C# versions older than 8.0.",
+                Location.None);
+        }
+
         public static Diagnostic UnexpectedError(string className, string message, string stackTrace)
         {
             return CreateDiagnosticError(
@@ -82,7 +92,7 @@ public static Diagnostic ClassUnclearDefinition(string className, Location locat
             return CreateDiagnosticError(
                 Id.ClassUnclearDefinition,
                 "Realm classes cannot implement multiple class interfaces",
-                $"Class {className} is declared as implementing multiple class interfaces.A class can implement only one interface between IRealmObject, IEmbeddedObject, IAsymmetricObject.",
+                $"Class {className} is declared as implementing multiple class interfaces. A class can implement only one interface between IRealmObject, IEmbeddedObject, IAsymmetricObject.",
                 location);
         }
 

Realm/Realm.SourceGenerator/DiagnosticsEmitter.cs

@@ -59,6 +59,8 @@ public void Emit(ParsingResults parsingResults)
                     throw;
                 }
             }
+
+            parsingResults.GeneralDiagnostics.ForEach(_context.ReportDiagnostic);
         }
 
         private static void SerializeDiagnostics(GeneratorExecutionContext context, ClassInfo classInfo)

Realm/Realm.SourceGenerator/Parser.cs

@@ -46,6 +46,14 @@ public ParsingResults Parse(IEnumerable<RealmClassDefinition> realmClasses)
             var classNames = new HashSet<string>();
             var duplicateClassNames = new HashSet<string>();
 
+            if (realmClasses.Any() &&
+                _context.Compilation is CSharpCompilation comp &&
+                comp.LanguageVersion < LanguageVersion.CSharp8)
+            {
+                result.GeneralDiagnostics.Add(Diagnostics.OldCSharpVersion());
+                return result;
+            }
+
             foreach (var rc in realmClasses)
             {
                 var classSymbol = rc.ClassSymbol;
@@ -556,5 +564,7 @@ private static string RemoveUsingKeyword(UsingDirectiveSyntax syntax)
     internal record ParsingResults
     {
         public List<ClassInfo> ClassInfo { get; } = new();
+
+        public List<Diagnostic> GeneralDiagnostics { get; } = new();
     }
 }