Preserve nullable struct null-check semantics in UA0003

tests/Opc.Ua.MigrationAnalyzer.Tests/Analyzers/UA0003Tests.cs

@@ -123,6 +123,42 @@ class C
             Assert.That(diags.Any(d => d.Id == "UA0003"), Is.False);
         }
 
+        [Test]
+        public async Task DoesNotReportOnNullableNodeIdEqualsNullAsync()
+        {
+            const string source = """
+                using Opc.Ua;
+                class C
+                {
+                    static bool M(NodeId? n) => n == null;
+                }
+                """;
+
+            ImmutableArray<Diagnostic> diags = await AnalyzerHarness
+                .GetAnalyzerDiagnosticsAsync(new UA0003NullCheckOnStructTypeAnalyzer(), source)
+                .ConfigureAwait(false);
+
+            Assert.That(diags.Any(d => d.Id == "UA0003"), Is.False);
+        }
+
+        [Test]
+        public async Task DoesNotReportOnNullableLocalizedTextNotEqualsNullAsync()
+        {
+            const string source = """
+                using Opc.Ua;
+                class C
+                {
+                    static bool M(LocalizedText? value) => null != value;
+                }
+                """;
+
+            ImmutableArray<Diagnostic> diags = await AnalyzerHarness
+                .GetAnalyzerDiagnosticsAsync(new UA0003NullCheckOnStructTypeAnalyzer(), source)
+                .ConfigureAwait(false);
+
+            Assert.That(diags.Any(d => d.Id == "UA0003"), Is.False);
+        }
+
         [Test]
         public async Task DoesNotReportOnEqualsMethodCallAsync()
         {

tools/Opc.Ua.MigrationAnalyzer/Analyzers/UA0003NullCheckOnStructTypeAnalyzer.cs

@@ -85,11 +85,10 @@ private static void AnalyzeBinary(OperationAnalysisContext context, UaSymbols sy
             {
                 return;
             }
-            if (valueType.OriginalDefinition?.SpecialType == SpecialType.System_Nullable_T &&
-                valueType is INamedTypeSymbol named &&
-                named.TypeArguments.Length == 1)
+            if (valueType is INamedTypeSymbol namedType &&
+                namedType.OriginalDefinition.SpecialType == SpecialType.System_Nullable_T)
             {
-                valueType = named.TypeArguments[0];
+                return;
             }
 
             if (!symbols.IsBuiltInStructType(valueType))