Fix CodeQL issues

src/PublicApiGenerator/CecilEx.cs

@@ -167,17 +167,14 @@ private static IEnumerable<TypeDefinition> GetBaseTypes(TypeDefinition type)
 
     private static CodeTypeReference ModifyCodeTypeReference(CodeTypeReference typeReference, string modifier)
     {
-        using (var provider = new CSharpCodeProvider())
-        {
-            if (typeReference.TypeArguments.Count == 0)
-                // For types without generic arguments we resolve the output type directly to turn System.String into string
-                return new CodeTypeReference(modifier + " " + provider.GetTypeOutput(typeReference));
-            else
-                // For types with generic types the BaseType is GenericType`<Arity>. Then we cannot resolve the output type and need to pass on the BaseType
-                // to avoid falling into hardcoded assumptions in CodeTypeReference that cuts of the type after the 4th comma. i.ex. readonly Func<string, string, string, string>
-                // works but readonly Func<string, string, string, string, string> would turn into readonly Func<string
-                return new CodeTypeReference(modifier + " " + typeReference.BaseType, typeReference.TypeArguments.Cast<CodeTypeReference>().ToArray());
-        }
+        using var provider = new CSharpCodeProvider();
+        return typeReference.TypeArguments.Count == 0
+            // For types without generic arguments we resolve the output type directly to turn System.String into string
+            ? new CodeTypeReference(modifier + " " + provider.GetTypeOutput(typeReference))
+            // For types with generic types the BaseType is GenericType`<Arity>. Then we cannot resolve the output type and need to pass on the BaseType
+            // to avoid falling into hardcoded assumptions in CodeTypeReference that cuts of the type after the 4th comma. i.ex. readonly Func<string, string, string, string>
+            // works but readonly Func<string, string, string, string, string> would turn into readonly Func<string
+            : new CodeTypeReference(modifier + " " + typeReference.BaseType, typeReference.TypeArguments.Cast<CodeTypeReference>().ToArray());
     }
 
     internal static bool? IsNew<TDefinition>(this TDefinition methodDefinition, Func<TypeDefinition, Collection<TDefinition>?> selector, Func<TDefinition, bool> predicate)

src/PublicApiGenerator/CodeTypeReferenceBuilder.cs

@@ -18,7 +18,9 @@ private static CodeTypeReference CreateCodeTypeReferenceWithNullabilityMap(TypeR
         if (type.IsValueType && type.Name == "Nullable`1" && type.Namespace == "System")
         {
             // unwrap System.Nullable<Type> into Type? for readability
-            var genericArgs = type is IGenericInstance instance ? instance.GenericArguments : type.HasGenericParameters ? type.GenericParameters.Cast<TypeReference>() : null;
+            var genericArgs = type is IGenericInstance instance
+                ? instance.GenericArguments
+                : type.HasGenericParameters ? type.GenericParameters.Cast<TypeReference>() : throw new NotSupportedException(type.ToString());
             return CreateCodeTypeReferenceWithNullabilityMap(genericArgs.Single(), nullabilityMap, NullableMode.Force, disableNested);
         }
         else

src/PublicApiGenerator/NullableContext.cs

@@ -12,8 +12,7 @@ private static Stack<ICustomAttributeProvider> NullableContextProviders
     {
         get
         {
-            if (_nullableContextProviders == null)
-                _nullableContextProviders = new Stack<ICustomAttributeProvider>();
+            _nullableContextProviders ??= new Stack<ICustomAttributeProvider>();
             return _nullableContextProviders;
         }
     }

src/PublicApiGeneratorTests/Property_methods.cs

@@ -139,12 +139,12 @@ namespace Examples
     {
         public class PropertyReadWrite
         {
-            public string Value { get { return string.Empty; } set { } }
+            public string Value { get => string.Empty; set { } }
         }
 
         public class PropertyReadOnly
         {
-            public string Value { get { return string.Empty; } }
+            public string Value => string.Empty;
         }
 
         public class PropertyWriteOnly
@@ -166,17 +166,14 @@ public class PropertyIndexer
         {
             public string this[int index]
             {
-                get { return string.Empty; }
+                get => string.Empty;
                 set { }
             }
         }
 
         public class PropertyIndexerReadOnly
         {
-            public string this[int index]
-            {
-                get { return string.Empty; }
-            }
+            public string this[int index] => string.Empty;
         }
 
         public class PropertyIndexerWriteOnly
@@ -191,7 +188,7 @@ public class PropertyIndexerMultipleParameters
         {
             public string this[int index, int order]
             {
-                get { return string.Empty; }
+                get => string.Empty;
                 set { }
             }
         }