Adjust code review findings

Author: tamasvajk

csharp/extractor/Semmle.Extraction.CIL/Entities/Instruction.cs

@@ -419,14 +419,14 @@ public override IEnumerable<IExtractionProduct> Contents
                         break;
                     case Payload.Arg8:
                     case Payload.Arg16:
-                        if (!(Method.Parameters is null))
+                        if (Method.Parameters is object)
                         {
                             yield return Tuples.cil_access(this, Method.Parameters[(int)UnsignedPayloadValue]);
                         }
                         break;
                     case Payload.Local8:
                     case Payload.Local16:
-                        if (!(Method.LocalVariables is null))
+                        if (Method.LocalVariables is object)
                         {
                             yield return Tuples.cil_access(this, Method.LocalVariables[(int)UnsignedPayloadValue]);
                         }

csharp/extractor/Semmle.Extraction.CIL/Entities/Method.cs

@@ -45,7 +45,7 @@ protected Method(GenericContext gc) : base(gc.cx)
         public abstract string Name { get; }
 
         public virtual IList<LocalVariable>? LocalVariables => throw new NotImplementedException();
-        public IList<Parameter>? Parameters { get; private set; }
+        public IList<Parameter>? Parameters { get; protected set; }
 
         public override void WriteId(TextWriter trapFile) => WriteMethodId(trapFile, DeclaringType, NameLabel);
 
@@ -76,11 +76,6 @@ internal protected void WriteMethodId(TextWriter trapFile, Type parent, string m
 
         public override string IdSuffix => ";cil-method";
 
-        protected void PopulateParameters(IEnumerable<Type> parameterTypes)
-        {
-            Parameters = MakeParameters(parameterTypes).ToArray();
-        }
-
         protected IEnumerable<IExtractionProduct> PopulateFlags
         {
             get
@@ -92,7 +87,7 @@ protected IEnumerable<IExtractionProduct> PopulateFlags
 
         public abstract bool IsStatic { get; }
 
-        private IEnumerable<Parameter> MakeParameters(IEnumerable<Type> parameterTypes)
+        protected IEnumerable<Parameter> MakeParameters(IEnumerable<Type> parameterTypes)
         {
             int i = 0;
 
@@ -206,9 +201,9 @@ public override IEnumerable<IExtractionProduct> Contents
 
                 var typeSignature = md.DecodeSignature(cx.TypeSignatureDecoder, this);
 
-                PopulateParameters(typeSignature.ParameterTypes);
+                Parameters = MakeParameters(typeSignature.ParameterTypes).ToArray();
 
-                foreach (var c in Parameters!)
+                foreach (var c in Parameters)
                     yield return c;
 
                 foreach (var c in PopulateFlags)
@@ -466,8 +461,8 @@ public override IEnumerable<IExtractionProduct> Contents
 
                 var typeSignature = mr.DecodeMethodSignature(cx.TypeSignatureDecoder, this);
 
-                PopulateParameters(typeSignature.ParameterTypes);
-                foreach (var p in Parameters!) yield return p;
+                Parameters = MakeParameters(typeSignature.ParameterTypes).ToArray();
+                foreach (var p in Parameters) yield return p;
 
                 foreach (var f in PopulateFlags) yield return f;
 
@@ -550,8 +545,8 @@ public override IEnumerable<IExtractionProduct> Contents
                         throw new InternalError($"Unexpected constructed method handle kind {ms.Method.Kind}");
                 }
 
-                PopulateParameters(constructedTypeSignature.ParameterTypes);
-                foreach (var p in Parameters!)
+                Parameters = MakeParameters(constructedTypeSignature.ParameterTypes).ToArray();
+                foreach (var p in Parameters)
                     yield return p;
 
                 foreach (var f in PopulateFlags)