Fix code review findings

Author: tamasvajk

csharp/change-notes/2020-12-18-extract-custom-modifiers.md

@@ -1,4 +1,4 @@
 lgtm,codescanning
 * CIL extraction has been improved to store `modreq` and `modopt` custom modifiers.
 The extracted information is surfaced through the `CustomModifierReceiver` class. Additionally,
-the information is also used to evaluate the new `Setter.isInitOnly` predicate.
+the information is also used to evaluate the new `Setter::isInitOnly` predicate.

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

@@ -33,17 +33,10 @@ public ModifiedType(Context cx, Type unmodified, Type modifier, bool isRequired)
 
         public override Type Construct(IEnumerable<Type> typeArguments) => throw new NotImplementedException();
 
-        public override string Name => Unmodified.Name + (IsRequired ? " modreq" : " modopt") + $"({Modifier.Name})";
+        public override string Name => $"{Unmodified.Name} {(IsRequired ? "modreq" : "modopt")}({Modifier.Name})";
 
-        public override void WriteAssemblyPrefix(TextWriter trapFile) => Unmodified.WriteAssemblyPrefix(trapFile);
+        public override void WriteAssemblyPrefix(TextWriter trapFile) => throw new NotImplementedException();
 
-        public override void WriteId(TextWriter trapFile, bool inContext)
-        {
-            Unmodified.WriteId(trapFile, inContext);
-            trapFile.Write(IsRequired ? " modreq" : " modopt");
-            trapFile.Write("(");
-            Modifier.WriteId(trapFile, inContext);
-            trapFile.Write(")");
-        }
+        public override void WriteId(TextWriter trapFile, bool inContext) => throw new NotImplementedException();
     }
 }

csharp/ql/src/semmle/code/cil/CustomModifierReceiver.qll

@@ -6,7 +6,7 @@ private import CIL
 private import dotnet
 
 /**
- * A class to represent entities that can recive custom modifiers. Custom modifiers can be attached to
+ * A class to represent entities that can receive custom modifiers. Custom modifiers can be attached to
  * - the type of a `Field`,
  * - the return type of a `Method` or `Property`,
  * - the type of parameters.
@@ -18,12 +18,4 @@ class CustomModifierReceiver extends Declaration, @cil_custom_modifier_receiver
 
   /** Holds if this targeted type has `modifier` applied as `modopt`. */
   predicate hasOptionalCustomModifier(Type modifier) { cil_custom_modifiers(this, modifier, 0) }
-
-  /**
-   * Holds if this targeted type has `modifier` applied as `kind`. `kind` 1 means `modreq`,
-   * `kind` 0 represents `modopt`.
-   */
-  predicate hasCustomModifier(Type modifier, int kind) {
-    cil_custom_modifiers(this, modifier, kind)
-  }
 }

csharp/ql/src/semmle/code/cil/Method.qll

@@ -251,7 +251,7 @@ class Setter extends Accessor {
   /** Holds if this setter is an `init` accessor. */
   predicate isInitOnly() {
     exists(Type t | t.getQualifiedName() = "System.Runtime.CompilerServices.IsExternalInit" |
-      cil_custom_modifiers(this, t, 1)
+      this.hasRequiredCustomModifier(t)
     )
   }
 }

csharp/ql/test/library-tests/cil/init-only-prop/customModifiers.ql

@@ -7,7 +7,7 @@ from string receiver, string modifier, int kind
 where
   exists(Type modType, CustomModifierReceiver cmr |
     receiver = cmr.toString() and
-    cmr.hasCustomModifier(modType, kind) and
+    cil_custom_modifiers(cmr, modType, kind) and
     modType.getQualifiedName() = modifier
   )
 select receiver, modifier, getKind(kind)