C#: Add dynamic casts to useless upcast test

Author: tamasvajk

csharp/ql/src/Language Abuse/UselessUpcast.ql

@@ -207,6 +207,17 @@ class ExplicitUpcast extends ExplicitCast {
   }
 }
 
+// Stop external filepaths from appearing in the results
+class ValueOrRefTypeLocation extends ValueOrRefType {
+  override predicate hasLocationInfo(string path, int sl, int sc, int el, int ec) {
+    exists(string fullPath | super.hasLocationInfo(fullPath, sl, sc, el, ec) |
+      if exists(this.getFile().getRelativePath())
+      then path = fullPath
+      else path = fullPath.regexpReplaceAll(".*/", "<external>/")
+    )
+  }
+}
+
 from ExplicitUpcast u, ValueOrRefType src, ValueOrRefType dest
 where
   src = u.getSourceType() and

csharp/ql/test/query-tests/Language Abuse/UselessUpcast/UselessUpcast.cs

@@ -17,8 +17,8 @@ public void M(A a) { }
 
 class B : A
 {
-    public static bool operator==(B b1, B b2) { return false; }
-    public static bool operator!=(B b1, B b2) { return true; }
+    public static bool operator ==(B b1, B b2) { return false; }
+    public static bool operator !=(B b1, B b2) { return true; }
     public void M(B b) { }
 }
 
@@ -68,11 +68,11 @@ void Test1(string[] args)
 
         ((I2)a).Foo(); // GOOD: Cast to an interface
 
-        o = a==(A)b; // GOOD: EQExpr
+        o = a == (A)b; // GOOD: EQExpr
 
-        o = b==(B)b; // GOOD: Operator call
+        o = b == (B)b; // GOOD: Operator call
 
-        var act = (Action) (() => { }); // GOOD
+        var act = (Action)(() => { }); // GOOD
 
         var objects = args.Select(arg => (object)arg); // GOOD
 
@@ -126,9 +126,9 @@ public static void M2(this I3 i) =>
 
 static class StaticMethods
 {
-   public static void M1(A _) { }
-   public static void M1(B _) { }
-   public static void M2(B _) { }
+    public static void M1(A _) { }
+    public static void M1(B _) { }
+    public static void M2(B _) { }
 }
 
 class Constructors : I2
@@ -162,4 +162,12 @@ void M(SubSub ss)
             new Sub((Sub)ss); // BAD
         }
     }
+
+    class Dynamic
+    {
+        void M(object o)
+        {
+            var s0 = ((dynamic)o).ToString(); // GOOD
+        }
+    }
 }

csharp/ql/test/query-tests/Language Abuse/UselessUpcast/UselessUpcast.expected

@@ -6,4 +6,5 @@
 | UselessUpcast.cs:103:16:103:19 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:25:7:25:7 | C | C | UselessUpcast.cs:18:7:18:7 | B | B |
 | UselessUpcast.cs:158:34:158:40 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:156:11:156:16 | SubSub | SubSub | UselessUpcast.cs:151:11:151:13 | Sub | Sub |
 | UselessUpcast.cs:162:21:162:27 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:156:11:156:16 | SubSub | SubSub | UselessUpcast.cs:151:11:151:13 | Sub | Sub |
+| UselessUpcast.cs:170:23:170:32 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | file://<external>/System.Private.CoreLib.dll:0:0:0:0 | Object | Object | file://<external>/System.Private.CoreLib.dll:0:0:0:0 | dynamic | dynamic |
 | UselessUpcastBad.cs:9:23:9:32 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcastBad.cs:4:11:4:13 | Sub | Sub | UselessUpcastBad.cs:3:11:3:15 | Super | Super |