C# Exclude dynamic casts from useless casts check

Author: tamasvajk

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

@@ -204,17 +204,8 @@ class ExplicitUpcast extends ExplicitCast {
     this = any(LocalVariableDeclAndInitExpr decl | decl.isImplicitlyTyped()).getInitializer()
     or
     exists(LambdaExpr c | c.canReturn(this))
-  }
-}
-
-// 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>/")
-    )
+    or
+    dest instanceof DynamicType
   }
 }
 

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

@@ -6,5 +6,4 @@
 | 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 |