C#: Teach cs/useless-upcast about disambiguating constructor calls

hvitved · hvitved · commit 6b99e1a1bf50 · 2019-05-29T15:16:08.000+02:00
diff --git a/csharp/ql/src/Language Abuse/UselessUpcast.ql b/csharp/ql/src/Language Abuse/UselessUpcast.ql
@@ -65,6 +65,13 @@ int getMaximumArguments(Callable c) {
   result = c.getNumberOfParameters()
 }
 
+private class ConstructorCall extends Call {
+  ConstructorCall() {
+    this instanceof ObjectCreation or
+    this instanceof ConstructorInitializer
+  }
+}
+
 /** An explicit upcast. */
 class ExplicitUpcast extends ExplicitCast {
   ValueOrRefType src;
@@ -140,6 +147,17 @@ class ExplicitUpcast extends ExplicitCast {
     )
   }
 
+  /** Holds if this upcast may be used to disambiguate the target of a constructor call. */
+  pragma[nomagic]
+  private predicate isDisambiguatingConstructorCall(Constructor other, int args) {
+    exists(ConstructorCall cc, Constructor target, ValueOrRefType t | this.isArgument(cc, target) |
+      t = target.getDeclaringType() and
+      t.hasMember(other) and
+      args = cc.getNumberOfArguments() and
+      other != target
+    )
+  }
+
   /** Holds if this upcast may be used to disambiguate the target of a call. */
   private predicate isDisambiguatingCall() {
     exists(Callable other, int args |
@@ -148,6 +166,8 @@ class ExplicitUpcast extends ExplicitCast {
       this.isDisambiguatingExtensionCall(other, args)
       or
       this.isDisambiguatingStaticCall(other, args)
+      or
+      this.isDisambiguatingConstructorCall(other, args)
     |
       args >= getMinimumArguments(other) and
       not args > getMaximumArguments(other)
diff --git a/csharp/ql/test/query-tests/Language Abuse/UselessUpcast/UselessUpcast.expected b/csharp/ql/test/query-tests/Language Abuse/UselessUpcast/UselessUpcast.expected
@@ -4,8 +4,6 @@
 | UselessUpcast.cs:85:12:85:15 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:20:7:20:7 | B | B | UselessUpcast.cs:13:7:13:7 | A | A |
 | UselessUpcast.cs:94:12:94:15 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:20:7:20:7 | B | B | UselessUpcast.cs:13:7:13:7 | A | A |
 | UselessUpcast.cs:105:16:105:19 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:27:7:27:7 | C | C | UselessUpcast.cs:20:7:20:7 | B | B |
-| UselessUpcast.cs:141:32:141:36 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:153:11:153:13 | Sub | Sub | UselessUpcast.cs:9:11:9:12 | I2 | I2 |
-| UselessUpcast.cs:146:26:146:30 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:136:7:136:18 | Constructors | Constructors | UselessUpcast.cs:9:11:9:12 | I2 | I2 |
 | UselessUpcast.cs:160:34:160:40 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:158:11:158:16 | SubSub | SubSub | UselessUpcast.cs:153:11:153:13 | Sub | Sub |
 | UselessUpcast.cs:164:21:164:27 | (...) ... | There is no need to upcast from $@ to $@ - the conversion can be done implicitly. | UselessUpcast.cs:158:11:158:16 | SubSub | SubSub | UselessUpcast.cs:153:11:153:13 | Sub | Sub |
 | 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 |
