Kotlin: Improve java/abstract-to-concrete-cast to handle when branches

Author: tamasvajk

java/ql/src/Violations of Best Practice/Implementation Hiding/AbstractToConcreteCollection.ql

@@ -16,8 +16,11 @@ import java
 import semmle.code.java.Collections
 
 predicate guardedByInstanceOf(VarAccess e, RefType t) {
-  exists(IfStmt s, InstanceOfExpr instanceCheck, RefType checkType |
-    s.getCondition() = instanceCheck and
+  exists(Stmt s, InstanceOfExpr instanceCheck, RefType checkType |
+    (
+      s.(IfStmt).getCondition() = instanceCheck or
+      s.(WhenBranch).getCondition() = instanceCheck
+    ) and
     instanceCheck.getCheckedType() = checkType and
     // The same variable appears as the subject of the `instanceof`.
     instanceCheck.getExpr() = e.getVariable().getAnAccess() and
@@ -27,7 +30,11 @@ predicate guardedByInstanceOf(VarAccess e, RefType t) {
     (checkType = t or checkType = t.getSourceDeclaration().(GenericType).getRawType()) and
     // The expression appears in one of the branches.
     // (We do not verify here whether the guard is correctly implemented.)
-    exists(Stmt branch | branch = s.getThen() or branch = s.getElse() |
+    exists(Stmt branch |
+      branch = s.(IfStmt).getThen() or
+      branch = s.(IfStmt).getElse() or
+      branch = s.(WhenBranch).getRhs()
+    |
       branch = e.getEnclosingStmt().getEnclosingStmt+()
     )
   )

java/ql/test/kotlin/query-tests/AbstractToConcreteCollection/AbstractToConcreteCollection.expected

@@ -1 +0,0 @@
-| Test.kt:3:9:3:9 | <implicit cast> | $@ is cast to the concrete type $@, losing abstraction. | file:///modules/java.base/java/util/List.class:0:0:0:0 | List | List<Integer> | file:///modules/java.base/java/util/ArrayList.class:0:0:0:0 | ArrayList | ArrayList<Integer> |