Merge pull request github#10961 from tamasvajk/kotlin-abstract-collection-cast

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

@@ -0,0 +1 @@
+Violations of Best Practice/Implementation Hiding/AbstractToConcreteCollection.ql

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

@@ -0,0 +1,5 @@
+fun fn(m: MutableList<Int>) {
+    if (m is ArrayList) {
+        m.ensureCapacity(5)
+    }
+}