Kotlin: cover invokedynamic when extraction

Add a JVM 21 regression test for when generation using invokedynamic. The
same expected source AST also passes with inline when generation.

The backend choice does not change the IR observed by the extractor. This
commit adds coverage only and requires no extractor change.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: andersfugmann

java/ql/test-kotlin2/library-tests/when-indy/PrintAst.expected

@@ -0,0 +1,38 @@
+test.kt:
+#    0| [CompilationUnit] test
+#    0|   1: [Class] TestKt
+#    3|     1: [Method] classify
+#    3|       3: [TypeAccess] int
+#-----|       4: (Parameters)
+#    3|         0: [Parameter] value
+#    3|           0: [TypeAccess] Object
+#    4|       5: [BlockStmt] { ... }
+#    8|         0: [ReturnStmt] return ...
+#    4|           0: [StmtExpr] <Stmt>
+#    4|             0: [BlockStmt] { ... }
+#    4|               0: [LocalVariableDeclStmt] var ...;
+#    4|                 1: [LocalVariableDeclExpr] tmp0_subject
+#    4|                   0: [VarAccess] value
+#    4|               1: [ExprStmt] <Expr>;
+#    4|                 0: [WhenExpr] when ...
+#    5|                   0: [WhenBranch] ... -> ...
+#    5|                     0: [InstanceOfExpr] ...instanceof...
+#    5|                       0: [VarAccess] tmp0_subject
+#    5|                       1: [TypeAccess] String
+#    5|                     1: [ExprStmt] <Expr>;
+#    5|                       0: [MethodCall] length(...)
+#    5|                         -1: [ImplicitCastExpr] <implicit cast>
+#    5|                           0: [TypeAccess] String
+#    5|                           1: [VarAccess] value
+#    6|                   1: [WhenBranch] ... -> ...
+#    6|                     0: [InstanceOfExpr] ...instanceof...
+#    6|                       0: [VarAccess] tmp0_subject
+#    6|                       1: [TypeAccess] int
+#    6|                     1: [ExprStmt] <Expr>;
+#    6|                       0: [ImplicitCastExpr] <implicit cast>
+#    6|                         0: [TypeAccess] int
+#    6|                         1: [VarAccess] value
+#    7|                   2: [WhenBranch] ... -> ...
+#    7|                     0: [BooleanLiteral] true
+#    7|                     1: [ExprStmt] <Expr>;
+#    7|                       0: [IntegerLiteral] -1

java/ql/test-kotlin2/library-tests/when-indy/PrintAst.qlref

@@ -0,0 +1 @@
+semmle/code/java/PrintAst.ql

java/ql/test-kotlin2/library-tests/when-indy/test.kt

@@ -0,0 +1,8 @@
+// codeql-extractor-kotlin-options: -language-version 2.4 -jvm-target 21 -Xwhen-expressions=indy
+
+fun classify(value: Any): Int =
+    when (value) {
+        is String -> value.length
+        is Int -> value
+        else -> -1
+    }