Add mixed-slot closure stress test

lynglib/src/commonTest/kotlin/NumericSlotMixTest.kt

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+import kotlinx.coroutines.test.runTest
+import net.sergeych.lyng.eval
+import kotlin.test.Test
+
+class NumericSlotMixTest {
+
+    @Test
+    fun testMixedSlotsInClosuresAndLoops() = runTest {
+        eval(
+            """
+            fun makeMulAdd(k) {
+                return { x ->
+                    val tmp = x * k
+                    tmp + 0.5
+                }
+            }
+
+            fun testMix() {
+                var sum = 0.0
+                var isum = 0
+                val f = makeMulAdd(2.0)
+                for (i in 1..20) {
+                    val base = i
+                    val g = { y -> y + base }
+                    var inner = 0.0
+                    for (j in 1..5) {
+                        val v = f(j) + g(j)
+                        if (j % 2 == 0)
+                            inner += v
+                        else
+                            inner += v / 2.0
+                        when (j) {
+                            1 -> isum += j
+                            2 -> isum += j * 2
+                            3 -> isum += j + base
+                            else -> isum += j
+                        }
+                    }
+                    if (i % 3 == 0)
+                        sum += inner + 0.25
+                    else
+                        sum += inner + 1.0
+                }
+                assert(sum is Real)
+                assert(isum is Int)
+                sum + isum
+            }
+
+            val result = testMix()
+            assert(result is Real)
+            assert(abs(result - 1965.5) < 1.0e-9)
+            """.trimIndent()
+        )
+    }
+}