Fix ctor param reassignment regression

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt

@@ -3266,7 +3266,13 @@ class Compiler(
                                     this.currentClassCtx = cls
                                     try {
                                         (thisObj as? ObjInstance)?.let { i ->
-                                            annotatedFnBody.execute(ClosureScope(this, i.instanceScope))
+                                            val execScope = i.instanceScope.createChildScope(
+                                                pos = this.pos,
+                                                args = this.args,
+                                                newThisObj = i
+                                            )
+                                            execScope.currentClassCtx = cls
+                                            annotatedFnBody.execute(execScope)
                                         } ?: annotatedFnBody.execute(thisObj.autoInstanceScope(this))
                                     } finally {
                                         this.currentClassCtx = savedCtx

lynglib/src/commonTest/kotlin/OOTest.kt

@@ -911,4 +911,19 @@ class OOTest {
             assertEquals("{\"a\":\"foo\",\"b\":\"bar\"}",T("foo", "bar").toJsonString())
         """.trimIndent())
     }
+
+    @Test
+    fun testAssignToUnqualifiedParams() = runTest {
+        eval("""
+            class T(x) {
+                fun setx(v) { x = v }
+                fun incr(v) { x += v }
+            }
+            val t = T(1)
+            t.setx(2)
+            assertEquals(2, t.x)
+            t.incr(3)
+            assertEquals(5, t.x)
+        """.trimIndent())
+    }
 }

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -5035,5 +5035,13 @@ class ScriptTest {
             assertEquals(10.0, 15.5.clamp(0.0..10.0))
         """.trimIndent())
     }
+
+    @Test
+    fun testEmptySpreadList() = runTest {
+        eval("""
+            fun t(a, tags=[]) { [a, ...tags] }
+            assertEquals( [1], t(1) )
+        """.trimIndent())
+    }
 }
 

lynglib/src/commonTest/kotlin/ValReassignRegressionTest.kt

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2026 Sergey S. Chernov
+ *
+ * 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 ValReassignRegressionTest {
+
+    @Test
+    fun reassign_ctor_param_field_should_work() = runTest {
+        eval(
+            """
+            class Wallet(balance = 0) {
+                fun add(amount) {
+                    balance += amount
+                }
+                fun transfer(amount) {
+                    val balance = 0
+                    add(amount)
+                }
+                fun get() { balance }
+            }
+            val w = Wallet()
+            w.transfer(1)
+            assertEquals(1, w.get())
+            """.trimIndent()
+        )
+    }
+
+    @Test
+    fun reassign_field_should_not_see_caller_locals() = runTest {
+        eval(
+            """
+            class Wallet(balance = 0) {
+                fun add(amount) { balance += amount }
+                fun get() { balance }
+            }
+            fun doTransfer(w, amount) {
+                val balance = 0
+                w.add(amount)
+            }
+            val w = Wallet()
+            doTransfer(w, 2)
+            assertEquals(2, w.get())
+            """.trimIndent()
+        )
+    }
+
+    @Test
+    fun reassign_field_should_not_see_caller_param() = runTest {
+        eval(
+            """
+            class Wallet(balance = 0) {
+                fun add(amount) { balance += amount }
+                fun get() { balance }
+            }
+            fun doTransfer(balance, w, amount) {
+                w.add(amount)
+            }
+            val w = Wallet()
+            doTransfer(0, w, 3)
+            assertEquals(3, w.get())
+            """.trimIndent()
+        )
+    }
+
+    @Test
+    fun reassign_field_should_not_see_block_local() = runTest {
+        eval(
+            """
+            class Wallet(balance = 0) {
+                fun add(amount) { balance += amount }
+                fun get() { balance }
+            }
+            val w = Wallet()
+            run {
+                val balance = 0
+                w.add(4)
+            }
+            assertEquals(4, w.get())
+            """.trimIndent()
+        )
+    }
+}