docs/fix-scope-parent-cycle.md

@@ -1,34 +0,0 @@
-## Fix: prevent cycles in scope parent chain during pooled frame reuse
-
-### What changed
-- Scope.resetForReuse now fully detaches a reused scope from its previous chain/state before re-parenting:
-  - sets `parent = null` and regenerates `frameId`
-  - clears locals/slots/bindings caches
-  - only after that, validates the new parent with `ensureNoCycle` and assigns it
-- ScopePool.borrow on all targets (JVM, Android, JS, Native, Wasm) now has a defensive fallback:
-  - if `resetForReuse` throws `IllegalStateException` indicating a parent-chain cycle, the pool allocates a fresh `Scope` instead of failing.
-
-### Why
-In some nested call patterns (notably instance method calls where an instance is produced by another function and immediately used), the same pooled `Scope` object can be rebound into a chain that already (transitively) contains it. Reassigning `parent` in that case forms a structural cycle, which `ensureNoCycle` correctly detects and throws. This could surface as:
-
-```
-IllegalStateException: cycle detected in scope parent chain assignment
-  at net.sergeych.lyng.Scope.ensureNoCycle(...)
-  at net.sergeych.lyng.Scope.resetForReuse(...)
-  at net.sergeych.lyng.ScopePool.borrow(...)
-  ... during instance method invocation
-```
-
-The fix removes the failure mode by:
-1) Detaching the reused frame from its prior chain/state before validating and assigning the new parent.
-2) Falling back to a new frame allocation if a cycle is still detected (extremely rare and cheap vs. a crash).
-
-### Expected effects
-- Eliminates sporadic `cycle detected in scope parent chain` crashes during instance method invocation.
-- No change to public API or normal semantics.
-- Pooling remains enabled by default; the fallback only triggers on the detected cycle edge case.
-- Negligible performance impact: fresh allocation is used only when a cycle would have crashed the VM previously.
-
-### Notes
-- The fix is platform-wide (all ScopePool actuals are covered).
-- We recommend adding/keeping a regression test that exercises: a class with a method, a function returning an instance, and an exported function calling the instance method. The test should pass without exceptions.

lynglib/src/androidMain/kotlin/net/sergeych/lyng/ScopePoolAndroid.kt

@@ -39,18 +39,12 @@ actual object ScopePool {
     actual fun borrow(parent: Scope, args: Arguments, pos: Pos, thisObj: Obj): Scope {
         val pool = pool()
         val s = if (pool.isNotEmpty()) pool.removeLast() else Scope(parent, args, pos, thisObj)
-        return try {
         if (s.parent !== parent || s.args !== args || s.pos !== pos || s.thisObj !== thisObj) {
             s.resetForReuse(parent, args, pos, thisObj)
         } else {
             s.frameId = nextFrameId()
         }
-            s
+        return s
-        } catch (e: IllegalStateException) {
-            if (e.message?.contains("cycle") == true && e.message?.contains("scope parent chain") == true) {
-                Scope(parent, args, pos, thisObj)
-            } else throw e
-        }
     }
 
     actual fun release(scope: Scope) {

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

@@ -302,9 +302,11 @@ open class Scope(
      * Clears locals and slots, assigns new frameId, and sets parent/args/pos/thisObj.
      */
     fun resetForReuse(parent: Scope?, args: Arguments, pos: Pos, thisObj: Obj) {
-        // Fully detach from any previous chain/state first to avoid residual ancestry
+        ensureNoCycle(parent)
-        // that could interact badly with the new parent and produce a cycle.
+        this.parent = parent
-        this.parent = null
+        this.args = args
+        this.pos = pos
+        this.thisObj = thisObj
         this.skipScopeCreation = false
         // fresh identity for PIC caches
         this.frameId = nextFrameId()
@@ -313,12 +315,6 @@ open class Scope(
         slots.clear()
         nameToSlot.clear()
         localBindings.clear()
-        // Now safe to validate and re-parent
-        ensureNoCycle(parent)
-        this.parent = parent
-        this.args = args
-        this.pos = pos
-        this.thisObj = thisObj
         // Pre-size local slots for upcoming parameter assignment where possible
         reserveLocalCapacity(args.list.size + 4)
     }

lynglib/src/commonTest/kotlin/ScopeCycleRegressionTest.kt

@@ -1,34 +0,0 @@
-/*
- * Regression test for scope parent-chain cycle when reusing pooled frames
- */
-
-import kotlinx.coroutines.test.runTest
-import net.sergeych.lyng.eval
-import kotlin.test.Test
-
-class ScopeCycleRegressionTest {
-    @Test
-    fun instanceMethodCallDoesNotCycle() = runTest {
-        eval(
-            (
-                """
-                class Whatever {
-                    fun something() {
-                        println
-                    }
-                }
-
-                fun ll() { Whatever() }
-
-                fun callTest1() {
-                    val l = ll()
-                    l.something()
-                    "ok"
-                }
-
-                assertEquals("ok", callTest1())
-                """
-                ).trimIndent()
-        )
-    }
-}

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -4159,86 +4159,4 @@ class ScriptTest {
         """)
     }
 
-    @Test
-    fun testUsingClassConstructorVars() = runTest {
-        val r = eval("""
-            import lyng.time
-            
-            class Request {
-                static val id = "rqid"
-            }
-            enum Action { 
-                Test
-            }
-            class LogEntry(vaultId, action, data=null, createdAt=Instant.now().truncateToSecond()) {
-
-                /*
-                Convert to a map object that can be easily decoded outsude the
-                contract execution scope.
-                */
-                fun toApi() {
-                    { createdAt:, requestId: Request.id, vaultId:, action: action.name, data: Map() }
-                }
-            }
-            fun test() {
-                LogEntry("v1", Action.Test).toApi()
-            }
-            
-            test()
-        """.trimIndent()).toJson()
-        println(r)
-    }
-
-    @Test
-    fun testScopeShortCircuit() = runTest() {
-        val baseScope = Script.newScope()
-
-        baseScope.eval("""
-                val exports = Map()
-                fun Export(name,f) {
-                    exports[name] = f
-                    f
-                }
-        """.trimIndent()
-        )
-
-        val exports: MutableMap<Obj, Obj> = (baseScope.eval("exports") as ObjMap).map
-
-        baseScope.eval("""
-            class A(val a) {
-                fun methodA() {
-                    a + 1
-                }
-            }
-            val a0 = 100
-            
-            fun someFunction(x) {
-                val ia = A(x)
-                ia.methodA()
-            }            
-            
-            @Export
-            fun exportedFunction(x) {
-                someFunction(x)
-            }
-        """.trimIndent())
-        // Calling from the script is ok:
-        val instanceScope = baseScope.createChildScope()
-        instanceScope.eval("""
-            val a1 = a0 + 1
-        """.trimIndent())
-        assertEquals( ObjInt(2), instanceScope.eval("""
-            exportedFunction(1)
-        """))
-        assertEquals( ObjInt(103), instanceScope.eval("""
-            exportedFunction(a1 + 1)
-        """))
-        val dummyThis = Obj()
-        // but we should be able to call it directly
-        val otherScope = baseScope.createChildScope()
-        val r = (exports["exportedFunction".toObj()] as Statement).invoke(otherScope, dummyThis,ObjInt(50))
-        println(r)
-        assertEquals(51, r.toInt())
-    }
-
 }

lynglib/src/jsMain/kotlin/net/sergeych/lyng/ScopePoolJs.kt

@@ -29,18 +29,12 @@ actual object ScopePool {
 
     actual fun borrow(parent: Scope, args: Arguments, pos: Pos, thisObj: Obj): Scope {
         val s = if (pool.isNotEmpty()) pool.removeLast() else Scope(parent, args, pos, thisObj)
-        return try {
         if (s.parent !== parent || s.args !== args || s.pos !== pos || s.thisObj !== thisObj) {
             s.resetForReuse(parent, args, pos, thisObj)
         } else {
             s.frameId = nextFrameId()
         }
-            s
+        return s
-        } catch (e: IllegalStateException) {
-            if (e.message?.contains("cycle") == true && e.message?.contains("scope parent chain") == true) {
-                Scope(parent, args, pos, thisObj)
-            } else throw e
-        }
     }
 
     actual fun release(scope: Scope) {

lynglib/src/jvmMain/kotlin/net/sergeych/lyng/ScopePoolJvm.kt

@@ -33,19 +33,9 @@ actual object ScopePool {
     actual fun borrow(parent: Scope, args: Arguments, pos: Pos, thisObj: Obj): Scope {
         val pool = threadLocalPool.get()
         val s = if (pool.isNotEmpty()) pool.removeLast() else Scope(parent, args, pos, thisObj)
-        return try {
         // Always reset state on borrow to guarantee fresh-frame semantics
         s.resetForReuse(parent, args, pos, thisObj)
-            s
+        return s
-        } catch (e: IllegalStateException) {
-            // Defensive fallback: if a cycle in scope parent chain is detected during reuse,
-            // discard pooled instance for this call frame and allocate a fresh scope instead.
-            if (e.message?.contains("cycle") == true && e.message?.contains("scope parent chain") == true) {
-                Scope(parent, args, pos, thisObj)
-            } else {
-                throw e
-            }
-        }
     }
 
     actual fun release(scope: Scope) {

lynglib/src/nativeMain/kotlin/net/sergeych/lyng/ScopePoolNative.kt

@@ -29,18 +29,12 @@ actual object ScopePool {
 
     actual fun borrow(parent: Scope, args: Arguments, pos: Pos, thisObj: Obj): Scope {
         val s = if (pool.isNotEmpty()) pool.removeLast() else Scope(parent, args, pos, thisObj)
-        return try {
         if (s.parent !== parent || s.args !== args || s.pos !== pos || s.thisObj !== thisObj) {
             s.resetForReuse(parent, args, pos, thisObj)
         } else {
             s.frameId = nextFrameId()
         }
-            s
+        return s
-        } catch (e: IllegalStateException) {
-            if (e.message?.contains("cycle") == true && e.message?.contains("scope parent chain") == true) {
-                Scope(parent, args, pos, thisObj)
-            } else throw e
-        }
     }
 
     actual fun release(scope: Scope) {

lynglib/src/wasmJsMain/kotlin/net/sergeych/lyng/ScopePoolWasm.kt

@@ -29,18 +29,12 @@ actual object ScopePool {
 
     actual fun borrow(parent: Scope, args: Arguments, pos: Pos, thisObj: Obj): Scope {
         val s = if (pool.isNotEmpty()) pool.removeLast() else Scope(parent, args, pos, thisObj)
-        return try {
         if (s.parent !== parent || s.args !== args || s.pos !== pos || s.thisObj !== thisObj) {
             s.resetForReuse(parent, args, pos, thisObj)
         } else {
             s.frameId = nextFrameId()
         }
-            s
+        return s
-        } catch (e: IllegalStateException) {
-            if (e.message?.contains("cycle") == true && e.message?.contains("scope parent chain") == true) {
-                Scope(parent, args, pos, thisObj)
-            } else throw e
-        }
     }
 
     actual fun release(scope: Scope) {