Fix exception class lookup and add lazy delegate

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

@@ -458,11 +458,15 @@ class Compiler(
 
     private fun seedResolutionFromScope(scope: Scope, pos: Pos) {
         val sink = resolutionSink ?: return
-        for ((name, record) in scope.objects) {
+        var current: Scope? = scope
+        while (current != null) {
+            for ((name, record) in current.objects) {
                 if (!record.visibility.isPublic) continue
                 if (!resolutionPredeclared.add(name)) continue
                 sink.declareSymbol(name, SymbolKind.LOCAL, record.isMutable, pos)
             }
+            current = current.parent
+        }
     }
 
     private var anonCounter = 0
@@ -2635,6 +2639,13 @@ class Compiler(
             if (stmt.captureSlots.isEmpty()) return stmt
             return BlockStatement(stmt.block, stmt.slotPlan, emptyList(), stmt.pos)
         }
+        fun resolveExceptionClass(scope: Scope, name: String): ObjClass {
+            val rec = scope[name]
+            val cls = rec?.value as? ObjClass
+            if (cls != null) return cls
+            if (name == "Exception") return ObjException.Root
+            scope.raiseSymbolNotFound("error class does not exist or is not a class: $name")
+        }
 
         val body = unwrapBytecodeDeep(parseBlock())
         val catches = mutableListOf<CatchBlockData>()
@@ -2742,8 +2753,7 @@ class Compiler(
                     for (cdata in catches) {
                         var match: Obj? = null
                         for (exceptionClassName in cdata.classNames) {
-                            val exObj = scope[exceptionClassName]?.value as? ObjClass
-                                ?: scope.raiseSymbolNotFound("error class does not exist or is not a class: $exceptionClassName")
+                            val exObj = resolveExceptionClass(scope, exceptionClassName)
                             if (caughtObj.isInstanceOf(exObj)) {
                                 match = caughtObj
                                 break
@@ -3131,9 +3141,12 @@ class Compiler(
                     // accessors, constructor registration, etc.
                     // Resolve parent classes by name at execution time
                     val parentClasses = baseSpecs.map { baseSpec ->
-                        val rec =
-                            scope[baseSpec.name] ?: throw ScriptError(nameToken.pos, "unknown base class: ${baseSpec.name}")
-                        (rec.value as? ObjClass) ?: throw ScriptError(nameToken.pos, "${baseSpec.name} is not a class")
+                        val rec = scope[baseSpec.name]
+                        val cls = rec?.value as? ObjClass
+                        if (cls != null) return@map cls
+                        if (baseSpec.name == "Exception") return@map ObjException.Root
+                        if (rec == null) throw ScriptError(nameToken.pos, "unknown base class: ${baseSpec.name}")
+                        throw ScriptError(nameToken.pos, "${baseSpec.name} is not a class")
                     }
 
                     val newClass = ObjInstanceClass(className, *parentClasses.toTypedArray()).also {

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

@@ -126,6 +126,14 @@ open class Scope(
         }
         s.getSlotIndexOf(name)?.let { idx ->
             val rec = s.getSlotRecord(idx)
+            val hasDirectBinding =
+                s.objects.containsKey(name) ||
+                    s.localBindings.containsKey(name) ||
+                    (caller?.let { ctx ->
+                        s.objects.containsKey(ctx.mangledName(name)) ||
+                            s.localBindings.containsKey(ctx.mangledName(name))
+                    } ?: false)
+            if (!hasDirectBinding && rec.value === ObjUnset) return null
             if (rec.declaringClass == null || canAccessMember(rec.visibility, rec.declaringClass, caller, name)) return rec
         }
         return null

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

@@ -55,8 +55,34 @@ class Script(
                 scope.updateSlotFor(name, scope.objects[name]!!)
                 continue
             }
-            parent.get(name)?.let { scope.updateSlotFor(name, it) }
+            val seed = findSeedRecord(parent, name)
+            if (seed != null) {
+                if (name == "Exception" && seed.value !is ObjClass) {
+                    scope.updateSlotFor(name, ObjRecord(ObjException.Root, isMutable = false))
+                } else {
+                    scope.updateSlotFor(name, seed)
                 }
+                continue
+            }
+            if (name == "Exception") {
+                scope.updateSlotFor(name, ObjRecord(ObjException.Root, isMutable = false))
+            }
+        }
+    }
+
+    private fun findSeedRecord(scope: Scope?, name: String): ObjRecord? {
+        var s = scope
+        var hops = 0
+        while (s != null && hops++ < 1024) {
+            s.objects[name]?.let { return it }
+            s.localBindings[name]?.let { return it }
+            s.getSlotIndexOf(name)?.let { idx ->
+                val rec = s.getSlotRecord(idx)
+                if (rec.value !== ObjUnset) return rec
+            }
+            s = s.parent
+        }
+        return null
     }
 
     internal fun debugStatements(): List<Statement> = statements
@@ -363,6 +389,10 @@ class Script(
                 }
                 thunk
             }
+            addFn("lazy") {
+                val builder = requireOnlyArg<Statement>()
+                ObjLazyDelegate(builder, this)
+            }
 
             addVoidFn("delay") {
                 val a = args.firstAndOnly()

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/BytecodeStatement.kt

@@ -36,6 +36,7 @@ class BytecodeStatement private constructor(
     override val pos: Pos = original.pos
 
     override suspend fun execute(scope: Scope): Obj {
+        scope.pos = pos
         return CmdVm().execute(function, scope, scope.args.list)
     }
 

lynglib/src/commonMain/kotlin/net/sergeych/lyng/obj/ObjException.kt

@@ -344,7 +344,11 @@ fun Obj.isLyngException(): Boolean = isInstanceOf("Exception")
  */
 suspend fun Obj.getLyngExceptionMessage(scope: Scope? = null): String {
     require(this.isLyngException())
-    val s = scope ?: Script.newScope()
+    val s = scope ?: when (this) {
+        is ObjException -> this.scope
+        is ObjInstance -> this.instanceScope
+        else -> Script.newScope()
+    }
     return invokeInstanceMethod(s, "message").toString(s).value
 }
 
@@ -361,16 +365,25 @@ suspend fun Obj.getLyngExceptionMessage(scope: Scope? = null): String {
  */
 suspend fun Obj.getLyngExceptionMessageWithStackTrace(scope: Scope? = null,showDetails:Boolean=true): String {
     require(this.isLyngException())
-    val s = scope ?: Script.newScope()
+    val s = scope ?: when (this) {
+        is ObjException -> this.scope
+        is ObjInstance -> this.instanceScope
+        else -> Script.newScope()
+    }
     val msg = getLyngExceptionMessage(s)
     val trace = getLyngExceptionStackTrace(s)
     var at = "unknown"
-//    var firstLine = true
     val stack = if (!trace.list.isEmpty()) {
         val first = trace.list[0]
         at = (first.readField(s, "at").value as ObjString).value
         "\n" + trace.list.map { "    at " + it.toString(s).value }.joinToString("\n")
-    } else ""
+    } else {
+        val pos = s.pos
+        if (pos.source.fileName.isNotEmpty() && pos.currentLine.isNotEmpty()) {
+            at = "${pos.source.fileName}:${pos.line + 1}:${pos.column + 1}"
+        }
+        ""
+    }
     return "$at: $msg$stack"
 }
 
@@ -396,9 +409,16 @@ suspend fun Obj.getLyngExceptionString(scope: Scope): String =
  * Rethrow this object as a Kotlin [ExecutionError] if it's an exception.
  */
 suspend fun Obj.raiseAsExecutionError(scope: Scope? = null): Nothing {
-    if (this is ObjException) raise()
-    val sc = scope ?: Script.newScope()
-    val msg = getLyngExceptionMessage(sc)
-    val pos = (this as? ObjInstance)?.instanceScope?.pos ?: Pos.builtIn
+    val sc = scope ?: when (this) {
+        is ObjException -> this.scope
+        is ObjInstance -> this.instanceScope
+        else -> Script.newScope()
+    }
+    val msg = getLyngExceptionMessageWithStackTrace(sc)
+    val pos = when (this) {
+        is ObjException -> this.scope.pos
+        is ObjInstance -> this.instanceScope.pos
+        else -> Pos.builtIn
+    }
     throw ExecutionError(this, pos, msg)
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/obj/ObjLazyDelegate.kt

@@ -0,0 +1,57 @@
+/*
+ * 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.
+ */
+
+package net.sergeych.lyng.obj
+
+import net.sergeych.lyng.Arguments
+import net.sergeych.lyng.Scope
+import net.sergeych.lyng.Statement
+
+/**
+ * Lazy delegate used by `val x by lazy { ... }`.
+ */
+class ObjLazyDelegate(
+    private val builder: Statement,
+    private val capturedScope: Scope,
+) : Obj() {
+    override val objClass: ObjClass = type
+
+    private var calculated = false
+    private var cachedValue: Obj = ObjVoid
+
+    override suspend fun invokeInstanceMethod(
+        scope: Scope,
+        name: String,
+        args: Arguments,
+        onNotFoundResult: (suspend () -> Obj?)?,
+    ): Obj {
+        return when (name) {
+            "getValue" -> {
+                if (!calculated) {
+                    cachedValue = builder.execute(capturedScope)
+                    calculated = true
+                }
+                cachedValue
+            }
+            "setValue" -> scope.raiseIllegalAssignment("lazy delegate is read-only")
+            else -> super.invokeInstanceMethod(scope, name, args, onNotFoundResult)
+        }
+    }
+
+    companion object {
+        val type = ObjClass("LazyDelegate")
+    }
+}

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -3696,7 +3696,6 @@ class ScriptTest {
         )
     }
 
-    @Ignore("incremental enable: stackTrace member not resolved in bytecode path")
     @Test
     fun testExceptionSerialization() = runTest {
         eval(
@@ -3854,7 +3853,6 @@ class ScriptTest {
         )
     }
 
-    @Ignore("incremental enable: extension resolution for toList in chained call")
     @Test
     fun binarySearchTest2() = runTest {
         eval(
@@ -4829,7 +4827,6 @@ class ScriptTest {
         )
     }
 
-    @Ignore("incremental enable: raiseAsExecutionError missing source name in trace")
     @Test
     fun testRaiseAsError() = runTest {
         var x = evalNamed(
@@ -4891,7 +4888,6 @@ class ScriptTest {
     }
 
 
-    @Ignore("incremental enable: exception helper missing source info")
     @Test
     fun testLyngToKotlinExceptionHelpers() = runTest {
         var x = evalNamed(
@@ -4949,7 +4945,6 @@ class ScriptTest {
         )
     }
 
-    @Ignore("incremental enable: lazy delegate not resolved in new compiler")
     @Test
     fun testLazyLocals() = runTest() {
         eval(