Step 24A: bytecode capture tables for lambdas

bytecode_migration_plan.md

@@ -85,12 +85,37 @@ Goal: migrate the compiler so all values live in frames/bytecode, keeping JVM te
   - [x] Force delegated locals into local slots (even module) and avoid scope-slot resolution.
   - [x] Drop opcode/runtime support for `ASSIGN_SCOPE_SLOT`.
 
+## Frame-Only Execution (new, before interpreter removal)
+
+- [x] Step 24A: Bytecode capture tables for lambdas (compiler only).
+  - [x] Emit per-lambda capture tables containing (ownerFrameKind, ownerSlotId).
+  - [x] Create captures only when detected; do not allocate scope slots.
+  - [x] Add disassembler output for capture tables.
+  - [x] JVM tests must be green before commit.
+- [ ] Step 24B: Frame-slot captures in bytecode runtime.
+  - [ ] Build lambdas from bytecode + capture table (no capture names).
+  - [ ] Read captured values via `FrameSlotRef` only.
+  - [ ] Forbid `resolveCaptureRecord` in bytecode paths; keep only in interpreter.
+  - [ ] JVM tests must be green before commit.
+- [ ] Step 24C: Remove scope local mirroring in bytecode execution.
+  - [ ] Remove/disable any bytecode runtime code that writes locals into Scope for execution.
+  - [ ] Keep Scope creation only for reflection/Kotlin interop paths.
+  - [ ] JVM tests must be green before commit.
+- [ ] Step 24D: Eliminate `ClosureScope` usage on bytecode execution paths.
+  - [ ] Avoid `ClosureScope` in bytecode-related call paths (Block/Lambda/ObjDynamic/ObjProperty).
+  - [ ] Keep interpreter path using `ClosureScope` until interpreter removal.
+  - [ ] JVM tests must be green before commit.
+- [ ] Step 24E: Isolate interpreter-only capture logic.
+  - [ ] Mark `resolveCaptureRecord` paths as interpreter-only.
+  - [ ] Guard or delete any bytecode path that tries to sync captures into scopes.
+  - [ ] JVM tests must be green before commit.
+
 ## Interpreter Removal (next)
 
-- [x] Step 25: Replace Statement-based declaration calls in bytecode.
-  - [x] Add bytecode const/op for class/enum/function declarations (no `Statement` objects in constants).
-  - [x] Replace `emitStatementCall` usage for `ClassDeclStatement`, `FunctionDeclStatement`, `EnumDeclStatement`.
-  - [x] Add JVM disasm coverage to ensure module init has no `CALL_SLOT` to `Callable@...` for declarations.
+- [ ] Step 25: Replace Statement-based declaration calls in bytecode.
+  - [ ] Add bytecode const/op for class/enum/function declarations (no `Statement` objects in constants).
+  - [ ] Replace `emitStatementCall` usage for `ClassDeclStatement`, `FunctionDeclStatement`, `EnumDeclStatement`.
+  - [ ] Add JVM disasm coverage to ensure module init has no `CALL_SLOT` to `Callable@...` for declarations.
 - [ ] Step 26: Bytecode-backed lambdas (remove `ValueFnRef` runtime execution).
   - [ ] Compile lambda bodies to bytecode and emit an opcode to create a callable from bytecode + capture plan.
   - [ ] Remove `containsValueFnRef`/`forceScopeSlots` workaround once lambdas are bytecode.

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

@@ -168,6 +168,8 @@ class Compiler(
     private val callableReturnTypeByScopeId: MutableMap<Int, MutableMap<Int, ObjClass>> = mutableMapOf()
     private val callableReturnTypeByName: MutableMap<String, ObjClass> = mutableMapOf()
     private val lambdaReturnTypeByRef: MutableMap<ObjRef, ObjClass> = mutableMapOf()
+    private val lambdaCaptureEntriesByRef: MutableMap<ValueFnRef, List<net.sergeych.lyng.bytecode.LambdaCaptureEntry>> =
+        mutableMapOf()
     private val classFieldTypesByName: MutableMap<String, MutableMap<String, ObjClass>> = mutableMapOf()
     private val classScopeMembersByClassName: MutableMap<String, MutableSet<String>> = mutableMapOf()
     private val classScopeCallableMembersByClassName: MutableMap<String, MutableSet<String>> = mutableMapOf()
@@ -1561,7 +1563,8 @@ class Compiler(
                         classFieldTypesByName = classFieldTypesByName,
                         enumEntriesByName = enumEntriesByName,
                         callableReturnTypeByScopeId = callableReturnTypeByScopeId,
-                        callableReturnTypeByName = callableReturnTypeByName
+                        callableReturnTypeByName = callableReturnTypeByName,
+                        lambdaCaptureEntriesByRef = lambdaCaptureEntriesByRef
                     ) as BytecodeStatement
                     unwrapped to bytecodeStmt.bytecodeFunction()
                 } else {
@@ -1857,7 +1860,8 @@ class Compiler(
             classFieldTypesByName = classFieldTypesByName,
             enumEntriesByName = enumEntriesByName,
             callableReturnTypeByScopeId = callableReturnTypeByScopeId,
-            callableReturnTypeByName = callableReturnTypeByName
+            callableReturnTypeByName = callableReturnTypeByName,
+            lambdaCaptureEntriesByRef = lambdaCaptureEntriesByRef
         )
     }
 
@@ -1892,7 +1896,8 @@ class Compiler(
             classFieldTypesByName = classFieldTypesByName,
             enumEntriesByName = enumEntriesByName,
             callableReturnTypeByScopeId = callableReturnTypeByScopeId,
-            callableReturnTypeByName = callableReturnTypeByName
+            callableReturnTypeByName = callableReturnTypeByName,
+            lambdaCaptureEntriesByRef = lambdaCaptureEntriesByRef
         )
     }
 
@@ -2929,6 +2934,22 @@ class Compiler(
         if (returnClass != null) {
             lambdaReturnTypeByRef[ref] = returnClass
         }
+        val moduleScopeId = moduleSlotPlan()?.id
+        val captureEntries = captureSlots.map { capture ->
+            val owner = capturePlan.captureOwners[capture.name]
+                ?: error("Missing capture owner for ${capture.name}")
+            val kind = if (moduleScopeId != null && owner.scopeId == moduleScopeId) {
+                net.sergeych.lyng.bytecode.CaptureOwnerFrameKind.MODULE
+            } else {
+                net.sergeych.lyng.bytecode.CaptureOwnerFrameKind.LOCAL
+            }
+            net.sergeych.lyng.bytecode.LambdaCaptureEntry(
+                ownerKind = kind,
+                ownerScopeId = owner.scopeId,
+                ownerSlotId = owner.slot
+            )
+        }
+        lambdaCaptureEntriesByRef[ref] = captureEntries
         return ref
     }
 

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

@@ -33,6 +33,7 @@ class BytecodeCompiler(
     private val enumEntriesByName: Map<String, List<String>> = emptyMap(),
     private val callableReturnTypeByScopeId: Map<Int, Map<Int, ObjClass>> = emptyMap(),
     private val callableReturnTypeByName: Map<String, ObjClass> = emptyMap(),
+    private val lambdaCaptureEntriesByRef: Map<ValueFnRef, List<LambdaCaptureEntry>> = emptyMap(),
 ) {
     private var builder = CmdBuilder()
     private var nextSlot = 0
@@ -607,6 +608,9 @@ class BytecodeCompiler(
     }
 
     private fun compileValueFnRef(ref: ValueFnRef): CompiledValue? {
+        lambdaCaptureEntriesByRef[ref]?.let { captures ->
+            builder.addConst(BytecodeConst.CaptureTable(captures))
+        }
         val id = builder.addConst(BytecodeConst.ValueFn(ref.valueFn()))
         val slot = allocSlot()
         builder.emit(Opcode.MAKE_VALUE_FN, id, slot)

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

@@ -36,6 +36,7 @@ sealed class BytecodeConst {
     data class ValueFn(val fn: suspend (net.sergeych.lyng.Scope) -> net.sergeych.lyng.obj.ObjRecord) : BytecodeConst()
     data class DeclExec(val executable: net.sergeych.lyng.DeclExecutable) : BytecodeConst()
     data class SlotPlan(val plan: Map<String, Int>, val captures: List<String> = emptyList()) : BytecodeConst()
+    data class CaptureTable(val entries: List<LambdaCaptureEntry>) : BytecodeConst()
     data class ExtensionPropertyDecl(
         val extTypeName: String,
         val property: ObjProperty,

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

@@ -20,6 +20,7 @@ package net.sergeych.lyng.bytecode
 import net.sergeych.lyng.*
 import net.sergeych.lyng.obj.Obj
 import net.sergeych.lyng.obj.ObjClass
+import net.sergeych.lyng.obj.ValueFnRef
 
 class BytecodeStatement private constructor(
     val original: Statement,
@@ -50,6 +51,7 @@ class BytecodeStatement private constructor(
             enumEntriesByName: Map<String, List<String>> = emptyMap(),
             callableReturnTypeByScopeId: Map<Int, Map<Int, ObjClass>> = emptyMap(),
             callableReturnTypeByName: Map<String, ObjClass> = emptyMap(),
+            lambdaCaptureEntriesByRef: Map<ValueFnRef, List<LambdaCaptureEntry>> = emptyMap(),
         ): Statement {
             if (statement is BytecodeStatement) return statement
             val hasUnsupported = containsUnsupportedStatement(statement)
@@ -73,7 +75,8 @@ class BytecodeStatement private constructor(
                 classFieldTypesByName = classFieldTypesByName,
                 enumEntriesByName = enumEntriesByName,
                 callableReturnTypeByScopeId = callableReturnTypeByScopeId,
-                callableReturnTypeByName = callableReturnTypeByName
+                callableReturnTypeByName = callableReturnTypeByName,
+                lambdaCaptureEntriesByRef = lambdaCaptureEntriesByRef
             )
             val compiled = compiler.compileStatement(nameHint, statement)
             val fn = compiled ?: throw BytecodeCompileException(

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

@@ -50,6 +50,23 @@ object CmdDisassembler {
             }
             out.append('\n')
         }
+        val captureConsts = fn.constants.withIndex().mapNotNull { (idx, constVal) ->
+            val table = constVal as? BytecodeConst.CaptureTable ?: return@mapNotNull null
+            idx to table
+        }
+        if (captureConsts.isNotEmpty()) {
+            out.append("consts:\n")
+            for ((idx, table) in captureConsts) {
+                val entries = if (table.entries.isEmpty()) {
+                    "[]"
+                } else {
+                    table.entries.joinToString(prefix = "[", postfix = "]") { entry ->
+                        "${entry.ownerKind}#${entry.ownerScopeId}:${entry.ownerSlotId}"
+                    }
+                }
+                out.append("k").append(idx).append(" CAPTURE_TABLE ").append(entries).append('\n')
+            }
+        }
         return out.toString()
     }
 

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

@@ -0,0 +1,25 @@
+/*
+ * 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.bytecode
+
+enum class CaptureOwnerFrameKind { MODULE, LOCAL }
+
+data class LambdaCaptureEntry(
+    val ownerKind: CaptureOwnerFrameKind,
+    val ownerScopeId: Int,
+    val ownerSlotId: Int,
+)