/Languages/Ruby/Ruby/Runtime/RubyOps.cs

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/* ****************************************************************************
 *
 * Copyright (c) Microsoft Corporation. 
 *
 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 
 * copy of the license can be found in the License.html file at the root of this distribution. If 
 * you cannot locate the  Apache License, Version 2.0, please send an email to 
 * ironruby@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 
 * by the terms of the Apache License, Version 2.0.
 *
 * You must not remove this notice, or any other, from this software.
 *
 *
 * ***************************************************************************/

#if FEATURE_CORE_DLR
using MSA = System.Linq.Expressions;
#else
using MSA = Microsoft.Scripting.Ast;
#endif

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Dynamic;
using System.Globalization;
using System.IO;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.Serialization;
using System.Threading;
using IronRuby.Builtins;
using IronRuby.Compiler;
using IronRuby.Compiler.Generation;
using IronRuby.Runtime.Calls;
using Microsoft.Scripting;
using Microsoft.Scripting.Interpreter;
using Microsoft.Scripting.Math;
using Microsoft.Scripting.Runtime;
using Microsoft.Scripting.Utils;
using IronRuby.Compiler.Ast;
using IronRuby.Runtime.Conversions;

namespace IronRuby.Runtime {
    [ReflectionCached, CLSCompliant(false)]
    public static partial class RubyOps {
        [Emitted]
        public static readonly object DefaultArgument = new object();
        
        // Returned by a virtual site if a base call should be performed.
        [Emitted]
        public static readonly object ForwardToBase = new object();

        // an instance of a dummy type that causes any rule based on instance type check to fail
        private sealed class _NeedsUpdate {
        }

        [Emitted]
        public static readonly object NeedsUpdate = new _NeedsUpdate();

        #region Scopes

        [Emitted]
        public static MutableTuple GetLocals(RubyScope/*!*/ scope) {
            return scope.Locals;
        }

        [Emitted]
        public static MutableTuple GetParentLocals(RubyScope/*!*/ scope) {
            return scope.Parent.Locals;
        }

        [Emitted]
        public static RubyScope/*!*/ GetParentScope(RubyScope/*!*/ scope) {
            return scope.Parent;
        }

        [Emitted]
        public static Proc GetMethodBlockParameter(RubyScope/*!*/ scope) {
            var methodScope = scope.GetInnerMostMethodScope();
            return methodScope != null ? methodScope.BlockParameter : null;
        }

        [Emitted]
        public static object GetMethodBlockParameterSelf(RubyScope/*!*/ scope) {
            Proc proc = scope.GetInnerMostMethodScope().BlockParameter;
            Debug.Assert(proc != null, "CreateBfcForYield is called before this method and it checks non-nullity");
            return proc.Self;
        }

        [Emitted]
        public static object GetProcSelf(Proc/*!*/ proc) {
            return proc.Self;
        }

        [Emitted]
        public static int GetProcArity(Proc/*!*/ proc) {
            return proc.Dispatcher.Arity;
        }

        [Emitted]
        public static void InitializeScope(RubyScope/*!*/ scope, MutableTuple locals, string[] variableNames, 
            InterpretedFrame interpretedFrame) {

            if (!scope.LocalsInitialized) {
                scope.SetLocals(locals, variableNames ?? ArrayUtils.EmptyStrings);
            }
            scope.InterpretedFrame = interpretedFrame;
        }
        
        [Emitted]
        public static void InitializeScopeNoLocals(RubyScope/*!*/ scope, InterpretedFrame interpretedFrame) {
            scope.InterpretedFrame = interpretedFrame;
        }

        [Emitted]
        public static void SetDataConstant(RubyScope/*!*/ scope, string/*!*/ dataPath, int dataOffset) {
            Debug.Assert(dataOffset >= 0);
            RubyFile dataFile;
            RubyContext context = scope.RubyContext;
            if (context.DomainManager.Platform.FileExists(dataPath)) {
                dataFile = new RubyFile(context, dataPath, IOMode.ReadOnly);
                dataFile.Seek(dataOffset, SeekOrigin.Begin);
            } else {
                dataFile = null;
            }

            context.ObjectClass.SetConstant("DATA", dataFile);
        }

        [Emitted]
        public static RubyModuleScope/*!*/ CreateModuleScope(MutableTuple locals, string[] variableNames, 
            RubyScope/*!*/ parent, RubyModule/*!*/ module) {

            if (parent.RubyContext != module.Context) {
                throw RubyExceptions.CreateTypeError("Cannot open a module `{0}' defined in a foreign runtime #{1}", module.Name, module.Context.RuntimeId);
            }

            RubyModuleScope scope = new RubyModuleScope(parent, module);
            scope.SetDebugName((module.IsClass ? "class" : "module") + " " + module.Name);
            scope.SetLocals(locals, variableNames ?? ArrayUtils.EmptyStrings);
            return scope;
        }

        [Emitted]
        public static RubyMethodScope/*!*/ CreateMethodScope(MutableTuple locals, string[] variableNames, int visibleParameterCount,
            RubyScope/*!*/ parentScope, RubyModule/*!*/ declaringModule, string/*!*/ definitionName, 
            object selfObject, Proc blockParameter, InterpretedFrame interpretedFrame) {

            return new RubyMethodScope(
                locals, variableNames ?? ArrayUtils.EmptyStrings, visibleParameterCount,
                parentScope, declaringModule, definitionName, selfObject, blockParameter,
                interpretedFrame
            );            
        }

        [Emitted]
        public static RubyScope/*!*/ CreateFileInitializerScope(MutableTuple locals, string[] variableNames, RubyScope/*!*/ parent) {
            return new RubyFileInitializerScope(locals, variableNames ?? ArrayUtils.EmptyStrings, parent);
        }

        [Emitted]
        public static RubyBlockScope/*!*/ CreateBlockScope(MutableTuple locals, string[] variableNames, 
            BlockParam/*!*/ blockParam, object selfObject, InterpretedFrame interpretedFrame) {

            return new RubyBlockScope(locals, variableNames ?? ArrayUtils.EmptyStrings, blockParam, selfObject, interpretedFrame);
        }

        [Emitted]
        public static void TraceMethodCall(RubyMethodScope/*!*/ scope, string fileName, int lineNumber) {
            // MRI: 
            // Reports DeclaringModule even though an aliased method in a sub-module is called.
            // Also works for singleton module-function, which shares DeclaringModule with instance module-function.
            RubyModule module = scope.DeclaringModule;
            scope.RubyContext.ReportTraceEvent("call", scope, module, scope.DefinitionName, fileName, lineNumber);
        }

        [Emitted]
        public static void TraceMethodReturn(RubyMethodScope/*!*/ scope, string fileName, int lineNumber) {
            RubyModule module = scope.DeclaringModule;
            scope.RubyContext.ReportTraceEvent("return", scope, module, scope.DefinitionName, fileName, lineNumber);
        }

        [Emitted]
        public static void TraceBlockCall(RubyBlockScope/*!*/ scope, BlockParam/*!*/ block, string fileName, int lineNumber) {
            var method = block.Proc.Method;
            if (method != null) {
                scope.RubyContext.ReportTraceEvent("call", scope, method.DeclaringModule, method.DefinitionName, fileName, lineNumber);
            }
        }

        [Emitted]
        public static void TraceBlockReturn(RubyBlockScope/*!*/ scope, BlockParam/*!*/ block, string fileName, int lineNumber) {
            var method = block.Proc.Method;
            if (method != null) {
                scope.RubyContext.ReportTraceEvent("return", scope, method.DeclaringModule, method.DefinitionName, fileName, lineNumber);
            }
        }

        [Emitted]
        public static void PrintInteractiveResult(RubyScope/*!*/ scope, MutableString/*!*/ value) {
            var writer = scope.RubyContext.DomainManager.SharedIO.OutputStream;
            writer.WriteByte((byte)'=');
            writer.WriteByte((byte)'>');
            writer.WriteByte((byte)' ');
            var bytes = value.ToByteArray();
            writer.Write(bytes, 0, bytes.Length);
            writer.WriteByte((byte)'\r');
            writer.WriteByte((byte)'\n');
        }

        [Emitted]
        public static object GetLocalVariable(RubyScope/*!*/ scope, string/*!*/ name) {
            return scope.ResolveLocalVariable(name);
        }

        [Emitted]
        public static object SetLocalVariable(object value, RubyScope/*!*/ scope, string/*!*/ name) {
            return scope.ResolveAndSetLocalVariable(name, value);
        }

        [Emitted]
        public static VersionHandle/*!*/ GetSelfClassVersionHandle(RubyScope/*!*/ scope) {
            return scope.SelfImmediateClass.Version;
        }

        #endregion

        #region Context

        [Emitted]
        public static RubyContext/*!*/ GetContextFromModule(RubyModule/*!*/ module) {
            return module.Context;
        }
        
        [Emitted]
        public static RubyContext/*!*/ GetContextFromIRubyObject(IRubyObject/*!*/ obj) {
            return obj.ImmediateClass.Context;
        }
        
        [Emitted]
        public static RubyContext/*!*/ GetContextFromScope(RubyScope/*!*/ scope) {
            return scope.RubyContext;
        }

        [Emitted]
        public static RubyContext/*!*/ GetContextFromMethod(RubyMethod/*!*/ method) {
            return method.Info.Context;
        }

        [Emitted]
        public static RubyContext/*!*/ GetContextFromBlockParam(BlockParam/*!*/ block) {
            return block.RubyContext;
        }

        [Emitted]
        public static RubyContext/*!*/ GetContextFromProc(Proc/*!*/ proc) {
            return proc.LocalScope.RubyContext;
        }

        [Emitted]
        public static RubyScope/*!*/ GetEmptyScope(RubyContext/*!*/ context) {
            return context.EmptyScope;
        }

        [Emitted]
        public static Scope/*!*/ GetGlobalScopeFromScope(RubyScope/*!*/ scope) {
            return scope.GlobalScope.Scope;
        }

        #endregion

        #region Blocks

        [Emitted]
        public static Proc InstantiateBlock(RubyScope/*!*/ scope, object self, BlockDispatcher/*!*/ dispatcher) {
            return (dispatcher.Method != null) ? new Proc(ProcKind.Block, self, scope, dispatcher) : null;
        }
        [Emitted]
        public static Proc InstantiateLambda(RubyScope/*!*/ scope, object self, BlockDispatcher/*!*/ dispatcher) {
            return (dispatcher.Method != null) ? new Proc(ProcKind.Lambda, self, scope, dispatcher) : null;
        }

        [Emitted]
        public static Proc/*!*/ DefineBlock(RubyScope/*!*/ scope, object self, BlockDispatcher/*!*/ dispatcher, object/*!*/ clrMethod) {
#if !WIN8
            // DLR closures should not be used:
            Debug.Assert(!(((Delegate)clrMethod).Target is Closure) || ((Closure)((Delegate)clrMethod).Target).Locals == null);
#endif
            return new Proc(ProcKind.Block, self, scope, dispatcher.SetMethod(clrMethod));
        }

        [Emitted]
        public static Proc/*!*/ DefineLambda(RubyScope/*!*/ scope, object self, BlockDispatcher/*!*/ dispatcher, object/*!*/ clrMethod) {
#if !WIN8
            // DLR closures should not be used:
            Debug.Assert(!(((Delegate)clrMethod).Target is Closure) || ((Closure)((Delegate)clrMethod).Target).Locals == null);
#endif
            return new Proc(ProcKind.Lambda, self, scope, dispatcher.SetMethod(clrMethod));
        }

        /// <summary>
        /// Used in a method call with a block to reset proc-kind when the call is retried
        /// </summary>
        [Emitted]
        public static void InitializeBlock(Proc/*!*/ proc) {
            Assert.NotNull(proc);
            proc.Kind = ProcKind.Block;
        }

        /// <summary>
        /// Implements END block - like if it was a call to at_exit { ... } library method.
        /// </summary>
        [Emitted]
        public static void RegisterShutdownHandler(Proc/*!*/ proc) {
            proc.LocalScope.RubyContext.RegisterShutdownHandler(proc);
        }

        #endregion

        #region Yield: TODO: generate

        [Emitted] 
        public static object Yield0(Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.Invoke(blockParam, self, procArg);
            } catch(EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object Yield1(object arg1, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.Invoke(blockParam, self, procArg, arg1);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        // YieldNoAutoSplat1 uses InvokeNoAutoSplat instead of Invoke (used by Call1)
        internal static object YieldNoAutoSplat1(object arg1, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.InvokeNoAutoSplat(blockParam, self, procArg, arg1);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object Yield2(object arg1, object arg2, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.Invoke(blockParam, self, procArg, arg1, arg2);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object Yield3(object arg1, object arg2, object arg3, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.Invoke(blockParam, self, procArg, arg1, arg2, arg3);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object Yield4(object arg1, object arg2, object arg3, object arg4, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.Invoke(blockParam, self, procArg, arg1, arg2, arg3, arg4);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object YieldN(object[]/*!*/ args, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            Debug.Assert(args.Length > BlockDispatcher.MaxBlockArity);

            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.Invoke(blockParam, self, procArg, args);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        internal static object Yield(object[]/*!*/ args, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            switch (args.Length) {
                case 0: return RubyOps.Yield0(procArg, self, blockParam);
                case 1: return RubyOps.Yield1(args[0], procArg, self, blockParam);
                case 2: return RubyOps.Yield2(args[0], args[1], procArg, self, blockParam);
                case 3: return RubyOps.Yield3(args[0], args[1], args[2], procArg, self, blockParam);
                case 4: return RubyOps.Yield4(args[0], args[1], args[2], args[3], procArg, self, blockParam);
                default: return RubyOps.YieldN(args, procArg, self, blockParam); 
            }
        }

        [Emitted]
        public static object YieldSplat0(IList/*!*/ splattee, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.InvokeSplat(blockParam, self, procArg, splattee);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object YieldSplat1(object arg1, IList/*!*/ splattee, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.InvokeSplat(blockParam, self, procArg, arg1, splattee);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object YieldSplat2(object arg1, object arg2, IList/*!*/ splattee, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.InvokeSplat(blockParam, self, procArg, arg1, arg2, splattee);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object YieldSplat3(object arg1, object arg2, object arg3, IList/*!*/ splattee, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.InvokeSplat(blockParam, self, procArg, arg1, arg2, arg3, splattee);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object YieldSplat4(object arg1, object arg2, object arg3, object arg4, IList/*!*/ splattee, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.InvokeSplat(blockParam, self, procArg, arg1, arg2, arg3, arg4, splattee);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object YieldSplatN(object[]/*!*/ args, IList/*!*/ splattee, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.InvokeSplat(blockParam, self, procArg, args, splattee);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        [Emitted]
        public static object YieldSplatNRhs(object[]/*!*/ args, IList/*!*/ splattee, object rhs, Proc procArg, object self, BlockParam/*!*/ blockParam) {
            object result;
            var proc = blockParam.Proc;
            try {
                result = proc.Dispatcher.InvokeSplatRhs(blockParam, self, procArg, args, splattee, rhs);
            } catch (EvalUnwinder evalUnwinder) {
                result = blockParam.GetUnwinderResult(evalUnwinder);
            }

            return result;
        }

        #endregion

        #region Methods

        [Emitted] // MethodDeclaration:
        public static object DefineMethod(object target, RubyScope/*!*/ scope, RubyMethodBody/*!*/ body) {
            Assert.NotNull(body, scope);

            RubyModule instanceOwner, singletonOwner;
            RubyMemberFlags instanceFlags, singletonFlags;
            bool moduleFunction = false;

            if (body.HasTarget) {
                if (!RubyUtils.CanDefineSingletonMethod(target)) {
                    throw RubyExceptions.CreateTypeError("can't define singleton method for literals");
                }

                instanceOwner = null;
                instanceFlags = RubyMemberFlags.Invalid;
                singletonOwner = scope.RubyContext.GetOrCreateSingletonClass(target);
                singletonFlags = RubyMemberFlags.Public;
            } else {
                var attributesScope = scope.GetMethodAttributesDefinitionScope();
                if ((attributesScope.MethodAttributes & RubyMethodAttributes.ModuleFunction) == RubyMethodAttributes.ModuleFunction) {
                    // Singleton module-function's scope points to the instance method's RubyMemberInfo.
                    // This affects:
                    // 1) super call
                    //    Super call is looking for Method.DeclaringModule while searching MRO, which would fail if the singleton module-function
                    //    was in MRO. Since module-function can only be used on module the singleton method could only be on module's singleton.
                    //    Module's singleton is never part of MRO so we are safe.
                    // 2) trace
                    //    Method call trace reports non-singleton module.

                    // MRI 1.8: instance method owner is self -> it is possible (via define_method) to define m.f. on a class (bug)
                    // MRI 1.9: instance method owner GetMethodDefinitionOwner
                    // MRI allows to define m.f. on classes but then doesn't work correctly with it.
                    instanceOwner = scope.GetMethodDefinitionOwner();
                    if (instanceOwner.IsClass) {
                        throw RubyExceptions.CreateTypeError("A module function cannot be defined on a class.");
                    }

                    instanceFlags = RubyMemberFlags.Private;
                    singletonOwner = instanceOwner.GetOrCreateSingletonClass();
                    singletonFlags = RubyMemberFlags.Public;
                    moduleFunction = true;
                } else {
                    instanceOwner = scope.GetMethodDefinitionOwner();
                    instanceFlags = (RubyMemberFlags)RubyUtils.GetSpecialMethodVisibility(attributesScope.Visibility, body.Name);
                    singletonOwner = null;
                    singletonFlags = RubyMemberFlags.Invalid;
                }
            }
            
            RubyMethodInfo instanceMethod = null, singletonMethod = null;

            if (instanceOwner != null) {
                SetMethod(scope.RubyContext, instanceMethod =
                    new RubyMethodInfo(body, scope, instanceOwner, instanceFlags)
                );
            }

            if (singletonOwner != null) {
                SetMethod(scope.RubyContext, singletonMethod =
                    new RubyMethodInfo(body, scope, singletonOwner, singletonFlags)
                );
            }

            // the method's scope saves the result => singleton module-function uses instance-method
            var method = instanceMethod ?? singletonMethod;

            method.DeclaringModule.MethodAdded(body.Name);

            if (moduleFunction) {
                Debug.Assert(!method.DeclaringModule.IsClass);
                method.DeclaringModule.GetOrCreateSingletonClass().MethodAdded(body.Name);
            }

            return null;
        }

        private static void SetMethod(RubyContext/*!*/ callerContext, RubyMethodInfo/*!*/ method) {
            var owner = method.DeclaringModule;

            // Do not trigger the add-method event just yet, we need to assign the result into closure before executing any user code.
            // If the method being defined is "method_added" itself, we would call that method before the info gets assigned to the closure.
            owner.SetMethodNoEvent(callerContext, method.DefinitionName, method);

            // expose RubyMethod in the scope (the method is bound to the main singleton instance):
            if (owner.GlobalScope != null) {
                RubyOps.ScopeSetMember(
                    owner.GlobalScope.Scope,
                    method.DefinitionName,
                    new RubyMethod(owner.GlobalScope.MainObject, method, method.DefinitionName)
                );
            }
        }

        [Emitted] // AliasStatement:
        public static void AliasMethod(RubyScope/*!*/ scope, string/*!*/ newName, string/*!*/ oldName) {
            scope.GetMethodDefinitionOwner().AddMethodAlias(newName, oldName);
        }

        [Emitted] // UndefineMethod:
        public static void UndefineMethod(RubyScope/*!*/ scope, string/*!*/ name) {
            RubyModule owner = scope.GetMethodDefinitionOwner();

            if (!owner.ResolveMethod(name, VisibilityContext.AllVisible).Found) {
                throw RubyExceptions.CreateUndefinedMethodError(owner, name);
            }
            owner.UndefineMethod(name);
        }

        #endregion

        #region Modules

        [Emitted]
        public static RubyModule/*!*/ DefineGlobalModule(RubyScope/*!*/ scope, string/*!*/ name) {
            return DefineModule(scope, scope.Top.TopModuleOrObject, name);
        }

        [Emitted]
        public static RubyModule/*!*/ DefineNestedModule(RubyScope/*!*/ scope, string/*!*/ name) {
            return DefineModule(scope, scope.GetInnerMostModuleForConstantLookup(), name);
        }

        [Emitted]
        public static RubyModule/*!*/ DefineModule(RubyScope/*!*/ scope, object target, string/*!*/ name) {
            return DefineModule(scope, RubyUtils.GetModuleFromObject(scope, target), name);
        }

        // thread-safe:
        private static RubyModule/*!*/ DefineModule(RubyScope/*!*/ scope, RubyModule/*!*/ owner, string/*!*/ name) {
            Assert.NotNull(scope, owner);

            ConstantStorage existing;
            if (owner.TryGetConstant(scope.GlobalScope, name, out existing)) {
                RubyModule module = existing.Value as RubyModule;
                if (module == null || module.IsClass) {
                    throw RubyExceptions.CreateTypeError(String.Format("{0} is not a module", name));
                }
                return module;
            } else {
                // create class/module object:
                return owner.Context.DefineModule(owner, name);
            }
        }

        #endregion

        #region Classes

        [Emitted]
        public static RubyClass/*!*/ DefineSingletonClass(RubyScope/*!*/ scope, object obj) {
            if (!RubyUtils.HasSingletonClass(obj)) {
                throw RubyExceptions.CreateTypeError(String.Format("no virtual class for {0}", scope.RubyContext.GetClassOf(obj).Name));
            }
            return scope.RubyContext.GetOrCreateSingletonClass(obj);
        }

        [Emitted] 
        public static RubyModule/*!*/ DefineGlobalClass(RubyScope/*!*/ scope, string/*!*/ name, object superClassObject) {
            return DefineClass(scope, scope.Top.TopModuleOrObject, name, superClassObject);
        }

        [Emitted]
        public static RubyModule/*!*/ DefineNestedClass(RubyScope/*!*/ scope, string/*!*/ name, object superClassObject) {
            return DefineClass(scope, scope.GetInnerMostModuleForConstantLookup(), name, superClassObject);
        }

        [Emitted]
        public static RubyModule/*!*/ DefineClass(RubyScope/*!*/ scope, object target, string/*!*/ name, object superClassObject) {
            return DefineClass(scope, RubyUtils.GetModuleFromObject(scope, target), name, superClassObject);
        }

        // thread-safe:
        private static RubyClass/*!*/ DefineClass(RubyScope/*!*/ scope, RubyModule/*!*/ owner, string/*!*/ name, object superClassObject) {
            Assert.NotNull(owner);
            RubyClass superClass = ToSuperClass(owner.Context, superClassObject);

            ConstantStorage existing;
            if (owner.IsObjectClass
                ? owner.TryResolveConstant(scope.GlobalScope, name, out existing)
                : owner.TryGetConstant(scope.GlobalScope, name, out existing)) {

                RubyClass cls = existing.Value as RubyClass;
                if (cls == null || !cls.IsClass) {
                    throw RubyExceptions.CreateTypeError("{0} is not a class", name);
                }

                if (superClassObject != null && !ReferenceEquals(cls.SuperClass, superClass)) {
                    throw RubyExceptions.CreateTypeError("superclass mismatch for class {0}", name);
                }
                return cls;
            } else {
                return owner.Context.DefineClass(owner, name, superClass, null);
            }
        }

        private static RubyClass/*!*/ ToSuperClass(RubyContext/*!*/ ec, object superClassObject) {
            if (superClassObject != null) {
                RubyClass superClass = superClassObject as RubyClass;
                if (superClass == null) {
                    throw RubyExceptions.CreateTypeError("superclass must be a Class ({0} given)", ec.GetClassOf(superClassObject).Name);
                }

                if (superClass.IsSingletonClass) {
                    throw RubyExceptions.CreateTypeError("can't make subclass of virtual class");
                }

                return superClass;
            } else {
                return ec.ObjectClass;
            }
        }

        #endregion

        #region Constants

        /// <summary>
        /// A
        /// ::A
        /// </summary>
        [Emitted]
        public static object GetUnqualifiedConstant(RubyScope/*!*/ scope, ConstantSiteCache/*!*/ cache, string/*!*/ name, bool isGlobal) {
            object result = null;
            RubyModule missingConstantOwner;
            var context = scope.RubyContext;
            using (context.ClassHierarchyLocker()) {
                // Thread safety:
                // Another thread could have already updated the value, so the site version might be the same as CAV.
                // We do the lookup anyways since it is no-op and this only happens rarely.
                //
                // An important invariant holds here: in any time after initialized for the first time the Value field contains a valid value.
                // Threads can read an older value (the previous version) but that is still correct since we don't guarantee immediate
                // propagation of the constant write to all readers.
                // 
                // if (site.Version = CAV) {
                //   <- another thread could increment CAV here - we may return old or new value (both are ok)
                //   value = site.Value;
                // } else {
                //   <- another thread could get here as well and update the site before we get to update it.
                //   GetConstant(...)
                // }

                // Constants might be updated during constant resolution due to autoload. 
                // Any such updates need to invalidate the cache hence we need to capture the version before resolving the constant.
                int newVersion = context.ConstantAccessVersion;

                ConstantStorage storage;
                if (!isGlobal) {
                    missingConstantOwner = scope.TryResolveConstantNoLock(scope.GlobalScope, name, out storage);
                } else if (context.ObjectClass.TryResolveConstantNoLock(scope.GlobalScope, name, out storage)) {
                    missingConstantOwner = null;
                } else {
                    missingConstantOwner = context.ObjectClass;
                }

                object newCacheValue;
                if (missingConstantOwner == null) {
                    if (storage.WeakValue != null) {
                        result = storage.Value;
                        newCacheValue = storage.WeakValue;
                    } else {
                        result = newCacheValue = storage.Value;
                    }
                } else {
                    newCacheValue = ConstantSiteCache.WeakMissingConstant;
                }

                cache.Update(newCacheValue, newVersion);
            }

            if (missingConstantOwner != null) {
                result = missingConstantOwner.ConstantMissing(name);
            }

            return result;
        }

        /// <summary>
        /// A1::..::AN
        /// ::A1::..::AN
        /// </summary>
        [Emitted]
        public static object GetQualifiedConstant(RubyScope/*!*/ scope, ConstantSiteCache/*!*/ cache, string/*!*/[]/*!*/ qualifiedName, bool isGlobal) {
            var globalScope = scope.GlobalScope;
            var context = globalScope.Context;

            using (context.ClassHierarchyLocker()) {
                int newVersion = context.ConstantAccessVersion;
                
                ConstantStorage storage;
                bool anyMissing;
                RubyModule topModule = isGlobal ? context.ObjectClass : null;
                object result = ResolveQualifiedConstant(scope, qualifiedName, topModule, true, out storage, out anyMissing);

                // cache result only if no constant was missing:
                if (!anyMissing) {
                    Debug.Assert(result == storage.Value);
                    cache.Update(storage.WeakValue ?? result, newVersion);
                }

                return result;
            }
        }

        /// <summary>
        /// {expr}::A1::..::AN
        /// </summary>
        [Emitted]
        public static object GetExpressionQualifiedConstant(object target, RubyScope/*!*/ scope, ExpressionQualifiedConstantSiteCache/*!*/ cache,
            string/*!*/[]/*!*/ qualifiedName) {
            RubyModule module = target as RubyModule;
            if (module == null) {
                throw RubyUtils.CreateNotModuleException(scope, target);
            }

            var condition = cache.Condition;
            RubyContext context = module.Context;

            // Note that the module can be bound to another runtime:
            if (module.Id == condition.ModuleId && context.ConstantAccessVersion == condition.Version) {
                object value = cache.Value;
                if (value.GetType() == typeof(WeakReference)) {
                    return ((WeakReference)value).Target;
                } else {
                    return value;
                }
            }

            using (context.ClassHierarchyLocker()) {
                int newVersion = context.ConstantAccessVersion;
                
                ConstantStorage storage;
                bool anyMissing;
                object result = ResolveQualifiedConstant(scope, qualifiedName, module, true, out storage, out anyMissing);

                // cache result only if no constant was missing:
                if (!anyMissing) {
                    Debug.Assert(result == storage.Value);
                    cache.Update(storage.WeakValue ?? result, newVersion, module);
                }

                return result;
            }
        }

        /// <summary>
        /// defined? A
        /// </summary>
        [Emitted]
        public static bool IsDefinedUnqualifiedConstant(RubyScope/*!*/ scope, IsDefinedConstantSiteCache/*!*/ cache, string/*!*/ name) {
            var context = scope.RubyContext;
            using (context.ClassHierarchyLocker()) {
                int newVersion = context.ConstantAccessVersion;
                
                ConstantStorage storage;
                bool exists = scope.TryResolveConstantNoLock(null, name, out storage) == null;
                cache.Update(exists, newVersion);
                return exists;
            }
        }

        /// <summary>
        /// defined? ::A
        /// </summary>
        [Emitted]
        public static bool IsDefinedGlobalConstant(RubyScope/*!*/ scope, IsDefinedConstantSiteCache/*!*/ cache, string/*!*/ name) {
            var context = scope.RubyContext;
            using (context.ClassHierarchyLocker()) {
                int newVersion = context.ConstantAccessVersion;

                ConstantStorage storage;
                bool exists = context.ObjectClass.TryResolveConstantNoLock(null, name, out storage);
                cache.Update(exists, newVersion);
                return exists;
            }
        }

        /// <summary>
        /// defined? A1::..::AN
        /// defined? ::A1::..::AN
        /// </summary>
        [Emitted]
        public static bool IsDefinedQualifiedConstant(RubyScope/*!*/ scope, IsDefinedConstantSiteCache/*!*/ cache,
            string/*!*/[]/*!*/ qualifiedName, bool isGlobal) {

            var context = scope.RubyContext;
            using (context.ClassHierarchyLocker()) {
                int newVersion = context.ConstantAccessVersion;

                ConstantStorage storage;
                bool anyMissing;
                RubyModule topModule = isGlobal ? context.ObjectClass : null;
                RubyModule owner;
                try {
                    owner = ResolveQualifiedConstant(scope, qualifiedName, topModule, false, out storage, out anyMissing) as RubyModule;
                } catch {
                    // autoload can raise an exception
                    scope.RubyContext.SetCurrentException(null);
                    return false;
                }
                
                // Note that the owner could be another runtime's module:
                bool exists = owner != null && owner.TryResolveConstant(context, null, qualifiedName[qualifiedName.Length - 1], out storage);
                
                // cache result only if no constant was missing:
                if (!anyMissing) {
                    cache.Update(exists, newVersion);
                }

                return exists;
            }
        }

        /// <summary>
        /// defined? {expr}::A
        /// defined? {expr}::A1::..::AN
        /// </summary>
        [Emitted]
        public static bool IsDefinedExpressionQualifiedConstant(object target, RubyScope/*!*/ scope,
            ExpressionQualifiedIsDefinedConstantSiteCache/*!*/ cache, string/*!*/[]/*!*/ qualifiedName) {

            RubyModule module = target as RubyModule;
            if (module == null) {
                return false;
            }

            var condition = cache.Condition;
            RubyContext context = module.Context;

            // Note that the module can be bound to another runtime:
            if (module.Id == condition.ModuleId && context.ConstantAccessVersion == condition.Version) {
                return cache.Value;
            }

            using (context.ClassHierarchyLocker()) {
                int newVersion = context.ConstantAccessVersion;

                ConstantStorage storage;
                bool exists;
                if (qualifiedName.Length == 1) {
                    // Note that the owner could be another runtime's module:
                    exists = module.TryResolveConstant(context, null, qualifiedName[0], out storage);
                } else {
                    bool anyMissing;
                    RubyModule owner;
                    try {
                        owner = ResolveQualifiedConstant(scope, qualifiedName, module, false, out storage, out anyMissing) as RubyModule;
                    } catch {
                        // autoload can raise an exception:
                        return false;
                    }

                    // Note that the owner could be another runtime's module:
                    exists = owner != null && owner.TryResolveConstant(context, null, qualifiedName[qualifiedName.Length - 1], out storage);

                    // cache result only if no constant was missing:
                    if (anyMissing) {
                        return exists;
                    } 
                }

                cache.Update(exists, newVersion, module);
                return exists;
            }
        }

        private static object ResolveQualifiedConstant(RubyScope/*!*/ scope, string/*!*/[]/*!*/ qualifiedName, RubyModule topModule, bool isGet,
            out ConstantStorage storage, out bool anyMissing) {

            Debug.Assert(qualifiedName.Length >= 2 || qualifiedName.Length == 1 && isGet);
            RubyContext context = scope.RubyContext;
            context.RequiresClassHierarchyLock();

            RubyModule missingConstantOwner;
            RubyGlobalScope globalScope = scope.GlobalScope;
            int nameCount = (isGet) ? qualifiedName.Length : qualifiedName.Length - 1;

            string name = qualifiedName[0];
            if (topModule == null) {
                missingConstantOwner = scope.TryResolveConstantNoLock(globalScope, name, out storage);
            } else if (topModule.TryResolveConstant(context, globalScope, name, out storage)) {
                missingConstantOwner = null;
            } else {
                missingConstantOwner = topModule;
            }

            object result;
            if (missingConstantOwner == null) {
                result = storage.Value;
                anyMissing = false;
            } else {
                anyMissing = true;
                using (context.ClassHierarchyUnlocker()) {
                    result = missingConstantOwner.ConstantMissing(name);
                }
            }

            for (int i = 1; i < nameCount; i++) {
                RubyModule owner = RubyUtils.GetModuleFromObject(scope, result);
                // Note that the owner could be another runtime's module:
                name = qualifiedName[i];
                if (owner.TryResolveConstant(context, globalScope, name, out storage)) {
                    
                    // Constant write updates constant version in a single runtime only. 
                    // Therefore if the chain mixes modules from different runtimes we cannot cache the result.
                    if (owner.Context != context) {
                        anyMissing = true;
                    }
                    
                    result = storage.Value;
                } else {
                    anyMissing = true;
                    using (context.ClassHierarchyUnlocker()) {
                        result = owner.ConstantMissing(name);
                    }
                }
            }

            return result;
        }

        [Emitted]
        public static object GetMissingConstant(RubyScope/*!*/ scope, ConstantSiteCache/*!*/ cache, string/*!*/ name) {
            return scope.GetInnerMostModuleForConstantLookup().ConstantMissing(name);
        }

        [Emitted]
        public static object GetGlobalMissingConstant(RubyScope/*!*/ scope, ConstantSiteCache/*!*/ cache, string/*!*/ name) {
            return scope.RubyContext.ObjectClass.ConstantMissing(name);
        }


        [Emitted] // ConstantVariable:
        public static object SetGlobalConstant(object value, RubyScope/*!*/ scope, string/*!*/ name) {
            RubyUtils.SetConstant(scope.RubyContext.ObjectClass, name, value);
            return value;
        }

        [Emitted] // ConstantVariable:
        public static object SetUnqualifiedConstant(object value, RubyScope/*!*/ scope, string/*!*/ name) {
            RubyUtils.SetConstant(scope.GetInnerMostModuleForConstantLookup(), name, value);
            return value;
        }

        [Emitted] // ConstantVariable:
        public static object SetQualifiedConstant(object value, object target, RubyScope/*!*/ scope, string/*!*/ name) {
            RubyUtils.SetConstant(RubyUtils.GetModuleFromObject(scope, target), name, value);
            return value;
        }

        #endregion

        // MakeArray*
        public const int OptimizedOpCallParamCount = 5;
        
        #region MakeArray
        
        [Emitted]
        public static RubyArray/*!*/ MakeArray0() {
            return new RubyArray(0);
        }

        [Emitted]
        public static RubyArray/*!*/ MakeArray1(object item1) {
            RubyArray result = new RubyArray(1);
            result.Add(item1);
            return result;
        }

        [Emitted]
        public static RubyArray/*!*/ MakeArray2(object item1, object item2) {
            RubyArray result = new RubyArray(2);
            result.Add(item1);
            result.Add(item2);
            return result;
        }

        [Emitted]
        public static RubyArray/*!*/ MakeArray3(object item1, object item2, object item3) {
            RubyArray result = new RubyArray(3);
            result.Add(item1);
            result.Add(item2);
            result.Add(item3);
            return result;
        }

        [Emitted]
        public static RubyArray/*!*/ MakeArray4(object item1, object item2, object item3, object item4) {
            RubyArray result = new RubyArray(4);
            result.Add(item1);
            result.Add(item2);
            result.Add(item3);
            result.Add(item4);
            return result;
        }

        [Emitted]
        public static RubyArray/*!*/ MakeArray5(object item1, object item2, object item3, object item4, object item5) {
            RubyArray result = new RubyArray(5);
            result.Add(item1);
            result.Add(item2);
            result.Add(item3);
            result.Add(item4);
            result.Add(item5);
            return result;
        }

        [Emitted]
        public static RubyArray/*!*/ MakeArrayN(object[]/*!*/ items) {
            Debug.Assert(items != null);
            var array = new RubyArray(items.Length);
            array.AddVector(items, 0, items.Length);
            return array;
        }

        #endregion

        #region MakeHash

        [Emitted]
        public static Hash/*!*/ MakeHash0(RubyScope/*!*/ scope) {
            return new Hash(scope.RubyContext.EqualityComparer, 0);
        }
        
        [Emitted]
        public static Hash/*!*/ MakeHash(RubyScope/*!*/ scope, object[]/*!*/ items) {
            return RubyUtils.SetHashElements(scope.RubyContext, new Hash(scope.RubyContext.EqualityComparer, items.Length / 2), items);
        }

        #endregion

        #region Array

        [Emitted]
        public static RubyArray/*!*/ AddRange(RubyArray/*!*/ array, IList/*!*/ list) {
            return array.AddRange(list);
        }

        [Emitted] // method call:
        public static RubyArray/*!*/ AddSubRange(RubyArray/*!*/ result, IList/*!*/ array, int start, int count) {
            return result.AddRange(array, start, count);
        }

        [Emitted]
        public static RubyArray/*!*/ AddItem(RubyArray/*!*/ array, object item) {
            array.Add(item);
            return array;
        }

        [Emitted]
        public static IList/*!*/ SplatAppend(IList/*!*/ array, IList/*!*/ list) {
            Utils.AddRange(array, list);
            return array;
        }

        [Emitted]
        public static object Splat(IList/*!*/ list) {
            if (list.Count <= 1) {
                return (list.Count > 0) ? list[0] : null;
            }

            return list;
        }

        // 1.8 behavior
        [Emitted]
        public static object SplatPair(object value, IList/*!*/ list) {
            if (list.Count == 0) {
                return value;
            }

            RubyArray result = new RubyArray(list.Count + 1);
            result.Add(value);
            result.AddRange(list);
            return result;
        }

        [Emitted]
        public static IList/*!*/ Unsplat(object splattee) {
            var list = splattee as IList;
            if (list == null) {
                list = new RubyArray(1);
                list.Add(splattee);
            }
            return list;
        }

        // CaseExpression
        [Emitted]
        public static bool ExistsUnsplatCompare(CallSite<Func<CallSite, object, object, object>>/*!*/ comparisonSite, object splattee, object value) {
            var list = splattee as IList;
            if (list != null) {
                for (int i = 0; i < list.Count; i++) {
                    if (IsTrue(comparisonSite.Target(comparisonSite, list[i], value))) {
                        return true;
                    }
                }
                return false;
            } else {
                return IsTrue(comparisonSite.Target(comparisonSite, splattee, value)); 
            }
        }

        // CaseExpression
        [Emitted]
        public static bool ExistsUnsplat(object splattee) {
            var list = splattee as IList;
            if (list != null) {
                for (int i = 0; i < list.Count; i++) {
                    if (IsTrue(list[i])) {
                        return true;
                    }
                }
                return false;
            } else {
                return IsTrue(splattee);
            }
        }

        [Emitted] // parallel assignment:
        public static object GetArrayItem(IList/*!*/ array, int index) {
            Debug.Assert(index >= 0);
     …