shared source/sscli20/jscript/engine/return.cs

   1 // ==++==
   2 //
   3 //
   4 //    Copyright (c) 2006 Microsoft Corporation.  All rights reserved.
   5 //
   6 //    The use and distribution terms for this software are contained in the file
   7 //    named license.txt, which can be found in the root of this distribution.
   8 //    By using this software in any fashion, you are agreeing to be bound by the
   9 //    terms of this license.
  10 //
  11 //    You must not remove this notice, or any other, from this software.
  12 //
  13 //
  14 // ==--==
  15
  16 namespace Microsoft.JScript {
  17
  18     using System;
  19     using System.Reflection;
  20     using System.Reflection.Emit;
  21
  22     internal sealed class Return : AST{
  23       private Completion completion;
  24       private AST operand;
  25       private FunctionScope enclosingFunctionScope;
  26       private bool leavesFinally;
  27
  28       internal Return(Context context, AST operand, bool leavesFinally)
  29         : base(context) {
  30         this.completion = new Completion();
  31         this.completion.Return = true;
  32         this.operand = operand;
  33         ScriptObject scope = Globals.ScopeStack.Peek();
  34         while (!(scope is FunctionScope)){
  35           scope = scope.GetParent();
  36           if (scope == null){
  37             this.context.HandleError(JSError.BadReturn);
  38             scope = new FunctionScope(null);
  39           }
  40         }
  41         this.enclosingFunctionScope = ((FunctionScope)scope);
  42         if (this.operand != null && this.enclosingFunctionScope.returnVar == null)
  43           this.enclosingFunctionScope.AddReturnValueField();
  44         this.leavesFinally = leavesFinally;
  45       }
  46
  47       internal override Object Evaluate(){
  48         if (this.operand != null)
  49           this.completion.value = this.operand.Evaluate();
  50         return this.completion;
  51       }
  52
  53       internal override bool HasReturn(){
  54         return true;
  55       }
  56
  57       internal override AST PartiallyEvaluate(){
  58         if (this.leavesFinally)
  59           this.context.HandleError(JSError.BadWayToLeaveFinally);
  60         if (this.operand != null){
  61           this.operand = this.operand.PartiallyEvaluate();
  62           if (this.enclosingFunctionScope.returnVar != null)
  63             if (this.enclosingFunctionScope.returnVar.type == null){
  64               this.enclosingFunctionScope.returnVar.SetInferredType(this.operand.InferType(this.enclosingFunctionScope.returnVar), this.operand);
  65             }else
  66               Binding.AssignmentCompatible(this.enclosingFunctionScope.returnVar.type.ToIReflect(), this.operand, this.operand.InferType(null), true);
  67           else{ //returning something from a function explicitly typed as Void
  68             this.context.HandleError(JSError.CannotReturnValueFromVoidFunction);
  69             this.operand = null;
  70           }
  71         }else if (this.enclosingFunctionScope.returnVar != null)
  72           this.enclosingFunctionScope.returnVar.SetInferredType(Typeob.Object, null);
  73         return this;
  74       }
  75
  76       internal override void TranslateToIL(ILGenerator il, Type rtype){
  77         //This assumes that rtype == Void.class.
  78         this.context.EmitLineInfo(il);
  79         if (this.operand != null)
  80           this.operand.TranslateToIL(il, this.enclosingFunctionScope.returnVar.FieldType);
  81         else if (this.enclosingFunctionScope.returnVar != null){
  82           il.Emit(OpCodes.Ldsfld, CompilerGlobals.undefinedField);
  83           Convert.Emit(this, il, Typeob.Object, this.enclosingFunctionScope.returnVar.FieldType);
  84         }
  85         if (this.enclosingFunctionScope.returnVar != null)
  86           il.Emit(OpCodes.Stloc, (LocalBuilder)this.enclosingFunctionScope.returnVar.GetMetaData());
  87         if (this.leavesFinally){
  88           il.Emit(OpCodes.Newobj, CompilerGlobals.returnOutOfFinallyConstructor);
  89           il.Emit(OpCodes.Throw);
  90         }else if (compilerGlobals.InsideProtectedRegion)
  91           il.Emit(OpCodes.Leave, this.enclosingFunctionScope.owner.returnLabel);
  92         else
  93           il.Emit(OpCodes.Br, this.enclosingFunctionScope.owner.returnLabel);
  94       }
  95
  96       internal override void TranslateToILInitializer(ILGenerator il){
  97         if (this.operand != null)
  98           this.operand.TranslateToILInitializer(il);
  99       }
 100     }
 101  }