[Mono.Debugger.Soft] Implement IsGenericType/Method for protocol < 2.12
[mono.git] / mcs / mcs / nullable.cs
index 646bdf74941d6c8d4dda1b639f71cf8993f3ae24..75048365c4ed5d25514508dafba7bcdd1fafac50 100644 (file)
@@ -9,39 +9,42 @@
 //
 // Copyright 2001, 2002, 2003 Ximian, Inc (http://www.ximian.com)
 // Copyright 2004-2008 Novell, Inc
+// Copyright 2011 Xamarin Inc
 //
 
 using System;
+
+#if STATIC
+using IKVM.Reflection.Emit;
+#else
 using System.Reflection.Emit;
+#endif
        
 namespace Mono.CSharp.Nullable
 {
        public class NullableType : TypeExpr
        {
-               TypeExpr underlying;
+               readonly TypeSpec underlying;
 
-               public NullableType (TypeExpr underlying, Location l)
+               public NullableType (TypeSpec type, Location loc)
                {
-                       this.underlying = underlying;
-                       loc = l;
-
-                       eclass = ExprClass.Type;
+                       this.underlying = type;
+                       this.loc = loc;
                }
 
-               public NullableType (TypeSpec type, Location loc)
-                       : this (new TypeExpression (type, loc), loc)
-               { }
-
-               protected override TypeExpr DoResolveAsTypeStep (IMemberContext ec)
+               public override TypeSpec ResolveAsType (IMemberContext ec)
                {
-                       if (TypeManager.generic_nullable_type == null) {
-                               TypeManager.generic_nullable_type = TypeManager.CoreLookupType (ec.Compiler,
-                                       "System", "Nullable", 1, MemberKind.Struct, true);
-                       }
+                       eclass = ExprClass.Type;
+
+                       var otype = ec.Module.PredefinedTypes.Nullable.Resolve ();
+                       if (otype == null)
+                               return null;
 
-                       TypeArguments args = new TypeArguments (underlying);
-                       GenericTypeExpr ctype = new GenericTypeExpr (TypeManager.generic_nullable_type, args, loc);
-                       return ctype.ResolveAsTypeTerminal (ec, false);
+                       TypeArguments args = new TypeArguments (new TypeExpression (underlying, loc));
+                       GenericTypeExpr ctype = new GenericTypeExpr (otype, args, loc);
+                       
+                       type = ctype.ResolveAsType (ec);
+                       return type;
                }
        }
 
@@ -49,7 +52,8 @@ namespace Mono.CSharp.Nullable
        {
                public static MethodSpec GetConstructor (TypeSpec nullableType)
                {
-                       return TypeManager.GetPredefinedConstructor (nullableType, Location.Null, GetUnderlyingType (nullableType));
+                       return (MethodSpec) MemberCache.FindMember (nullableType,
+                               MemberFilter.Constructor (ParametersCompiled.CreateFullyResolved (GetUnderlyingType (nullableType))), BindingRestriction.DeclaredOnly);
                }
 
                public static MethodSpec GetHasValue (TypeSpec nullableType)
@@ -74,14 +78,9 @@ namespace Mono.CSharp.Nullable
                {
                        return ((InflatedTypeSpec) nullableType).TypeArguments[0];
                }
-
-               public static bool IsNullableType (TypeSpec type)
-               {
-                       throw new NotImplementedException ("net");
-               }
        }
 
-       public class Unwrap : Expression, IMemoryLocation, IAssignMethod
+       public class Unwrap : Expression, IMemoryLocation
        {
                Expression expr;
 
@@ -98,6 +97,11 @@ namespace Mono.CSharp.Nullable
                        eclass = expr.eclass;
                }
 
+               public override bool ContainsEmitWithAwait ()
+               {
+                       return expr.ContainsEmitWithAwait ();
+               }
+
                public static Expression Create (Expression expr)
                {
                        //
@@ -134,16 +138,24 @@ namespace Mono.CSharp.Nullable
                public override void Emit (EmitContext ec)
                {
                        Store (ec);
+
+                       var call = new CallEmitter ();
+                       call.InstanceExpression = this;
+
                        if (useDefaultValue)
-                               Invocation.EmitCall (ec, this, NullableInfo.GetGetValueOrDefault (expr.Type), null, loc);
+                               call.EmitPredefined (ec, NullableInfo.GetGetValueOrDefault (expr.Type), null);
                        else
-                               Invocation.EmitCall (ec, this, NullableInfo.GetValue (expr.Type), null, loc);
+                               call.EmitPredefined (ec, NullableInfo.GetValue (expr.Type), null);
                }
 
                public void EmitCheck (EmitContext ec)
                {
                        Store (ec);
-                       Invocation.EmitCall (ec, this, NullableInfo.GetHasValue (expr.Type), null, loc);
+
+                       var call = new CallEmitter ();
+                       call.InstanceExpression = this;
+
+                       call.EmitPredefined (ec, NullableInfo.GetHasValue (expr.Type), null);
                }
 
                public override bool Equals (object obj)
@@ -171,10 +183,10 @@ namespace Mono.CSharp.Nullable
 
                void Store (EmitContext ec)
                {
-                       if (expr is VariableReference)
+                       if (temp != null)
                                return;
 
-                       if (temp != null)
+                       if (expr is VariableReference)
                                return;
 
                        expr.Emit (ec);
@@ -213,51 +225,6 @@ namespace Mono.CSharp.Nullable
                                return temp;
                        }
                }
-
-               public void Emit (EmitContext ec, bool leave_copy)
-               {
-                       if (leave_copy)
-                               Load (ec);
-
-                       Emit (ec);
-               }
-
-               public void EmitAssign (EmitContext ec, Expression source,
-                                       bool leave_copy, bool prepare_for_load)
-               {
-                       InternalWrap wrap = new InternalWrap (source, expr.Type, loc);
-                       ((IAssignMethod) expr).EmitAssign (ec, wrap, leave_copy, false);
-               }
-
-               class InternalWrap : Expression
-               {
-                       public Expression expr;
-
-                       public InternalWrap (Expression expr, TypeSpec type, Location loc)
-                       {
-                               this.expr = expr;
-                               this.loc = loc;
-                               this.type = type;
-
-                               eclass = ExprClass.Value;
-                       }
-
-                       public override Expression CreateExpressionTree (ResolveContext ec)
-                       {
-                               throw new NotSupportedException ("ET");
-                       }
-
-                       protected override Expression DoResolve (ResolveContext ec)
-                       {
-                               return this;
-                       }
-
-                       public override void Emit (EmitContext ec)
-                       {
-                               expr.Emit (ec);
-                               ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
-                       }
-               }
        }
 
        //
@@ -282,7 +249,9 @@ namespace Mono.CSharp.Nullable
 
                public override void Emit (EmitContext ec)
                {
-                       Invocation.EmitCall (ec, Child, NullableInfo.GetValue (Child.Type), null, loc);
+                       var call = new CallEmitter ();
+                       call.InstanceExpression = Child;
+                       call.EmitPredefined (ec, NullableInfo.GetValue (Child.Type), null);
                }
        }
 
@@ -356,6 +325,7 @@ namespace Mono.CSharp.Nullable
                        value_target.AddressOf (ec, AddressOp.Store);
                        ec.Emit (OpCodes.Initobj, type);
                        value_target.Emit (ec);
+                       value_target.Release (ec);
                }
 
                public void AddressOf (EmitContext ec, AddressOp Mode)
@@ -388,6 +358,11 @@ namespace Mono.CSharp.Nullable
                        : this (expr, unwrap as Unwrap, type)
                {
                }
+
+               public override bool ContainsEmitWithAwait ()
+               {
+                       return unwrap.ContainsEmitWithAwait ();
+               }
                
                public override Expression CreateExpressionTree (ResolveContext ec)
                {
@@ -401,7 +376,7 @@ namespace Mono.CSharp.Nullable
                        //
                        if (unwrap == null) {
                                // S -> T? is wrap only
-                               if (TypeManager.IsNullableType (type))
+                               if (type.IsNullableType)
                                        return Wrap.Create (expr, type);
 
                                // S -> T can be simplified
@@ -409,13 +384,13 @@ namespace Mono.CSharp.Nullable
                        }
 
                        // Wrap target for T?
-                       if (TypeManager.IsNullableType (type)) {
+                       if (type.IsNullableType) {
                                expr = Wrap.Create (expr, type);
                                if (expr == null)
                                        return null;
 
                                null_value = LiftedNull.Create (type, loc);
-                       } else if (TypeManager.IsValueType (type)) {
+                       } else if (TypeSpec.IsValueType (type)) {
                                null_value = LiftedNull.Create (type, loc);
                        } else {
                                null_value = new NullConstant (type, loc);
@@ -521,18 +496,17 @@ namespace Mono.CSharp.Nullable
 
                Expression LiftExpression (ResolveContext ec, Expression expr)
                {
-                       TypeExpr lifted_type = new NullableType (expr.Type, expr.Location);
-                       lifted_type = lifted_type.ResolveAsTypeTerminal (ec, false);
-                       if (lifted_type == null)
+                       var lifted_type = new NullableType (expr.Type, expr.Location);
+                       if (lifted_type.ResolveAsType (ec) == null)
                                return null;
 
                        expr.Type = lifted_type.Type;
                        return expr;
                }
 
-               protected override Expression ResolveEnumOperator (ResolveContext ec, Expression expr)
+               protected override Expression ResolveEnumOperator (ResolveContext ec, Expression expr, TypeSpec[] predefined)
                {
-                       expr = base.ResolveEnumOperator (ec, expr);
+                       expr = base.ResolveEnumOperator (ec, expr, predefined);
                        if (expr == null)
                                return null;
 
@@ -573,8 +547,8 @@ namespace Mono.CSharp.Nullable
                bool IsBitwiseBoolean {
                        get {
                                return (Oper == Operator.BitwiseAnd || Oper == Operator.BitwiseOr) &&
-                               ((left_unwrap != null && left_unwrap.Type == TypeManager.bool_type) ||
-                                (right_unwrap != null && right_unwrap.Type == TypeManager.bool_type));
+                               ((left_unwrap != null && left_unwrap.Type.BuiltinType == BuiltinTypeSpec.Type.Bool) ||
+                                (right_unwrap != null && right_unwrap.Type.BuiltinType == BuiltinTypeSpec.Type.Bool));
                        }
                }
 
@@ -606,14 +580,14 @@ namespace Mono.CSharp.Nullable
                Constant CreateNullConstant (ResolveContext ec, Expression expr)
                {
                        // FIXME: Handle side effect constants
-                       Constant c = new BoolConstant (Oper == Operator.Inequality, loc).Resolve (ec);
+                       Constant c = new BoolConstant (ec.BuiltinTypes, Oper == Operator.Inequality, loc);
 
                        if ((Oper & Operator.EqualityMask) != 0) {
                                ec.Report.Warning (472, 2, loc, "The result of comparing value type `{0}' with null is `{1}'",
-                                       TypeManager.CSharpName (expr.Type), c.AsString ());
+                                       TypeManager.CSharpName (expr.Type), c.GetValueAsLiteral ());
                        } else {
                                ec.Report.Warning (464, 2, loc, "The result of comparing type `{0}' with null is always `{1}'",
-                                       TypeManager.CSharpName (expr.Type), c.AsString ());
+                                       TypeManager.CSharpName (expr.Type), c.GetValueAsLiteral ());
                        }
 
                        return ReducedExpression.Create (c, this);
@@ -628,14 +602,14 @@ namespace Mono.CSharp.Nullable
 
                        bool use_default_call = (Oper & (Operator.BitwiseMask | Operator.EqualityMask)) != 0;
                        left_orig = left;
-                       if (TypeManager.IsNullableType (left.Type)) {
+                       if (left.Type.IsNullableType) {
                                left = left_unwrap = Unwrap.Create (left, use_default_call);
                                if (left == null)
                                        return null;
                        }
 
                        right_orig = right;
-                       if (TypeManager.IsNullableType (right.Type)) {
+                       if (right.Type.IsNullableType) {
                                right = right_unwrap = Unwrap.Create (right, use_default_call);
                                if (right == null)
                                        return null;
@@ -649,17 +623,17 @@ namespace Mono.CSharp.Nullable
                        if (left_orig is NullLiteral) {
                                left = right;
                                state |= State.LeftNullLifted;
-                               type = TypeManager.bool_type;
+                               type = ec.BuiltinTypes.Bool;
                        }
 
                        if (right_orig.IsNull) {
                                if ((Oper & Operator.ShiftMask) != 0)
-                                       right = new EmptyExpression (TypeManager.int32_type);
+                                       right = new EmptyExpression (ec.BuiltinTypes.Int);
                                else
                                        right = left;
 
                                state |= State.RightNullLifted;
-                               type = TypeManager.bool_type;
+                               type = ec.BuiltinTypes.Bool;
                        }
 
                        eclass = ExprClass.Value;
@@ -680,7 +654,7 @@ namespace Mono.CSharp.Nullable
                        }
 
                        left_unwrap.Emit (ec);
-                       ec.Emit (OpCodes.Brtrue_S, load_right);
+                       ec.Emit (OpCodes.Brtrue, load_right);
 
                        // value & null, value | null
                        if (right_unwrap != null) {
@@ -736,7 +710,7 @@ namespace Mono.CSharp.Nullable
                        if (left_unwrap != null && (IsRightNullLifted || right.IsNull)) {
                                left_unwrap.EmitCheck (ec);
                                if (Oper == Binary.Operator.Equality) {
-                                       ec.Emit (OpCodes.Ldc_I4_0);
+                                       ec.EmitInt (0);
                                        ec.Emit (OpCodes.Ceq);
                                }
                                return;
@@ -745,7 +719,7 @@ namespace Mono.CSharp.Nullable
                        if (right_unwrap != null && (IsLeftNullLifted || left.IsNull)) {
                                right_unwrap.EmitCheck (ec);
                                if (Oper == Binary.Operator.Equality) {
-                                       ec.Emit (OpCodes.Ldc_I4_0);
+                                       ec.EmitInt (0);
                                        ec.Emit (OpCodes.Ceq);
                                }
                                return;
@@ -758,6 +732,11 @@ namespace Mono.CSharp.Nullable
                                user_operator.Emit (ec);
                                ec.Emit (Oper == Operator.Equality ? OpCodes.Brfalse_S : OpCodes.Brtrue_S, dissimilar_label);
                        } else {
+                               if (ec.HasSet (BuilderContext.Options.AsyncBody) && right.ContainsEmitWithAwait ()) {
+                                       left = left.EmitToField (ec);
+                                       right = right.EmitToField (ec);
+                               }
+
                                left.Emit (ec);
                                right.Emit (ec);
 
@@ -777,7 +756,7 @@ namespace Mono.CSharp.Nullable
                                        ec.Emit (OpCodes.Ceq);
                        } else {
                                if (Oper == Operator.Inequality) {
-                                       ec.Emit (OpCodes.Ldc_I4_0);
+                                       ec.EmitInt (0);
                                        ec.Emit (OpCodes.Ceq);
                                }
                        }
@@ -786,9 +765,9 @@ namespace Mono.CSharp.Nullable
 
                        ec.MarkLabel (dissimilar_label);
                        if (Oper == Operator.Inequality)
-                               ec.Emit (OpCodes.Ldc_I4_1);
+                               ec.EmitInt (1);
                        else
-                               ec.Emit (OpCodes.Ldc_I4_0);
+                               ec.EmitInt (0);
 
                        ec.MarkLabel (end_label);
                }
@@ -842,7 +821,7 @@ namespace Mono.CSharp.Nullable
                        ec.MarkLabel (is_null_label);
 
                        if ((Oper & Operator.ComparisonMask) != 0) {
-                               ec.Emit (OpCodes.Ldc_I4_0);
+                               ec.EmitInt (0);
                        } else {
                                LiftedNull.Create (type, loc).Emit (ec);
                        }
@@ -857,34 +836,38 @@ namespace Mono.CSharp.Nullable
                                return;
                        }
 
-                       if (TypeManager.IsNullableType (l))
-                               l = TypeManager.GetTypeArguments (l) [0];
+                       if (left.Type.IsNullableType) {
+                               l = NullableInfo.GetUnderlyingType (left.Type);
+                               left = EmptyCast.Create (left, l);
+                       }
+
+                       if (right.Type.IsNullableType) {
+                               right = EmptyCast.Create (right, NullableInfo.GetUnderlyingType (right.Type));
+                       }
 
                        base.EmitOperator (ec, l);
                }
 
                Expression LiftResult (ResolveContext ec, Expression res_expr)
                {
-                       TypeExpr lifted_type;
+                       TypeSpec lifted_type;
 
                        //
                        // Avoid double conversion
                        //
                        if (left_unwrap == null || IsLeftNullLifted || left_unwrap.Type != left.Type || (left_unwrap != null && IsRightNullLifted)) {
-                               lifted_type = new NullableType (left.Type, loc);
-                               lifted_type = lifted_type.ResolveAsTypeTerminal (ec, false);
+                               lifted_type = new NullableType (left.Type, loc).ResolveAsType (ec);
                                if (lifted_type == null)
                                        return null;
 
                                if (left is UserCast || left is TypeCast)
-                                       left.Type = lifted_type.Type;
+                                       left.Type = lifted_type;
                                else
-                                       left = EmptyCast.Create (left, lifted_type.Type);
+                                       left = EmptyCast.Create (left, lifted_type);
                        }
 
                        if (left != right && (right_unwrap == null || IsRightNullLifted || right_unwrap.Type != right.Type || (right_unwrap != null && IsLeftNullLifted))) {
-                               lifted_type = new NullableType (right.Type, loc);
-                               lifted_type = lifted_type.ResolveAsTypeTerminal (ec, false);
+                               lifted_type = new NullableType (right.Type, loc).ResolveAsType (ec);
                                if (lifted_type == null)
                                        return null;
 
@@ -893,19 +876,18 @@ namespace Mono.CSharp.Nullable
                                        r = ((ReducedExpression) r).OriginalExpression;
 
                                if (r is UserCast || r is TypeCast)
-                                       r.Type = lifted_type.Type;
+                                       r.Type = lifted_type;
                                else
-                                       right = EmptyCast.Create (right, lifted_type.Type);
+                                       right = EmptyCast.Create (right, lifted_type);
                        }
 
                        if ((Oper & Operator.ComparisonMask) == 0) {
-                               lifted_type = new NullableType (res_expr.Type, loc);
-                               lifted_type = lifted_type.ResolveAsTypeTerminal (ec, false);
+                               lifted_type = new NullableType (res_expr.Type, loc).ResolveAsType (ec);
                                if (lifted_type == null)
                                        return null;
 
-                               wrap_ctor = NullableInfo.GetConstructor (lifted_type.Type);
-                               type = res_expr.Type = lifted_type.Type;
+                               wrap_ctor = NullableInfo.GetConstructor (lifted_type);
+                               type = res_expr.Type = lifted_type;
                        }
 
                        if (IsLeftNullLifted) {
@@ -914,7 +896,7 @@ namespace Mono.CSharp.Nullable
                                //
                                // Special case for bool?, the result depends on both null right side and left side value
                                //
-                               if ((Oper == Operator.BitwiseAnd || Oper == Operator.BitwiseOr) && NullableInfo.GetUnderlyingType (type) == TypeManager.bool_type) {
+                               if ((Oper == Operator.BitwiseAnd || Oper == Operator.BitwiseOr) && NullableInfo.GetUnderlyingType (type).BuiltinType == BuiltinTypeSpec.Type.Bool) {
                                        return res_expr;
                                }
 
@@ -925,7 +907,7 @@ namespace Mono.CSharp.Nullable
                                // Value types and null comparison
                                //
                                if (right_unwrap == null || (Oper & Operator.RelationalMask) != 0)
-                                       return CreateNullConstant (ec, right_orig).Resolve (ec);
+                                       return CreateNullConstant (ec, right_orig);
                        }
 
                        if (IsRightNullLifted) {
@@ -934,7 +916,7 @@ namespace Mono.CSharp.Nullable
                                //
                                // Special case for bool?, the result depends on both null right side and left side value
                                //
-                               if ((Oper == Operator.BitwiseAnd || Oper == Operator.BitwiseOr) && NullableInfo.GetUnderlyingType (type) == TypeManager.bool_type) {
+                               if ((Oper == Operator.BitwiseAnd || Oper == Operator.BitwiseOr) && NullableInfo.GetUnderlyingType (type).BuiltinType == BuiltinTypeSpec.Type.Bool) {
                                        return res_expr;
                                }
 
@@ -998,7 +980,7 @@ namespace Mono.CSharp.Nullable
                        // Lift the result in the case it can be null and predefined or user operator
                        // result type is of a value type
                        //
-                       if (!TypeManager.IsValueType (expr.Type))
+                       if (!TypeSpec.IsValueType (expr.Type))
                                return null;
 
                        if (state != orig_state)
@@ -1025,6 +1007,18 @@ namespace Mono.CSharp.Nullable
                        this.right = right;
                        this.loc = loc;
                }
+
+               public Expression LeftExpression {
+                       get {
+                               return left;
+                       }
+               }
+
+               public Expression RightExpression {
+                       get {
+                               return right;
+                       }
+               }
                
                public override Expression CreateExpressionTree (ResolveContext ec)
                {
@@ -1063,7 +1057,7 @@ namespace Mono.CSharp.Nullable
                        // If left is a nullable type and an implicit conversion exists from right to underlying type of left,
                        // the result is underlying type of left
                        //
-                       if (TypeManager.IsNullableType (ltype)) {
+                       if (ltype.IsNullableType) {
                                unwrap = Unwrap.Create (left, false);
                                if (unwrap == null)
                                        return null;
@@ -1081,7 +1075,7 @@ namespace Mono.CSharp.Nullable
                                        //
                                        // If right is a dynamic expression, the result type is dynamic
                                        //
-                                       if (right.Type == InternalType.Dynamic) {
+                                       if (right.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                                type = right.Type;
 
                                                // Need to box underlying value type
@@ -1093,12 +1087,12 @@ namespace Mono.CSharp.Nullable
                                        type = ltype;
                                        return this;
                                }
-                       } else if (TypeManager.IsReferenceType (ltype)) {
+                       } else if (TypeSpec.IsReferenceType (ltype)) {
                                if (Convert.ImplicitConversionExists (ec, right, ltype)) {
                                        //
                                        // If right is a dynamic expression, the result type is dynamic
                                        //
-                                       if (right.Type == InternalType.Dynamic) {
+                                       if (right.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                                type = right.Type;
                                                return this;
                                        }
@@ -1108,7 +1102,7 @@ namespace Mono.CSharp.Nullable
                                        //
                                        Constant lc = left as Constant;
                                        if (lc != null && !lc.IsDefaultValue)
-                                               return ReducedExpression.Create (lc, this).Resolve (ec);
+                                               return ReducedExpression.Create (lc, this);
 
                                        //
                                        // Reduce (left ?? null) to left OR (null-constant ?? right) to right
@@ -1120,6 +1114,14 @@ namespace Mono.CSharp.Nullable
                                        type = ltype;
                                        return this;
                                }
+
+                               //
+                               // Special case null ?? null
+                               //
+                               if (ltype == right.Type) {
+                                       type = ltype;
+                                       return this;
+                               }
                        } else {
                                return null;
                        }
@@ -1132,13 +1134,21 @@ namespace Mono.CSharp.Nullable
                        // Reduce (null ?? right) to right
                        //
                        if (left.IsNull)
-                               return ReducedExpression.Create (right, this);
+                               return ReducedExpression.Create (right, this).Resolve (ec);
 
                        left = Convert.ImplicitConversion (ec, unwrap != null ? unwrap : left, rtype, loc);
                        type = rtype;
                        return this;
                }
 
+               public override bool ContainsEmitWithAwait ()
+               {
+                       if (unwrap != null)
+                               return unwrap.ContainsEmitWithAwait () || right.ContainsEmitWithAwait ();
+
+                       return left.ContainsEmitWithAwait () || right.ContainsEmitWithAwait ();
+               }
+
                protected override Expression DoResolve (ResolveContext ec)
                {
                        left = left.Resolve (ec);
@@ -1200,77 +1210,65 @@ namespace Mono.CSharp.Nullable
                        target.left = left.Clone (clonectx);
                        target.right = right.Clone (clonectx);
                }
-       }
-
-       public class LiftedUnaryMutator : ExpressionStatement
-       {
-               public readonly UnaryMutator.Mode Mode;
-               Expression expr;
-               UnaryMutator underlying;
-               Unwrap unwrap;
-
-               public LiftedUnaryMutator (UnaryMutator.Mode mode, Expression expr, Location loc)
+               
+               public override object Accept (StructuralVisitor visitor)
                {
-                       this.expr = expr;
-                       this.Mode = mode;
-                       this.loc = loc;
+                       return visitor.Visit (this);
                }
+       }
 
-               public override Expression CreateExpressionTree (ResolveContext ec)
+       class LiftedUnaryMutator : UnaryMutator
+       {
+               public LiftedUnaryMutator (Mode mode, Expression expr, Location loc)
+                       : base (mode, expr, loc)
                {
-                       return new SimpleAssign (this, this).CreateExpressionTree (ec);
                }
 
                protected override Expression DoResolve (ResolveContext ec)
                {
-                       expr = expr.Resolve (ec);
-                       if (expr == null)
-                               return null;
+                       var orig_expr = expr;
 
-                       unwrap = Unwrap.Create (expr, false);
-                       if (unwrap == null)
-                               return null;
+                       expr = Unwrap.Create (expr);
 
-                       underlying = (UnaryMutator) new UnaryMutator (Mode, unwrap, loc).Resolve (ec);
-                       if (underlying == null)
-                               return null;
+                       var res = base.DoResolveOperation (ec);
 
-
-                       eclass = ExprClass.Value;
+                       expr = orig_expr;
                        type = expr.Type;
-                       return this;
+
+                       return res;
                }
 
-               void DoEmit (EmitContext ec, bool is_expr)
+               protected override void EmitOperation (EmitContext ec)
                {
                        Label is_null_label = ec.DefineLabel ();
                        Label end_label = ec.DefineLabel ();
 
-                       unwrap.EmitCheck (ec);
+                       LocalTemporary lt = new LocalTemporary (type);
+
+                       // Value is on the stack
+                       lt.Store (ec);
+
+                       var call = new CallEmitter ();
+                       call.InstanceExpression = lt;
+                       call.EmitPredefined (ec, NullableInfo.GetHasValue (expr.Type), null);
+
                        ec.Emit (OpCodes.Brfalse, is_null_label);
 
-                       if (is_expr) {
-                               underlying.Emit (ec);
-                               ec.Emit (OpCodes.Br_S, end_label);
-                       } else {
-                               underlying.EmitStatement (ec);
-                       }
+                       call = new CallEmitter ();
+                       call.InstanceExpression = lt;
+                       call.EmitPredefined (ec, NullableInfo.GetValue (expr.Type), null);
 
-                       ec.MarkLabel (is_null_label);
-                       if (is_expr)
-                               LiftedNull.Create (type, loc).Emit (ec);
+                       lt.Release (ec);
 
-                       ec.MarkLabel (end_label);
-               }
+                       base.EmitOperation (ec);
 
-               public override void Emit (EmitContext ec)
-               {
-                       DoEmit (ec, true);
-               }
+                       ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
+                       ec.Emit (OpCodes.Br_S, end_label);
 
-               public override void EmitStatement (EmitContext ec)
-               {
-                       DoEmit (ec, false);
+                       ec.MarkLabel (is_null_label);
+                       LiftedNull.Create (type, loc).Emit (ec);
+
+                       ec.MarkLabel (end_label);
                }
        }
 }