2 // nullable.cs: Nullable types support
4 // Authors: Martin Baulig (martin@ximian.com)
5 // Miguel de Icaza (miguel@ximian.com)
6 // Marek Safar (marek.safar@gmail.com)
8 // Dual licensed under the terms of the MIT X11 or GNU GPL
10 // Copyright 2001, 2002, 2003 Ximian, Inc (http://www.ximian.com)
11 // Copyright 2004-2008 Novell, Inc
15 using System.Reflection;
16 using System.Reflection.Emit;
18 namespace Mono.CSharp.Nullable
20 public class NullableType : TypeExpr
24 public NullableType (TypeExpr underlying, Location l)
26 this.underlying = underlying;
29 eclass = ExprClass.Type;
32 public NullableType (TypeSpec type, Location loc)
33 : this (new TypeExpression (type, loc), loc)
36 protected override TypeExpr DoResolveAsTypeStep (IMemberContext ec)
38 if (TypeManager.generic_nullable_type == null) {
39 TypeManager.generic_nullable_type = TypeManager.CoreLookupType (ec.Compiler,
40 "System", "Nullable", 1, MemberKind.Struct, true);
43 TypeArguments args = new TypeArguments (underlying);
44 GenericTypeExpr ctype = new GenericTypeExpr (TypeManager.generic_nullable_type, args, loc);
45 return ctype.ResolveAsTypeTerminal (ec, false);
49 static class NullableInfo
51 public static MethodSpec GetConstructor (TypeSpec nullableType)
53 return TypeManager.GetPredefinedConstructor (nullableType, Location.Null, GetUnderlyingType (nullableType));
56 public static MethodSpec GetHasValue (TypeSpec nullableType)
58 return (MethodSpec) MemberCache.FindMember (nullableType,
59 MemberFilter.Method ("get_HasValue", 0, ParametersCompiled.EmptyReadOnlyParameters, null), BindingRestriction.None);
62 public static MethodSpec GetGetValueOrDefault (TypeSpec nullableType)
64 return (MethodSpec) MemberCache.FindMember (nullableType,
65 MemberFilter.Method ("GetValueOrDefault", 0, ParametersCompiled.EmptyReadOnlyParameters, null), BindingRestriction.None);
68 public static MethodSpec GetValue (TypeSpec nullableType)
70 return (MethodSpec) MemberCache.FindMember (nullableType,
71 MemberFilter.Method ("get_Value", 0, ParametersCompiled.EmptyReadOnlyParameters, null), BindingRestriction.None);
74 public static TypeSpec GetUnderlyingType (TypeSpec nullableType)
76 return ((InflatedTypeSpec) nullableType).TypeArguments[0];
79 public static bool IsNullableType (TypeSpec type)
81 throw new NotImplementedException ("net");
85 public class Unwrap : Expression, IMemoryLocation, IAssignMethod
90 readonly bool useDefaultValue;
92 Unwrap (Expression expr, bool useDefaultValue)
95 this.loc = expr.Location;
96 this.useDefaultValue = useDefaultValue;
98 type = NullableInfo.GetUnderlyingType (expr.Type);
102 public static Expression Create (Expression expr)
105 // Avoid unwraping and wraping of same type
107 Wrap wrap = expr as Wrap;
111 return Create (expr, false);
114 public static Unwrap Create (Expression expr, bool useDefaultValue)
116 return new Unwrap (expr, useDefaultValue);
119 public override Expression CreateExpressionTree (ResolveContext ec)
121 return expr.CreateExpressionTree (ec);
124 protected override Expression DoResolve (ResolveContext ec)
129 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
131 expr = expr.DoResolveLValue (ec, right_side);
135 public override void Emit (EmitContext ec)
139 Invocation.EmitCall (ec, this, NullableInfo.GetGetValueOrDefault (expr.Type), null, loc);
141 Invocation.EmitCall (ec, this, NullableInfo.GetValue (expr.Type), null, loc);
144 public void EmitCheck (EmitContext ec)
147 Invocation.EmitCall (ec, this, NullableInfo.GetHasValue (expr.Type), null, loc);
150 public override bool Equals (object obj)
152 Unwrap uw = obj as Unwrap;
153 return uw != null && expr.Equals (uw.expr);
156 public Expression Original {
162 public override int GetHashCode ()
164 return expr.GetHashCode ();
167 public override bool IsNull {
173 void Store (EmitContext ec)
175 if (expr is VariableReference)
182 LocalVariable.Store (ec);
185 public void Load (EmitContext ec)
187 if (expr is VariableReference)
190 LocalVariable.Emit (ec);
193 public override System.Linq.Expressions.Expression MakeExpression (BuilderContext ctx)
195 return expr.MakeExpression (ctx);
198 public void AddressOf (EmitContext ec, AddressOp mode)
200 IMemoryLocation ml = expr as VariableReference;
202 ml.AddressOf (ec, mode);
204 LocalVariable.AddressOf (ec, mode);
208 // Keeps result of non-variable expression
210 LocalTemporary LocalVariable {
213 temp = new LocalTemporary (expr.Type);
218 public void Emit (EmitContext ec, bool leave_copy)
226 public void EmitAssign (EmitContext ec, Expression source,
227 bool leave_copy, bool prepare_for_load)
229 InternalWrap wrap = new InternalWrap (source, expr.Type, loc);
230 ((IAssignMethod) expr).EmitAssign (ec, wrap, leave_copy, false);
233 class InternalWrap : Expression
235 public Expression expr;
237 public InternalWrap (Expression expr, TypeSpec type, Location loc)
243 eclass = ExprClass.Value;
246 public override Expression CreateExpressionTree (ResolveContext ec)
248 throw new NotSupportedException ("ET");
251 protected override Expression DoResolve (ResolveContext ec)
256 public override void Emit (EmitContext ec)
259 ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
264 public class Wrap : TypeCast
266 private Wrap (Expression expr, TypeSpec type)
269 eclass = ExprClass.Value;
272 public override Expression CreateExpressionTree (ResolveContext ec)
274 TypeCast child_cast = child as TypeCast;
275 if (child_cast != null) {
277 return child_cast.CreateExpressionTree (ec);
280 return base.CreateExpressionTree (ec);
283 public static Expression Create (Expression expr, TypeSpec type)
286 // Avoid unwraping and wraping of the same type
288 Unwrap unwrap = expr as Unwrap;
289 if (unwrap != null && expr.Type == NullableInfo.GetUnderlyingType (type))
290 return unwrap.Original;
292 return new Wrap (expr, type);
295 public override void Emit (EmitContext ec)
298 ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
303 // Represents null literal lifted to nullable type
305 public class LiftedNull : NullConstant, IMemoryLocation
307 private LiftedNull (TypeSpec nullable_type, Location loc)
308 : base (nullable_type, loc)
310 eclass = ExprClass.Value;
313 public static Constant Create (TypeSpec nullable, Location loc)
315 return new LiftedNull (nullable, loc);
318 public static Expression CreateFromExpression (ResolveContext ec, Expression e)
320 ec.Report.Warning (458, 2, e.Location, "The result of the expression is always `null' of type `{0}'",
321 TypeManager.CSharpName (e.Type));
323 return ReducedExpression.Create (Create (e.Type, e.Location), e);
326 public override void Emit (EmitContext ec)
328 // TODO: generate less temporary variables
329 LocalTemporary value_target = new LocalTemporary (type);
331 value_target.AddressOf (ec, AddressOp.Store);
332 ec.Emit (OpCodes.Initobj, type);
333 value_target.Emit (ec);
336 public void AddressOf (EmitContext ec, AddressOp Mode)
338 LocalTemporary value_target = new LocalTemporary (type);
340 value_target.AddressOf (ec, AddressOp.Store);
341 ec.Emit (OpCodes.Initobj, type);
342 ((IMemoryLocation) value_target).AddressOf (ec, Mode);
347 // Generic lifting expression, supports all S/S? -> T/T? cases
349 public class Lifted : Expression, IMemoryLocation
351 Expression expr, null_value;
354 public Lifted (Expression expr, Unwrap unwrap, TypeSpec type)
357 this.unwrap = unwrap;
358 this.loc = expr.Location;
362 public Lifted (Expression expr, Expression unwrap, TypeSpec type)
363 : this (expr, unwrap as Unwrap, type)
367 public override Expression CreateExpressionTree (ResolveContext ec)
369 return expr.CreateExpressionTree (ec);
372 protected override Expression DoResolve (ResolveContext ec)
375 // It's null when lifting non-nullable type
377 if (unwrap == null) {
378 // S -> T? is wrap only
379 if (TypeManager.IsNullableType (type))
380 return Wrap.Create (expr, type);
382 // S -> T can be simplified
386 // Wrap target for T?
387 if (TypeManager.IsNullableType (type)) {
388 expr = Wrap.Create (expr, type);
392 null_value = LiftedNull.Create (type, loc);
393 } else if (TypeManager.IsValueType (type)) {
394 null_value = LiftedNull.Create (type, loc);
396 null_value = new NullConstant (type, loc);
399 eclass = ExprClass.Value;
403 public override void Emit (EmitContext ec)
405 Label is_null_label = ec.DefineLabel ();
406 Label end_label = ec.DefineLabel ();
408 unwrap.EmitCheck (ec);
409 ec.Emit (OpCodes.Brfalse, is_null_label);
413 ec.Emit (OpCodes.Br, end_label);
414 ec.MarkLabel (is_null_label);
416 null_value.Emit (ec);
417 ec.MarkLabel (end_label);
420 public void AddressOf (EmitContext ec, AddressOp mode)
422 unwrap.AddressOf (ec, mode);
426 public class LiftedUnaryOperator : Unary, IMemoryLocation
429 Expression user_operator;
431 public LiftedUnaryOperator (Unary.Operator op, Expression expr, Location loc)
432 : base (op, expr, loc)
436 public void AddressOf (EmitContext ec, AddressOp mode)
438 unwrap.AddressOf (ec, mode);
441 public override Expression CreateExpressionTree (ResolveContext ec)
443 if (user_operator != null)
444 return user_operator.CreateExpressionTree (ec);
446 if (Oper == Operator.UnaryPlus)
447 return Expr.CreateExpressionTree (ec);
449 return base.CreateExpressionTree (ec);
452 protected override Expression DoResolve (ResolveContext ec)
454 unwrap = Unwrap.Create (Expr, false);
458 Expression res = base.ResolveOperator (ec, unwrap);
460 if (user_operator == null)
463 res = Expr = LiftExpression (ec, Expr);
469 eclass = ExprClass.Value;
474 public override void Emit (EmitContext ec)
476 Label is_null_label = ec.DefineLabel ();
477 Label end_label = ec.DefineLabel ();
479 unwrap.EmitCheck (ec);
480 ec.Emit (OpCodes.Brfalse, is_null_label);
482 if (user_operator != null) {
483 user_operator.Emit (ec);
485 EmitOperator (ec, NullableInfo.GetUnderlyingType (type));
488 ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
489 ec.Emit (OpCodes.Br_S, end_label);
491 ec.MarkLabel (is_null_label);
492 LiftedNull.Create (type, loc).Emit (ec);
494 ec.MarkLabel (end_label);
497 Expression LiftExpression (ResolveContext ec, Expression expr)
499 TypeExpr lifted_type = new NullableType (expr.Type, expr.Location);
500 lifted_type = lifted_type.ResolveAsTypeTerminal (ec, false);
501 if (lifted_type == null)
504 expr.Type = lifted_type.Type;
508 protected override Expression ResolveEnumOperator (ResolveContext ec, Expression expr)
510 expr = base.ResolveEnumOperator (ec, expr);
514 Expr = LiftExpression (ec, Expr);
515 return LiftExpression (ec, expr);
518 protected override Expression ResolveUserOperator (ResolveContext ec, Expression expr)
520 expr = base.ResolveUserOperator (ec, expr);
525 // When a user operator is of non-nullable type
527 if (Expr is Unwrap) {
528 user_operator = LiftExpression (ec, expr);
529 return user_operator;
536 public class LiftedBinaryOperator : Binary
538 Unwrap left_unwrap, right_unwrap;
539 bool left_null_lifted, right_null_lifted;
540 Expression left_orig, right_orig;
541 Expression user_operator;
542 MethodSpec wrap_ctor;
544 public LiftedBinaryOperator (Binary.Operator op, Expression left, Expression right, Location loc)
545 : base (op, left, right, loc)
549 public override Expression CreateExpressionTree (ResolveContext ec)
551 if (user_operator != null)
552 return user_operator.CreateExpressionTree (ec);
554 return base.CreateExpressionTree (ec);
558 // CSC 2 has this behavior, it allows structs to be compared
559 // with the null literal *outside* of a generics context and
560 // inlines that as true or false.
562 Expression CreateNullConstant (ResolveContext ec, Expression expr)
564 // FIXME: Handle side effect constants
565 Constant c = new BoolConstant (Oper == Operator.Inequality, loc).Resolve (ec);
567 if ((Oper & Operator.EqualityMask) != 0) {
568 ec.Report.Warning (472, 2, loc, "The result of comparing value type `{0}' with null is `{1}'",
569 TypeManager.CSharpName (expr.Type), c.AsString ());
571 ec.Report.Warning (464, 2, loc, "The result of comparing type `{0}' with null is always `{1}'",
572 TypeManager.CSharpName (expr.Type), c.AsString ());
575 return ReducedExpression.Create (c, this);
578 protected override Expression DoResolve (ResolveContext ec)
580 if ((Oper & Operator.LogicalMask) != 0) {
581 Error_OperatorCannotBeApplied (ec, left, right);
585 bool use_default_call = (Oper & (Operator.BitwiseMask | Operator.EqualityMask)) != 0;
587 if (TypeManager.IsNullableType (left.Type)) {
588 left = left_unwrap = Unwrap.Create (left, use_default_call);
594 if (TypeManager.IsNullableType (right.Type)) {
595 right = right_unwrap = Unwrap.Create (right, use_default_call);
601 // Some details are in 6.4.2, 7.2.7
602 // Arguments can be lifted for equal operators when the return type is bool and both
603 // arguments are of same type
605 if (left_orig.IsNull) {
607 left_null_lifted = true;
608 type = TypeManager.bool_type;
611 if (right_orig.IsNull) {
613 right_null_lifted = true;
614 type = TypeManager.bool_type;
617 eclass = ExprClass.Value;
618 return DoResolveCore (ec, left_orig, right_orig);
621 void EmitBitwiseBoolean (EmitContext ec)
623 Label load_left = ec.DefineLabel ();
624 Label load_right = ec.DefineLabel ();
625 Label end_label = ec.DefineLabel ();
627 left_unwrap.Emit (ec);
628 ec.Emit (OpCodes.Brtrue_S, load_right);
630 right_unwrap.Emit (ec);
631 ec.Emit (OpCodes.Brtrue_S, load_left);
633 left_unwrap.EmitCheck (ec);
634 ec.Emit (OpCodes.Brfalse_S, load_right);
637 ec.MarkLabel (load_left);
639 if (Oper == Operator.BitwiseAnd) {
640 left_unwrap.Load (ec);
642 right_unwrap.Load (ec);
643 right_unwrap = left_unwrap;
645 ec.Emit (OpCodes.Br_S, end_label);
648 ec.MarkLabel (load_right);
649 right_unwrap.Load (ec);
651 ec.MarkLabel (end_label);
655 // Emits optimized equality or inequality operator when possible
657 void EmitEquality (EmitContext ec)
660 // Either left or right is null
662 if (left_unwrap != null && (right_null_lifted || right.IsNull)) {
663 left_unwrap.EmitCheck (ec);
664 if (Oper == Binary.Operator.Equality) {
665 ec.Emit (OpCodes.Ldc_I4_0);
666 ec.Emit (OpCodes.Ceq);
671 if (right_unwrap != null && (left_null_lifted || left.IsNull)) {
672 right_unwrap.EmitCheck (ec);
673 if (Oper == Binary.Operator.Equality) {
674 ec.Emit (OpCodes.Ldc_I4_0);
675 ec.Emit (OpCodes.Ceq);
680 Label dissimilar_label = ec.DefineLabel ();
681 Label end_label = ec.DefineLabel ();
683 if (user_operator != null) {
684 user_operator.Emit (ec);
685 ec.Emit (Oper == Operator.Equality ? OpCodes.Brfalse_S : OpCodes.Brtrue_S, dissimilar_label);
690 ec.Emit (OpCodes.Bne_Un_S, dissimilar_label);
693 if (left_unwrap != null)
694 left_unwrap.EmitCheck (ec);
696 if (right_unwrap != null)
697 right_unwrap.EmitCheck (ec);
699 if (left_unwrap != null && right_unwrap != null) {
700 if (Oper == Operator.Inequality)
701 ec.Emit (OpCodes.Xor);
703 ec.Emit (OpCodes.Ceq);
705 if (Oper == Operator.Inequality) {
706 ec.Emit (OpCodes.Ldc_I4_0);
707 ec.Emit (OpCodes.Ceq);
711 ec.Emit (OpCodes.Br_S, end_label);
713 ec.MarkLabel (dissimilar_label);
714 if (Oper == Operator.Inequality)
715 ec.Emit (OpCodes.Ldc_I4_1);
717 ec.Emit (OpCodes.Ldc_I4_0);
719 ec.MarkLabel (end_label);
722 public override void EmitBranchable (EmitContext ec, Label target, bool onTrue)
725 ec.Emit (onTrue ? OpCodes.Brtrue : OpCodes.Brfalse, target);
728 public override void Emit (EmitContext ec)
731 // Optimize same expression operation
733 if (right_unwrap != null && right.Equals (left))
734 right_unwrap = left_unwrap;
736 if (user_operator == null && IsBitwiseBoolean) {
737 EmitBitwiseBoolean (ec);
741 if ((Oper & Operator.EqualityMask) != 0) {
746 Label is_null_label = ec.DefineLabel ();
747 Label end_label = ec.DefineLabel ();
749 if (left_unwrap != null) {
750 left_unwrap.EmitCheck (ec);
751 ec.Emit (OpCodes.Brfalse, is_null_label);
755 // Don't emit HasValue check when left and right expressions are same
757 if (right_unwrap != null && !left.Equals (right)) {
758 right_unwrap.EmitCheck (ec);
759 ec.Emit (OpCodes.Brfalse, is_null_label);
762 EmitOperator (ec, left.Type);
764 if (wrap_ctor != null)
765 ec.Emit (OpCodes.Newobj, wrap_ctor);
767 ec.Emit (OpCodes.Br_S, end_label);
768 ec.MarkLabel (is_null_label);
770 if ((Oper & Operator.ComparisonMask) != 0) {
771 ec.Emit (OpCodes.Ldc_I4_0);
773 LiftedNull.Create (type, loc).Emit (ec);
776 ec.MarkLabel (end_label);
779 protected override void EmitOperator (EmitContext ec, TypeSpec l)
781 if (user_operator != null) {
782 user_operator.Emit (ec);
786 if (TypeManager.IsNullableType (l))
787 l = TypeManager.GetTypeArguments (l) [0];
789 base.EmitOperator (ec, l);
792 bool IsBitwiseBoolean {
794 return (Oper & Operator.BitwiseMask) != 0 && left_unwrap != null && right_unwrap != null &&
795 left_unwrap.Type == TypeManager.bool_type && right_unwrap.Type == TypeManager.bool_type;
799 Expression LiftResult (ResolveContext ec, Expression res_expr)
801 TypeExpr lifted_type;
804 // Avoid double conversion
806 if (left_unwrap == null || left_null_lifted || left_unwrap.Type != left.Type || (left_unwrap != null && right_null_lifted)) {
807 lifted_type = new NullableType (left.Type, loc);
808 lifted_type = lifted_type.ResolveAsTypeTerminal (ec, false);
809 if (lifted_type == null)
812 if (left is UserCast || left is TypeCast)
813 left.Type = lifted_type.Type;
815 left = EmptyCast.Create (left, lifted_type.Type);
818 if (left != right && (right_unwrap == null || right_null_lifted || right_unwrap.Type != right.Type || (right_unwrap != null && left_null_lifted))) {
819 lifted_type = new NullableType (right.Type, loc);
820 lifted_type = lifted_type.ResolveAsTypeTerminal (ec, false);
821 if (lifted_type == null)
824 if (right is UserCast || right is TypeCast)
825 right.Type = lifted_type.Type;
827 right = EmptyCast.Create (right, lifted_type.Type);
830 if ((Oper & Operator.ComparisonMask) == 0) {
831 lifted_type = new NullableType (res_expr.Type, loc);
832 lifted_type = lifted_type.ResolveAsTypeTerminal (ec, false);
833 if (lifted_type == null)
836 wrap_ctor = NullableInfo.GetConstructor (lifted_type.Type);
837 type = res_expr.Type = lifted_type.Type;
840 if (left_null_lifted) {
841 left = LiftedNull.Create (right.Type, left.Location);
843 if ((Oper & (Operator.ArithmeticMask | Operator.ShiftMask | Operator.BitwiseMask)) != 0)
844 return LiftedNull.CreateFromExpression (ec, res_expr);
847 // Value types and null comparison
849 if (right_unwrap == null || (Oper & Operator.RelationalMask) != 0)
850 return CreateNullConstant (ec, right_orig).Resolve (ec);
853 if (right_null_lifted) {
854 right = LiftedNull.Create (left.Type, right.Location);
856 if ((Oper & (Operator.ArithmeticMask | Operator.ShiftMask | Operator.BitwiseMask)) != 0)
857 return LiftedNull.CreateFromExpression (ec, res_expr);
860 // Value types and null comparison
862 if (left_unwrap == null || (Oper & Operator.RelationalMask) != 0)
863 return CreateNullConstant (ec, left_orig);
869 protected override Expression ResolveOperatorPredefined (ResolveContext ec, Binary.PredefinedOperator [] operators, bool primitives_only, TypeSpec enum_type)
871 Expression e = base.ResolveOperatorPredefined (ec, operators, primitives_only, enum_type);
873 if (e == this || enum_type != null)
874 return LiftResult (ec, e);
877 // 7.9.9 Equality operators and null
879 // The == and != operators permit one operand to be a value of a nullable type and
880 // the other to be the null literal, even if no predefined or user-defined operator
881 // (in unlifted or lifted form) exists for the operation.
883 if (e == null && (Oper & Operator.EqualityMask) != 0) {
884 if ((left_null_lifted && right_unwrap != null) || (right_null_lifted && left_unwrap != null))
885 return LiftResult (ec, this);
891 protected override Expression ResolveUserOperator (ResolveContext ec, TypeSpec l, TypeSpec r)
893 Expression expr = base.ResolveUserOperator (ec, l, r);
897 expr = LiftResult (ec, expr);
898 if (expr is Constant)
902 user_operator = expr;
907 public class NullCoalescingOperator : Expression
909 Expression left, right;
912 public NullCoalescingOperator (Expression left, Expression right, Location loc)
919 public override Expression CreateExpressionTree (ResolveContext ec)
921 if (left is NullLiteral)
922 ec.Report.Error (845, loc, "An expression tree cannot contain a coalescing operator with null left side");
924 UserCast uc = left as UserCast;
925 Expression conversion = null;
929 Arguments c_args = new Arguments (2);
930 c_args.Add (new Argument (uc.CreateExpressionTree (ec)));
931 c_args.Add (new Argument (left.CreateExpressionTree (ec)));
932 conversion = CreateExpressionFactoryCall (ec, "Lambda", c_args);
935 Arguments args = new Arguments (3);
936 args.Add (new Argument (left.CreateExpressionTree (ec)));
937 args.Add (new Argument (right.CreateExpressionTree (ec)));
938 if (conversion != null)
939 args.Add (new Argument (conversion));
941 return CreateExpressionFactoryCall (ec, "Coalesce", args);
944 Expression ConvertExpression (ResolveContext ec)
946 // TODO: ImplicitConversionExists should take care of this
947 if (left.eclass == ExprClass.MethodGroup)
950 TypeSpec ltype = left.Type;
953 // If left is a nullable type and an implicit conversion exists from right to underlying type of left,
954 // the result is underlying type of left
956 if (TypeManager.IsNullableType (ltype)) {
957 unwrap = Unwrap.Create (left, false);
961 if (Convert.ImplicitConversionExists (ec, right, unwrap.Type)) {
964 right = Convert.ImplicitConversion (ec, right, type, loc);
967 } else if (TypeManager.IsReferenceType (ltype)) {
968 if (Convert.ImplicitConversionExists (ec, right, ltype)) {
970 // Reduce (constant ?? expr) to constant
972 Constant lc = left as Constant;
973 if (lc != null && !lc.IsDefaultValue)
974 return new SideEffectConstant (lc, right, loc).Resolve (ec);
977 // Reduce (left ?? null) to left OR (null-constant ?? right) to right
979 if (right.IsNull || lc != null)
980 return ReducedExpression.Create (lc != null ? right : left, this);
982 right = Convert.ImplicitConversion (ec, right, ltype, loc);
990 TypeSpec rtype = right.Type;
991 if (!Convert.ImplicitConversionExists (ec, unwrap != null ? unwrap : left, rtype) || right.eclass == ExprClass.MethodGroup)
995 // Reduce (null ?? right) to right
998 return ReducedExpression.Create (right, this);
1000 left = Convert.ImplicitConversion (ec, unwrap != null ? unwrap : left, rtype, loc);
1005 protected override Expression DoResolve (ResolveContext ec)
1007 left = left.Resolve (ec);
1008 right = right.Resolve (ec);
1010 if (left == null || right == null)
1013 eclass = ExprClass.Value;
1015 Expression e = ConvertExpression (ec);
1017 Binary.Error_OperatorCannotBeApplied (ec, left, right, "??", loc);
1024 public override void Emit (EmitContext ec)
1026 Label end_label = ec.DefineLabel ();
1028 if (unwrap != null) {
1029 Label is_null_label = ec.DefineLabel ();
1031 unwrap.EmitCheck (ec);
1032 ec.Emit (OpCodes.Brfalse, is_null_label);
1035 ec.Emit (OpCodes.Br, end_label);
1037 ec.MarkLabel (is_null_label);
1040 ec.MarkLabel (end_label);
1045 ec.Emit (OpCodes.Dup);
1047 // Only to make verifier happy
1048 if (left.Type.IsGenericParameter)
1049 ec.Emit (OpCodes.Box, left.Type);
1051 ec.Emit (OpCodes.Brtrue, end_label);
1053 ec.Emit (OpCodes.Pop);
1056 ec.MarkLabel (end_label);
1059 protected override void CloneTo (CloneContext clonectx, Expression t)
1061 NullCoalescingOperator target = (NullCoalescingOperator) t;
1063 target.left = left.Clone (clonectx);
1064 target.right = right.Clone (clonectx);
1068 public class LiftedUnaryMutator : ExpressionStatement
1070 public readonly UnaryMutator.Mode Mode;
1072 UnaryMutator underlying;
1075 public LiftedUnaryMutator (UnaryMutator.Mode mode, Expression expr, Location loc)
1082 public override Expression CreateExpressionTree (ResolveContext ec)
1084 return new SimpleAssign (this, this).CreateExpressionTree (ec);
1087 protected override Expression DoResolve (ResolveContext ec)
1089 expr = expr.Resolve (ec);
1093 unwrap = Unwrap.Create (expr, false);
1097 underlying = (UnaryMutator) new UnaryMutator (Mode, unwrap, loc).Resolve (ec);
1098 if (underlying == null)
1102 eclass = ExprClass.Value;
1107 void DoEmit (EmitContext ec, bool is_expr)
1109 Label is_null_label = ec.DefineLabel ();
1110 Label end_label = ec.DefineLabel ();
1112 unwrap.EmitCheck (ec);
1113 ec.Emit (OpCodes.Brfalse, is_null_label);
1116 underlying.Emit (ec);
1117 ec.Emit (OpCodes.Br_S, end_label);
1119 underlying.EmitStatement (ec);
1122 ec.MarkLabel (is_null_label);
1124 LiftedNull.Create (type, loc).Emit (ec);
1126 ec.MarkLabel (end_label);
1129 public override void Emit (EmitContext ec)
1134 public override void EmitStatement (EmitContext ec)