2 // assign.cs: Assignments.
5 // Miguel de Icaza (miguel@ximian.com)
6 // Martin Baulig (martin@ximian.com)
7 // Marek Safar (marek.safar@gmail.com)
9 // Dual licensed under the terms of the MIT X11 or GNU GPL
11 // Copyright 2001, 2002, 2003 Ximian, Inc.
12 // Copyright 2004-2008 Novell, Inc
13 // Copyright 2011 Xamarin Inc
18 using IKVM.Reflection.Emit;
20 using System.Reflection.Emit;
23 namespace Mono.CSharp {
26 /// This interface is implemented by expressions that can be assigned to.
29 /// This interface is implemented by Expressions whose values can not
30 /// store the result on the top of the stack.
32 /// Expressions implementing this (Properties, Indexers and Arrays) would
33 /// perform an assignment of the Expression "source" into its final
36 /// No values on the top of the stack are expected to be left by
37 /// invoking this method.
39 public interface IAssignMethod {
41 // This is an extra version of Emit. If leave_copy is `true'
42 // A copy of the expression will be left on the stack at the
43 // end of the code generated for EmitAssign
45 void Emit (EmitContext ec, bool leave_copy);
48 // This method does the assignment
49 // `source' will be stored into the location specified by `this'
50 // if `leave_copy' is true, a copy of `source' will be left on the stack
51 // if `prepare_for_load' is true, when `source' is emitted, there will
52 // be data on the stack that it can use to compuatate its value. This is
53 // for expressions like a [f ()] ++, where you can't call `f ()' twice.
55 void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
58 For simple assignments, this interface is very simple, EmitAssign is called with source
59 as the source expression and leave_copy and prepare_for_load false.
61 For compound assignments it gets complicated.
63 EmitAssign will be called as before, however, prepare_for_load will be
64 true. The @source expression will contain an expression
65 which calls Emit. So, the calls look like:
67 this.EmitAssign (ec, source, false, true) ->
70 this.Emit (ec, false); ->
71 end this.Emit (ec, false); ->
74 end this.EmitAssign (ec, source, false, true)
77 When prepare_for_load is true, EmitAssign emits a `token' on the stack that
78 Emit will use for its state.
80 Let's take FieldExpr as an example. assume we are emitting f ().y += 1;
82 Here is the call tree again. This time, each call is annotated with the IL
85 this.EmitAssign (ec, source, false, true)
90 this.Emit (ec, false);
92 end this.Emit (ec, false);
102 end this.EmitAssign (ec, source, false, true)
105 1) EmitAssign left a token on the stack. It was the result of f ().
106 2) This token was used by Emit
108 leave_copy (in both EmitAssign and Emit) tells the compiler to leave a copy
109 of the expression at that point in evaluation. This is used for pre/post inc/dec
110 and for a = x += y. Let's do the above example with leave_copy true in EmitAssign
112 this.EmitAssign (ec, source, true, true)
117 this.Emit (ec, false);
119 end this.Emit (ec, false);
132 end this.EmitAssign (ec, source, true, true)
134 And with it true in Emit
136 this.EmitAssign (ec, source, false, true)
141 this.Emit (ec, true);
145 end this.Emit (ec, true);
156 end this.EmitAssign (ec, source, false, true)
158 Note that these two examples are what happens for ++x and x++, respectively.
163 /// An Expression to hold a temporary value.
166 /// The LocalTemporary class is used to hold temporary values of a given
167 /// type to "simulate" the expression semantics. The local variable is
170 /// The local temporary is used to alter the normal flow of code generation
171 /// basically it creates a local variable, and its emit instruction generates
172 /// code to access this value, return its address or save its value.
174 /// If `is_address' is true, then the value that we store is the address to the
175 /// real value, and not the value itself.
177 /// This is needed for a value type, because otherwise you just end up making a
178 /// copy of the value on the stack and modifying it. You really need a pointer
179 /// to the origional value so that you can modify it in that location. This
180 /// Does not happen with a class because a class is a pointer -- so you always
181 /// get the indirection.
184 public class LocalTemporary : Expression, IMemoryLocation, IAssignMethod {
185 LocalBuilder builder;
187 public LocalTemporary (TypeSpec t)
190 eclass = ExprClass.Value;
193 public LocalTemporary (LocalBuilder b, TypeSpec t)
199 public void Release (EmitContext ec)
201 ec.FreeTemporaryLocal (builder, type);
205 public override bool ContainsEmitWithAwait ()
210 public override Expression CreateExpressionTree (ResolveContext ec)
212 Arguments args = new Arguments (1);
213 args.Add (new Argument (this));
214 return CreateExpressionFactoryCall (ec, "Constant", args);
217 protected override Expression DoResolve (ResolveContext ec)
222 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
227 public override void Emit (EmitContext ec)
230 throw new InternalErrorException ("Emit without Store, or after Release");
232 ec.Emit (OpCodes.Ldloc, builder);
235 #region IAssignMethod Members
237 public void Emit (EmitContext ec, bool leave_copy)
245 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
248 throw new NotImplementedException ();
260 public LocalBuilder Builder {
261 get { return builder; }
264 public void Store (EmitContext ec)
267 builder = ec.GetTemporaryLocal (type);
269 ec.Emit (OpCodes.Stloc, builder);
272 public void AddressOf (EmitContext ec, AddressOp mode)
275 builder = ec.GetTemporaryLocal (type);
277 if (builder.LocalType.IsByRef) {
279 // if is_address, than this is just the address anyways,
280 // so we just return this.
282 ec.Emit (OpCodes.Ldloc, builder);
284 ec.Emit (OpCodes.Ldloca, builder);
290 /// The Assign node takes care of assigning the value of source into
291 /// the expression represented by target.
293 public abstract class Assign : ExpressionStatement {
294 protected Expression target, source;
296 protected Assign (Expression target, Expression source, Location loc)
298 this.target = target;
299 this.source = source;
303 public Expression Target {
304 get { return target; }
307 public Expression Source {
313 public override Location StartLocation {
315 return target.StartLocation;
319 public override bool ContainsEmitWithAwait ()
321 return target.ContainsEmitWithAwait () || source.ContainsEmitWithAwait ();
324 public override Expression CreateExpressionTree (ResolveContext ec)
326 ec.Report.Error (832, loc, "An expression tree cannot contain an assignment operator");
330 protected override Expression DoResolve (ResolveContext ec)
333 source = source.Resolve (ec);
335 if (source == null) {
337 source = EmptyExpression.Null;
340 target = target.ResolveLValue (ec, source);
342 if (target == null || !ok)
345 TypeSpec target_type = target.Type;
346 TypeSpec source_type = source.Type;
348 eclass = ExprClass.Value;
351 if (!(target is IAssignMethod)) {
352 target.Error_ValueAssignment (ec, source);
356 if (target_type != source_type) {
357 Expression resolved = ResolveConversions (ec);
359 if (resolved != this)
366 #if NET_4_0 || MONODROID
367 public override System.Linq.Expressions.Expression MakeExpression (BuilderContext ctx)
369 var tassign = target as IDynamicAssign;
371 throw new InternalErrorException (target.GetType () + " does not support dynamic assignment");
373 var target_object = tassign.MakeAssignExpression (ctx, source);
376 // Some hacking is needed as DLR does not support void type and requires
377 // always have object convertible return type to support caching and chaining
379 // We do this by introducing an explicit block which returns RHS value when
382 if (target_object.NodeType == System.Linq.Expressions.ExpressionType.Block)
383 return target_object;
385 System.Linq.Expressions.UnaryExpression source_object;
386 if (ctx.HasSet (BuilderContext.Options.CheckedScope)) {
387 source_object = System.Linq.Expressions.Expression.ConvertChecked (source.MakeExpression (ctx), target_object.Type);
389 source_object = System.Linq.Expressions.Expression.Convert (source.MakeExpression (ctx), target_object.Type);
392 return System.Linq.Expressions.Expression.Assign (target_object, source_object);
395 protected virtual Expression ResolveConversions (ResolveContext ec)
397 source = Convert.ImplicitConversionRequired (ec, source, target.Type, source.Location);
404 void Emit (EmitContext ec, bool is_statement)
406 IAssignMethod t = (IAssignMethod) target;
407 t.EmitAssign (ec, source, !is_statement, this is CompoundAssign);
410 public override void Emit (EmitContext ec)
415 public override void EmitStatement (EmitContext ec)
420 protected override void CloneTo (CloneContext clonectx, Expression t)
422 Assign _target = (Assign) t;
424 _target.target = target.Clone (clonectx);
425 _target.source = source.Clone (clonectx);
428 public override object Accept (StructuralVisitor visitor)
430 return visitor.Visit (this);
434 public class SimpleAssign : Assign
436 public SimpleAssign (Expression target, Expression source)
437 : this (target, source, target.Location)
441 public SimpleAssign (Expression target, Expression source, Location loc)
442 : base (target, source, loc)
446 bool CheckEqualAssign (Expression t)
448 if (source is Assign) {
449 Assign a = (Assign) source;
450 if (t.Equals (a.Target))
452 return a is SimpleAssign && ((SimpleAssign) a).CheckEqualAssign (t);
454 return t.Equals (source);
457 protected override Expression DoResolve (ResolveContext ec)
459 Expression e = base.DoResolve (ec);
460 if (e == null || e != this)
463 if (CheckEqualAssign (target))
464 ec.Report.Warning (1717, 3, loc, "Assignment made to same variable; did you mean to assign something else?");
470 public class RuntimeExplicitAssign : Assign
472 public RuntimeExplicitAssign (Expression target, Expression source)
473 : base (target, source, target.Location)
477 protected override Expression ResolveConversions (ResolveContext ec)
479 source = EmptyCast.Create (source, target.Type);
485 // Compiler generated assign
487 class CompilerAssign : Assign
489 public CompilerAssign (Expression target, Expression source, Location loc)
490 : base (target, source, loc)
492 if (target.Type != null) {
494 eclass = ExprClass.Value;
498 protected override Expression DoResolve (ResolveContext ec)
500 var expr = base.DoResolve (ec);
501 var vr = target as VariableReference;
502 if (vr != null && vr.VariableInfo != null)
503 vr.VariableInfo.IsEverAssigned = false;
508 public void UpdateSource (Expression source)
510 base.source = source;
515 // Implements fields and events class initializers
517 public class FieldInitializer : Assign
520 // Field initializers are tricky for partial classes. They have to
521 // share same constructor (block) for expression trees resolve but
522 // they have they own resolve scope
524 sealed class FieldInitializerContext : ResolveContext
526 ExplicitBlock ctor_block;
528 public FieldInitializerContext (IMemberContext mc, ResolveContext constructorContext)
529 : base (mc, Options.FieldInitializerScope | Options.ConstructorScope)
531 this.ctor_block = constructorContext.CurrentBlock.Explicit;
534 public override ExplicitBlock ConstructorBlock {
542 // Keep resolved value because field initializers have their own rules
544 ExpressionStatement resolved;
547 public FieldInitializer (FieldBase mc, Expression expression, Location loc)
548 : base (new FieldExpr (mc.Spec, expression.Location), expression, loc)
552 ((FieldExpr)target).InstanceExpression = new CompilerGeneratedThis (mc.CurrentType, expression.Location);
555 public override Location StartLocation {
561 protected override Expression DoResolve (ResolveContext ec)
563 // Field initializer can be resolved (fail) many times
567 if (resolved == null) {
568 var ctx = new FieldInitializerContext (mc, ec);
569 resolved = base.DoResolve (ctx) as ExpressionStatement;
575 public override void EmitStatement (EmitContext ec)
577 if (resolved == null)
581 // Emit sequence symbol info even if we are in compiler generated
582 // block to allow debugging field initializers when constructor is
583 // compiler generated
585 if (ec.HasSet (BuilderContext.Options.OmitDebugInfo) && ec.HasMethodSymbolBuilder) {
586 using (ec.With (BuilderContext.Options.OmitDebugInfo, false)) {
591 if (resolved != this)
592 resolved.EmitStatement (ec);
594 base.EmitStatement (ec);
597 public bool IsDefaultInitializer {
599 Constant c = source as Constant;
603 FieldExpr fe = (FieldExpr)target;
604 return c.IsDefaultInitializer (fe.Type);
608 public override bool IsSideEffectFree {
610 return source.IsSideEffectFree;
616 // This class is used for compound assignments.
618 public class CompoundAssign : Assign
620 // This is just a hack implemented for arrays only
621 public sealed class TargetExpression : Expression
623 readonly Expression child;
625 public TargetExpression (Expression child)
628 this.loc = child.Location;
631 public override bool ContainsEmitWithAwait ()
633 return child.ContainsEmitWithAwait ();
636 public override Expression CreateExpressionTree (ResolveContext ec)
638 throw new NotSupportedException ("ET");
641 protected override Expression DoResolve (ResolveContext ec)
644 eclass = ExprClass.Value;
648 public override void Emit (EmitContext ec)
653 public override Expression EmitToField (EmitContext ec)
655 return child.EmitToField (ec);
659 // Used for underlying binary operator
660 readonly Binary.Operator op;
664 public CompoundAssign (Binary.Operator op, Expression target, Expression source)
665 : base (target, source, target.Location)
671 public CompoundAssign (Binary.Operator op, Expression target, Expression source, Expression left)
672 : this (op, target, source)
677 public Binary.Operator Operator {
683 protected override Expression DoResolve (ResolveContext ec)
685 right = right.Resolve (ec);
689 MemberAccess ma = target as MemberAccess;
690 using (ec.Set (ResolveContext.Options.CompoundAssignmentScope)) {
691 target = target.Resolve (ec);
697 if (target is MethodGroupExpr){
698 ec.Report.Error (1656, loc,
699 "Cannot assign to `{0}' because it is a `{1}'",
700 ((MethodGroupExpr)target).Name, target.ExprClassName);
704 var event_expr = target as EventExpr;
705 if (event_expr != null) {
706 source = Convert.ImplicitConversionRequired (ec, right, target.Type, loc);
711 if (op == Binary.Operator.Addition)
712 rside = EmptyExpression.EventAddition;
713 else if (op == Binary.Operator.Subtraction)
714 rside = EmptyExpression.EventSubtraction;
718 target = target.ResolveLValue (ec, rside);
722 eclass = ExprClass.Value;
723 type = event_expr.Operator.ReturnType;
728 // Only now we can decouple the original source/target
729 // into a tree, to guarantee that we do not have side
733 left = new TargetExpression (target);
735 source = new Binary (op, left, right, true);
737 if (target is DynamicMemberAssignable) {
738 Arguments targs = ((DynamicMemberAssignable) target).Arguments;
739 source = source.Resolve (ec);
741 Arguments args = new Arguments (targs.Count + 1);
742 args.AddRange (targs);
743 args.Add (new Argument (source));
745 var binder_flags = CSharpBinderFlags.ValueFromCompoundAssignment;
748 // Compound assignment does target conversion using additional method
749 // call, set checked context as the binary operation can overflow
751 if (ec.HasSet (ResolveContext.Options.CheckedScope))
752 binder_flags |= CSharpBinderFlags.CheckedContext;
754 if (target is DynamicMemberBinder) {
755 source = new DynamicMemberBinder (ma.Name, binder_flags, args, loc).Resolve (ec);
757 // Handles possible event addition/subtraction
758 if (op == Binary.Operator.Addition || op == Binary.Operator.Subtraction) {
759 args = new Arguments (targs.Count + 1);
760 args.AddRange (targs);
761 args.Add (new Argument (right));
762 string method_prefix = op == Binary.Operator.Addition ?
763 Event.AEventAccessor.AddPrefix : Event.AEventAccessor.RemovePrefix;
765 var invoke = DynamicInvocation.CreateSpecialNameInvoke (
766 new MemberAccess (right, method_prefix + ma.Name, loc), args, loc).Resolve (ec);
768 args = new Arguments (targs.Count);
769 args.AddRange (targs);
770 source = new DynamicEventCompoundAssign (ma.Name, args,
771 (ExpressionStatement) source, (ExpressionStatement) invoke, loc).Resolve (ec);
774 source = new DynamicIndexBinder (binder_flags, args, loc).Resolve (ec);
780 return base.DoResolve (ec);
783 protected override Expression ResolveConversions (ResolveContext ec)
786 // LAMESPEC: Under dynamic context no target conversion is happening
787 // This allows more natual dynamic behaviour but breaks compatibility
788 // with static binding
790 if (target is RuntimeValueExpression)
793 TypeSpec target_type = target.Type;
796 // 1. the return type is implicitly convertible to the type of target
798 if (Convert.ImplicitConversionExists (ec, source, target_type)) {
799 source = Convert.ImplicitConversion (ec, source, target_type, loc);
804 // Otherwise, if the selected operator is a predefined operator
806 Binary b = source as Binary;
808 if (source is ReducedExpression)
809 b = ((ReducedExpression) source).OriginalExpression as Binary;
810 else if (source is ReducedExpression.ReducedConstantExpression) {
811 b = ((ReducedExpression.ReducedConstantExpression) source).OriginalExpression as Binary;
812 } else if (source is Nullable.LiftedBinaryOperator) {
813 var po = ((Nullable.LiftedBinaryOperator) source);
814 if (po.UserOperator == null)
816 } else if (source is TypeCast) {
817 b = ((TypeCast) source).Child as Binary;
823 // 2a. the operator is a shift operator
825 // 2b. the return type is explicitly convertible to the type of x, and
826 // y is implicitly convertible to the type of x
828 if ((b.Oper & Binary.Operator.ShiftMask) != 0 ||
829 Convert.ImplicitConversionExists (ec, right, target_type)) {
830 source = Convert.ExplicitConversion (ec, source, target_type, loc);
835 if (source.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
836 Arguments arg = new Arguments (1);
837 arg.Add (new Argument (source));
838 return new SimpleAssign (target, new DynamicConversion (target_type, CSharpBinderFlags.ConvertExplicit, arg, loc), loc).Resolve (ec);
841 right.Error_ValueCannotBeConverted (ec, target_type, false);
845 protected override void CloneTo (CloneContext clonectx, Expression t)
847 CompoundAssign ctarget = (CompoundAssign) t;
849 ctarget.right = ctarget.source = source.Clone (clonectx);
850 ctarget.target = target.Clone (clonectx);
853 public override object Accept (StructuralVisitor visitor)
855 return visitor.Visit (this);