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 = ErrorExpression.Instance;
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 || MOBILE_DYNAMIC
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 public override void FlowAnalysis (FlowAnalysisContext fc)
422 source.FlowAnalysis (fc);
424 if (target is ArrayAccess || target is IndexerExpr || target is PropertyExpr)
425 target.FlowAnalysis (fc);
428 protected override void CloneTo (CloneContext clonectx, Expression t)
430 Assign _target = (Assign) t;
432 _target.target = target.Clone (clonectx);
433 _target.source = source.Clone (clonectx);
436 public override object Accept (StructuralVisitor visitor)
438 return visitor.Visit (this);
442 public class SimpleAssign : Assign
444 public SimpleAssign (Expression target, Expression source)
445 : this (target, source, target.Location)
449 public SimpleAssign (Expression target, Expression source, Location loc)
450 : base (target, source, loc)
454 bool CheckEqualAssign (Expression t)
456 if (source is Assign) {
457 Assign a = (Assign) source;
458 if (t.Equals (a.Target))
460 return a is SimpleAssign && ((SimpleAssign) a).CheckEqualAssign (t);
462 return t.Equals (source);
465 protected override Expression DoResolve (ResolveContext ec)
467 Expression e = base.DoResolve (ec);
468 if (e == null || e != this)
471 if (CheckEqualAssign (target))
472 ec.Report.Warning (1717, 3, loc, "Assignment made to same variable; did you mean to assign something else?");
477 public override void FlowAnalysis (FlowAnalysisContext fc)
479 base.FlowAnalysis (fc);
481 var vr = target as VariableReference;
483 if (vr.VariableInfo != null)
484 fc.SetVariableAssigned (vr.VariableInfo);
489 var fe = target as FieldExpr;
491 fe.SetFieldAssigned (fc);
496 public override void MarkReachable (Reachability rc)
498 var es = source as ExpressionStatement;
500 es.MarkReachable (rc);
504 public class RuntimeExplicitAssign : Assign
506 public RuntimeExplicitAssign (Expression target, Expression source)
507 : base (target, source, target.Location)
511 protected override Expression ResolveConversions (ResolveContext ec)
513 source = EmptyCast.Create (source, target.Type);
519 // Compiler generated assign
521 class CompilerAssign : Assign
523 public CompilerAssign (Expression target, Expression source, Location loc)
524 : base (target, source, loc)
526 if (target.Type != null) {
528 eclass = ExprClass.Value;
532 protected override Expression DoResolve (ResolveContext ec)
534 var expr = base.DoResolve (ec);
535 var vr = target as VariableReference;
536 if (vr != null && vr.VariableInfo != null)
537 vr.VariableInfo.IsEverAssigned = false;
542 public void UpdateSource (Expression source)
544 base.source = source;
549 // Implements fields and events class initializers
551 public class FieldInitializer : Assign
554 // Field initializers are tricky for partial classes. They have to
555 // share same constructor (block) for expression trees resolve but
556 // they have they own resolve scope
558 sealed class FieldInitializerContext : BlockContext
560 readonly ExplicitBlock ctor_block;
562 public FieldInitializerContext (IMemberContext mc, BlockContext constructorContext)
563 : base (mc, null, constructorContext.ReturnType)
565 flags |= Options.FieldInitializerScope | Options.ConstructorScope;
566 this.ctor_block = constructorContext.CurrentBlock.Explicit;
568 if (ctor_block.IsCompilerGenerated)
569 CurrentBlock = ctor_block;
572 public override ExplicitBlock ConstructorBlock {
580 // Keep resolved value because field initializers have their own rules
582 ExpressionStatement resolved;
585 public FieldInitializer (FieldBase mc, Expression expression, Location loc)
586 : base (new FieldExpr (mc.Spec, expression.Location), expression, loc)
590 ((FieldExpr)target).InstanceExpression = new CompilerGeneratedThis (mc.CurrentType, expression.Location);
593 public int AssignmentOffset { get; private set; }
595 public FieldBase Field {
601 public override Location StartLocation {
607 protected override Expression DoResolve (ResolveContext rc)
609 // Field initializer can be resolved (fail) many times
613 if (resolved == null) {
614 var bc = (BlockContext) rc;
615 var ctx = new FieldInitializerContext (mc, bc);
616 resolved = base.DoResolve (ctx) as ExpressionStatement;
617 AssignmentOffset = ctx.AssignmentInfoOffset - bc.AssignmentInfoOffset;
623 public override void EmitStatement (EmitContext ec)
625 if (resolved == null)
629 // Emit sequence symbol info even if we are in compiler generated
630 // block to allow debugging field initializers when constructor is
631 // compiler generated
633 if (ec.HasSet (BuilderContext.Options.OmitDebugInfo) && ec.HasMethodSymbolBuilder) {
634 using (ec.With (BuilderContext.Options.OmitDebugInfo, false)) {
639 if (resolved != this)
640 resolved.EmitStatement (ec);
642 base.EmitStatement (ec);
645 public override void FlowAnalysis (FlowAnalysisContext fc)
647 source.FlowAnalysis (fc);
650 public bool IsDefaultInitializer {
652 Constant c = source as Constant;
656 FieldExpr fe = (FieldExpr)target;
657 return c.IsDefaultInitializer (fe.Type);
661 public override bool IsSideEffectFree {
663 return source.IsSideEffectFree;
668 class PrimaryConstructorAssign : SimpleAssign
670 readonly Field field;
671 readonly Parameter parameter;
673 public PrimaryConstructorAssign (Field field, Parameter parameter)
674 : base (null, null, parameter.Location)
677 this.parameter = parameter;
680 protected override Expression DoResolve (ResolveContext rc)
682 target = new FieldExpr (field, loc);
683 source = rc.CurrentBlock.ParametersBlock.GetParameterInfo (parameter).CreateReferenceExpression (rc, loc);
684 return base.DoResolve (rc);
687 public override void EmitStatement (EmitContext ec)
689 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
690 base.EmitStatement (ec);
696 // This class is used for compound assignments.
698 public class CompoundAssign : Assign
700 // This is just a hack implemented for arrays only
701 public sealed class TargetExpression : Expression
703 readonly Expression child;
705 public TargetExpression (Expression child)
708 this.loc = child.Location;
711 public override bool ContainsEmitWithAwait ()
713 return child.ContainsEmitWithAwait ();
716 public override Expression CreateExpressionTree (ResolveContext ec)
718 throw new NotSupportedException ("ET");
721 protected override Expression DoResolve (ResolveContext ec)
724 eclass = ExprClass.Value;
728 public override void Emit (EmitContext ec)
733 public override Expression EmitToField (EmitContext ec)
735 return child.EmitToField (ec);
739 // Used for underlying binary operator
740 readonly Binary.Operator op;
744 public CompoundAssign (Binary.Operator op, Expression target, Expression source)
745 : base (target, source, target.Location)
751 public CompoundAssign (Binary.Operator op, Expression target, Expression source, Expression left)
752 : this (op, target, source)
757 public Binary.Operator Operator {
763 protected override Expression DoResolve (ResolveContext ec)
765 right = right.Resolve (ec);
769 MemberAccess ma = target as MemberAccess;
770 using (ec.Set (ResolveContext.Options.CompoundAssignmentScope)) {
771 target = target.Resolve (ec);
777 if (target is MethodGroupExpr){
778 ec.Report.Error (1656, loc,
779 "Cannot assign to `{0}' because it is a `{1}'",
780 ((MethodGroupExpr)target).Name, target.ExprClassName);
784 var event_expr = target as EventExpr;
785 if (event_expr != null) {
786 source = Convert.ImplicitConversionRequired (ec, right, target.Type, loc);
791 if (op == Binary.Operator.Addition)
792 rside = EmptyExpression.EventAddition;
793 else if (op == Binary.Operator.Subtraction)
794 rside = EmptyExpression.EventSubtraction;
798 target = target.ResolveLValue (ec, rside);
802 eclass = ExprClass.Value;
803 type = event_expr.Operator.ReturnType;
808 // Only now we can decouple the original source/target
809 // into a tree, to guarantee that we do not have side
813 left = new TargetExpression (target);
815 source = new Binary (op, left, right, true);
817 if (target is DynamicMemberAssignable) {
818 Arguments targs = ((DynamicMemberAssignable) target).Arguments;
819 source = source.Resolve (ec);
821 Arguments args = new Arguments (targs.Count + 1);
822 args.AddRange (targs);
823 args.Add (new Argument (source));
825 var binder_flags = CSharpBinderFlags.ValueFromCompoundAssignment;
828 // Compound assignment does target conversion using additional method
829 // call, set checked context as the binary operation can overflow
831 if (ec.HasSet (ResolveContext.Options.CheckedScope))
832 binder_flags |= CSharpBinderFlags.CheckedContext;
834 if (target is DynamicMemberBinder) {
835 source = new DynamicMemberBinder (ma.Name, binder_flags, args, loc).Resolve (ec);
837 // Handles possible event addition/subtraction
838 if (op == Binary.Operator.Addition || op == Binary.Operator.Subtraction) {
839 args = new Arguments (targs.Count + 1);
840 args.AddRange (targs);
841 args.Add (new Argument (right));
842 string method_prefix = op == Binary.Operator.Addition ?
843 Event.AEventAccessor.AddPrefix : Event.AEventAccessor.RemovePrefix;
845 var invoke = DynamicInvocation.CreateSpecialNameInvoke (
846 new MemberAccess (right, method_prefix + ma.Name, loc), args, loc).Resolve (ec);
848 args = new Arguments (targs.Count);
849 args.AddRange (targs);
850 source = new DynamicEventCompoundAssign (ma.Name, args,
851 (ExpressionStatement) source, (ExpressionStatement) invoke, loc).Resolve (ec);
854 source = new DynamicIndexBinder (binder_flags, args, loc).Resolve (ec);
860 return base.DoResolve (ec);
863 public override void FlowAnalysis (FlowAnalysisContext fc)
865 target.FlowAnalysis (fc);
866 source.FlowAnalysis (fc);
869 protected override Expression ResolveConversions (ResolveContext ec)
872 // LAMESPEC: Under dynamic context no target conversion is happening
873 // This allows more natual dynamic behaviour but breaks compatibility
874 // with static binding
876 if (target is RuntimeValueExpression)
879 TypeSpec target_type = target.Type;
882 // 1. the return type is implicitly convertible to the type of target
884 if (Convert.ImplicitConversionExists (ec, source, target_type)) {
885 source = Convert.ImplicitConversion (ec, source, target_type, loc);
890 // Otherwise, if the selected operator is a predefined operator
892 Binary b = source as Binary;
894 if (source is ReducedExpression)
895 b = ((ReducedExpression) source).OriginalExpression as Binary;
896 else if (source is ReducedExpression.ReducedConstantExpression) {
897 b = ((ReducedExpression.ReducedConstantExpression) source).OriginalExpression as Binary;
898 } else if (source is Nullable.LiftedBinaryOperator) {
899 var po = ((Nullable.LiftedBinaryOperator) source);
900 if (po.UserOperator == null)
902 } else if (source is TypeCast) {
903 b = ((TypeCast) source).Child as Binary;
909 // 2a. the operator is a shift operator
911 // 2b. the return type is explicitly convertible to the type of x, and
912 // y is implicitly convertible to the type of x
914 if ((b.Oper & Binary.Operator.ShiftMask) != 0 ||
915 Convert.ImplicitConversionExists (ec, right, target_type)) {
916 source = Convert.ExplicitConversion (ec, source, target_type, loc);
921 if (source.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
922 Arguments arg = new Arguments (1);
923 arg.Add (new Argument (source));
924 return new SimpleAssign (target, new DynamicConversion (target_type, CSharpBinderFlags.ConvertExplicit, arg, loc), loc).Resolve (ec);
927 right.Error_ValueCannotBeConverted (ec, target_type, false);
931 protected override void CloneTo (CloneContext clonectx, Expression t)
933 CompoundAssign ctarget = (CompoundAssign) t;
935 ctarget.right = ctarget.source = source.Clone (clonectx);
936 ctarget.target = target.Clone (clonectx);
939 public override object Accept (StructuralVisitor visitor)
941 return visitor.Visit (this);