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
15 using System
.Reflection
;
16 using System
.Reflection
.Emit
;
18 namespace Mono
.CSharp
{
21 /// This interface is implemented by expressions that can be assigned to.
24 /// This interface is implemented by Expressions whose values can not
25 /// store the result on the top of the stack.
27 /// Expressions implementing this (Properties, Indexers and Arrays) would
28 /// perform an assignment of the Expression "source" into its final
31 /// No values on the top of the stack are expected to be left by
32 /// invoking this method.
34 public interface IAssignMethod
{
36 // This is an extra version of Emit. If leave_copy is `true'
37 // A copy of the expression will be left on the stack at the
38 // end of the code generated for EmitAssign
40 void Emit (EmitContext ec
, bool leave_copy
);
43 // This method does the assignment
44 // `source' will be stored into the location specified by `this'
45 // if `leave_copy' is true, a copy of `source' will be left on the stack
46 // if `prepare_for_load' is true, when `source' is emitted, there will
47 // be data on the stack that it can use to compuatate its value. This is
48 // for expressions like a [f ()] ++, where you can't call `f ()' twice.
50 void EmitAssign (EmitContext ec
, Expression source
, bool leave_copy
, bool prepare_for_load
);
53 For simple assignments, this interface is very simple, EmitAssign is called with source
54 as the source expression and leave_copy and prepare_for_load false.
56 For compound assignments it gets complicated.
58 EmitAssign will be called as before, however, prepare_for_load will be
59 true. The @source expression will contain an expression
60 which calls Emit. So, the calls look like:
62 this.EmitAssign (ec, source, false, true) ->
65 this.Emit (ec, false); ->
66 end this.Emit (ec, false); ->
69 end this.EmitAssign (ec, source, false, true)
72 When prepare_for_load is true, EmitAssign emits a `token' on the stack that
73 Emit will use for its state.
75 Let's take FieldExpr as an example. assume we are emitting f ().y += 1;
77 Here is the call tree again. This time, each call is annotated with the IL
80 this.EmitAssign (ec, source, false, true)
85 this.Emit (ec, false);
87 end this.Emit (ec, false);
97 end this.EmitAssign (ec, source, false, true)
100 1) EmitAssign left a token on the stack. It was the result of f ().
101 2) This token was used by Emit
103 leave_copy (in both EmitAssign and Emit) tells the compiler to leave a copy
104 of the expression at that point in evaluation. This is used for pre/post inc/dec
105 and for a = x += y. Let's do the above example with leave_copy true in EmitAssign
107 this.EmitAssign (ec, source, true, true)
112 this.Emit (ec, false);
114 end this.Emit (ec, false);
127 end this.EmitAssign (ec, source, true, true)
129 And with it true in Emit
131 this.EmitAssign (ec, source, false, true)
136 this.Emit (ec, true);
140 end this.Emit (ec, true);
151 end this.EmitAssign (ec, source, false, true)
153 Note that these two examples are what happens for ++x and x++, respectively.
158 /// An Expression to hold a temporary value.
161 /// The LocalTemporary class is used to hold temporary values of a given
162 /// type to "simulate" the expression semantics on property and indexer
163 /// access whose return values are void.
165 /// The local temporary is used to alter the normal flow of code generation
166 /// basically it creates a local variable, and its emit instruction generates
167 /// code to access this value, return its address or save its value.
169 /// If `is_address' is true, then the value that we store is the address to the
170 /// real value, and not the value itself.
172 /// This is needed for a value type, because otherwise you just end up making a
173 /// copy of the value on the stack and modifying it. You really need a pointer
174 /// to the origional value so that you can modify it in that location. This
175 /// Does not happen with a class because a class is a pointer -- so you always
176 /// get the indirection.
179 public class LocalTemporary
: Expression
, IMemoryLocation
, IAssignMethod
{
180 LocalBuilder builder
;
182 public LocalTemporary (TypeSpec t
)
185 eclass
= ExprClass
.Value
;
188 public LocalTemporary (LocalBuilder b
, TypeSpec t
)
194 public void Release (EmitContext ec
)
196 ec
.FreeTemporaryLocal (builder
, type
);
200 public override Expression
CreateExpressionTree (ResolveContext ec
)
202 Arguments args
= new Arguments (1);
203 args
.Add (new Argument (this));
204 return CreateExpressionFactoryCall (ec
, "Constant", args
);
207 protected override Expression
DoResolve (ResolveContext ec
)
212 public override Expression
DoResolveLValue (ResolveContext ec
, Expression right_side
)
217 public override void Emit (EmitContext ec
)
220 throw new InternalErrorException ("Emit without Store, or after Release");
222 ec
.Emit (OpCodes
.Ldloc
, builder
);
225 #region IAssignMethod Members
227 public void Emit (EmitContext ec
, bool leave_copy
)
235 public void EmitAssign (EmitContext ec
, Expression source
, bool leave_copy
, bool prepare_for_load
)
237 if (prepare_for_load
)
238 throw new NotImplementedException ();
250 public LocalBuilder Builder
{
251 get { return builder; }
254 public void Store (EmitContext ec
)
257 builder
= ec
.GetTemporaryLocal (type
);
259 ec
.Emit (OpCodes
.Stloc
, builder
);
262 public void AddressOf (EmitContext ec
, AddressOp mode
)
265 builder
= ec
.GetTemporaryLocal (type
);
267 if (builder
.LocalType
.IsByRef
) {
269 // if is_address, than this is just the address anyways,
270 // so we just return this.
272 ec
.Emit (OpCodes
.Ldloc
, builder
);
274 ec
.Emit (OpCodes
.Ldloca
, builder
);
280 /// The Assign node takes care of assigning the value of source into
281 /// the expression represented by target.
283 public abstract class Assign
: ExpressionStatement
{
284 protected Expression target
, source
;
286 protected Assign (Expression target
, Expression source
, Location loc
)
288 this.target
= target
;
289 this.source
= source
;
293 public override Expression
CreateExpressionTree (ResolveContext ec
)
295 ec
.Report
.Error (832, loc
, "An expression tree cannot contain an assignment operator");
299 public Expression Target
{
300 get { return target; }
303 public Expression Source
{
304 get { return source; }
307 protected override Expression
DoResolve (ResolveContext ec
)
310 source
= source
.Resolve (ec
);
312 if (source
== null) {
314 source
= EmptyExpression
.Null
;
317 target
= target
.ResolveLValue (ec
, source
);
319 if (target
== null || !ok
)
322 TypeSpec target_type
= target
.Type
;
323 TypeSpec source_type
= source
.Type
;
325 eclass
= ExprClass
.Value
;
328 if (!(target
is IAssignMethod
)) {
329 Error_ValueAssignment (ec
, loc
);
333 if ((RootContext
.Version
== LanguageVersion
.ISO_1
) && (source
is MethodGroupExpr
)){
334 ((MethodGroupExpr
) source
).ReportUsageError (ec
);
338 if (!TypeManager
.IsEqual (target_type
, source_type
)) {
339 Expression resolved
= ResolveConversions (ec
);
341 if (resolved
!= this)
349 public override System
.Linq
.Expressions
.Expression
MakeExpression (BuilderContext ctx
)
351 var tassign
= target
as IDynamicAssign
;
353 throw new InternalErrorException (target
.GetType () + " does not support dynamic assignment");
355 var target_object
= tassign
.MakeAssignExpression (ctx
);
358 // Some hacking is needed as DLR does not support void type and requires
359 // always have object convertible return type to support caching and chaining
361 // We do this by introducing an explicit block which returns RHS value when
364 if (target_object
.NodeType
== System
.Linq
.Expressions
.ExpressionType
.Block
)
365 return target_object
;
367 var source_object
= System
.Linq
.Expressions
.Expression
.Convert (source
.MakeExpression (ctx
), target_object
.Type
);
368 return System
.Linq
.Expressions
.Expression
.Assign (target_object
, source_object
);
371 protected virtual Expression
ResolveConversions (ResolveContext ec
)
373 source
= Convert
.ImplicitConversionRequired (ec
, source
, target
.Type
, loc
);
380 void Emit (EmitContext ec
, bool is_statement
)
382 IAssignMethod t
= (IAssignMethod
) target
;
383 t
.EmitAssign (ec
, source
, !is_statement
, this is CompoundAssign
);
386 public override void Emit (EmitContext ec
)
391 public override void EmitStatement (EmitContext ec
)
396 protected override void CloneTo (CloneContext clonectx
, Expression t
)
398 Assign _target
= (Assign
) t
;
400 _target
.target
= target
.Clone (clonectx
);
401 _target
.source
= source
.Clone (clonectx
);
405 public class SimpleAssign
: Assign
{
406 public SimpleAssign (Expression target
, Expression source
)
407 : this (target
, source
, target
.Location
)
411 public SimpleAssign (Expression target
, Expression source
, Location loc
)
412 : base (target
, source
, loc
)
416 bool CheckEqualAssign (Expression t
)
418 if (source
is Assign
) {
419 Assign a
= (Assign
) source
;
420 if (t
.Equals (a
.Target
))
422 return a
is SimpleAssign
&& ((SimpleAssign
) a
).CheckEqualAssign (t
);
424 return t
.Equals (source
);
427 protected override Expression
DoResolve (ResolveContext ec
)
429 Expression e
= base.DoResolve (ec
);
430 if (e
== null || e
!= this)
433 if (CheckEqualAssign (target
))
434 ec
.Report
.Warning (1717, 3, loc
, "Assignment made to same variable; did you mean to assign something else?");
440 // This class implements fields and events class initializers
441 public class FieldInitializer
: Assign
444 // Keep resolved value because field initializers have their own rules
446 ExpressionStatement resolved
;
449 public FieldInitializer (FieldBase field
, Expression expression
, IMemberContext rc
)
450 : base (new FieldExpr (field
, expression
.Location
), expression
, expression
.Location
)
454 ((FieldExpr
)target
).InstanceExpression
= CompilerGeneratedThis
.Instance
;
457 protected override Expression
DoResolve (ResolveContext ec
)
459 // Field initializer can be resolved (fail) many times
463 if (resolved
== null) {
465 // Field initializers are tricky for partial classes. They have to
466 // share same constructor (block) but they have they own resolve scope.
469 IMemberContext old
= ec
.MemberContext
;
470 ec
.MemberContext
= rc
;
472 using (ec
.Set (ResolveContext
.Options
.FieldInitializerScope
)) {
473 resolved
= base.DoResolve (ec
) as ExpressionStatement
;
476 ec
.MemberContext
= old
;
482 public override void EmitStatement (EmitContext ec
)
484 if (resolved
== null)
487 if (resolved
!= this)
488 resolved
.EmitStatement (ec
);
490 base.EmitStatement (ec
);
493 public bool IsComplexInitializer
{
494 get { return !(source is Constant); }
497 public bool IsDefaultInitializer
{
499 Constant c
= source
as Constant
;
503 FieldExpr fe
= (FieldExpr
)target
;
504 return c
.IsDefaultInitializer (fe
.Type
);
509 class EventAddOrRemove
: ExpressionStatement
{
514 public EventAddOrRemove (Expression target
, Binary
.Operator op
, Expression source
, Location loc
)
516 this.target
= target
as EventExpr
;
518 this.source
= source
;
522 public override Expression
CreateExpressionTree (ResolveContext ec
)
524 return new SimpleAssign (target
, source
).CreateExpressionTree (ec
);
527 protected override Expression
DoResolve (ResolveContext ec
)
529 if (op
!= Binary
.Operator
.Addition
&& op
!= Binary
.Operator
.Subtraction
)
530 target
.Error_AssignmentEventOnly (ec
);
532 source
= source
.Resolve (ec
);
536 source
= Convert
.ImplicitConversionRequired (ec
, source
, target
.Type
, loc
);
540 eclass
= ExprClass
.Value
;
541 type
= TypeManager
.void_type
;
545 public override void Emit (EmitContext ec
)
547 if (RootContext
.EvalMode
)
550 throw new InternalErrorException ("don't know what to emit");
553 public override void EmitStatement (EmitContext ec
)
555 target
.EmitAddOrRemove (ec
, op
== Binary
.Operator
.Addition
, source
);
560 // This class is used for compound assignments.
562 public class CompoundAssign
: Assign
564 // This is just a hack implemented for arrays only
565 public sealed class TargetExpression
: Expression
568 public TargetExpression (Expression child
)
571 this.loc
= child
.Location
;
574 public override Expression
CreateExpressionTree (ResolveContext ec
)
576 throw new NotSupportedException ("ET");
579 protected override Expression
DoResolve (ResolveContext ec
)
582 eclass
= ExprClass
.Value
;
586 public override void Emit (EmitContext ec
)
592 // Used for underlying binary operator
593 readonly Binary
.Operator op
;
597 public CompoundAssign (Binary
.Operator op
, Expression target
, Expression source
)
598 : base (target
, source
, target
.Location
)
604 public CompoundAssign (Binary
.Operator op
, Expression target
, Expression source
, Expression left
)
605 : this (op
, target
, source
)
610 protected override Expression
DoResolve (ResolveContext ec
)
612 right
= right
.Resolve (ec
);
616 MemberAccess ma
= target
as MemberAccess
;
617 using (ec
.Set (ResolveContext
.Options
.CompoundAssignmentScope
)) {
618 target
= target
.Resolve (ec
);
624 if (target
is MethodGroupExpr
){
625 ec
.Report
.Error (1656, loc
,
626 "Cannot assign to `{0}' because it is a `{1}'",
627 ((MethodGroupExpr
)target
).Name
, target
.ExprClassName
);
631 if (target
is EventExpr
)
632 return new EventAddOrRemove (target
, op
, right
, loc
).Resolve (ec
);
635 // Only now we can decouple the original source/target
636 // into a tree, to guarantee that we do not have side
640 left
= new TargetExpression (target
);
642 source
= new Binary (op
, left
, right
, true, loc
);
644 if (target
is DynamicMemberBinder
) {
645 Arguments targs
= ((DynamicMemberBinder
) target
).Arguments
;
646 source
= source
.Resolve (ec
);
648 Arguments args
= new Arguments (2);
649 args
.AddRange (targs
);
650 args
.Add (new Argument (source
));
651 source
= new DynamicMemberBinder (ma
.Name
, args
, loc
).ResolveLValue (ec
, right
);
653 // Handles possible event addition/subtraction
654 if (op
== Binary
.Operator
.Addition
|| op
== Binary
.Operator
.Subtraction
) {
655 args
= new Arguments (2);
656 args
.AddRange (targs
);
657 args
.Add (new Argument (right
));
658 string method_prefix
= op
== Binary
.Operator
.Addition
?
659 Event
.AEventAccessor
.AddPrefix
: Event
.AEventAccessor
.RemovePrefix
;
661 var invoke
= DynamicInvocation
.CreateSpecialNameInvoke (
662 new MemberAccess (right
, method_prefix
+ ma
.Name
, loc
), args
, loc
).Resolve (ec
);
664 args
= new Arguments (1);
665 args
.AddRange (targs
);
666 source
= new DynamicEventCompoundAssign (ma
.Name
, args
,
667 (ExpressionStatement
) source
, (ExpressionStatement
) invoke
, loc
).Resolve (ec
);
673 return base.DoResolve (ec
);
676 protected override Expression
ResolveConversions (ResolveContext ec
)
678 TypeSpec target_type
= target
.Type
;
681 // 1. the return type is implicitly convertible to the type of target
683 if (Convert
.ImplicitConversionExists (ec
, source
, target_type
)) {
684 source
= Convert
.ImplicitConversion (ec
, source
, target_type
, loc
);
689 // Otherwise, if the selected operator is a predefined operator
691 Binary b
= source
as Binary
;
694 // 2a. the operator is a shift operator
696 // 2b. the return type is explicitly convertible to the type of x, and
697 // y is implicitly convertible to the type of x
699 if ((b
.Oper
& Binary
.Operator
.ShiftMask
) != 0 ||
700 Convert
.ImplicitConversionExists (ec
, right
, target_type
)) {
701 source
= Convert
.ExplicitConversion (ec
, source
, target_type
, loc
);
706 if (source
.Type
== InternalType
.Dynamic
) {
707 Arguments arg
= new Arguments (1);
708 arg
.Add (new Argument (source
));
709 return new SimpleAssign (target
, new DynamicConversion (target_type
, CSharpBinderFlags
.ConvertExplicit
, arg
, loc
), loc
).Resolve (ec
);
712 right
.Error_ValueCannotBeConverted (ec
, loc
, target_type
, false);
716 protected override void CloneTo (CloneContext clonectx
, Expression t
)
718 CompoundAssign ctarget
= (CompoundAssign
) t
;
720 ctarget
.right
= ctarget
.source
= source
.Clone (clonectx
);
721 ctarget
.target
= target
.Clone (clonectx
);