2 // assign.cs: Assignments.
5 // Miguel de Icaza (miguel@ximian.com)
6 // Martin Baulig (martin@gnome.org)
8 // (C) 2001, 2002, 2003 Ximian, Inc.
11 using System
.Reflection
;
12 using System
.Reflection
.Emit
;
14 namespace Mono
.CSharp
{
17 /// This interface is implemented by expressions that can be assigned to.
20 /// This interface is implemented by Expressions whose values can not
21 /// store the result on the top of the stack.
23 /// Expressions implementing this (Properties, Indexers and Arrays) would
24 /// perform an assignment of the Expression "source" into its final
27 /// No values on the top of the stack are expected to be left by
28 /// invoking this method.
30 public interface IAssignMethod
{
32 // This is an extra version of Emit. If leave_copy is `true'
33 // A copy of the expression will be left on the stack at the
34 // end of the code generated for EmitAssign
36 void Emit (EmitContext ec
, bool leave_copy
);
39 // This method does the assignment
40 // `source' will be stored into the location specified by `this'
41 // if `leave_copy' is true, a copy of `source' will be left on the stack
42 // if `prepare_for_load' is true, when `source' is emitted, there will
43 // be data on the stack that it can use to compuatate its value. This is
44 // for expressions like a [f ()] ++, where you can't call `f ()' twice.
46 void EmitAssign (EmitContext ec
, Expression source
, bool leave_copy
, bool prepare_for_load
);
49 For simple assignments, this interface is very simple, EmitAssign is called with source
50 as the source expression and leave_copy and prepare_for_load false.
52 For compound assignments it gets complicated.
54 EmitAssign will be called as before, however, prepare_for_load will be
55 true. The @source expression will contain an expression
56 which calls Emit. So, the calls look like:
58 this.EmitAssign (ec, source, false, true) ->
61 this.Emit (ec, false); ->
62 end this.Emit (ec, false); ->
65 end this.EmitAssign (ec, source, false, true)
68 When prepare_for_load is true, EmitAssign emits a `token' on the stack that
69 Emit will use for its state.
71 Let's take FieldExpr as an example. assume we are emitting f ().y += 1;
73 Here is the call tree again. This time, each call is annotated with the IL
76 this.EmitAssign (ec, source, false, true)
81 this.Emit (ec, false);
83 end this.Emit (ec, false);
93 end this.EmitAssign (ec, source, false, true)
96 1) EmitAssign left a token on the stack. It was the result of f ().
97 2) This token was used by Emit
99 leave_copy (in both EmitAssign and Emit) tells the compiler to leave a copy
100 of the expression at that point in evaluation. This is used for pre/post inc/dec
101 and for a = x += y. Let's do the above example with leave_copy true in EmitAssign
103 this.EmitAssign (ec, source, true, true)
108 this.Emit (ec, false);
110 end this.Emit (ec, false);
123 end this.EmitAssign (ec, source, true, true)
125 And with it true in Emit
127 this.EmitAssign (ec, source, false, true)
132 this.Emit (ec, true);
136 end this.Emit (ec, true);
147 end this.EmitAssign (ec, source, false, true)
149 Note that these two examples are what happens for ++x and x++, respectively.
154 /// An Expression to hold a temporary value.
157 /// The LocalTemporary class is used to hold temporary values of a given
158 /// type to "simulate" the expression semantics on property and indexer
159 /// access whose return values are void.
161 /// The local temporary is used to alter the normal flow of code generation
162 /// basically it creates a local variable, and its emit instruction generates
163 /// code to access this value, return its address or save its value.
165 /// If `is_address' is true, then the value that we store is the address to the
166 /// real value, and not the value itself.
168 /// This is needed for a value type, because otherwise you just end up making a
169 /// copy of the value on the stack and modifying it. You really need a pointer
170 /// to the origional value so that you can modify it in that location. This
171 /// Does not happen with a class because a class is a pointer -- so you always
172 /// get the indirection.
174 /// The `is_address' stuff is really just a hack. We need to come up with a better
175 /// way to handle it.
177 public class LocalTemporary
: Expression
, IMemoryLocation
{
178 LocalBuilder builder
;
181 public LocalTemporary (EmitContext ec
, Type t
) : this (ec
, t
, false) {}
183 public LocalTemporary (EmitContext ec
, Type t
, bool is_address
)
186 eclass
= ExprClass
.Value
;
188 builder
= ec
.GetTemporaryLocal (is_address
? TypeManager
.GetReferenceType (t
): t
);
189 this.is_address
= is_address
;
192 public LocalTemporary (LocalBuilder b
, Type t
)
195 eclass
= ExprClass
.Value
;
200 public void Release (EmitContext ec
)
202 ec
.FreeTemporaryLocal (builder
, type
);
206 public override Expression
DoResolve (EmitContext ec
)
211 public override void Emit (EmitContext ec
)
213 ILGenerator ig
= ec
.ig
;
215 ig
.Emit (OpCodes
.Ldloc
, builder
);
216 // we need to copy from the pointer
218 LoadFromPtr (ig
, type
);
221 // NB: if you have `is_address' on the stack there must
222 // be a managed pointer. Otherwise, it is the type from
224 public void Store (EmitContext ec
)
226 ILGenerator ig
= ec
.ig
;
227 ig
.Emit (OpCodes
.Stloc
, builder
);
230 public void AddressOf (EmitContext ec
, AddressOp mode
)
232 // if is_address, than this is just the address anyways,
233 // so we just return this.
234 ILGenerator ig
= ec
.ig
;
237 ig
.Emit (OpCodes
.Ldloc
, builder
);
239 ig
.Emit (OpCodes
.Ldloca
, builder
);
242 public bool PointsToAddress
{
250 /// The Assign node takes care of assigning the value of source into
251 /// the expression represented by target.
253 public class Assign
: ExpressionStatement
{
254 protected Expression target
, source
, real_source
;
255 protected LocalTemporary temp
= null, real_temp
= null;
256 protected Assign embedded
= null;
257 protected bool is_embedded
= false;
258 protected bool must_free_temp
= false;
260 public Assign (Expression target
, Expression source
, Location l
)
262 this.target
= target
;
263 this.source
= this.real_source
= source
;
267 protected Assign (Assign embedded
, Location l
)
268 : this (embedded
.target
, embedded
.source
, l
)
270 this.is_embedded
= true;
273 protected virtual Assign
GetEmbeddedAssign (Location loc
)
275 return new Assign (this, loc
);
278 public Expression Target
{
288 public Expression Source
{
298 public static void error70 (EventInfo ei
, Location l
)
300 Report
.Error (70, l
, "The event '" + ei
.Name
+
301 "' can only appear on the left-side of a += or -= (except when" +
302 " used from within the type '" + ei
.DeclaringType
+ "')");
306 // Will return either `this' or an instance of `New'.
308 public override Expression
DoResolve (EmitContext ec
)
310 // Create an embedded assignment if our source is an assignment.
311 if (source
is Assign
)
312 source
= embedded
= ((Assign
) source
).GetEmbeddedAssign (loc
);
314 real_source
= source
= source
.Resolve (ec
);
319 // This is used in an embedded assignment.
320 // As an example, consider the statement "A = X = Y = Z".
322 if (is_embedded
&& !(source
is Constant
)) {
323 // If this is the innermost assignment (the "Y = Z" in our example),
324 // create a new temporary local, otherwise inherit that variable
325 // from our child (the "X = (Y = Z)" inherits the local from the
326 // "Y = Z" assignment).
328 if (embedded
== null) {
329 if (this is CompoundAssign
)
330 real_temp
= temp
= new LocalTemporary (ec
, target
.Type
);
332 real_temp
= temp
= new LocalTemporary (ec
, source
.Type
);
334 temp
= embedded
.temp
;
336 // Set the source to the new temporary variable.
337 // This means that the following target.ResolveLValue () will tell
338 // the target to read it's source value from that variable.
342 // If we have an embedded assignment, use the embedded assignment's temporary
343 // local variable as source.
344 if (embedded
!= null)
345 source
= (embedded
.temp
!= null) ? embedded
.temp
: embedded
.source
;
347 target
= target
.ResolveLValue (ec
, source
);
352 Type target_type
= target
.Type
;
353 Type source_type
= real_source
.Type
;
355 // If we're an embedded assignment, our parent will reuse our source as its
356 // source, it won't read from our target.
361 eclass
= ExprClass
.Value
;
364 if (target
is EventExpr
) {
365 EventInfo ei
= ((EventExpr
) target
).EventInfo
;
367 Expression ml
= MemberLookup (
368 ec
, ec
.ContainerType
, ei
.Name
,
369 MemberTypes
.Event
, AllBindingFlags
| BindingFlags
.DeclaredOnly
, loc
);
373 // If this is the case, then the Event does not belong
374 // to this Type and so, according to the spec
375 // is allowed to only appear on the left hand of
376 // the += and -= operators
378 // Note that target will not appear as an EventExpr
379 // in the case it is being referenced within the same type container;
380 // it will appear as a FieldExpr in that case.
383 if (!(source
is BinaryDelegate
)) {
390 if (!(target
is IAssignMethod
) && (target
.eclass
!= ExprClass
.EventAccess
)) {
391 Report
.Error (131, loc
,
392 "Left hand of an assignment must be a variable, " +
393 "a property or an indexer");
397 if ((source
.eclass
== ExprClass
.Type
) && (source
is TypeExpr
)) {
398 source
.Error_UnexpectedKind ("variable or value", loc
);
400 } else if ((RootContext
.Version
== LanguageVersion
.ISO_1
) &&
401 (source
is MethodGroupExpr
)){
402 ((MethodGroupExpr
) source
).ReportUsageError ();
407 if (target_type
== source_type
){
408 if (source
is New
&& target_type
.IsValueType
&&
409 (target
.eclass
!= ExprClass
.IndexerAccess
) && (target
.eclass
!= ExprClass
.PropertyAccess
)){
410 New n
= (New
) source
;
412 if (n
.SetValueTypeVariable (target
))
422 // If this assignemnt/operator was part of a compound binary
423 // operator, then we allow an explicit conversion, as detailed
427 if (this is CompoundAssign
){
428 CompoundAssign a
= (CompoundAssign
) this;
430 Binary b
= source
as Binary
;
433 // 1. if the source is explicitly convertible to the
437 source
= Convert
.ExplicitConversion (ec
, source
, target_type
, loc
);
439 Convert
.Error_CannotImplicitConversion (loc
, source_type
, target_type
);
444 // 2. and the original right side is implicitly convertible to
445 // the type of target
447 if (Convert
.ImplicitStandardConversionExists (ec
, a
.original_source
, target_type
))
451 // In the spec 2.4 they added: or if type of the target is int
452 // and the operator is a shift operator...
454 if (source_type
== TypeManager
.int32_type
&&
455 (b
.Oper
== Binary
.Operator
.LeftShift
|| b
.Oper
== Binary
.Operator
.RightShift
))
458 Convert
.Error_CannotImplicitConversion (loc
, a
.original_source
.Type
, target_type
);
463 source
= Convert
.ImplicitConversionRequired (ec
, source
, target_type
, loc
);
467 // If we're an embedded assignment, we need to create a new temporary variable
468 // for the converted value. Our parent will use this new variable as its source.
469 // The same applies when we have an embedded assignment - in this case, we need
470 // to convert our embedded assignment's temporary local variable to the correct
471 // type and store it in a new temporary local.
472 if (is_embedded
|| embedded
!= null) {
474 temp
= new LocalTemporary (ec
, type
);
475 must_free_temp
= true;
481 Expression
EmitEmbedded (EmitContext ec
)
483 // Emit an embedded assignment.
485 if (real_temp
!= null) {
486 // If we're the innermost assignment, `real_source' is the right-hand
487 // expression which gets assigned to all the variables left of it.
488 // Emit this expression and store its result in real_temp.
489 real_source
.Emit (ec
);
490 real_temp
.Store (ec
);
493 if (embedded
!= null)
494 embedded
.EmitEmbedded (ec
);
496 // This happens when we've done a type conversion, in this case source will be
497 // the expression which does the type conversion from real_temp.
498 // So emit it and store the result in temp; this is the var which will be read
500 if (temp
!= real_temp
) {
505 Expression temp_source
= (temp
!= null) ? temp
: source
;
506 ((IAssignMethod
) target
).EmitAssign (ec
, temp_source
, false, false);
510 void ReleaseEmbedded (EmitContext ec
)
512 if (embedded
!= null)
513 embedded
.ReleaseEmbedded (ec
);
515 if (real_temp
!= null)
516 real_temp
.Release (ec
);
522 void Emit (EmitContext ec
, bool is_statement
)
524 if (target
is EventExpr
) {
525 ((EventExpr
) target
).EmitAddOrRemove (ec
, source
);
529 IAssignMethod am
= (IAssignMethod
) target
;
531 Expression temp_source
;
532 if (embedded
!= null) {
533 temp_source
= embedded
.EmitEmbedded (ec
);
541 temp_source
= source
;
543 am
.EmitAssign (ec
, temp_source
, !is_statement
, this is CompoundAssign
);
545 if (embedded
!= null) {
548 embedded
.ReleaseEmbedded (ec
);
552 public override void Emit (EmitContext ec
)
557 public override void EmitStatement (EmitContext ec
)
565 // This class is used for compound assignments.
567 class CompoundAssign
: Assign
{
569 public Expression original_source
;
571 public CompoundAssign (Binary
.Operator op
, Expression target
, Expression source
, Location l
)
572 : base (target
, source
, l
)
574 original_source
= source
;
578 protected CompoundAssign (CompoundAssign embedded
, Location l
)
579 : this (embedded
.op
, embedded
.target
, embedded
.source
, l
)
581 this.is_embedded
= true;
584 protected override Assign
GetEmbeddedAssign (Location loc
)
586 return new CompoundAssign (this, loc
);
589 public Expression
ResolveSource (EmitContext ec
)
591 return original_source
.Resolve (ec
);
594 public override Expression
DoResolve (EmitContext ec
)
596 original_source
= original_source
.Resolve (ec
);
597 if (original_source
== null)
600 target
= target
.Resolve (ec
);
605 // Only now we can decouple the original source/target
606 // into a tree, to guarantee that we do not have side
609 source
= new Binary (op
, target
, original_source
, loc
);
610 return base.DoResolve (ec
);