2 // assign.cs: Assignments.
5 // Miguel de Icaza (miguel@ximian.com)
6 // Martin Baulig (martin@ximian.com)
8 // (C) 2001, 2002, 2003 Ximian, Inc.
9 // (C) 2004 Novell, Inc
12 using System
.Reflection
;
13 using System
.Reflection
.Emit
;
15 namespace Mono
.CSharp
{
18 /// This interface is implemented by expressions that can be assigned to.
21 /// This interface is implemented by Expressions whose values can not
22 /// store the result on the top of the stack.
24 /// Expressions implementing this (Properties, Indexers and Arrays) would
25 /// perform an assignment of the Expression "source" into its final
28 /// No values on the top of the stack are expected to be left by
29 /// invoking this method.
31 public interface IAssignMethod
{
33 // This is an extra version of Emit. If leave_copy is `true'
34 // A copy of the expression will be left on the stack at the
35 // end of the code generated for EmitAssign
37 void Emit (EmitContext ec
, bool leave_copy
);
40 // This method does the assignment
41 // `source' will be stored into the location specified by `this'
42 // if `leave_copy' is true, a copy of `source' will be left on the stack
43 // if `prepare_for_load' is true, when `source' is emitted, there will
44 // be data on the stack that it can use to compuatate its value. This is
45 // for expressions like a [f ()] ++, where you can't call `f ()' twice.
47 void EmitAssign (EmitContext ec
, Expression source
, bool leave_copy
, bool prepare_for_load
);
50 For simple assignments, this interface is very simple, EmitAssign is called with source
51 as the source expression and leave_copy and prepare_for_load false.
53 For compound assignments it gets complicated.
55 EmitAssign will be called as before, however, prepare_for_load will be
56 true. The @source expression will contain an expression
57 which calls Emit. So, the calls look like:
59 this.EmitAssign (ec, source, false, true) ->
62 this.Emit (ec, false); ->
63 end this.Emit (ec, false); ->
66 end this.EmitAssign (ec, source, false, true)
69 When prepare_for_load is true, EmitAssign emits a `token' on the stack that
70 Emit will use for its state.
72 Let's take FieldExpr as an example. assume we are emitting f ().y += 1;
74 Here is the call tree again. This time, each call is annotated with the IL
77 this.EmitAssign (ec, source, false, true)
82 this.Emit (ec, false);
84 end this.Emit (ec, false);
94 end this.EmitAssign (ec, source, false, true)
97 1) EmitAssign left a token on the stack. It was the result of f ().
98 2) This token was used by Emit
100 leave_copy (in both EmitAssign and Emit) tells the compiler to leave a copy
101 of the expression at that point in evaluation. This is used for pre/post inc/dec
102 and for a = x += y. Let's do the above example with leave_copy true in EmitAssign
104 this.EmitAssign (ec, source, true, true)
109 this.Emit (ec, false);
111 end this.Emit (ec, false);
124 end this.EmitAssign (ec, source, true, true)
126 And with it true in Emit
128 this.EmitAssign (ec, source, false, true)
133 this.Emit (ec, true);
137 end this.Emit (ec, true);
148 end this.EmitAssign (ec, source, false, true)
150 Note that these two examples are what happens for ++x and x++, respectively.
155 /// An Expression to hold a temporary value.
158 /// The LocalTemporary class is used to hold temporary values of a given
159 /// type to "simulate" the expression semantics on property and indexer
160 /// access whose return values are void.
162 /// The local temporary is used to alter the normal flow of code generation
163 /// basically it creates a local variable, and its emit instruction generates
164 /// code to access this value, return its address or save its value.
166 /// If `is_address' is true, then the value that we store is the address to the
167 /// real value, and not the value itself.
169 /// This is needed for a value type, because otherwise you just end up making a
170 /// copy of the value on the stack and modifying it. You really need a pointer
171 /// to the origional value so that you can modify it in that location. This
172 /// Does not happen with a class because a class is a pointer -- so you always
173 /// get the indirection.
175 /// The `is_address' stuff is really just a hack. We need to come up with a better
176 /// way to handle it.
178 public class LocalTemporary
: Expression
, IMemoryLocation
{
179 LocalBuilder builder
;
182 public LocalTemporary (EmitContext ec
, Type t
) : this (ec
, t
, false) {}
184 public LocalTemporary (EmitContext ec
, Type t
, bool is_address
)
187 eclass
= ExprClass
.Value
;
189 builder
= ec
.GetTemporaryLocal (is_address
? TypeManager
.GetReferenceType (t
): t
);
190 this.is_address
= is_address
;
193 public LocalTemporary (LocalBuilder b
, Type t
)
196 eclass
= ExprClass
.Value
;
201 public void Release (EmitContext ec
)
203 ec
.FreeTemporaryLocal (builder
, type
);
207 public override Expression
DoResolve (EmitContext ec
)
212 public override void Emit (EmitContext ec
)
214 ILGenerator ig
= ec
.ig
;
216 ig
.Emit (OpCodes
.Ldloc
, builder
);
217 // we need to copy from the pointer
219 LoadFromPtr (ig
, type
);
222 // NB: if you have `is_address' on the stack there must
223 // be a managed pointer. Otherwise, it is the type from
225 public void Store (EmitContext ec
)
227 ILGenerator ig
= ec
.ig
;
228 ig
.Emit (OpCodes
.Stloc
, builder
);
231 public void AddressOf (EmitContext ec
, AddressOp mode
)
233 // if is_address, than this is just the address anyways,
234 // so we just return this.
235 ILGenerator ig
= ec
.ig
;
238 ig
.Emit (OpCodes
.Ldloc
, builder
);
240 ig
.Emit (OpCodes
.Ldloca
, builder
);
243 public bool PointsToAddress
{
251 /// The Assign node takes care of assigning the value of source into
252 /// the expression represented by target.
254 public class Assign
: ExpressionStatement
{
255 protected Expression target
, source
, real_source
;
256 protected LocalTemporary temp
= null, real_temp
= null;
257 protected Assign embedded
= null;
258 protected bool is_embedded
= false;
259 protected bool must_free_temp
= false;
261 public Assign (Expression target
, Expression source
)
262 : this (target
, source
, target
.Location
)
266 public Assign (Expression target
, Expression source
, Location l
)
268 this.target
= target
;
269 this.source
= this.real_source
= source
;
273 protected Assign (Assign embedded
, Location l
)
274 : this (embedded
.target
, embedded
.source
, l
)
276 this.is_embedded
= true;
279 protected virtual Assign
GetEmbeddedAssign (Location loc
)
281 return new Assign (this, loc
);
284 public Expression Target
{
294 public Expression Source
{
304 public static void error70 (EventInfo ei
, Location l
)
306 Report
.Error (70, l
, "The event `" + TypeManager
.CSharpSignature (ei
) +
307 "' can only appear on the left hand side of += or -= (except when" +
308 " used from within the type `" + ei
.DeclaringType
+ "')");
312 // Will return either `this' or an instance of `New'.
314 public override Expression
DoResolve (EmitContext ec
)
316 // Create an embedded assignment if our source is an assignment.
317 if (source
is Assign
)
318 source
= embedded
= ((Assign
) source
).GetEmbeddedAssign (loc
);
320 real_source
= source
= source
.Resolve (ec
);
321 if (source
== null) {
322 // Ensure that we don't propagate the error as spurious "uninitialized variable" errors.
323 target
= target
.ResolveLValue (ec
, EmptyExpression
.Null
, Location
);
328 // This is used in an embedded assignment.
329 // As an example, consider the statement "A = X = Y = Z".
331 if (is_embedded
&& !(source
is Constant
)) {
332 // If this is the innermost assignment (the "Y = Z" in our example),
333 // create a new temporary local, otherwise inherit that variable
334 // from our child (the "X = (Y = Z)" inherits the local from the
335 // "Y = Z" assignment).
337 if (embedded
== null) {
338 if (this is CompoundAssign
)
339 real_temp
= temp
= new LocalTemporary (ec
, target
.Type
);
341 real_temp
= temp
= new LocalTemporary (ec
, source
.Type
);
343 temp
= embedded
.temp
;
345 // Set the source to the new temporary variable.
346 // This means that the following target.ResolveLValue () will tell
347 // the target to read it's source value from that variable.
351 // If we have an embedded assignment, use the embedded assignment's temporary
352 // local variable as source.
353 if (embedded
!= null)
354 source
= (embedded
.temp
!= null) ? embedded
.temp
: embedded
.source
;
356 target
= target
.ResolveLValue (ec
, source
, Location
);
361 if (source
.Equals (target
)) {
362 Report
.Warning (1717, 3, loc
, "Assignment made to same variable; did you mean to assign something else?");
365 Type target_type
= target
.Type
;
366 Type source_type
= real_source
.Type
;
368 // If we're an embedded assignment, our parent will reuse our source as its
369 // source, it won't read from our target.
374 eclass
= ExprClass
.Value
;
377 if (target
is EventExpr
) {
378 EventInfo ei
= ((EventExpr
) target
).EventInfo
;
380 Expression ml
= MemberLookup (
381 ec
, ec
.ContainerType
, ei
.Name
,
382 MemberTypes
.Event
, AllBindingFlags
| BindingFlags
.DeclaredOnly
, loc
);
386 // If this is the case, then the Event does not belong
387 // to this Type and so, according to the spec
388 // is allowed to only appear on the left hand of
389 // the += and -= operators
391 // Note that target will not appear as an EventExpr
392 // in the case it is being referenced within the same type container;
393 // it will appear as a FieldExpr in that case.
396 if (!(source
is BinaryDelegate
)) {
403 FieldExpr field_exp
= target
as FieldExpr
;
404 if (field_exp
!= null && field_exp
.DeclaringType
.IsValueType
&& !ec
.IsConstructor
&& !ec
.IsFieldInitializer
) {
405 field_exp
= field_exp
.InstanceExpression
as FieldExpr
;
406 if (field_exp
!= null && field_exp
.FieldInfo
.IsInitOnly
) {
407 if (field_exp
.IsStatic
) {
408 Report
.Error (1650, loc
, "Fields of static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
409 field_exp
.GetSignatureForError ());
411 Report
.Error (1648, loc
, "Members of readonly field `{0}' cannot be modified (except in a constructor or a variable initializer)",
412 field_exp
.GetSignatureForError ());
418 if (!(target
is IAssignMethod
) && (target
.eclass
!= ExprClass
.EventAccess
)) {
419 Report
.Error (131, loc
,
420 "Left hand of an assignment must be a variable, " +
421 "a property or an indexer");
425 if ((source
.eclass
== ExprClass
.Type
) && (source
is TypeExpr
)) {
426 source
.Error_UnexpectedKind (ec
, "variable or value", loc
);
428 } else if ((RootContext
.Version
== LanguageVersion
.ISO_1
) &&
429 (source
is MethodGroupExpr
)){
430 ((MethodGroupExpr
) source
).ReportUsageError ();
435 if (target_type
== source_type
){
436 if (source
is New
&& target_type
.IsValueType
&&
437 (target
.eclass
!= ExprClass
.IndexerAccess
) && (target
.eclass
!= ExprClass
.PropertyAccess
)){
438 New n
= (New
) source
;
440 if (n
.SetValueTypeVariable (target
))
450 // If this assignment/operator was part of a compound binary
451 // operator, then we allow an explicit conversion, as detailed
455 if (this is CompoundAssign
){
456 CompoundAssign a
= (CompoundAssign
) this;
458 Binary b
= source
as Binary
;
461 // 1. if the source is explicitly convertible to the
465 source
= Convert
.ExplicitConversion (ec
, source
, target_type
, loc
);
467 a
.original_source
.Error_ValueCannotBeConverted (loc
, target_type
, true);
472 // 2. and the original right side is implicitly convertible to
473 // the type of target
475 if (Convert
.ImplicitStandardConversionExists (ec
, a
.original_source
, target_type
))
479 // In the spec 2.4 they added: or if type of the target is int
480 // and the operator is a shift operator...
482 if (source_type
== TypeManager
.int32_type
&&
483 (b
.Oper
== Binary
.Operator
.LeftShift
|| b
.Oper
== Binary
.Operator
.RightShift
))
486 a
.original_source
.Error_ValueCannotBeConverted (loc
, target_type
, false);
491 if (source
.eclass
== ExprClass
.MethodGroup
&& !TypeManager
.IsDelegateType (target_type
)) {
492 Report
.Error (428, source
.Location
, "Cannot convert method group `{0}' to non-delegate type `{1}'. Did you intend to invoke the method?",
493 ((MethodGroupExpr
)source
).Name
, target
.GetSignatureForError ());
497 source
= Convert
.ImplicitConversionRequired (ec
, source
, target_type
, loc
);
502 // If we're an embedded assignment, we need to create a new temporary variable
503 // for the converted value. Our parent will use this new variable as its source.
504 // The same applies when we have an embedded assignment - in this case, we need
505 // to convert our embedded assignment's temporary local variable to the correct
506 // type and store it in a new temporary local.
507 if (is_embedded
|| embedded
!= null) {
509 temp
= new LocalTemporary (ec
, type
);
510 must_free_temp
= true;
516 Expression
EmitEmbedded (EmitContext ec
)
518 // Emit an embedded assignment.
520 if (real_temp
!= null) {
521 // If we're the innermost assignment, `real_source' is the right-hand
522 // expression which gets assigned to all the variables left of it.
523 // Emit this expression and store its result in real_temp.
524 real_source
.Emit (ec
);
525 real_temp
.Store (ec
);
528 if (embedded
!= null)
529 embedded
.EmitEmbedded (ec
);
531 // This happens when we've done a type conversion, in this case source will be
532 // the expression which does the type conversion from real_temp.
533 // So emit it and store the result in temp; this is the var which will be read
535 if (temp
!= real_temp
) {
540 Expression temp_source
= (temp
!= null) ? temp
: source
;
541 ((IAssignMethod
) target
).EmitAssign (ec
, temp_source
, false, false);
545 void ReleaseEmbedded (EmitContext ec
)
547 if (embedded
!= null)
548 embedded
.ReleaseEmbedded (ec
);
550 if (real_temp
!= null)
551 real_temp
.Release (ec
);
557 void Emit (EmitContext ec
, bool is_statement
)
559 if (target
is EventExpr
) {
560 ((EventExpr
) target
).EmitAddOrRemove (ec
, source
);
564 IAssignMethod am
= (IAssignMethod
) target
;
566 Expression temp_source
;
567 if (embedded
!= null) {
568 temp_source
= embedded
.EmitEmbedded (ec
);
576 temp_source
= source
;
578 am
.EmitAssign (ec
, temp_source
, !is_statement
, this is CompoundAssign
);
580 if (embedded
!= null) {
583 embedded
.ReleaseEmbedded (ec
);
587 public override void Emit (EmitContext ec
)
592 public override void EmitStatement (EmitContext ec
)
600 // This class is used for compound assignments.
602 class CompoundAssign
: Assign
{
604 public Expression original_source
;
606 public CompoundAssign (Binary
.Operator op
, Expression target
, Expression source
)
607 : base (target
, source
, target
.Location
)
609 original_source
= source
;
613 protected CompoundAssign (CompoundAssign embedded
, Location l
)
614 : this (embedded
.op
, embedded
.target
, embedded
.source
)
616 this.is_embedded
= true;
619 protected override Assign
GetEmbeddedAssign (Location loc
)
621 return new CompoundAssign (this, loc
);
624 public Expression
ResolveSource (EmitContext ec
)
626 return original_source
.Resolve (ec
);
629 public override Expression
DoResolve (EmitContext ec
)
631 original_source
= original_source
.Resolve (ec
);
632 if (original_source
== null)
635 target
= target
.Resolve (ec
);
640 // Only now we can decouple the original source/target
641 // into a tree, to guarantee that we do not have side
644 source
= new Binary (op
, target
, original_source
);
645 return base.DoResolve (ec
);