2 // assign.cs: Assignments.
5 // Miguel de Icaza (miguel@ximian.com)
6 // Martin Baulig (martin@gnome.org)
8 // (C) 2001, 2002 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 method will emit the code for the actual assignment
34 void EmitAssign (EmitContext ec, Expression source);
37 // This method is invoked before any code generation takes
38 // place, and it is a mechanism to inform that the expression
39 // will be invoked more than once, and that the method should
40 // use temporary values to avoid having side effects
42 // Example: a [ g () ] ++
44 void CacheTemporaries (EmitContext ec);
48 /// An Expression to hold a temporary value.
51 /// The LocalTemporary class is used to hold temporary values of a given
52 /// type to "simulate" the expression semantics on property and indexer
53 /// access whose return values are void.
55 /// The local temporary is used to alter the normal flow of code generation
56 /// basically it creates a local variable, and its emit instruction generates
57 /// code to access this value, return its address or save its value.
59 public class LocalTemporary : Expression, IMemoryLocation {
62 public LocalTemporary (EmitContext ec, Type t)
65 eclass = ExprClass.Value;
67 builder = ec.GetTemporaryStorage (t);
70 public void Release (EmitContext ec)
72 ec.FreeTemporaryStorage (builder);
76 public LocalTemporary (LocalBuilder b, Type t)
79 eclass = ExprClass.Value;
84 public override Expression DoResolve (EmitContext ec)
89 public override void Emit (EmitContext ec)
91 ec.ig.Emit (OpCodes.Ldloc, builder);
94 public void Store (EmitContext ec)
96 ec.ig.Emit (OpCodes.Stloc, builder);
99 public void AddressOf (EmitContext ec, AddressOp mode)
101 ec.ig.Emit (OpCodes.Ldloca, builder);
106 /// The Assign node takes care of assigning the value of source into
107 /// the expression represented by target.
109 public class Assign : ExpressionStatement {
110 protected Expression target, source, real_source;
111 protected LocalTemporary temp = null, real_temp = null;
112 protected Assign embedded = null;
113 protected bool is_embedded = false;
114 protected bool must_free_temp = false;
116 public Assign (Expression target, Expression source, Location l)
118 this.target = target;
119 this.source = this.real_source = source;
123 protected Assign (Assign embedded, Location l)
124 : this (embedded.target, embedded.source, l)
126 this.is_embedded = true;
129 public Expression Target {
139 public Expression Source {
149 public static void error70 (EventInfo ei, Location l)
151 Report.Error (70, l, "The event '" + ei.Name +
152 "' can only appear on the left-side of a += or -= (except when" +
153 " used from within the type '" + ei.DeclaringType + "')");
157 // Will return either `this' or an instance of `New'.
159 public override Expression DoResolve (EmitContext ec)
161 // Create an embedded assignment if our source is an assignment.
162 if (source is Assign)
163 source = embedded = new Assign ((Assign) source, loc);
165 real_source = source = source.Resolve (ec);
170 // This is used in an embedded assignment.
171 // As an example, consider the statement "A = X = Y = Z".
173 if (is_embedded && !(source is Constant)) {
174 // If this is the innermost assignment (the "Y = Z" in our example),
175 // create a new temporary local, otherwise inherit that variable
176 // from our child (the "X = (Y = Z)" inherits the local from the
177 // "Y = Z" assignment).
178 if (embedded == null)
179 real_temp = temp = new LocalTemporary (ec, source.Type);
181 temp = embedded.temp;
183 // Set the source to the new temporary variable.
184 // This means that the following target.ResolveLValue () will tell
185 // the target to read it's source value from that variable.
189 // If we have an embedded assignment, use the embedded assignment's temporary
190 // local variable as source.
191 if (embedded != null)
192 source = (embedded.temp != null) ? embedded.temp : embedded.source;
194 target = target.ResolveLValue (ec, source);
199 Type target_type = target.Type;
200 Type source_type = real_source.Type;
202 // If we're an embedded assignment, our parent will reuse our source as its
203 // source, it won't read from our target.
208 eclass = ExprClass.Value;
211 // If we are doing a property assignment, then
212 // set the `value' field on the property, and Resolve
215 if (target is PropertyExpr){
216 PropertyExpr property_assign = (PropertyExpr) target;
218 if (source_type != target_type){
219 source = ConvertImplicitRequired (ec, source, target_type, loc);
225 // FIXME: Maybe handle this in the LValueResolve
227 if (!property_assign.VerifyAssignable ())
233 if (target is IndexerAccess) {
237 if (target is EventExpr) {
240 EventInfo ei = ((EventExpr) target).EventInfo;
243 Expression ml = MemberLookup (
244 ec, ec.ContainerType, ei.Name,
245 MemberTypes.Event, AllBindingFlags, loc);
249 // If this is the case, then the Event does not belong
250 // to this Type and so, according to the spec
251 // is allowed to only appear on the left hand of
252 // the += and -= operators
254 // Note that target will not appear as an EventExpr
255 // in the case it is being referenced within the same type container;
256 // it will appear as a FieldExpr in that case.
259 if (!(source is Binary)) {
263 tmp = ((Binary) source);
264 if (tmp.Oper != Binary.Operator.Addition &&
265 tmp.Oper != Binary.Operator.Subtraction) {
273 if (source is New && target_type.IsValueType){
274 New n = (New) source;
276 n.ValueTypeVariable = target;
280 if (target.eclass != ExprClass.Variable && target.eclass != ExprClass.EventAccess){
281 Report.Error (131, loc,
282 "Left hand of an assignment must be a variable, " +
283 "a property or an indexer");
287 if ((source.eclass == ExprClass.Type) && (source is TypeExpr)) {
288 source.Error118 ("variable or value");
290 } else if (source is MethodGroupExpr){
291 ((MethodGroupExpr) source).ReportUsageError ();
295 if (target_type == source_type)
299 // If this assignemnt/operator was part of a compound binary
300 // operator, then we allow an explicit conversion, as detailed
304 if (this is CompoundAssign){
305 CompoundAssign a = (CompoundAssign) this;
307 Binary b = source as Binary;
308 if (b != null && b.IsBuiltinOperator){
310 // 1. if the source is explicitly convertible to the
314 source = ConvertExplicit (ec, source, target_type, loc);
316 Error_CannotConvertImplicit (loc, source_type, target_type);
321 // 2. and the original right side is implicitly convertible to
322 // the type of target_type.
324 if (StandardConversionExists (a.original_source, target_type))
327 Error_CannotConvertImplicit (loc, a.original_source.Type, target_type);
332 source = ConvertImplicitRequired (ec, source, target_type, loc);
336 // If we're an embedded assignment, we need to create a new temporary variable
337 // for the converted value. Our parent will use this new variable as its source.
338 // The same applies when we have an embedded assignment - in this case, we need
339 // to convert our embedded assignment's temporary local variable to the correct
340 // type and store it in a new temporary local.
341 if (is_embedded || embedded != null) {
343 temp = new LocalTemporary (ec, type);
344 must_free_temp = true;
350 Expression EmitEmbedded (EmitContext ec)
352 // Emit an embedded assignment.
354 if (real_temp != null) {
355 // If we're the innermost assignment, `real_source' is the right-hand
356 // expression which gets assigned to all the variables left of it.
357 // Emit this expression and store its result in real_temp.
358 real_source.Emit (ec);
359 real_temp.Store (ec);
362 if (embedded != null)
363 embedded.EmitEmbedded (ec);
365 // This happens when we've done a type conversion, in this case source will be
366 // the expression which does the type conversion from real_temp.
367 // So emit it and store the result in temp; this is the var which will be read
369 if (temp != real_temp) {
374 Expression temp_source = (temp != null) ? temp : source;
375 ((IAssignMethod) target).EmitAssign (ec, temp_source);
379 void ReleaseEmbedded (EmitContext ec)
381 if (embedded != null)
382 embedded.ReleaseEmbedded (ec);
384 if (real_temp != null)
385 real_temp.Release (ec);
391 void Emit (EmitContext ec, bool is_statement)
393 if (target is EventExpr) {
394 ((EventExpr) target).EmitAddOrRemove (ec, source);
399 // FIXME! We need a way to "probe" if the process can
400 // just use `dup' to propagate the result
402 IAssignMethod am = (IAssignMethod) target;
404 if (this is CompoundAssign){
405 am.CacheTemporaries (ec);
408 Expression temp_source;
409 if (embedded != null) {
410 temp_source = embedded.EmitEmbedded (ec);
418 temp_source = source;
421 am.EmitAssign (ec, temp_source);
423 LocalTemporary tempo;
425 tempo = new LocalTemporary (ec, source.Type);
427 temp_source.Emit (ec);
429 am.EmitAssign (ec, tempo);
434 if (embedded != null) {
437 embedded.ReleaseEmbedded (ec);
441 public override void Emit (EmitContext ec)
446 public override void EmitStatement (EmitContext ec)
454 // This class is used for compound assignments.
456 class CompoundAssign : Assign {
458 public Expression original_source;
460 public CompoundAssign (Binary.Operator op, Expression target, Expression source, Location l)
461 : base (target, source, l)
463 original_source = source;
467 public Expression ResolveSource (EmitContext ec)
469 return original_source.Resolve (ec);
472 public override Expression DoResolve (EmitContext ec)
474 target = target.ResolveLValue (ec, source);
478 original_source = original_source.Resolve (ec);
479 if (original_source == null)
483 // Only now we can decouple the original source/target
484 // into a tree, to guarantee that we do not have side
487 source = new Binary (op, target, original_source, loc);
488 return base.DoResolve (ec);