//
// assign.cs: Assignments.
//
// Author:
// Miguel de Icaza (miguel@ximian.com)
//
// (C) 2001 Ximian, Inc.
//
using System;
using System.Reflection;
using System.Reflection.Emit;
namespace Mono.CSharp {
///
/// This interface is implemented by expressions that can be assigned to.
///
///
/// This interface is implemented by Expressions whose values can not
/// store the result on the top of the stack.
///
/// Expressions implementing this (Properties, Indexers and Arrays) would
/// perform an assignment of the Expression "source" into its final
/// location.
///
/// No values on the top of the stack are expected to be left by
/// invoking this method.
///
public interface IAssignMethod {
void EmitAssign (EmitContext ec, Expression source);
}
///
/// An Expression to hold a temporary value.
///
///
/// The LocalTemporary class is used to hold temporary values of a given
/// type to "simulate" the expression semantics on property and indexer
/// access whose return values are void.
///
/// The local temporary is used to alter the normal flow of code generation
/// basically it creates a local variable, and its emit instruction generates
/// code to access this value, return its address or save its value.
///
public class LocalTemporary : Expression, IMemoryLocation {
LocalBuilder builder;
public LocalTemporary (EmitContext ec, Type t)
{
type = t;
eclass = ExprClass.Value;
builder = ec.GetTemporaryStorage (t);
}
public void Release (EmitContext ec)
{
ec.FreeTemporaryStorage (builder);
builder = null;
}
public LocalTemporary (LocalBuilder b, Type t)
{
type = t;
eclass = ExprClass.Value;
builder = b;
}
public override Expression DoResolve (EmitContext ec)
{
return this;
}
public override void Emit (EmitContext ec)
{
ec.ig.Emit (OpCodes.Ldloc, builder);
}
public void Store (EmitContext ec)
{
ec.ig.Emit (OpCodes.Stloc, builder);
}
public void AddressOf (EmitContext ec, AddressOp mode)
{
ec.ig.Emit (OpCodes.Ldloca, builder);
}
}
///
/// The Assign node takes care of assigning the value of source into
/// the expression represented by target.
///
public class Assign : ExpressionStatement {
Expression target, source;
Location l;
public Assign (Expression target, Expression source, Location l)
{
this.target = target;
this.source = source;
this.l = l;
}
public Expression Target {
get {
return target;
}
set {
target = value;
}
}
public Expression Source {
get {
return source;
}
set {
source = value;
}
}
public static void error70 (EventInfo ei, Location l)
{
Report.Error (70, l, "The event '" + ei.Name +
"' can only appear on the left-side of a += or -= (except when" +
" used from within the type '" + ei.DeclaringType + "')");
}
public override Expression DoResolve (EmitContext ec)
{
source = source.Resolve (ec);
if (source == null)
return null;
target = target.ResolveLValue (ec, source);
if (target == null)
return null;
Type target_type = target.Type;
Type source_type = source.Type;
type = target_type;
eclass = ExprClass.Value;
//
// If we are doing a property assignment, then
// set the `value' field on the property, and Resolve
// it.
//
if (target is PropertyExpr){
PropertyExpr property_assign = (PropertyExpr) target;
//
// FIXME: Maybe handle this in the LValueResolve
//
if (!property_assign.VerifyAssignable ())
return null;
return this;
}
if (target is IndexerAccess){
IndexerAccess ia = (IndexerAccess) target;
return this;
}
if (target is EventExpr) {
Binary tmp;
EventInfo ei = ((EventExpr) target).EventInfo;
Expression ml = MemberLookup (
ec, ec.ContainerType, ei.Name,
MemberTypes.Event, AllBindingFlags, l);
if (ml == null) {
//
// If this is the case, then the Event does not belong
// to this TypeContainer and so, according to the spec
// is allowed to only appear on the left hand of
// the += and -= operators
//
// Note that if target will not appear as an EventExpr
// in the case it is being referenced within the same type container;
// it will appear as a FieldExpr in that case.
//
if (!(source is Binary)) {
error70 (ei, l);
return null;
} else {
tmp = ((Binary) source);
if (tmp.Oper != Binary.Operator.Addition &&
tmp.Oper != Binary.Operator.Subtraction) {
error70 (ei, l);
return null;
}
}
}
}
if (source is New && target_type.IsSubclassOf (TypeManager.value_type)){
New n = (New) source;
n.ValueTypeVariable = target;
return n;
}
if (target_type != source_type){
source = ConvertImplicitRequired (ec, source, target_type, l);
if (source == null)
return null;
}
if (target.eclass != ExprClass.Variable && target.eclass != ExprClass.EventAccess){
Report.Error (131, l,
"Left hand of an assignment must be a variable, " +
"a property or an indexer");
return null;
}
return this;
}
void Emit (EmitContext ec, bool is_statement)
{
if (target is EventExpr) {
((EventExpr) target).EmitAddOrRemove (ec, source);
return;
}
//
// FIXME! We need a way to "probe" if the process can
// just use `dup' to propagate the result
//
IAssignMethod am = (IAssignMethod) target;
if (is_statement)
am.EmitAssign (ec, source);
else {
LocalTemporary tempo;
tempo = new LocalTemporary (ec, source.Type);
source.Emit (ec);
tempo.Store (ec);
am.EmitAssign (ec, tempo);
tempo.Emit (ec);
tempo.Release (ec);
}
}
public override void Emit (EmitContext ec)
{
Emit (ec, false);
}
public override void EmitStatement (EmitContext ec)
{
Emit (ec, true);
}
}
}