//
// assign.cs: Assignments.
//
// Author:
// Miguel de Icaza (miguel@ximian.com)
// Martin Baulig (martin@gnome.org)
//
// (C) 2001, 2002, 2003 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 {
//
// This method will emit the code for the actual assignment
//
void EmitAssign (EmitContext ec, Expression source);
//
// This method is invoked before any code generation takes
// place, and it is a mechanism to inform that the expression
// will be invoked more than once, and that the method should
// use temporary values to avoid having side effects
//
// Example: a [ g () ] ++
//
void CacheTemporaries (EmitContext ec);
}
///
/// 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;
loc = Location.Null;
builder = ec.GetTemporaryLocal (t);
}
public void Release (EmitContext ec)
{
ec.FreeTemporaryLocal (builder, type);
builder = null;
}
public LocalTemporary (LocalBuilder b, Type t)
{
type = t;
eclass = ExprClass.Value;
loc = Location.Null;
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 {
protected Expression target, source, real_source;
protected LocalTemporary temp = null, real_temp = null;
protected Assign embedded = null;
protected bool is_embedded = false;
protected bool must_free_temp = false;
public Assign (Expression target, Expression source, Location l)
{
this.target = target;
this.source = this.real_source = source;
this.loc = l;
}
protected Assign (Assign embedded, Location l)
: this (embedded.target, embedded.source, l)
{
this.is_embedded = true;
}
protected virtual Assign GetEmbeddedAssign (Location loc)
{
return new Assign (this, loc);
}
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 + "')");
}
//
// Will return either `this' or an instance of `New'.
//
public override Expression DoResolve (EmitContext ec)
{
// Create an embedded assignment if our source is an assignment.
if (source is Assign)
source = embedded = ((Assign) source).GetEmbeddedAssign (loc);
real_source = source = source.Resolve (ec);
if (source == null)
return null;
//
// This is used in an embedded assignment.
// As an example, consider the statement "A = X = Y = Z".
//
if (is_embedded && !(source is Constant)) {
// If this is the innermost assignment (the "Y = Z" in our example),
// create a new temporary local, otherwise inherit that variable
// from our child (the "X = (Y = Z)" inherits the local from the
// "Y = Z" assignment).
if (embedded == null) {
if (this is CompoundAssign)
real_temp = temp = new LocalTemporary (ec, target.Type);
else
real_temp = temp = new LocalTemporary (ec, source.Type);
} else
temp = embedded.temp;
// Set the source to the new temporary variable.
// This means that the following target.ResolveLValue () will tell
// the target to read it's source value from that variable.
source = temp;
}
// If we have an embedded assignment, use the embedded assignment's temporary
// local variable as source.
if (embedded != null)
source = (embedded.temp != null) ? embedded.temp : embedded.source;
target = target.ResolveLValue (ec, source);
if (target == null)
return null;
Type target_type = target.Type;
Type source_type = real_source.Type;
// If we're an embedded assignment, our parent will reuse our source as its
// source, it won't read from our target.
if (is_embedded)
type = source_type;
else
type = target_type;
eclass = ExprClass.Value;
if (target is EventExpr) {
EventInfo ei = ((EventExpr) target).EventInfo;
Expression ml = MemberLookup (
ec, ec.ContainerType, ei.Name,
MemberTypes.Event, AllBindingFlags | BindingFlags.DeclaredOnly, loc);
if (ml == null) {
//
// If this is the case, then the Event does not belong
// to this Type and so, according to the spec
// is allowed to only appear on the left hand of
// the += and -= operators
//
// Note that 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 BinaryDelegate)) {
error70 (ei, loc);
return null;
}
}
}
if (source is New && target_type.IsValueType &&
(target.eclass != ExprClass.IndexerAccess) && (target.eclass != ExprClass.PropertyAccess)){
New n = (New) source;
if (n.SetValueTypeVariable (target))
return n;
else
return null;
}
if (!(target is IAssignMethod) && (target.eclass != ExprClass.EventAccess)) {
Report.Error (131, loc,
"Left hand of an assignment must be a variable, " +
"a property or an indexer");
return null;
}
if ((source.eclass == ExprClass.Type) && (source is TypeExpr)) {
source.Error_UnexpectedKind ("variable or value");
return null;
} else if (!RootContext.V2 && (source is MethodGroupExpr)){
((MethodGroupExpr) source).ReportUsageError ();
return null;
}
if (target_type == source_type)
return this;
//
// If this assignemnt/operator was part of a compound binary
// operator, then we allow an explicit conversion, as detailed
// in the spec.
//
if (this is CompoundAssign){
CompoundAssign a = (CompoundAssign) this;
Binary b = source as Binary;
if (b != null){
//
// 1. if the source is explicitly convertible to the
// target_type
//
source = Convert.ExplicitConversion (ec, source, target_type, loc);
if (source == null){
Convert.Error_CannotImplicitConversion (loc, source_type, target_type);
return null;
}
//
// 2. and the original right side is implicitly convertible to
// the type of target
//
if (Convert.ImplicitStandardConversionExists (a.original_source, target_type))
return this;
//
// In the spec 2.4 they added: or if type of the target is int
// and the operator is a shift operator...
//
if (source_type == TypeManager.int32_type &&
(b.Oper == Binary.Operator.LeftShift || b.Oper == Binary.Operator.RightShift))
return this;
Convert.Error_CannotImplicitConversion (loc, a.original_source.Type, target_type);
return null;
}
}
source = Convert.ImplicitConversionRequired (ec, source, target_type, loc);
if (source == null)
return null;
// If we're an embedded assignment, we need to create a new temporary variable
// for the converted value. Our parent will use this new variable as its source.
// The same applies when we have an embedded assignment - in this case, we need
// to convert our embedded assignment's temporary local variable to the correct
// type and store it in a new temporary local.
if (is_embedded || embedded != null) {
type = target_type;
temp = new LocalTemporary (ec, type);
must_free_temp = true;
}
return this;
}
Expression EmitEmbedded (EmitContext ec)
{
// Emit an embedded assignment.
if (real_temp != null) {
// If we're the innermost assignment, `real_source' is the right-hand
// expression which gets assigned to all the variables left of it.
// Emit this expression and store its result in real_temp.
real_source.Emit (ec);
real_temp.Store (ec);
}
if (embedded != null)
embedded.EmitEmbedded (ec);
// This happens when we've done a type conversion, in this case source will be
// the expression which does the type conversion from real_temp.
// So emit it and store the result in temp; this is the var which will be read
// by our parent.
if (temp != real_temp) {
source.Emit (ec);
temp.Store (ec);
}
Expression temp_source = (temp != null) ? temp : source;
((IAssignMethod) target).EmitAssign (ec, temp_source);
return temp_source;
}
void ReleaseEmbedded (EmitContext ec)
{
if (embedded != null)
embedded.ReleaseEmbedded (ec);
if (real_temp != null)
real_temp.Release (ec);
if (must_free_temp)
temp.Release (ec);
}
void Emit (EmitContext ec, bool is_statement)
{
if (target is EventExpr) {
((EventExpr) target).EmitAddOrRemove (ec, source);
return;
}
bool use_temporaries = false;
//
// FIXME! We need a way to "probe" if the process can
// just use `dup' to propagate the result
//
IAssignMethod am = (IAssignMethod) target;
if (this is CompoundAssign)
am.CacheTemporaries (ec);
if (!is_statement)
use_temporaries = true;
Expression temp_source;
if (embedded != null) {
temp_source = embedded.EmitEmbedded (ec);
if (temp != null) {
source.Emit (ec);
temp.Store (ec);
temp_source = temp;
}
} else
temp_source = source;
if (use_temporaries){
//
// Doing this for every path is too expensive
// I wonder if we can work around this and have a less
// expensive path
//
LocalTemporary tempo;
tempo = new LocalTemporary (ec, source.Type);
temp_source.Emit (ec);
tempo.Store (ec);
am.EmitAssign (ec, tempo);
if (!is_statement)
tempo.Emit (ec);
tempo.Release (ec);
} else {
am.EmitAssign (ec, temp_source);
}
if (embedded != null) {
if (temp != null)
temp.Release (ec);
embedded.ReleaseEmbedded (ec);
}
}
public override void Emit (EmitContext ec)
{
Emit (ec, false);
}
public override void EmitStatement (EmitContext ec)
{
Emit (ec, true);
}
}
//
// This class is used for compound assignments.
//
class CompoundAssign : Assign {
Binary.Operator op;
public Expression original_source;
public CompoundAssign (Binary.Operator op, Expression target, Expression source, Location l)
: base (target, source, l)
{
original_source = source;
this.op = op;
}
protected CompoundAssign (CompoundAssign embedded, Location l)
: this (embedded.op, embedded.target, embedded.source, l)
{
this.is_embedded = true;
}
protected override Assign GetEmbeddedAssign (Location loc)
{
return new CompoundAssign (this, loc);
}
public Expression ResolveSource (EmitContext ec)
{
return original_source.Resolve (ec);
}
public override Expression DoResolve (EmitContext ec)
{
original_source = original_source.Resolve (ec);
if (original_source == null)
return null;
target = target.Resolve (ec);
if (target == null)
return null;
//
// Only now we can decouple the original source/target
// into a tree, to guarantee that we do not have side
// effects.
//
source = new Binary (op, target, original_source, loc);
return base.DoResolve (ec);
}
}
}