private Expression VisitAssign(BinaryExpression node)
{
int yields = _yields.Count;
Expression left = Visit(node.Left);
Expression right = Visit(node.Right);
if (left == node.Left && right == node.Right)
{
return(node);
}
if (yields == _yields.Count)
{
return(Expression.Assign(left, right));
}
var block = new ReadOnlyCollectionBuilder <Expression>();
if (_generator.RewriteAssignments)
{
// We need to make sure that LHS is evaluated before RHS. For example,
//
// {expr0}[{expr1},..,{exprN}] = {rhs}
// ->
// { l0 = {expr0}; l1 = {expr1}; ..; lN = {exprN}; r = {rhs}; l0[l1,..,lN] = r }
//
if (left == node.Left)
{
switch (left.NodeType)
{
case ExpressionType.MemberAccess:
var member = (MemberExpression)node.Left;
if (member.Expression != null)
{
left = member.Update(ToTemp(block, member.Expression));
}
break;
case ExpressionType.Index:
var index = (IndexExpression)node.Left;
left = index.Update((index.Object != null ? ToTemp(block, index.Object) : null), ToTemp(block, index.Arguments));
break;
case ExpressionType.Parameter:
// no action needed
break;
default:
// Extension should've been reduced by Visit above,
// and returned a different node
throw Assert.Unreachable;
}
}
else
{
// Get the last expression of the rewritten left side
var leftBlock = (BlockExpression)left;
block.AddRange(leftBlock.Expressions);
block.RemoveAt(block.Count - 1);
left = leftBlock.Expressions[leftBlock.Expressions.Count - 1];
}
}
if (right != node.Right)
{
right = ToTemp(block, right);
}
block.Add(Expression.Assign(left, right));
return(Expression.Block(block));
}