private Expression RewriteCallable <TException>(TException node, Expression[] arguments, Converter <TException, Expression> visitor, Func <TException, Expression[], TException> updater)
where TException : Expression
{
var codeInsertionPoint = context.CurrentStatement.PrologueCodeInserter();
var newNode = visitor(node);
if (newNode is TException typedExpr)
{
node = typedExpr;
}
else
{
return(newNode);
}
var hasAwait = false;
for (var i = arguments.LongLength - 1L; i >= 0L; i--)
{
ref Expression arg = ref arguments[i];
if (hasAwait |= ExpressionAttributes.Get(arg)?.ContainsAwait ?? false)
{
var tempVar = NewStateSlot(arg.Type);
codeInsertionPoint(Expression.Assign(tempVar, arg));
arg = tempVar;
}
}
private void AttachLabel(LabelTarget?target)
{
if (target is not null)
{
ExpressionAttributes.Get(CurrentStatement)?.Labels.Add(target);
target.GetUserData().GetOrSet(StateIdPlaceholder).StateId = stateId;
}
}
private void ContainsAwait()
{
foreach (var attr in attributes)
{
if (ReferenceEquals(ExpressionAttributes.Get(CurrentStatement), attr))
{
return;
}
attr.ContainsAwait = true;
}
}
protected override Expression VisitChildren(ExpressionVisitor visitor)
{
var filter = visitor.Visit(this.filter);
if (ExpressionAttributes.Get(filter)?.ContainsAwait ?? false)
{
throw new NotSupportedException(ExceptionMessages.FilterHasAwait);
}
var handler = visitor.Visit(Content);
handler = handler.AddPrologue(false, prologue).AddEpilogue(false, epilogue).AddEpilogue(false, FaultLabel.Goto());
return(IfThen(filter, handler));
}
protected override Expression VisitConditional(ConditionalExpression node)
{
if (node.Type == typeof(void))
{
node = node.Update(node.Test, Statement.Wrap(node.IfTrue), Statement.Wrap(node.IfFalse));
return(context.Rewrite(node, base.VisitConditional));
}
else if (node.IfTrue is BlockExpression && node.IfFalse is BlockExpression)
{
throw new NotSupportedException(ExceptionMessages.UnsupportedConditionalExpr);
}
else
{
/*
* x = a ? await b() : c();
* --transformed into--
* var temp;
* if(a)
* temp = await b();
* else
* temp = c();
* x = temp;
*/
var prologue = context.CurrentStatement.PrologueCodeInserter();
{
var result = context.Rewrite(node, base.VisitConditional);
if (result is ConditionalExpression conditional)
{
node = conditional;
}
else
{
return(result);
}
}
if ((ExpressionAttributes.Get(node.IfTrue)?.ContainsAwait ?? false) || (ExpressionAttributes.Get(node.IfFalse)?.ContainsAwait ?? false))
{
var tempVar = NewStateSlot(node.Type);
prologue(Expression.Condition(node.Test, Expression.Assign(tempVar, node.IfTrue), Expression.Assign(tempVar, node.IfFalse), typeof(void)));
return(tempVar);
}
else
{
return(node);
}
}
}
private Expression RewriteBinary(BinaryExpression node)
{
var codeInsertionPoint = context.CurrentStatement.PrologueCodeInserter();
var newNode = base.VisitBinary(node);
if (newNode is BinaryExpression binary)
{
node = binary;
}
else
{
return(newNode);
}
// do not place left operand at statement level because it has no side effects
if (node.Left is ParameterExpression || node.Left is ConstantExpression || IsAssignment(node))
{
return(node);
}
var leftIsAsync = ExpressionAttributes.Get(node.Left)?.ContainsAwait ?? false;
var rightIsAsync = ExpressionAttributes.Get(node.Right)?.ContainsAwait ?? false;
// left operand should be computed before right, so bump it before await expression
if (rightIsAsync && !leftIsAsync)
{
/*
* Method() + await a;
* --transformed into--
* state.field = Method();
* state.awaiter = a.GetAwaiter();
* MoveNext(state.awaiter, newState);
* return;
* newState: state.field + state.awaiter.GetResult();
*/
var leftTemp = NewStateSlot(node.Left.Type);
codeInsertionPoint(Expression.Assign(leftTemp, node.Left));
node = node.Update(leftTemp, node.Conversion, node.Right);
}
return(node);
}
internal IReadOnlyCollection <Expression> CreateJumpPrologue(GotoExpression @goto, ExpressionVisitor visitor)
{
var state = @goto.Target.GetUserData().GetOrSet(StateIdPlaceholder);
var result = new LinkedList <Expression>();
// iterate through snapshot of statements because collection can be modified
var statements = this.statements.ToArray();
foreach (var lookup in statements)
{
if (ExpressionAttributes.Get(lookup)?.Labels.Contains(@goto.Target) ?? false)
{
break;
}
if (lookup is TryCatchFinallyStatement statement)
{
result.AddLast(statement.InlineFinally(visitor, state));
}
}
Array.Clear(statements, 0, statements.Length);
return(result);
}