static void TransformProgArgsIfImplementingDeferredReturn([NotNull] ref ZilList bindingList, [NotNull] ref ZilListoidBase body)
{
// ends with <LVAL atom>?
if (!(body.EnumerateNonRecursive().LastOrDefault() is ZilForm lastExpr) || !lastExpr.IsLVAL(out var atom))
{
return;
}
// atom is bound in the prog?
if (!GetUninitializedAtomsFromBindingList(bindingList).Contains(atom))
{
return;
}
// atom is set earlier in the prog?
var setExpr = body.OfType <ZilForm>()
.FirstOrDefault(
form => form.HasLength(3) &&
(form.First as ZilAtom)?.StdAtom == StdAtom.SET &&
form.Rest?.First == atom);
if (setExpr == null)
{
return;
}
// atom is not referenced anywhere else?
if (!body.All(zo =>
ReferenceEquals(zo, setExpr) || ReferenceEquals(zo, lastExpr) || !RecursivelyContains(zo, atom)))
{
return;
}
// we got a winner!
bindingList = new ZilList(
bindingList.Where(zo => GetUninitializedAtomFromBindingListItem(zo) != atom));
body = new ZilList(
body
.Where(zo => !ReferenceEquals(zo, lastExpr))
.Select(zo => ReferenceEquals(zo, setExpr) ? ((IStructure)zo)[2] : zo));
}
