fix method ambiguities

Author: sjkelly

src/cursors.jl

@@ -364,6 +364,7 @@ TreeCursor(::HasNodeType, ::IndexedChildren, ::ParentLinks, ::SiblingLinks, node
 TreeCursor(::HasNodeType, ::NonIndexedChildren, ::ParentLinks, ::SiblingLinks, node) = StableCursor(node)
 
 TreeCursor(::NodeTypeUnknown, ::IndexedChildren, ::ParentLinks, ::SiblingLinks, node) = IndexedCursor(node)
+TreeCursor(::NodeTypeUnknown, ::IndexedChildren, ::ImplicitParents, ::StoredSiblings, node) = IndexedCursor(node)
 
 TreeCursor(::NodeTypeUnknown, ::ChildIndexing, ::StoredParents, ::StoredSiblings, node) = TrivialCursor(node)
 

src/iteration.jl

@@ -70,7 +70,7 @@ Base.eltype(ti::TreeIterator) = eltype(typeof(ti))
 
 Base.IteratorSize(::Type{<:TreeIterator}) = SizeUnknown()
 
-function Base.iterate(ti::TreeIterator, s::Union{Nothing,IteratorState}=initial(statetype(ti), ti.root))
+function Base.iterate(ti::TreeIterator, s=initial(statetype(ti), ti.root))
     isnothing(s) && return nothing
     (nodevalue(s.cursor), next(s))
 end