don't allow CellOrbitals{L,Colon} reach slicers

src/greenfunction.jl

@@ -105,12 +105,16 @@ function Base.getindex(g::GreenSolution, args...; post = identity, symmetrize =
 end
 
 Base.getindex(g::GreenSolution, i::AnyCellOrbitals, j::AnyCellOrbitals) =
-    slicer(g)[sanitize_cellorbs(i), sanitize_cellorbs(j)]
+    slicer(g)[sanitize_cellorbs(i, g), sanitize_cellorbs(j, g)]
 
 # must ensure that orbindices is not a scalar, to consistently obtain a Matrix
+# also, it should not be Colon, as GreenSlicers generally assume an explicit range
+sanitize_cellorbs(c::CellOrbitals, g) = sites_to_orbs(c, g)  # convert : to range
 sanitize_cellorbs(c::CellOrbitals) = c
-sanitize_cellorbs(c::CellOrbital) = CellOrbitals(cell(c), orbindex(c):orbindex(c))
-sanitize_cellorbs(c::CellOrbitalsGrouped) = CellOrbitals(cell(c), orbindices(c))
+sanitize_cellorbs(c::CellOrbital, _...) = CellOrbitals(cell(c), orbindex(c):orbindex(c))
+sanitize_cellorbs(c::CellOrbitalsGrouped, _...) = CellOrbitals(cell(c), orbindices(c))
+sanitize_cellorbs(::CellOrbitals{<:Any,Colon}) =
+    internalerror("sanitize_cellorbs: Colon indices leaked!")
 
 ## common getindex! shortcut in terms of GreenSlice
 
@@ -163,7 +167,7 @@ cell_orbindices(_, ::Missing) = Colon()
 
 ## GreenSlicer -> Matrix, dispatches to each solver's implementation
 
-# fallback conversion to CellOrbitals
+# simplify CellOrbitalGroups to CellOrbitals. No CellOrbitals{L,Colon} should get here
 Base.getindex(s::GreenSlicer, i::AnyCellOrbitals, j::AnyCellOrbitals = i; kw...) =
     getindex(s, sanitize_cellorbs(i), sanitize_cellorbs(j); kw...)
 

src/slices.jl

@@ -359,7 +359,7 @@ sites_to_orbs(c::SparseIndices{<:Any,<:Hamiltonian}, _) = c
 # unused
 # sites_to_orbs_nogroups(cs::CellOrbitals, _) =  cs
 
-## CellOrbitals{L,Colon} -> CellOrbitals with collected indices
+## CellOrbitals{L,Colon} -> CellOrbitals with explicit index range
 
 sites_to_orbs(cs::CellOrbitals{<:Any,Colon}, g) =
     sites_to_orbs_nogroups(sites(cell(cs), :), g)