allow empty sublats

src/types.jl

@@ -5,10 +5,6 @@
 struct Sublat{T<:AbstractFloat,E}
     sites::Vector{SVector{E,T}}
     name::Symbol
-    function Sublat{T,E}(sites, name) where {T<:AbstractFloat,E}
-        isempty(sites) && argerror("Sublattices cannot be empty")
-        return new(sites, name)
-    end
 end
 
 struct Unitcell{T<:AbstractFloat,E}
@@ -41,8 +37,6 @@ end
 
 #region ## Constructors ##
 
-Sublat(sites::Vector{SVector{E,T}}, name::Symbol) where {T,E} = Sublat{T,E}(sites, name)
-
 Bravais(::Type{T}, E, m) where {T} = Bravais(T, Val(E), m)
 Bravais(::Type{T}, ::Val{E}, m::Tuple{}) where {T,E} =
     Bravais{T,E,0}(sanitize_Matrix(T, E, ()))

test/test_greenfunction.jl

@@ -22,7 +22,7 @@ function testgreen(h, s; kw...)
     return nothing
 end
 
-@testset "bare greenfunctions" begin
+@testset "basic greenfunctions" begin
     h0 = LP.honeycomb() |> hamiltonian(hopping(SA[0 1; 1 0]), orbitals = 2) |> supercell(region = RP.circle(10))
     s0 = GS.SparseLU()
     h1 = LP.square() |> hamiltonian(@onsite((; o = 1) -> o*I) + hopping(SA[0 1; 1 0]), orbitals = 2) |> supercell((1,0), region = r -> abs(r[2]) < 2)
@@ -66,6 +66,9 @@ end
             testgreen(oh, s)
         end
     end
+    # contacts that don't include all sublattices
+    h = lattice(sublat(0, name = :L), sublat(1, name = :R)) |> hamiltonian
+    @test h |> attach(onsite(ω->1), sublats = :L) |> greenfunction isa GreenFunction
 end
 
 @testset "greenfunction KPM" begin

test/test_lattice.jl

@@ -31,7 +31,7 @@ end
     end
     @test sublat((3,)) isa Sublat{Float64,1}
     @test sublat(()) isa Sublat{Float64,0}
-    @test_throws ArgumentError sublat(SVector{3,Float64}[])
+    @test sublat(SVector{3,Float64}[]) isa Sublat{Float64,3}
 end
 
 @testset "lattice construction" begin