Only overload and test waic if defined

Author: sethaxen

ext/InferenceObjectsPosteriorStatsExt/InferenceObjectsPosteriorStatsExt.jl

@@ -13,7 +13,9 @@ maplayers = isdefined(DimensionalData, :maplayers) ? DimensionalData.maplayers :
 include("utils.jl")
 include("ci.jl")
 include("loo.jl")
-include("waic.jl")
+@static if isdefined(PosteriorStats, :waic)
+    include("waic.jl")
+end
 include("loo_pit.jl")
 include("r2_score.jl")
 include("summarize.jl")

test/posteriorstats.jl

@@ -172,7 +172,7 @@ _as_array(x::AbstractArray) = x
         end
     end
 
-    @testset "waic" begin
+    isdefined(PosteriorStats, :waic) && @testset "waic" begin
         @testset for sz in ((1000, 4), (1000, 4, 2), (100, 4, 2, 3))
             atol_perm = cbrt(eps())