Fix parse error with Julia 1.0

Author: devmotion

test/context_implementations.jl

@@ -4,7 +4,8 @@
         @model function test(x)
             μ ~ MvNormal(fill(0, 2), 2.0)
             z = Vector{Int}(undef, length(x))
-            z .~ Categorical.(fill([0.5, 0.5], length(x)))
+            # `z .~ Categorical.(ps)` cannot be parsed by Julia 1.0
+            (.~)(z, Categorical.(fill([0.5, 0.5], length(x))))
             for i in 1:length(x)
                 x[i] ~ Normal(μ[z[i]], 0.1)
             end