added testing of deprecation warning of @submodel + replaced some

usages in tests (though we don't support some of these so we cant' do
that yet)

src/submodel_macro.jl

@@ -224,7 +224,7 @@ function prefix_submodel_context(prefix::Bool, ctx)
     return ctx
 end
 
-const SUBMODEL_DEPWARN_MSG = "`@submodel model` is deprecated, use `left ~ to_sampleable(model)` instead."
+const SUBMODEL_DEPWARN_MSG = "`@submodel model` and `@submodel prefix=... model` are deprecated, use `left ~ to_sampleable(model)` and `left ~ to_sampleable(prefix(model, ...))`, respectively, instead."
 
 function submodel(prefix_expr, expr, ctx=esc(:__context__))
     prefix_left, prefix = getargs_assignment(prefix_expr)

test/compiler.jl

@@ -382,6 +382,27 @@ module Issue537 end
         @test demo2()() == 42
     end
 
+    @testset "@submodel is deprecated" begin
+        @model inner() = x ~ Normal()
+        @model outer() = @submodel x = inner()
+        @test_logs(
+            (
+                :warn,
+                "`@submodel model` and `@submodel prefix=... model` are deprecated, use `left ~ to_sampleable(model)` and `left ~ to_sampleable(prefix(model, ...))`, respectively, instead.",
+            ),
+            outer()()
+        )
+
+        @model outer_with_prefix() = @submodel prefix="sub" x = inner()
+        @test_logs(
+            (
+                :warn,
+                "`@submodel model` and `@submodel prefix=... model` are deprecated, use `left ~ to_sampleable(model)` and `left ~ to_sampleable(prefix(model, ...))`, respectively, instead.",
+            ),
+            outer_with_prefix()()
+        )
+    end
+
     @testset "submodel" begin
         # No prefix, 1 level.
         @model function demo1(x)
@@ -469,7 +490,7 @@ module Issue537 end
             num_steps = length(y[1])
             num_obs = length(y)
             @inbounds for i in 1:num_obs
-                @submodel prefix = "ar1_$i" x = AR1(num_steps, α, μ, σ)
+                x ~ to_sampleable(prefix(AR1(num_steps, α, μ, σ), "ar1_$i"))
                 y[i] ~ MvNormal(x, 0.01 * I)
             end
         end

test/debug_utils.jl

@@ -45,14 +45,14 @@
         @testset "submodel" begin
             @model ModelInner() = x ~ Normal()
             @model function ModelOuterBroken()
-                @submodel z = ModelInner()
+                z ~ to_sampleable(ModelInner())
                 return x ~ Normal()
             end
             model = ModelOuterBroken()
             @test_throws ErrorException check_model(model; error_on_failure=true)
 
             @model function ModelOuterWorking()
-                @submodel prefix = true z = ModelInner()
+                z = to_sampleable(prefix(ModelInner(), "z"))
                 x ~ Normal()
                 return z
             end