Fix inference bug

Author: willtebbutt

src/copyable_task.jl

@@ -22,7 +22,7 @@ See also: [`Libtask.consume`](@ref)
 """
 @noinline function produce(x)
     global __v = 4 # silly side-effect to prevent this call getting constant-folded away. Should really use the effects system.
-    return ProducedValue(x)
+    return x
 end
 
 function callable_ret_type(sig)

src/test_utils.jl

@@ -15,6 +15,9 @@ end
 function (case::Testcase)()
     testset = @testset "$(case.name)" begin
 
+        # Display some information.
+        @info "$(case.name)"
+
         # Construct the task.
         if case.kwargs === nothing
             t = TapedTask(case.dynamic_scope, case.fargs...)
@@ -132,6 +135,9 @@ function test_cases()
         Testcase("kwargs tester 2", nothing, (kwarg_tester, 4.0), (; y=5.0), []),
         Testcase("default kwarg tester", nothing, (default_kwarg_tester, 4.0), nothing, []),
         Testcase("default kwarg tester", nothing, (default_kwarg_tester, 4.0), (;), []),
+        Testcase(
+            "final statment produce", nothing, (final_statement_produce,), nothing, [1, 2]
+        ),
     ]
 end
 
@@ -270,4 +276,9 @@ kwarg_tester(x; y) = x + y
 
 default_kwarg_tester(x; y=5.0) = x * y
 
+function final_statement_produce()
+    produce(1)
+    return produce(2)
+end
+
 end