Issue #185

src/copyable_task.jl

@@ -72,6 +72,13 @@ the current world age, will make a copy of an existing `MistyClosure`. If not,
 will derive it from scratch (derive the IR + compile it etc).
 """
 function build_callable(sig::Type{<:Tuple})
+    if sig <: Tuple{typeof(produce),Any}
+        msg = """
+            Can not construct a TapedTask for a 'naked' call to `produce`.
+             Please wrap the call to `produce` in a function, and construct a
+             TapedTask from that function."""
+        throw(ArgumentError(msg))
+    end
     key = CacheKey(Base.get_world_counter(), sig)
     if haskey(mc_cache, key)
         return fresh_copy(mc_cache[key])
@@ -367,8 +374,8 @@ get_value(x) = x
 expression, otherwise `false`.
 """
 function is_produce_stmt(x)::Bool
-    if Meta.isexpr(x, :invoke) && length(x.args) == 3
-        return get_value(x.args[2]) === produce
+    if Meta.isexpr(x, :invoke) && length(x.args) == 3 && x.args[1] isa Core.MethodInstance
+        return x.args[1].specTypes <: Tuple{typeof(produce),Any}
     elseif Meta.isexpr(x, :call) && length(x.args) == 2
         return get_value(x.args[1]) === produce
     else

test/copyable_task.jl

@@ -138,6 +138,12 @@
                 @test ex isa BoundsError
             end
         end
+
+        @testset "Naked produce" begin
+            @test_throws "wrap the call to `produce` in a function" Libtask.consume(
+                Libtask.TapedTask(nothing, Libtask.produce, 0)
+            )
+        end
     end
 
     @testset "copying" begin
@@ -209,4 +215,9 @@
         end
         @test ex === nothing
     end
+
+    @testset "Issue #185" begin
+        g() = produce(rand() > -1.0 ? 2 : 0.1)
+        @test Libtask.consume(Libtask.TapedTask(nothing, g)) == 2
+    end
 end