Fix #207 (#209)

* Attempt to fix #207

* Add a test

* Bump patch version to 0.9.10

Author: mhauru

HISTORY.md

@@ -1,3 +1,7 @@
+# 0.9.10
+
+Fix a bug introduced in 0.9.9 that made certain phi nodes with Union types fail a type assertion.
+
 # 0.9.9
 
 Remove manual opaque closure optimisation functions in favour of setting the world age and letting the compiler do more work for us, and providing it with some more type information. This changes no functionality, and shouldn't change performance either, but simplifies code.

Project.toml

@@ -3,7 +3,7 @@ uuid = "6f1fad26-d15e-5dc8-ae53-837a1d7b8c9f"
 license = "MIT"
 desc = "Tape based task copying in Turing"
 repo = "https://github.com/TuringLang/Libtask.jl.git"
-version = "0.9.9"
+version = "0.9.10"
 
 [deps]
 MistyClosures = "dbe65cb8-6be2-42dd-bbc5-4196aaced4f4"

src/copyable_task.jl

@@ -1226,8 +1226,8 @@ end
 
 # Helper used in `derive_copyable_task_ir`.
 @inline function deref_phi(refs::R, n::TupleRef, ::Type{T}) where {R<:Tuple,T}
-    ref = refs[n.n]::Base.RefValue{T}
-    return ref[]
+    ref = refs[n.n]
+    return ref[]::T
 end
 @inline deref_phi(::R, x, t::Type) where {R<:Tuple} = x
 

test/copyable_task.jl

@@ -300,4 +300,31 @@
         @test Libtask.consume(tt) === 10
         @test Libtask.consume(tt) === nothing
     end
+
+    # Regression test against https://github.com/TuringLang/Libtask.jl/issues/207
+    @testset "Union deferencing" begin
+        function g(i::Int)
+            produce(1)
+            return i
+        end
+        function g(s::String)
+            produce(2)
+            return s
+        end
+        Libtask.@might_produce g
+
+        h(i::Int)::Int = i
+        h(s::String)::Int = length(s)
+
+        function f(x, g)
+            i_or_s = x > 0 ? 3 : "libtask"
+            gres = g(i_or_s)
+            return h(gres)
+        end
+
+        t = TapedTask(nothing, f, 1, g)
+        consume(t)
+        # This used to error
+        @test (consume(t); true)
+    end
 end