Fix non-concrete type near TRCache (#118)

* Fix non-concrete type near TRCache

* Add `@inferred` test

* Bump version to 0.6.8

Author: rikhuijzer

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 = "0.6.7"
+version = "0.6.8"
 
 [deps]
 IRTools = "7869d1d1-7146-5819-86e3-90919afe41df"

src/tapedfunction.jl

@@ -36,10 +36,8 @@ mutable struct ReturnInstruction{TA, T<:Taped} <: AbstractInstruction
     tape::T
 end
 
-const TRCache = LRU{Any, Any}(maxsize=10)
-
 mutable struct TapedFunction{F} <: Taped
-    func::F # maybe a function, a constructor, or a callable obejct
+    func::F # maybe a function, a constructor, or a callable object
     arity::Int
     ir::IRTools.IR
     tape::RawTape
@@ -53,7 +51,7 @@ mutable struct TapedFunction{F} <: Taped
         cache_key = (f, typeof.(args)...)
 
         if cache && haskey(TRCache, cache_key) # use cache
-            cached_tf = TRCache[cache_key]
+            cached_tf = TRCache[cache_key]::TapedFunction{F}
             tf = copy(cached_tf)
             tf.counter = 1
             return tf
@@ -77,6 +75,8 @@ mutable struct TapedFunction{F} <: Taped
     end
 end
 
+const TRCache = LRU{Tuple, TapedFunction}(maxsize=10)
+
 ## methods for Box
 val(x) = x
 val(x::Box) = x.val

src/tapedtask.jl

@@ -1,6 +1,6 @@
 struct TapedTaskException
     exc::Exception
-    backtrace
+    backtrace::Vector{Any}
 end
 
 struct TapedTask

test/ctask.jl

@@ -17,6 +17,8 @@
         @test consume(a) == 3
         @test consume(ctask) == 2
         @test consume(ctask) == 3
+
+        @inferred Libtask.TapedFunction(f)
     end
 
     # Test case 2: heap allocated objects are shallowly copied.