@rand: allow references to objects outside of rand calls

E.g. in `@rand rand(d::Die) = d.n`, `d.n` in not within a
`rand` call, and must be transformed into `d[].n` in the
"samplerized" version (where `d isa SamplerTrivial{Die}`).

Author: rfourquet

src/macros.jl

@@ -63,6 +63,10 @@ function as_sampler(ex, istrivial)
 end
 
 function samplerize!(sps, ex, name)
+    if ex == name
+        # not within a rand() call
+        return Expr(:ref, name) # name -> name[]
+    end
     ex isa Expr || return ex
     if ex.head == :call && ex.args[1] == :rand
         # TODO: handle Repetition == Val(Inf) for arrays

test/runtests.jl

@@ -573,14 +573,13 @@ end
 
 Base.eltype(::Type{Die}) = Int
 
-@rand function rand(d::Die)
-    7
-end
-
 @testset "@rand" begin
     d = Die(6)
     rng = MersenneTwister()
 
+    @rand function rand(d::Die)
+        7
+    end
     @test rand(d) == 7
 
     # redefinition
@@ -595,7 +594,11 @@ end
     @test rand(d) ∈ 11:16
     @test all(∈(11:16), rand(d, 10))
 
+    # redefinition access to argument not within rand call
+    @rand rand(d::Die) = rand(1:1) + d.n
+    @test all(==(7), rand(d, 10))
+
     # redefinition back to SamplerTrivial
-    @rand rand(d::Die) = 0
-    @test all(==(0), rand(d, 100))
+    @rand rand(d::Die) = d.n
+    @test all(==(6), rand(d, 100))
 end