Prevent type=inferability escaping for rrule of sortslices

Author: oxinabox

src/rulesets/Base/sort.jl

@@ -60,10 +60,13 @@ end
 
 function rrule(::typeof(sortslices), x::AbstractArray; dims::Integer, kw...)
     p = sortperm(collect(eachslice(x; dims=dims)); kw...)
-    inds = ntuple(d -> d == dims ? p : (:), ndims(x))
     function sortslices_pullback(dy)
-        return (NoTangent(), ∇getindex(x, unthunk(dy), inds...))
+        # avoid closing over `inds` as it doesn't  fully infer and that makes it worse
+        # recomputing is cheap
+        inds_inner = ntuple(d -> d == dims ? p : (:), ndims(x))
+        return (NoTangent(), ∇getindex(x, unthunk(dy), inds_inner...))
     end
+    inds = ntuple(d -> d == dims ? p : (:), ndims(x))
     return x[inds...], sortslices_pullback
 end
 

test/rulesets/Base/sort.jl

@@ -26,7 +26,7 @@
 
         test_rrule(sortslices, rand(3,4); fkwargs=(; dims=2))
         test_rrule(sortslices, rand(5,4); fkwargs=(; dims=1, rev=true, by=last))
-        test_rrule(sortslices, rand(3,4,5); fkwargs=(; dims=3, by=sum), check_inferred=false)
+        test_rrule(sortslices, rand(3,4,5); fkwargs=(; dims=3, by=sum))
 
         @test_throws Exception sortslices(Diagonal(1:3), dims=1)
     end