Only use hand-rolled fold workaround on Julia < 1.6

foldl over tuples infers fine from Julia 1.6 onward (verified on 1.6.7,
1.9.4, 1.10, 1.12, 1.13); only Julia 1.0.x needs the recursive
workaround, so keep using foldl on newer versions.

Created by generative AI.

Author: oschulz

src/with_ladj.jl

@@ -143,13 +143,20 @@ function _with_ladj_on_mapped(y_with_ladj::Tuple{NoLogAbsDetJacobian, Vararg{Uni
     return first(y_with_ladj)
 end
 
-# Hand-rolled foldl, foldl over tuples is not inferrable on older Julia versions:
-_foldl_combine_y_ladj(acc) = acc
-_foldl_combine_y_ladj(acc, b, bs...) = _foldl_combine_y_ladj(_combine_y_ladj(acc, b), bs...)
+@static if VERSION >= v"1.6"
+    function _with_ladj_on_mapped(y_with_ladj::Tuple{Tuple{Any,Real}, Vararg{Union{NoLogAbsDetJacobian, Tuple{Any,Real}}}})
+        a, bs = first(y_with_ladj), Base.tail(y_with_ladj)
+        return foldl(_combine_y_ladj, bs, init = ((a[1],), a[2]))
+    end
+else
+    # Hand-rolled foldl, foldl over tuples is not inferrable on Julia < 1.6:
+    _foldl_combine_y_ladj(acc) = acc
+    _foldl_combine_y_ladj(acc, b, bs...) = _foldl_combine_y_ladj(_combine_y_ladj(acc, b), bs...)
 
-function _with_ladj_on_mapped(y_with_ladj::Tuple{Tuple{Any,Real}, Vararg{Union{NoLogAbsDetJacobian, Tuple{Any,Real}}}})
-    a = first(y_with_ladj)
-    return _foldl_combine_y_ladj(((a[1],), a[2]), Base.tail(y_with_ladj)...)
+    function _with_ladj_on_mapped(y_with_ladj::Tuple{Tuple{Any,Real}, Vararg{Union{NoLogAbsDetJacobian, Tuple{Any,Real}}}})
+        a = first(y_with_ladj)
+        return _foldl_combine_y_ladj(((a[1],), a[2]), Base.tail(y_with_ladj)...)
+    end
 end
 
 @static if VERSION >= v"1.6"