Make _with_ladj_on_mapped for tuples inferrable on older Julia versions

foldl over a tuple is not fully inferrable on Julia v1.0, resulting in
tuple-length information getting lost. Use hand-rolled recursion instead.

Created by generative AI.

Author: oschulz

src/with_ladj.jl

@@ -143,9 +143,13 @@ 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...)
+
 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]))
+    a = first(y_with_ladj)
+    return _foldl_combine_y_ladj(((a[1],), a[2]), Base.tail(y_with_ladj)...)
 end
 
 @static if VERSION >= v"1.6"