Remove old warning about map (#825)

* Skip length check in map on newer Julia versions

Closes #798

* Apply suggestions from code review

Co-authored-by: David Müller-Widmann <[email protected]>

---------

Co-authored-by: David Müller-Widmann <[email protected]>

Author: moble

src/rulesets/Base/base.jl

@@ -281,8 +281,10 @@ function rrule(config::RuleConfig{>:HasReverseMode}, ::typeof(map), f::F, xs::Tu
     y = map(first, hobbits)
     num_xs = Val(length(xs))
     paddings = map(x -> ntuple(Returns(NoTangent()), (length(x) - length_y)), xs)
-    all(isempty, paddings) || @error """map(f, xs::Tuple...) does not allow mistmatched lengths!
-        But its `rrule` does; when JuliaLang/julia #42216 is fixed this warning should be removed."""
+    @static if VERSION < v"1.10.0-DEV.1194"
+        all(isempty, paddings) || @error """map(f, xs::Tuple...) does not allow mismatched lengths in Julia <1.10!
+        But its `rrule` does."""
+    end
     function map_pullback(dy_raw)
         dy = unthunk(dy_raw)
         # We want to call the pullbacks in `rrule_via_ad` in reverse sequence to the forward pass:

test/rulesets/Base/base.jl

@@ -253,8 +253,8 @@ end
         test_rrule(map, make_two_vec, (4.0, 5.0 + 6im), check_inferred=false)
         test_rrule(map, Multiplier(rand() + im), Tuple(rand(3)), check_inferred=false)
 
-        if try map(+, (1,), (2,3)); true catch e; false end
-            # True when https://github.com/JuliaLang/julia/issues/42216 has been fixed
+        if VERSION >= v"1.10.0-DEV.1194"
+            # Mismatched lengths were not allowed before 1.10
             test_rrule(map, Multiplier(4.5), (6.7, 8.9), (0.1, 0.2, 0.3), check_inferred=false)
         end
     end