Remove old warning about map

Closes #798

Author: moble

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRules"
 uuid = "082447d4-558c-5d27-93f4-14fc19e9eca2"
-version = "1.72.5"
+version = "1.72.6"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

src/rulesets/Base/base.jl

@@ -249,8 +249,6 @@ 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."""
     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: