fix last(::Enumerate) when indexing not supported (#59226)

Author: adienes

base/iterators.jl

@@ -198,7 +198,7 @@ size(e::Enumerate) = size(e.itr)
     n === nothing && return n
     (i, n[1]), (i+1, n[2])
 end
-last(e::Enumerate) = (length(e.itr), e.itr[end])
+last(e::Enumerate) = (length(e.itr), last(e.itr))
 
 eltype(::Type{Enumerate{I}}) where {I} = TupleOrBottom(Int, eltype(I))
 

test/iterators.jl

@@ -1070,6 +1070,7 @@ end
 @testset "last for iterators" begin
     @test last(Iterators.map(identity, 1:3)) == 3
     @test last(Iterators.filter(iseven, (Iterators.map(identity, 1:3)))) == 2
+    @test last(enumerate(Iterators.flatten((1,2,3)))) == (3,3)
 end
 
 @testset "isempty and isdone for Generators" begin