From 1bb509f5bf629fb2e1ff89bf66f0d0467b2b1ab1 Mon Sep 17 00:00:00 2001
From: KristofferC <kristoffer.carlsson@juliacomputing.com>
Date: Thu, 19 Oct 2023 14:31:02 +0200
Subject: [PATCH] fix eltype for partition iterators of substrings

---
 base/strings/util.jl | 2 ++
 test/iterators.jl    | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/base/strings/util.jl b/base/strings/util.jl
index 890afaf62b2ee..db4e7917c009e 100644
--- a/base/strings/util.jl
+++ b/base/strings/util.jl
@@ -571,6 +571,8 @@ end
 
 # Specialization for partition(s,n) to return a SubString
 eltype(::Type{PartitionIterator{T}}) where {T<:AbstractString} = SubString{T}
+# SubStrings do not nest
+eltype(::Type{PartitionIterator{T}}) where {T<:SubString} = T
 
 function iterate(itr::PartitionIterator{<:AbstractString}, state = firstindex(itr.c))
     state > ncodeunits(itr.c) && return nothing
diff --git a/test/iterators.jl b/test/iterators.jl
index 59588bdac9684..a60ec32bb9ac0 100644
--- a/test/iterators.jl
+++ b/test/iterators.jl
@@ -1001,3 +1001,7 @@ end
     end
     @test v == ()
 end
+
+@testset "collect partition substring" begin
+    @test collect(Iterators.partition(lstrip("01111", '0'), 2)) == ["11", "11"]
+end