From ab0c6dd56752c1860fa8d97471f0eafaac671a85 Mon Sep 17 00:00:00 2001
From: Pepijn de Vos <pepijndevos@gmail.com>
Date: Tue, 9 Nov 2021 19:41:54 +0100
Subject: [PATCH] Add missing type parameter to TakeWhile (#42958)

Without this `TakeWhile` has `eltype` of `Any`
---
 base/iterators.jl | 2 +-
 test/iterators.jl | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/base/iterators.jl b/base/iterators.jl
index c76f8b8d4c3a0..48f9017fddce5 100644
--- a/base/iterators.jl
+++ b/base/iterators.jl
@@ -790,7 +790,7 @@ end
 
 IteratorSize(::Type{<:TakeWhile}) = SizeUnknown()
 eltype(::Type{TakeWhile{I,P}} where P) where {I} = eltype(I)
-IteratorEltype(::Type{TakeWhile{I}} where P) where {I} = IteratorEltype(I)
+IteratorEltype(::Type{TakeWhile{I, P}} where P) where {I} = IteratorEltype(I)
 
 
 # dropwhile
diff --git a/test/iterators.jl b/test/iterators.jl
index b16b75291c270..8de847018255d 100644
--- a/test/iterators.jl
+++ b/test/iterators.jl
@@ -212,6 +212,7 @@ end
     @test collect(takewhile(Returns(true),5:10)) == 5:10
     @test collect(takewhile(isodd,[1,1,2,3])) == [1,1]
     @test collect(takewhile(<(2), takewhile(<(3), [1,1,2,3]))) == [1,1]
+    @test Base.IteratorEltype(typeof(takewhile(<(4),Iterators.map(identity, 1:10)))) isa Base.EltypeUnknown
 end
 
 # dropwhile
@@ -224,6 +225,7 @@ end
     @test isempty(dropwhile(Returns(true), 1:3))
     @test collect(dropwhile(isodd,[1,1,2,3])) == [2,3]
     @test collect(dropwhile(iseven,dropwhile(isodd,[1,1,2,3]))) == [3]
+    @test Base.IteratorEltype(typeof(dropwhile(<(4),Iterators.map(identity, 1:10)))) isa Base.EltypeUnknown
 end
 
 # cycle