From 44b24dd71734c1fe2c036ed4a856d5cb293f90af Mon Sep 17 00:00:00 2001
From: Sasank <56350738+sasi591@users.noreply.github.com>
Date: Thu, 3 Nov 2022 16:17:53 +0530
Subject: [PATCH] Fix isdone for empty product iterators, fixes #43921 (#43947)

* Fix the issue #43921

* add a test

Co-authored-by: Kristoffer <kcarlsson89@gmail.com>
(cherry picked from commit b8a77daf3832d4134ad46327049772a663e2643d)
---
 base/iterators.jl | 1 +
 test/iterators.jl | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/base/iterators.jl b/base/iterators.jl
index 3e339c59bebcb..e14880b6c0a33 100644
--- a/base/iterators.jl
+++ b/base/iterators.jl
@@ -1041,6 +1041,7 @@ iterate(::ProductIterator{Tuple{}}, state) = nothing
     done1 === true || return done1 # false or missing
     return _pisdone(tail(iters), tail(states)) # check tail
 end
+@inline isdone(::ProductIterator{Tuple{}}, states) = true
 @inline isdone(P::ProductIterator, states) = _pisdone(P.iterators, states)
 
 @inline _piterate() = ()
diff --git a/test/iterators.jl b/test/iterators.jl
index 0a038698ea07c..adf8d79e4429e 100644
--- a/test/iterators.jl
+++ b/test/iterators.jl
@@ -902,3 +902,11 @@ end
     @test last(Iterators.map(identity, 1:3)) == 3
     @test last(Iterators.filter(iseven, (Iterators.map(identity, 1:3)))) == 2
 end
+
+@testset "empty product iterators" begin
+    v = nothing
+    for (z,) in zip(Iterators.product())
+        v = z
+    end
+    @test v == ()
+end