From 3756bb381e5e98ad8294add65ac56f2f788c9098 Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@mit.edu>
Date: Fri, 31 May 2019 12:55:21 -0400
Subject: [PATCH] treat Pair as broadcast scalar

---
 NEWS.md           | 1 +
 base/broadcast.jl | 2 +-
 base/pair.jl      | 2 +-
 test/broadcast.jl | 4 ++++
 4 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 04ee2158d70d3..7c603f907e453 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -31,6 +31,7 @@ Standard library changes
   (environment, flags, working directory, etc) if `x` is the first interpolant and errors
   otherwise ([#24353]).
 * `IPAddr` subtypes now behave like scalars when used in broadcasting ([#32133]).
+* `Pair` is now treated as a scalar for broadcasting ([#32209]).
 
 #### LinearAlgebra
 
diff --git a/base/broadcast.jl b/base/broadcast.jl
index 4d5ca6b92fe19..2ff4e04dfc7b3 100644
--- a/base/broadcast.jl
+++ b/base/broadcast.jl
@@ -652,7 +652,7 @@ julia> Broadcast.broadcastable("hello") # Strings break convention of matching i
 Base.RefValue{String}("hello")
 ```
 """
-broadcastable(x::Union{Symbol,AbstractString,Function,UndefInitializer,Nothing,RoundingMode,Missing,Val,Ptr,Regex}) = Ref(x)
+broadcastable(x::Union{Symbol,AbstractString,Function,UndefInitializer,Nothing,RoundingMode,Missing,Val,Ptr,Regex,Pair}) = Ref(x)
 broadcastable(::Type{T}) where {T} = Ref{Type{T}}(T)
 broadcastable(x::Union{AbstractArray,Number,Ref,Tuple,Broadcasted}) = x
 # Default to collecting iterables — which will error for non-iterables
diff --git a/base/pair.jl b/base/pair.jl
index a059a55b765a8..3ce88177787cc 100644
--- a/base/pair.jl
+++ b/base/pair.jl
@@ -21,7 +21,7 @@ const => = Pair
 
 Construct a `Pair` object with type `Pair{typeof(x), typeof(y)}`. The elements
 are stored in the fields `first` and `second`. They can also be accessed via
-iteration.
+iteration (but a `Pair` is treated as a single "scalar" for broadcasting operations).
 
 See also: [`Dict`](@ref)
 
diff --git a/test/broadcast.jl b/test/broadcast.jl
index 5ee56cf94fe87..cab66a1534b4b 100644
--- a/test/broadcast.jl
+++ b/test/broadcast.jl
@@ -822,3 +822,7 @@ let a = rand(5), b = rand(5), c = copy(a)
     x[[1,1]] .+= 1
     @test x == [2]
 end
+
+# treat Pair as scalar:
+@test replace.(split("The quick brown fox jumps over the lazy dog"), r"[aeiou]"i => "_") ==
+      ["Th_", "q__ck", "br_wn", "f_x", "j_mps", "_v_r", "th_", "l_zy", "d_g"]