From b19ba88d9fe1ba18573049fd0f6aa574ce0870b7 Mon Sep 17 00:00:00 2001
From: Jarrett Revels <jarrettrevels@gmail.com>
Date: Tue, 8 May 2018 11:17:50 -0400
Subject: [PATCH] fix isvatuple to properly handle UnionAlls (#27018)

* fix isvatuple to properly handle UnionAlls

* add tests for #27018
---
 base/essentials.jl | 10 +++++++++-
 test/core.jl       | 10 ++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/base/essentials.jl b/base/essentials.jl
index 793a276827e14..8e2c019d4d14d 100644
--- a/base/essentials.jl
+++ b/base/essentials.jl
@@ -207,7 +207,15 @@ function isvarargtype(@nospecialize(t))
     return isa(t, DataType) && (t::DataType).name === _va_typename
 end
 
-isvatuple(t::DataType) = (n = length(t.parameters); n > 0 && isvarargtype(t.parameters[n]))
+function isvatuple(@nospecialize(t))
+    t = unwrap_unionall(t)
+    if isa(t, DataType)
+        n = length(t.parameters)
+        return n > 0 && isvarargtype(t.parameters[n])
+    end
+    return false
+end
+
 function unwrapva(@nospecialize(t))
     # NOTE: this returns a related type, but it's NOT a subtype of the original tuple
     t2 = unwrap_unionall(t)
diff --git a/test/core.jl b/test/core.jl
index 668221ed7bf0b..fb05c73b3a711 100644
--- a/test/core.jl
+++ b/test/core.jl
@@ -6051,3 +6051,13 @@ g2_23206(::Tuple{Type{Int}}) = 1
 let x26739 = Int[1]
     @test eval(:(identity.($x26739))) == x26739
 end
+
+# issue #27018
+@test Base.isvatuple(Tuple{Float64,Vararg{Int}})
+@test Base.isvatuple(Tuple{T,Vararg{Int}} where T)
+@test Base.isvatuple(Tuple{Int,Int,Vararg{Int,N}} where N)
+@test Base.isvatuple(Tuple{T,S,Vararg{T}} where T<:S where S)
+@test Base.isvatuple(Tuple{T,S,Vararg{T,3}} where T<:S where S)
+@test !Base.isvatuple(Tuple{Float64,Vararg{Int,1}})
+@test !Base.isvatuple(Tuple{T,Vararg{Int,2}} where T)
+@test !Base.isvatuple(Tuple{Int,Int,Vararg{Int,2}})