From 7257fa02528999a5fd0080d047bbab5df39209e9 Mon Sep 17 00:00:00 2001
From: Jeff Bezanson <jeff.bezanson@gmail.com>
Date: Thu, 13 Feb 2020 17:31:29 -0500
Subject: [PATCH] fix #34752, inference bug in varargs with constant prop

---
 base/compiler/inferenceresult.jl |  8 ++++++--
 test/compiler/inference.jl       | 11 +++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/base/compiler/inferenceresult.jl b/base/compiler/inferenceresult.jl
index a466a00df89df..24206369b3018 100644
--- a/base/compiler/inferenceresult.jl
+++ b/base/compiler/inferenceresult.jl
@@ -35,9 +35,13 @@ function matching_cache_argtypes(linfo::MethodInstance, given_argtypes::Vector)
     if linfo.def.isva
         isva_given_argtypes = Vector{Any}(undef, nargs)
         for i = 1:(nargs - 1)
-            isva_given_argtypes[i] = given_argtypes[i]
+            isva_given_argtypes[i] = argtype_by_index(given_argtypes, i)
+        end
+        if length(given_argtypes) >= nargs || !isvarargtype(given_argtypes[end])
+            isva_given_argtypes[nargs] = tuple_tfunc(given_argtypes[nargs:end])
+        else
+            isva_given_argtypes[nargs] = tuple_tfunc(given_argtypes[end:end])
         end
-        isva_given_argtypes[nargs] = tuple_tfunc(given_argtypes[nargs:end])
         given_argtypes = isva_given_argtypes
     end
     cache_argtypes, overridden_by_const = matching_cache_argtypes(linfo, nothing)
diff --git a/test/compiler/inference.jl b/test/compiler/inference.jl
index b275cdf904757..15e03aefd6a1b 100644
--- a/test/compiler/inference.jl
+++ b/test/compiler/inference.jl
@@ -2492,3 +2492,14 @@ struct X33954
 end
 f33954(x) = rand(Bool) ? f33954((x,)) : x
 @test Base.return_types(f33954, Tuple{X33954})[1] >: X33954
+
+# issue #34752
+struct a34752{T} end
+function a34752(c, d...)
+    length(d) > 1 || error()
+end
+function h34752()
+    g = Tuple[(42, Any[42][1], 42)][1]
+    a34752(g...)
+end
+@test h34752() === true