From 89502c6873c1be53cb183cf57d41a65b74a6bbe6 Mon Sep 17 00:00:00 2001
From: Erik Pilkington <erik.pilkington@gmail.com>
Date: Thu, 26 Jul 2018 23:40:42 +0000
Subject: [PATCH] [Sema] Fix a crash by completing a type before using it

Only apply this exception on a type that we're able to check.

rdar://41903969

Differential revision: https://reviews.llvm.org/D49868

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@338089 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaInit.cpp                         |  1 +
 ...xx1z-class-template-argument-deduction.cpp | 25 +++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index 9b5a918b71..0dddbdc36f 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -9130,6 +9130,7 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
       Expr *E = ListInit->getInit(0);
       auto *RD = E->getType()->getAsCXXRecordDecl();
       if (!isa<InitListExpr>(E) && RD &&
+          isCompleteType(Kind.getLocation(), E->getType()) &&
           isOrIsDerivedFromSpecializationOf(RD, Template))
         TryListConstructors = false;
     }
diff --git a/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp b/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
index de61e44a6e..f72cb886d8 100644
--- a/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
+++ b/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
@@ -348,6 +348,31 @@ namespace member_guides {
   };
 }
 
+namespace rdar41903969 {
+template <class T> struct A {};
+template <class T> struct B;
+template <class T> struct C {
+  C(A<T>&);
+  C(B<T>&);
+};
+
+void foo(A<int> &a, B<int> &b) {
+  (void)C{b};
+  (void)C{a};
+}
+
+template<typename T> struct X {
+  X(std::initializer_list<T>) = delete;
+  X(const X&);
+};
+
+template <class T> struct D : X<T> {};
+
+void bar(D<int>& d) {
+  (void)X{d};
+}
+}
+
 #else
 
 // expected-no-diagnostics
-- 
2.40.0