[Sema] Prevent InstantiateClass from checking unrelated exception specs.

Sema::InstantiateClass should check only exception specs added during
class instantiation and ignore already present delayed specs. This fixes
a case where we instantiate a class before parsing member initializers,
check exceptions for a different class and fail to find a member
initializer. Which is required for comparing exception specs for
explicitly-defaulted and implicit default constructor. With the fix we
are still checking exception specs but only after member initializers
are present.

Removing errors in crash-unparsed-exception.cpp is acceptable according
to discussion in PR24000 because other compilers accept code in
crash-unparsed-exception.cpp as valid.

rdar://problem/34167492

Reviewers: davide, rsmith

Reviewed By: rsmith

Subscribers: dim, cfe-commits

Differential Revision: https://reviews.llvm.org/D37881

llvm-svn: 313906

1 files changed, 27 insertions, 0 deletions

diff --git a/clang/test/SemaTemplate/default-arguments-cxx0x.cpp b/clang/test/SemaTemplate/default-arguments-cxx0x.cpp
index d9fa2b4a825..c24ed12a024 100644
--- a/clang/test/SemaTemplate/default-arguments-cxx0x.cpp
+++ b/clang/test/SemaTemplate/default-arguments-cxx0x.cpp
@@ -87,3 +87,30 @@ namespace PR13986 {
     A<1> m_target;
   };
 }
+
+// rdar://problem/34167492
+// Template B is instantiated during checking if defaulted A copy constructor
+// is constexpr. For this we check if S<int> copy constructor is constexpr. And
+// for this we check S constructor template with default argument that mentions
+// template B. In  turn, template instantiation triggers checking defaulted
+// members exception spec. The problem is that it checks defaulted members not
+// for instantiated class only, but all defaulted members so far. In this case
+// we try to check exception spec for A default constructor which requires
+// initializer for the field _a. But initializers are added after constexpr
+// check so we reject the code because cannot find _a initializer.
+namespace rdar34167492 {
+  template <typename T> struct B { using type = bool; };
+
+  template <typename T> struct S {
+    S() noexcept;
+
+    template <typename U, typename B<U>::type = true>
+    S(const S<U>&) noexcept;
+  };
+
+  class A {
+    A() noexcept = default;
+    A(const A&) noexcept = default;
+    S<int> _a{};
+  };
+}