From 37d341d1f0d786e0df31a6983a80cf96c30d5faf Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Thu, 12 Jul 2018 21:11:25 +0000
Subject: [PATCH] PR38141: check whether noexcept-specifications are equivalent
 in redeclarations

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@336946 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaExceptionSpec.cpp                | 14 ++++++++++----
 test/CXX/except/except.spec/p3.cpp            | 10 ++++++++++
 test/SemaCXX/cxx1z-noexcept-function-type.cpp |  2 +-
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/lib/Sema/SemaExceptionSpec.cpp b/lib/Sema/SemaExceptionSpec.cpp
index 8dce6d59c6..df5bc9b82b 100644
--- a/lib/Sema/SemaExceptionSpec.cpp
+++ b/lib/Sema/SemaExceptionSpec.cpp
@@ -530,10 +530,16 @@ static bool CheckEquivalentExceptionSpecImpl(
     }
   }
 
-  // FIXME: We treat dependent noexcept specifications as compatible even if
-  // their expressions are not equivalent.
-  if (OldEST == EST_DependentNoexcept && NewEST == EST_DependentNoexcept)
-    return false;
+  // C++14 [except.spec]p3:
+  //   Two exception-specifications are compatible if [...] both have the form
+  //   noexcept(constant-expression) and the constant-expressions are equivalent
+  if (OldEST == EST_DependentNoexcept && NewEST == EST_DependentNoexcept) {
+    llvm::FoldingSetNodeID OldFSN, NewFSN;
+    Old->getNoexceptExpr()->Profile(OldFSN, S.Context, true);
+    New->getNoexceptExpr()->Profile(NewFSN, S.Context, true);
+    if (OldFSN == NewFSN)
+      return false;
+  }
 
   // Dynamic exception specifications with the same set of adjusted types
   // are compatible.
diff --git a/test/CXX/except/except.spec/p3.cpp b/test/CXX/except/except.spec/p3.cpp
index 03f1d7626c..d5af465104 100644
--- a/test/CXX/except/except.spec/p3.cpp
+++ b/test/CXX/except/except.spec/p3.cpp
@@ -104,3 +104,13 @@ void* operator new(mysize_t);
 void* operator new[](mysize_t);
 void* operator new[](mysize_t) throw(std::bad_alloc);
 
+template<bool X> void equivalent() noexcept (X);
+template<bool X> void equivalent() noexcept (X);
+
+template<bool X, bool Y> void not_equivalent() noexcept (X); // expected-note {{previous}}
+template<bool X, bool Y> void not_equivalent() noexcept (Y); // expected-error {{does not match}}
+
+template<bool X> void missing() noexcept (X); // expected-note {{previous}}
+// FIXME: The missing exception specification that we report here doesn't make
+// sense in the context of this declaration.
+template<bool P> void missing(); // expected-error {{missing exception specification 'noexcept(X)'}}
diff --git a/test/SemaCXX/cxx1z-noexcept-function-type.cpp b/test/SemaCXX/cxx1z-noexcept-function-type.cpp
index 814b04c6e4..82ed724e1b 100644
--- a/test/SemaCXX/cxx1z-noexcept-function-type.cpp
+++ b/test/SemaCXX/cxx1z-noexcept-function-type.cpp
@@ -10,7 +10,7 @@ template<typename T> void redecl1() noexcept(noexcept(T())); // ok, same type
 template<typename T> void redecl1() noexcept(noexcept(T())) {} // expected-error {{redefinition}}
 
 template<bool A, bool B> void redecl2() noexcept(A); // expected-note {{previous}}
-template<bool A, bool B> void redecl2() noexcept(B); // expected-error {{conflicting types}}
+template<bool A, bool B> void redecl2() noexcept(B); // expected-error {{does not match previous}}
 
 // These have the same canonical type, but are still different.
 template<typename A, typename B> void redecl3() throw(A); // expected-note {{previous}}
-- 
2.40.0