From 5ae6554a1dcd2e39346030c06d364492901c9e8d Mon Sep 17 00:00:00 2001
From: Richard Smith <richard@metafoo.co.uk>
Date: Thu, 30 Jan 2020 17:42:17 -0800
Subject: [PATCH] PR41991: Accept attributes on defaulted and deleted friends.

Attributes are permitted on friend definitions, but we only checked for
a proper function body, not for the =default / =delete cases.
---
 clang/lib/Parse/ParseDeclCXX.cpp         | 2 +-
 clang/test/Parser/cxx-default-delete.cpp | 4 ++++
 clang/test/Parser/cxx2a-spaceship.cpp    | 6 ++++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index f872aa3a950c..09e5c7996fcd 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -2716,7 +2716,7 @@ Parser::ParseCXXClassMemberDeclaration(AccessSpecifier AS,
     // C++11 [dcl.attr.grammar] p4: If an attribute-specifier-seq appertains
     // to a friend declaration, that declaration shall be a definition.
     if (DeclaratorInfo.isFunctionDeclarator() &&
-        DefinitionKind != FDK_Definition && DS.isFriendSpecified()) {
+        DefinitionKind == FDK_Declaration && DS.isFriendSpecified()) {
       // Diagnose attributes that appear before decl specifier:
       // [[]] friend int foo();
       ProhibitAttributes(FnAttrs);
diff --git a/clang/test/Parser/cxx-default-delete.cpp b/clang/test/Parser/cxx-default-delete.cpp
index 8766d861732e..6c74937504b0 100644
--- a/clang/test/Parser/cxx-default-delete.cpp
+++ b/clang/test/Parser/cxx-default-delete.cpp
@@ -21,3 +21,7 @@ void baz() = delete;
 struct quux {
   int quux() = default; // expected-error{{constructor cannot have a return type}}
 };
+
+struct attrs {
+  [[noreturn]] friend void deleted_with_attrs() = delete;
+};
diff --git a/clang/test/Parser/cxx2a-spaceship.cpp b/clang/test/Parser/cxx2a-spaceship.cpp
index 24cece3eaa9d..f80420f89862 100644
--- a/clang/test/Parser/cxx2a-spaceship.cpp
+++ b/clang/test/Parser/cxx2a-spaceship.cpp
@@ -16,3 +16,9 @@ void f(X<0> x0, X<1> x1) {
   X<3> e = x0 < x0 <=> x0 << x0;
   X<3> f = x0 << x0 <=> x0 < x0; // expected-warning {{overloaded operator << has higher precedence than comparison operator}} expected-note 2{{}}
 }
+
+struct PR41991 {
+  [[nodiscard]] friend bool operator==(const PR41991&, const PR41991&) = default;
+  [[nodiscard]] friend bool operator!=(const PR41991&, const PR41991&) = delete;
+  [[nodiscard]] friend bool operator<(const PR41991&, const PR41991&); // expected-error {{an attribute list cannot appear here}}
+};