From: Marek Polacek <polacek@redhat.com>
Date: Sat, 25 May 2019 14:46:15 +0000 (+0000)
Subject: PR c++/90572 - wrong disambiguation in friend declaration.
X-Git-Tag: releases/gcc-9.2.0~319
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3d39d5a63a32383713f55f7a64483067b4237f52;p=thirdparty%2Fgcc.git

PR c++/90572 - wrong disambiguation in friend declaration.

	* parser.c (cp_parser_constructor_declarator_p): Don't allow missing
	typename for friend declarations.

	* g++.dg/cpp2a/typename16.C: New test.
	* g++.dg/parse/friend13.C: New test.

From-SVN: r271620
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 7548b65589c0..40c920280dc2 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,12 @@
+2019-05-25  Marek Polacek  <polacek@redhat.com>
+
+	Backported from mainline
+	2019-05-25  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/90572 - wrong disambiguation in friend declaration.
+	* parser.c (cp_parser_constructor_declarator_p): Don't allow missing
+	typename for friend declarations.
+
 2019-05-20  Jonathan Wakely  <jwakely@redhat.com>
 
 	Backported from mainline
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 3d908916ae3f..a7218e752b16 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -27629,9 +27629,19 @@ cp_parser_constructor_declarator_p (cp_parser *parser, cp_parser_flags flags,
 	  parser->num_template_parameter_lists = 0;
 
 	  /* Look for the type-specifier.  It's not optional, but its typename
-	     might be.  */
+	     might be.  Unless this is a friend declaration; we don't want to
+	     treat
+
+	       friend S (T::fn)(int);
+
+	     as a constructor, but with P0634, we might assume a type when
+	     looking for the type-specifier.  It is actually a function named
+	     `T::fn' that takes one parameter (of type `int') and returns a
+	     value of type `S'.  Constructors can be friends, but they must
+	     use a qualified name.  */
 	  cp_parser_type_specifier (parser,
-				    (flags & ~CP_PARSER_FLAGS_OPTIONAL),
+				    (friend_p ? CP_PARSER_FLAGS_NONE
+				     : (flags & ~CP_PARSER_FLAGS_OPTIONAL)),
 				    /*decl_specs=*/NULL,
 				    /*is_declarator=*/true,
 				    /*declares_class_or_enum=*/NULL,
diff --git a/gcc/testsuite/g++.dg/cpp2a/typename16.C b/gcc/testsuite/g++.dg/cpp2a/typename16.C
new file mode 100644
index 000000000000..7f4242a1dbae
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/typename16.C
@@ -0,0 +1,11 @@
+// PR c++/90572
+// { dg-do compile { target c++2a } }
+
+struct X { X(int); };
+
+template<typename T> struct S {
+  friend X::X(T::t);
+};
+
+struct W { using t = int; };
+S<W> s;
diff --git a/gcc/testsuite/g++.dg/parse/friend13.C b/gcc/testsuite/g++.dg/parse/friend13.C
new file mode 100644
index 000000000000..d716247a5da8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/friend13.C
@@ -0,0 +1,16 @@
+// PR c++/90572
+
+template <typename T> struct C {
+  friend C(T::fn)();
+  friend C(T::fn)(int);
+  friend C(T::fn)(int, int);
+};
+
+struct X { };
+
+template<typename T>
+struct B {
+  friend X(T::fn)();
+  friend X(T::fn)(int);
+  friend X(T::fn)(int, int);
+};