c++: C++20 DR 2237, disallow simple-template-id in cdtor.

This patch implements DR 2237 which says that a simple-template-id is
no longer valid as the declarator-id of a constructor or destructor;
see [diff.cpp17.class]#2.  It is not explicitly stated but out-of-line
destructors with a simple-template-id are also meant to be ill-formed
now.  (Out-of-line constructors like that are invalid since DR1435 I
think.)  This change only applies to C++20; it is not a DR against C++17.

I'm not crazy about the diagnostic in constructors but ISTM that
cp_parser_constructor_declarator_p shouldn't print errors.

	DR 2237
	* parser.c (cp_parser_unqualified_id): Reject simple-template-id as
	the declarator-id of a destructor.
	(cp_parser_constructor_declarator_p): Reject simple-template-id as
	the declarator-id of a constructor.

	* g++.dg/DRs/dr2237.C: New test.
	* g++.dg/parse/constructor2.C: Add dg-error for C++20.
	* g++.dg/parse/dtor12.C: Likewise.
	* g++.dg/parse/dtor4.C: Likewise.
	* g++.dg/template/dtor4.C: Adjust dg-error.
	* g++.dg/template/error34.C: Likewise.
	* g++.old-deja/g++.other/inline15.C: Only run for C++17 and lesses.
	* g++.old-deja/g++.pt/ctor2.C: Add dg-error for C++20.

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 9ed4c58b403900a3a20aee7aa15dea552d1932dc..cfe5cf003664d2062503770b49248d2f28f44e0e 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,11 @@
+2020-05-20  Marek Polacek  <polacek@redhat.com>
+
+       DR 2237
+       * parser.c (cp_parser_unqualified_id): Reject simple-template-id as
+       the declarator-id of a destructor.
+       (cp_parser_constructor_declarator_p): Reject simple-template-id as
+       the declarator-id of a constructor.
+
 2020-05-20  Marek Polacek  <polacek@redhat.com>
 
        DR 2289

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index a6a5d975af3edfe8c5cc7ff1b39280c37e463dbc..a8082d39aca25b51d261fb98f2d1e7e943a6673d 100644 (file)
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -6108,6 +6108,15 @@ cp_parser_unqualified_id (cp_parser* parser,
            return build_min_nt_loc (loc, BIT_NOT_EXPR, make_auto ());
          }
 
+       /* DR 2237 (C++20 only): A simple-template-id is no longer valid as the
+          declarator-id of a constructor or destructor.  */
+       if (token->type == CPP_TEMPLATE_ID && cxx_dialect >= cxx20)
+         {
+           if (!cp_parser_simulate_error (parser))
+             error_at (tilde_loc, "template-id not allowed for destructor");
+           return error_mark_node;
+         }
+
        /* If there was an explicit qualification (S::~T), first look
           in the scope given by the qualification (i.e., S).
 
@@ -28628,7 +28637,9 @@ cp_parser_constructor_declarator_p (cp_parser *parser, cp_parser_flags flags,
   if (next_token->type != CPP_NAME
       && next_token->type != CPP_SCOPE
       && next_token->type != CPP_NESTED_NAME_SPECIFIER
-      && next_token->type != CPP_TEMPLATE_ID)
+      /* DR 2237 (C++20 only): A simple-template-id is no longer valid as the
+        declarator-id of a constructor or destructor.  */
+      && (next_token->type != CPP_TEMPLATE_ID || cxx_dialect >= cxx20))
     return false;
 
   /* Parse tentatively; we are going to roll back all of the tokens

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9e437af7452c683161d1e52bad527ffe63dd06c6..e9d334d3aef9396359153e8fdda1af998ace1601 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,15 @@
+2020-05-20  Marek Polacek  <polacek@redhat.com>
+
+       DR 2237
+       * g++.dg/DRs/dr2237.C: New test.
+       * g++.dg/parse/constructor2.C: Add dg-error for C++20.
+       * g++.dg/parse/dtor12.C: Likewise.
+       * g++.dg/parse/dtor4.C: Likewise.
+       * g++.dg/template/dtor4.C: Adjust dg-error.
+       * g++.dg/template/error34.C: Likewise.
+       * g++.old-deja/g++.other/inline15.C: Only run for C++17 and lesses.
+       * g++.old-deja/g++.pt/ctor2.C: Add dg-error for C++20.
+
 2020-05-20  Marek Polacek  <polacek@redhat.com>
 
        DR 2289

diff --git a/gcc/testsuite/g++.dg/DRs/dr2237.C b/gcc/testsuite/g++.dg/DRs/dr2237.C
new file mode 100644 (file)
index 0000000..f3d6d11
--- /dev/null
+++ b/gcc/testsuite/g++.dg/DRs/dr2237.C
@@ -0,0 +1,18 @@
+// DR 2237 - Can a template-id name a constructor?
+
+template<class T>
+struct X {
+  X<T>(); // { dg-error "expected" "" { target c++20 } }
+  X(int); // OK, injected-class-name used
+  ~X<T>(); // { dg-error "template-id not allowed for destructor" "" { target c++20 } }
+};
+
+// ill-formed since DR1435
+template<typename T> X<T>::X<T>() {} // { dg-error "names the constructor|as no template constructors" }
+template<typename T> X<T>::~X<T>() {} // { dg-error "template-id not allowed for destructor" "" { target c++20 } }
+
+struct Q {
+  // ill-formed since DR1435
+  template<typename T> friend X<T>::X<T>(); // { dg-error "names the constructor|as no template constructors" }
+  template<typename T> friend X<T>::~X<T>(); // { dg-error "template-id not allowed for destructor" "" { target c++20 } }
+};

diff --git a/gcc/testsuite/g++.dg/parse/constructor2.C b/gcc/testsuite/g++.dg/parse/constructor2.C
index e514e9397e9278ed7143b7f0cfe4c89a056d10e0..d620f41e0279d469caafb3c79fe3a69164c88d54 100644 (file)
--- a/gcc/testsuite/g++.dg/parse/constructor2.C
+++ b/gcc/testsuite/g++.dg/parse/constructor2.C
@@ -5,7 +5,7 @@ class T
 { 
 public: 
   T(short,short f=0) {} 
-  T<TClass>(int f) {} 
-  T<TClass>(int f=0,const char* b=0) {} 
+  T<TClass>(int f) {} // { dg-error "expected" "" { target c++20 } }
+  T<TClass>(int f=0,const char* b=0) {} // { dg-error "expected" "" { target c++20 } }
 }; 
 

diff --git a/gcc/testsuite/g++.dg/parse/dtor12.C b/gcc/testsuite/g++.dg/parse/dtor12.C
index 1acdfa36b69d41f84b4be6bf6de2fd5577c64a84..dda7388192be21034b42958cfa02913cfa3f23e7 100644 (file)
--- a/gcc/testsuite/g++.dg/parse/dtor12.C
+++ b/gcc/testsuite/g++.dg/parse/dtor12.C
@@ -2,5 +2,5 @@
 
 template <class T> class a
 {
-  ~a<T>();
+  ~a<T>(); // { dg-error "template-id not allowed for destructor" "" { target c++20 } }
 };

diff --git a/gcc/testsuite/g++.dg/parse/dtor4.C b/gcc/testsuite/g++.dg/parse/dtor4.C
index 729ee2fa130dd2282b7529468abf8efede5f4513..1a1a8458745d1100dbcbd898d902f55fdbf83e86 100644 (file)
--- a/gcc/testsuite/g++.dg/parse/dtor4.C
+++ b/gcc/testsuite/g++.dg/parse/dtor4.C
@@ -7,4 +7,4 @@ template <int N> struct X {
 };
 
 template <int N>
-X<N>::~X<N>(){}
+X<N>::~X<N>(){} // { dg-error "template-id not allowed for destructor" "" { target c++20 } }

diff --git a/gcc/testsuite/g++.dg/template/dtor4.C b/gcc/testsuite/g++.dg/template/dtor4.C
index 4f277b248bda990075ba4675c488734cd146a680..917681fc13e0343cb6841133723764455fcada55 100644 (file)
--- a/gcc/testsuite/g++.dg/template/dtor4.C
+++ b/gcc/testsuite/g++.dg/template/dtor4.C
@@ -5,5 +5,5 @@
 
 template<int> struct A
 {
-  ~A<0>(); // { dg-error "parse error|declaration" }
+  ~A<0>(); // { dg-error "parse error|declaration|template-id" }
 };

diff --git a/gcc/testsuite/g++.dg/template/error34.C b/gcc/testsuite/g++.dg/template/error34.C
index d0cbcaef28e92a71b9b420c3850605bdf6d18754..ab688d9ba8c3625dcaa8f42f5ead599f3f268221 100644 (file)
--- a/gcc/testsuite/g++.dg/template/error34.C
+++ b/gcc/testsuite/g++.dg/template/error34.C
@@ -3,27 +3,27 @@
 
 template<typename T> struct A
 {
-  A<__builtin_offsetof(T, x)>();       // { dg-error "type/value mismatch|offsetof\\(T, x\\)" }
+  A<__builtin_offsetof(T, x)>();       // { dg-error "type/value mismatch|offsetof\\(T, x\\)|expected" }
 };
 
 template<typename T> struct B
 {
-  B<__builtin_offsetof(T, x.y)>();     // { dg-error "type/value mismatch|offsetof\\(T, x.y\\)" }
+  B<__builtin_offsetof(T, x.y)>();     // { dg-error "type/value mismatch|offsetof\\(T, x.y\\)|expected" }
 };
 
 template<typename T> struct C
 {
-  C<__builtin_offsetof(T, x[6])>();    // { dg-error "type/value mismatch|offsetof\\(T, x\\\[6\\\]\\)" }
+  C<__builtin_offsetof(T, x[6])>();    // { dg-error "type/value mismatch|offsetof\\(T, x\\\[6\\\]\\)|expected" }
 };
 
 template<typename T> struct D
 {
-  D<__builtin_offsetof(T, x.y[6].z)>();        // { dg-error "type/value mismatch|offsetof\\(T, x.y\\\[6\\\].z\\)" }
+  D<__builtin_offsetof(T, x.y[6].z)>();        // { dg-error "type/value mismatch|offsetof\\(T, x.y\\\[6\\\].z\\)|expected" }
 };
 
 struct E { int x; };
 
 template<typename T> struct F
 {
-  F<__builtin_offsetof(E, x)>();       // { dg-error "type/value mismatch|offsetof\\(E, x\\)" }
+  F<__builtin_offsetof(E, x)>();       // { dg-error "type/value mismatch|offsetof\\(E, x\\)|expected" }
 };

diff --git a/gcc/testsuite/g++.old-deja/g++.other/inline15.C b/gcc/testsuite/g++.old-deja/g++.other/inline15.C
index 43f7f5e3025015147ce3387da95b169b9905cdb7..a31c60960a5a834466c85da981ea1a55915b2d41 100644 (file)
--- a/gcc/testsuite/g++.old-deja/g++.other/inline15.C
+++ b/gcc/testsuite/g++.old-deja/g++.other/inline15.C
@@ -1,4 +1,4 @@
-// { dg-do assemble  }
+// { dg-do assemble { target c++17_down } }
 // { dg-options "-O1" }
 // Origin: Jakub Jelinek <jakub@redhat.com>
 

diff --git a/gcc/testsuite/g++.old-deja/g++.pt/ctor2.C b/gcc/testsuite/g++.old-deja/g++.pt/ctor2.C
index a8be91ddbb917f12fb01650045a01b24112115ef..bf418ba48c747bf0ba632a57930e592019aa2cb3 100644 (file)
--- a/gcc/testsuite/g++.old-deja/g++.pt/ctor2.C
+++ b/gcc/testsuite/g++.old-deja/g++.pt/ctor2.C
@@ -4,7 +4,7 @@
 
 template <class T>
 struct A {
-  A<T>();
+  A<T>(); // { dg-error "expected" "" { target c++20 } }
 };
 
 template <class T>