On Tue, Jan 08, 2019 at 03:45:54PM -0500, Jason Merrill wrote:
> On 1/8/19 10:42 AM, Marek Polacek wrote:
> > @@ -17020,6 +17020,18 @@ cp_parser_template_argument (cp_parser* parser)
> > argument = cp_parser_constant_expression (parser);
> > else
> > {
> > + /* In C++20, we can encounter a braced-init-list. */
> > + if (cxx_dialect >= cxx2a
> > + && cp_lexer_next_token_is (parser->lexer, CPP_OPEN_BRACE))
> > + {
> > + cp_parser_parse_tentatively (parser);
>
> Hmm, I wonder if we would get better diagnostics for an ill-formed
> braced-init-list without tentative parsing here. OK either way.
We get the same diagnostics with or without tentative parsing. But since
we've checked that the next following token is {, I think it would be
cleaner to just parse it for real.
This is what I'm about to commit then. Thanks for the reviews!
2019-01-08 Marek Polacek <[email protected]>
PR c++/88538 - braced-init-list in template-argument-list.
* parser.c (cp_parser_template_argument): Handle braced-init-list when
in C++20.
* g++.dg/cpp2a/nontype-class11.C: New test.
diff --git gcc/cp/parser.c gcc/cp/parser.c
index ca75c010e22..f441943dc8e 100644
--- gcc/cp/parser.c
+++ gcc/cp/parser.c
@@ -17026,6 +17026,14 @@ cp_parser_template_argument (cp_parser* parser)
argument = cp_parser_constant_expression (parser);
else
{
+ /* In C++20, we can encounter a braced-init-list. */
+ if (cxx_dialect >= cxx2a
+ && cp_lexer_next_token_is (parser->lexer, CPP_OPEN_BRACE))
+ {
+ bool expr_non_constant_p;
+ return cp_parser_braced_list (parser, &expr_non_constant_p);
+ }
+
/* With C++17 generalized non-type template arguments we need to handle
lvalue constant expressions, too. */
argument = cp_parser_assignment_expression (parser);
diff --git gcc/testsuite/g++.dg/cpp2a/nontype-class11.C
gcc/testsuite/g++.dg/cpp2a/nontype-class11.C
new file mode 100644
index 00000000000..8a06d23904b
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp2a/nontype-class11.C
@@ -0,0 +1,21 @@
+// PR c++/88538
+// { dg-do compile { target c++2a } }
+
+struct S {
+ unsigned a;
+ unsigned b;
+ constexpr S(unsigned _a, unsigned _b) noexcept: a{_a}, b{_b} { }
+};
+
+template <S p>
+void fnc()
+{
+}
+
+template<S s> struct X { };
+
+void f()
+{
+ fnc<{10,20}>();
+ X<{1, 2}> x;
+}
