C++ PATCH for c++/87781, detect invalid elaborated-type-specifier

[Marek Polacek]

On Wed, Nov 14, 2018 at 10:03:50AM -0500, Jason Merrill wrote:
> On Wed, Nov 14, 2018 at 9:55 AM Marek Polacek <polacek@redhat.com> wrote:
> >
> > In elaborated-type-specifier, the typename keyword can only follow a
> > nested-name-specifier:
> >
> >   class-key nested-name-specifier template[opt] simple-template-id
> >
> > but we weren't detecting it.
> >
> > Bootstrapped/regtested on x86_64-linux, ok for trunk?
> >
> > 2018-11-14  Marek Polacek  <polacek@redhat.com>
> >
> >         PR c++/87781 - detect invalid elaborated-type-specifier.
> >         * parser.c (cp_parser_elaborated_type_specifier): Ensure that
> >         typename follows a nested-name-specifier.
> >
> >         * g++.dg/parse/elab3.C: New test.
> >
> > diff --git gcc/cp/parser.c gcc/cp/parser.c
> > index e9e49b15702..0ab44ab93e3 100644
> > --- gcc/cp/parser.c
> > +++ gcc/cp/parser.c
> > @@ -17986,6 +17986,10 @@ cp_parser_elaborated_type_specifier (cp_parser* parser,
> >          template-id or not.  */
> >        if (!template_p)
> >         cp_parser_parse_tentatively (parser);
> > +      /* The `template' keyword must follow a nested-name-specifier.  */
> > +      else if (!nested_name_specifier)
> > +       return error_mark_node;
> 
> Don't we want a diagnostic here?

We'd get "invalid declarator" even without a diagnostic there but I guess it'd
be nicer so say what the actual problem is.  Unsure which diagnostic to go with,
this patch uses cp_parser_error though.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2018-11-14  Marek Polacek  <polacek@redhat.com>

	PR c++/87781 - detect invalid elaborated-type-specifier.
	* parser.c (cp_parser_elaborated_type_specifier): Ensure that
	typename follows a nested-name-specifier.

	* g++.dg/parse/elab3.C: New test.
	* g++.dg/template/crash115.C: Adjust dg-error.

diff --git gcc/cp/parser.c gcc/cp/parser.c
index e9e49b15702..bfcf42b0f39 100644
--- gcc/cp/parser.c
+++ gcc/cp/parser.c
@@ -17986,6 +17986,14 @@ cp_parser_elaborated_type_specifier (cp_parser* parser,
 	 template-id or not.  */
       if (!template_p)
 	cp_parser_parse_tentatively (parser);
+      /* The `template' keyword must follow a nested-name-specifier.  */
+      else if (!nested_name_specifier)
+	{
+	  cp_parser_error (parser, "%<template%> must follow a nested-"
+			   "name-specifier");
+	  return error_mark_node;
+	}
+
       /* Parse the template-id.  */
       token = cp_lexer_peek_token (parser->lexer);
       decl = cp_parser_template_id (parser, template_p,
diff --git gcc/testsuite/g++.dg/parse/elab3.C gcc/testsuite/g++.dg/parse/elab3.C
new file mode 100644
index 00000000000..61338fb7ac4
--- /dev/null
+++ gcc/testsuite/g++.dg/parse/elab3.C
@@ -0,0 +1,6 @@
+// PR c++/87781
+// { dg-do compile }
+// { dg-options "" }
+
+template<class> class A;
+class template A<int> *p; // { dg-error ".template. must follow|invalid" }
diff --git gcc/testsuite/g++.dg/template/crash115.C gcc/testsuite/g++.dg/template/crash115.C
index 5c9f525cd64..80f8683a136 100644
--- gcc/testsuite/g++.dg/template/crash115.C
+++ gcc/testsuite/g++.dg/template/crash115.C
@@ -1,3 +1,3 @@
 // PR c++/56534
 
-template < struct template rebind < > // { dg-error "expected" }
+template < struct template rebind < > // { dg-error "expected|must follow" }