[PATCH] PR c++/65750

[PATCH] PR c++/65750

[Adam Butcher]

	* cp/parser.c (cp_parser_simple_type_specifier): Don't synthesize
	implicit template parm if 'auto' is a placeholder for trailing return
	type.
---
 gcc/cp/parser.c                      | 23 +++++++++++++++++++++++
 gcc/testsuite/g++.dg/cpp1y/pr65750.C | 12 ++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/pr65750.C

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 4611be9..511ec85 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -14949,6 +14949,29 @@ cp_parser_simple_type_specifier (cp_parser* parser,
       maybe_warn_cpp0x (CPP0X_AUTO);
       if (parser->auto_is_implicit_function_template_parm_p)
 	{
+	  /* The 'auto' might be the placeholder return type for a function decl
+	     with trailing return type.  */
+	  bool have_trailing_return_fn_decl = false;
+	  if (cp_lexer_peek_nth_token (parser->lexer, 2)->type
+	      == CPP_OPEN_PAREN)
+	    {
+	      cp_parser_parse_tentatively (parser);
+	      cp_lexer_consume_token (parser->lexer);
+	      if (cp_parser_skip_to_closing_parenthesis (parser,
+							 /*recovering*/false,
+							 /*or_comma*/false,
+							 /*consume_paren*/true))
+		have_trailing_return_fn_decl
+		  = cp_lexer_next_token_is (parser->lexer, CPP_DEREF);
+	      cp_parser_abort_tentative_parse (parser);
+	    }
+
+	  if (have_trailing_return_fn_decl)
+	    {
+	      type = make_auto ();
+	      break;
+	    }
+
 	  if (cxx_dialect >= cxx14)
 	    type = synthesize_implicit_template_parm (parser);
 	  else
diff --git a/gcc/testsuite/g++.dg/cpp1y/pr65750.C b/gcc/testsuite/g++.dg/cpp1y/pr65750.C
new file mode 100644
index 0000000..798d13b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/pr65750.C
@@ -0,0 +1,12 @@
+// PR c++/65750
+// { dg-do compile { target c++14 } }
+
+template <typename T> struct F { };
+
+class a
+{
+  virtual auto f( F< void () > ) -> void;
+  virtual auto g( F< auto () -> void > ) -> void;
+};
+
+auto main() -> int { }
-- 
2.3.5

Re: [PATCH] PR c++/65750

[Adam Butcher]

On 2015-04-10 15:57, Adam Butcher wrote:
> +	      cp_lexer_consume_token (parser->lexer);

Actually there should be two of these as the 'auto' isn't consumed yet.

Re: [PATCH] PR c++/65750

[Jason Merrill]

On 04/14/2015 05:27 PM, Adam Butcher wrote:
> On 2015-04-10 15:57, Adam Butcher wrote:
>> +          cp_lexer_consume_token (parser->lexer);
>
> Actually there should be two of these as the 'auto' isn't consumed yet.

OK.

Jason

Re: [PATCH] PR c++/65750

[Paolo Carlini]

Hi,

On 04/14/2015 11:34 PM, Jason Merrill wrote:
> On 04/14/2015 05:27 PM, Adam Butcher wrote:
>> On 2015-04-10 15:57, Adam Butcher wrote:
>>> +          cp_lexer_consume_token (parser->lexer);
>>
>> Actually there should be two of these as the 'auto' isn't consumed yet.
> OK.

I'm finishing retesting the amended patch and, if everything goes well, 
I will apply it to trunk, as approved by Jason (only additional minor 
tweak: testcase in cpp0x instead of cpp1y).

What about gcc-5-branch? It's a regression.

Thanks,
Paolo.

Re: [PATCH] PR c++/65750

[Jason Merrill]

On 06/24/2015 06:55 AM, Paolo Carlini wrote:
> I'm finishing retesting the amended patch and, if everything goes well,
> I will apply it to trunk, as approved by Jason (only additional minor
> tweak: testcase in cpp0x instead of cpp1y).
>
> What about gcc-5-branch? It's a regression.

I think this is safe enough for the branch.

Jason