From 625dadaf5df5a2ae0d8c5660fd1eec8ba354479c Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Thu, 8 Apr 2021 14:39:28 -0400
Subject: [PATCH] c++: Fix two issues with auto function parameter [PR99806]

When we have a member function with auto parameter like this:

  struct S {
    void f(auto);
  };

cp_parser_member_declaration -> grokfield produces a FUNCTION_DECL
"void S::foo(auto:1)", and then finish_fully_implicit_template turns
that FUNCTION_DECL into a TEMPLATE_DECL.  The bug here is that we only
call cp_parser_save_default_args for a FUNCTION_DECL.  As a consequence,
abbrev10.C is rejected because we complain that the default argument has
not been defined, and abbrev11.C ICEs, because we don't re-parse the
delayed noexcept, so the DEFERRED_PARSE tree leaks into tsubst* where we
crash.  This patch fixes both issues.

gcc/cp/ChangeLog:

	PR c++/99806
	* parser.c (cp_parser_member_declaration): Call
	cp_parser_save_default_args even for function templates.  Use
	STRIP_TEMPLATE on the declaration we're passing.

gcc/testsuite/ChangeLog:

	PR c++/99806
	* g++.dg/concepts/abbrev10.C: New test.
	* g++.dg/concepts/abbrev11.C: New test.
---
 gcc/cp/parser.c                          |  4 ++--
 gcc/testsuite/g++.dg/concepts/abbrev10.C | 18 ++++++++++++++++++
 gcc/testsuite/g++.dg/concepts/abbrev11.C | 10 ++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/concepts/abbrev10.C
 create mode 100644 gcc/testsuite/g++.dg/concepts/abbrev11.C

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 59adac4..e6e6ed7 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -26433,8 +26433,8 @@ cp_parser_member_declaration (cp_parser* parser)
 		  || !DECL_DECLARES_FUNCTION_P (decl))
 		finish_member_declaration (decl);
 
-	      if (TREE_CODE (decl) == FUNCTION_DECL)
-		cp_parser_save_default_args (parser, decl);
+	      if (DECL_DECLARES_FUNCTION_P (decl))
+		cp_parser_save_default_args (parser, STRIP_TEMPLATE (decl));
 	      else if (TREE_CODE (decl) == FIELD_DECL
 		       && DECL_INITIAL (decl))
 		/* Add DECL to the queue of NSDMI to be parsed later.  */
diff --git a/gcc/testsuite/g++.dg/concepts/abbrev10.C b/gcc/testsuite/g++.dg/concepts/abbrev10.C
new file mode 100644
index 0000000..b611346
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/abbrev10.C
@@ -0,0 +1,18 @@
+// PR c++/99806
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-fconcepts" }
+
+struct S {
+  void f(auto, auto, int = 3);
+  void f2(auto, auto, int = 3) { }
+  template<typename T> static T g(T, auto, int = 3);
+};
+
+void
+g ()
+{
+  S::g(1, 2);
+  S s;
+  s.f(1, 2);
+  s.f2(1, 2);
+}
diff --git a/gcc/testsuite/g++.dg/concepts/abbrev11.C b/gcc/testsuite/g++.dg/concepts/abbrev11.C
new file mode 100644
index 0000000..ddb4793
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/abbrev11.C
@@ -0,0 +1,10 @@
+// PR c++/99806
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-fconcepts" }
+
+template <typename T> concept C = requires (T a) { a.f(0); };
+struct S {
+  void f(auto) noexcept(B);
+  static constexpr bool B = true;
+};
+static_assert(C<S>, "");
-- 
2.7.4