c++: Check satisfaction before non-dep convs. [CWG2369]

It's very hard to use concepts to protect a template from hard errors due to
unwanted instantiation if constraints aren't checked until after doing all
substitution and checking of non-dependent conversions.

It was pretty straightforward to insert the satisfaction check into the
logic, but I needed to make the 3-parameter version of
satisfy_declaration_constraints call push_tinst_level like the 2-parameter
version already does.  For simplicity, I also made it add any needed outer
template arguments from the TEMPLATE_DECL to the args.

The testsuite changes are mostly because this change causes unsatisfaction
to cause deduction to fail rather than reject the candidate later in
overload resolution.

gcc/cp/ChangeLog:

	DR 2369
	* cp-tree.h (push_tinst_level, push_tinst_level_loc): Declare.
	* constraint.cc (satisfy_declaration_constraints):
	Use add_outermost_template_args and push_tinst_level.
	* pt.c (add_outermost_template_args): Handle getting
	a TEMPLATE_DECL as the first argument.
	(push_tinst_level, push_tinst_level_loc): No longer static.
	(fn_type_unification): Check satisfaction before non-dependent
	conversions.

gcc/testsuite/ChangeLog:

	DR 2369
	* g++.dg/concepts/diagnostic10.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic13.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic2.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic3.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic4.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic5.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic9.C: Adjust expexcted errors.
	* g++.dg/concepts/expression2.C: Adjust expexcted errors.
	* g++.dg/concepts/fn5.C: Adjust expexcted errors.
	* g++.dg/concepts/placeholder5.C: Adjust expexcted errors.
	* g++.dg/concepts/pr67595.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-pr78752-2.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-pr84140.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-recursive-sat3.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-requires18.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-requires19.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts3.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-nondep1.C: New test.
	* g++.dg/cpp2a/concepts-nondep1a.C: New test.

1 files changed, 9 insertions, 3 deletions

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 48d52ec..7a2f3b9 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2814,16 +2814,22 @@ satisfy_declaration_constraints (tree t, tree args, subst_info info)
   info.in_decl = t;
 
   gcc_assert (TREE_CODE (t) == TEMPLATE_DECL);
+
+  args = add_outermost_template_args (t, args);
+
+  tree result = boolean_true_node;
   if (tree norm = normalize_template_requirements (t, info.noisy ()))
     {
+      if (!push_tinst_level (t, args))
+	return result;
       tree pattern = DECL_TEMPLATE_RESULT (t);
       push_access_scope (pattern);
-      tree result = satisfy_associated_constraints (norm, args, info);
+      result = satisfy_associated_constraints (norm, args, info);
       pop_access_scope (pattern);
-      return result;
+      pop_tinst_level ();
     }
 
-  return boolean_true_node;
+  return result;
 }
 
 static tree