c++: Missing SFINAE with lookup_fnfields [PR78446]

Here we're failing to do SFINAE in build_op_call when looking up the
class's operator() via lookup_fnfields, which calls lookup_member always
with complain=tf_warning_or_error; from there we would complain
about an ambiguous lookup for operator().

This patch fixes this by adding a tsubst_flags_t parameter to
lookup_fnfields and adjusting all its callers appropriately.

gcc/cp/ChangeLog:

	PR c++/78446
	* call.c (build_op_call): Pass complain to lookup_fnfields.
	(build_special_member_call): Likewise.
	* class.c (type_requires_array_cookie): Pass tf_warning_or_error
	to lookup_fnfields.
	* cp-tree.h (lookup_fnfields): Add tsubst_flags_t parameter.
	* except.c (build_throw): Pass tf_warning_or_error to
	lookup_fnfields.
	* init.c (build_new_1): Pass complain to lookup_fnfields.
	* method.c (locate_fn_flags): Likewise.
	* name-lookup.c (lookup_name_real_1): Pass tf_warning_or_error
	to lookup_fnfields.
	* pt.c (tsubst_baselink): Pass complain to lookup_fnfields.
	* search.c (lookup_fnfields): New 'complain' parameter.  Pass it
	to lookup_member.

gcc/testsuite/ChangeLog:

	PR c++/78446
	* g++.dg/template/sfinae31.C: New test.

12 files changed, 54 insertions, 13 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ba0d9e6..4374954 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,21 @@
+2020-05-14  Patrick Palka  <ppalka@redhat.com>
+
+	PR c++/78446
+	* call.c (build_op_call): Pass complain to lookup_fnfields.
+	(build_special_member_call): Likewise.
+	* class.c (type_requires_array_cookie): Pass tf_warning_or_error
+	to lookup_fnfields.
+	* cp-tree.h (lookup_fnfields): Add tsubst_flags_t parameter.
+	* except.c (build_throw): Pass tf_warning_or_error to
+	lookup_fnfields.
+	* init.c (build_new_1): Pass complain to lookup_fnfields.
+	* method.c (locate_fn_flags): Likewise.
+	* name-lookup.c (lookup_name_real_1): Pass tf_warning_or_error
+	to lookup_fnfields.
+	* pt.c (tsubst_baselink): Pass complain to lookup_fnfields.
+	* search.c (lookup_fnfields): New 'complain' parameter.  Pass it
+	to lookup_member.
+
 2020-05-14  Nathan Sidwell  <nathan@acm.org>
 
 	* parser.c (cp_parser_diagnose_invalid_typename): Mention
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 940e65d..c587197 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -4792,7 +4792,7 @@ build_op_call_1 (tree obj, vec<tree, va_gc> **args, tsubst_flags_t complain)
 
   if (TYPE_BINFO (type))
     {
-      fns = lookup_fnfields (TYPE_BINFO (type), call_op_identifier, 1);
+      fns = lookup_fnfields (TYPE_BINFO (type), call_op_identifier, 1, complain);
       if (fns == error_mark_node)
 	return error_mark_node;
     }
@@ -5978,7 +5978,7 @@ add_operator_candidates (z_candidate **candidates,
   tree arg2_type = nargs > 1 ? TREE_TYPE ((*arglist)[1]) : NULL_TREE;
   if (CLASS_TYPE_P (arg1_type))
     {
-      tree fns = lookup_fnfields (arg1_type, fnname, 1);
+      tree fns = lookup_fnfields (arg1_type, fnname, 1, complain);
       if (fns == error_mark_node)
 	return error_mark_node;
       if (fns)
@@ -6785,7 +6785,7 @@ build_op_delete_call (enum tree_code code, tree addr, tree size,
 
        Therefore, we ask lookup_fnfields to complain about ambiguity.  */
     {
-      fns = lookup_fnfields (TYPE_BINFO (type), fnname, 1);
+      fns = lookup_fnfields (TYPE_BINFO (type), fnname, 1, complain);
       if (fns == error_mark_node)
 	return error_mark_node;
     }
@@ -9806,7 +9806,7 @@ build_special_member_call (tree instance, tree name, vec<tree, va_gc> **args,
 	}
     }
 
-  fns = lookup_fnfields (binfo, name, 1);
+  fns = lookup_fnfields (binfo, name, 1, complain);
 
   /* When making a call to a constructor or destructor for a subobject
      that uses virtual base classes, pass down a pointer to a VTT for
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 15f490d..bab15524 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -5644,7 +5644,7 @@ type_requires_array_cookie (tree type)
      a cookie.  */
   fns = lookup_fnfields (TYPE_BINFO (type),
 			 ovl_op_identifier (false, VEC_DELETE_EXPR),
-			 /*protect=*/0);
+			 /*protect=*/0, tf_warning_or_error);
   /* If there are no `operator []' members, or the lookup is
      ambiguous, then we don't need a cookie.  */
   if (!fns || fns == error_mark_node)
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index f7c11bc..827b03d 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7056,7 +7056,7 @@ extern tree dcast_base_hint			(tree, tree);
 extern int accessible_p				(tree, tree, bool);
 extern int accessible_in_template_p		(tree, tree);
 extern tree lookup_field			(tree, tree, int, bool);
-extern tree lookup_fnfields			(tree, tree, int);
+extern tree lookup_fnfields			(tree, tree, int, tsubst_flags_t);
 extern tree lookup_member			(tree, tree, int, bool,
 						 tsubst_flags_t,
 						 access_failure_info *afi = NULL);
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index 7e93c51..9e1aa50 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -821,7 +821,8 @@ build_throw (location_t loc, tree exp)
       if (type_build_dtor_call (TREE_TYPE (object)))
 	{
 	  tree dtor_fn = lookup_fnfields (TYPE_BINFO (TREE_TYPE (object)),
-					  complete_dtor_identifier, 0);
+					  complete_dtor_identifier, 0,
+					  tf_warning_or_error);
 	  dtor_fn = BASELINK_FUNCTIONS (dtor_fn);
 	  mark_used (dtor_fn);
 	  if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (object)))
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index d4c883b..ef4b3c4 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3276,7 +3276,7 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
       /* Create the argument list.  */
       vec_safe_insert (*placement, 0, size);
       /* Do name-lookup to find the appropriate operator.  */
-      fns = lookup_fnfields (elt_type, fnname, /*protect=*/2);
+      fns = lookup_fnfields (elt_type, fnname, /*protect=*/2, complain);
       if (fns == NULL_TREE)
 	{
 	  if (complain & tf_error)
diff --git a/gcc/cp/method.c b/gcc/cp/method.c
index 3f8842b..2d31462 100644
--- a/gcc/cp/method.c
+++ b/gcc/cp/method.c
@@ -1646,7 +1646,7 @@ locate_fn_flags (tree type, tree name, tree argtype, int flags,
 	}
     }
 
-  fns = lookup_fnfields (binfo, name, 0);
+  fns = lookup_fnfields (binfo, name, 0, complain);
   rval = build_new_method_call (ob, fns, &args, binfo, flags, &fn, complain);
 
   if (fn && rval == error_mark_node)
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 4928b60..2ff85f1 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -6455,7 +6455,8 @@ lookup_name_real_1 (tree name, int prefer_type, int nonclass, bool block_p,
 
 	  /* Lookup the conversion operator in the class.  */
 	  class_type = level->this_entity;
-	  operators = lookup_fnfields (class_type, name, /*protect=*/0);
+	  operators = lookup_fnfields (class_type, name, /*protect=*/0,
+				       tf_warning_or_error);
 	  if (operators)
 	    return operators;
 	}
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 5ca659e..61e6fa7 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -16022,7 +16022,8 @@ tsubst_baselink (tree baselink, tree object_type,
 	/* Treat as-if non-dependent below.  */
 	dependent_p = false;
 
-      baselink = lookup_fnfields (qualifying_scope, name, /*protect=*/1);
+      baselink = lookup_fnfields (qualifying_scope, name, /*protect=*/1,
+				  complain);
       if (!baselink)
 	{
 	  if ((complain & tf_error)
diff --git a/gcc/cp/search.c b/gcc/cp/search.c
index d9a2d748..b9da2fc 100644
--- a/gcc/cp/search.c
+++ b/gcc/cp/search.c
@@ -1347,10 +1347,11 @@ lookup_field (tree xbasetype, tree name, int protect, bool want_type)
    return NULL_TREE.  */
 
 tree
-lookup_fnfields (tree xbasetype, tree name, int protect)
+lookup_fnfields (tree xbasetype, tree name, int protect,
+		 tsubst_flags_t complain)
 {
   tree rval = lookup_member (xbasetype, name, protect, /*want_type=*/false,
-			     tf_warning_or_error);
+			     complain);
 
   /* Ignore non-functions, but propagate the ambiguity list.  */
   if (!error_operand_p (rval)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e169468..b9b968a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-14  Patrick Palka  <ppalka@redhat.com>
+
+	PR c++/78446
+	* g++.dg/template/sfinae31.C: New test.
+
 2020-05-14  Uroš Bizjak  <ubizjak@gmail.com>
 
 	PR target/95046
diff --git a/gcc/testsuite/g++.dg/template/sfinae31.C b/gcc/testsuite/g++.dg/template/sfinae31.C
new file mode 100644
index 0000000..b31a5ae
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/sfinae31.C
@@ -0,0 +1,14 @@
+// PR c++/78446
+// { dg-do compile { target c++11 } }
+
+struct A { void operator()(); };
+struct B { void operator()(); };
+struct C : A, B {};
+
+template<class T>
+decltype(T()()) foo(int);
+
+template<class> int foo(...);
+
+using type = decltype(foo<C>(0));
+using type = int;